Tuesday, September 26, 2006
Thursday, September 21, 2006
NETWORK GLOSSARY
AppleTalk
A communications protocol developed by Apple Computer to allow networking between Macintoshes. All Macintosh computers have a LocalTalk port, running AppleTalk over a 230K bps serial line. AppleTalk also runs over Ethernet (EtherTalk) and Token Ring (TokenTalk)
Auto-Negotiate
Clause 28 of the IEEE 802.3u standard specifies a MAC sublayer for the identification of the speed and duplex mode of connection being supported by a device. Support of this feature is optional for individual vendors.
Auto-sense
Ability of a 10/100 Ethernet device to interpret the speed or duplex mode of the attached device and to adjust to that rate. Official term is Auto-Negotiation in Clause 28 of the IEEE 802.3u standard.
AUI
Attachment Unit Interface. A 15-pin shielded, twisted pair Ethernet cable used (optionally) to connect between network devices and a MAU.
Autobaud
Automatic determination and matching of transmission speed.
AWG
American Wire Gauge. A system that specifies wire size. The gauge varies inversely with the wire diameter size.
Backbone
The main cable in a network.
Bandwidth on Demand
Feature that allows a remote access device to initiate a second connection to a particular site to increase the amount of data transferred to that site to increase the desired threshold. The network manager configuring the remote access server will specify a number of bits or a percentage of connection bandwidth threshold which will trigger the secondary connection. Multilink PPP is an emerging standard to allow this feature to be interoperable, but right now the only way to ensure correct operation is to use devices on both end from the same vendor.
Baseband LAN
A LAN that uses a single carrier frequency over a single channel. Ethernet, Token Ring and Arcnet LANs use baseband transmission.
Baud
Unit of signal frequency in signals per second. Not synonymous with bits per second since signals can represent more than one bit. Baud equals bits per second only when the signal represents a single bit.
Binaries
Binary, machine readable forms of programs that have been compiled or assembled. As opposed to Source language forms of programs.
Binary
Characteristic of having only two states, such as current on and current off. The binary number system uses only ones and zeros.
Bitronics
Specification for parallel printing which allows bidirectional communication on a Centronics-type interface. Pioneered by Hewlett-Packard, mainly used for postscript printers.
Bit
The smallest unit of data processing information. A bit (or binary digit) assumes the value of either 1 or 0.
BNC
A standardized connector used with Thinnet and coaxial cable.
BOOTP
A TCP/IP network protocol that lets network nodes request configuration information from a
BOOTP "server" node.
bps
Bits per second, units of transmission speed.
Bridge
A networking device that connects two LANs and forwards or filters data packets between them, based on their destination addresses. Bridges operate at the data link level (or MAC-layer) of the OSI reference model, and are transparent to protocols and to higher level devices like routers.
Broadband
A data transmission technique allowing multiple high-speed signals to share the bandwidth of a single cable via frequency division multiplexing.
Broadband Network
A network that uses multiple carrier frequencies to transmit multiplexed signals on a single cable. Several networks may coexist on a single cable without interfering with one another.
Brouter
A device that routes specific protocols, such as TCP/IP and IPX, and bridges other protocols, thereby combining the functions of both routers and bridges.
Bus
A LAN topology in which all the nodes are connected to a single cable. All nodes are considered equal and receive all transmissions on the medium.
Byte
A data unit of eight bits.
Channel
The data path between two nodes.
CHAP
(Challenge Handshake Authentication Protocol) Authentication scheme for PPP where the password not only is required to begin connection but also is required during the connection - failure to provide correct password during either login or challenge mode will result in disconnect.
Coaxial Cable
An electrical cable with a solid wire conductor at its center surrounded by insulating materials and an outer metal screen conductor with an axis of curvature coinciding with the inner conductor - hence "coaxial." Examples are standard Ethernet cable and Thinwire Ethernet cable.
Collision
The result of two network nodes transmitting on the same channel at the same time. The transmitted data is not usable.
Collision Detect
A signal indicating that one or more stations are contending with the local station's transmission. The signal is sent by the Physical layer to the Data Link layer on an Ethernet/IEEE 802.3 node.
Communication Server
A dedicated, standalone system that manages communications activities for other computers.
Console
The terminal used to configure network devices at boot (start-up) time.
Crosstalk
Noise passed between communications cables or device elements.
Cut-through
Technique for examining incoming packets whereby an Ethernet switch looks only at the first few bytes of a packet before forwarding or filtering it. This process is faster than looking at the whole packet, but it also allows some bad packets to be forwarded.
CSMA/CD
Carrier Sense Multiple Access with Collision Detection is the Ethernet media access method. All network devices contend equally for access to transmit. If a device detects another device's signal while it is transmitting, it aborts transmission and retries after a brief pause.
Data Link
A logical connection between two nodes on the same circuit.
Data Link Layer
Layer 2 of the seven-layer OSI reference model for communication between computers on networks. This layer defines protocols for data packets and how they are transmitted to and from each network device. It is a medium-independent, link-level communications facility on top of the Physical layer, and is divided into two sublayers: medium-access control (MAC) and logical-link control (LLC).
DECnet?
Digital Equipment Corporation (DEC) proprietary network architecture, a system for networking computers. It runs on point-to-point, X.25 and Ethernet networks.
Dial on Demand
When a router detects the need to initiate a dial-up connection to a remote network, it does so automatically according to pre-defined parameters set by the network manager.
Dialback
A security feature that ensures people do not log into modems that they shouldn't have access to. When a connection is requested, the system checks the user name for validity, then "dials back" the number associated with that user name.
Distributed Processing
A system in which each computer or node in the network performs its own processing and manages some of its data while the network facilitates communications between the nodes.
Domain Name
A domain name is a text name appended to a host name to form a unique host name across internets.
Download
The transfer of a file or information from one network node to another. Generally refers to transferring a file from a "big" node, such as a computer, to a "small" node, such as a terminal server or printer.
End Node
A node such as a PC that can only send and receive information for its own use. It cannot route and forward information to another node.
Ethernet
The most popular LAN technology in use today. The IEEE standard 802.3 defines the rules for configuring an Ethernet network. It is a 10 Mbps, CSMA/CD baseband network that runs over thin coax, thick coax, twisted pair or fiber optic cable.
EtherTalk
Apple Computer's protocol for Ethernet transmissions.
FDDI
Fiberoptic Data Distribution Interface. A cable interface capable of transmitting data at 100 Mbps. Originally specified for fiber lines, FDDI can also operate over twisted-pair cable for short
distances.
Fiber-Optic Cable
A transmission medium composed of a central glass optical fiber cable surrounded by cladding and an outer protective sheath. It transmits digital signals in the form of modulated light from a laser or LED (light-emitting diode).
File Server
A computer that stores data for network users and provides network access to that data.
Filtering
Process whereby an Ethernet switch or bridge reads the contents of a packet and then finds that the packet does not need to be forwarded, and drops it. A filtering rate is the rate at which a device can receive packets and drop them without any loss of incoming packets or delay in processing.
Firmware
Alterable programs in semipermanent storage, e.g., some type of read-only or flash reprogrammable memory.
Forwarding
Process whereby an Ethernet switch or bridge reads the contents of a packet and then passes that packet on to the appropriate attached segment. A forwarding rate is the time that it takes the device to execute all of the steps.
Flash ROM
See ROM.
Framing
Dividing data for transmission into groups of bits, and adding a header and a check sequence to form a frame.
FTP
File Transfer Protocol, a TCP/IP protocol for file transfer.
Full-Duplex
Independent, simultaneous two-way transmission in both directions, as opposed to half-duplex transmission.
Gateway
A device for interconnecting two or more dissimilar networks. It can translate all protocol levels from the Physical layer up through the Applications layer of the OSI model, and can therefore interconnect entities that differ in all details.
Hardware Address
See Network Address.
Header
The initial part of a data packet or frame containing identifying information such as the source of the data, its destination, and length.
Heartbeat
Ethernet defined SQE signal quality test function.
Hertz (Hz)
A frequency unit equal to one cycle per second.
Host
Generally a node on a network that can be used interactively, i.e., logged into, like a computer.
Host Table
A list of TCP/IP hosts on the network along with their IP addresses.
IEEE 802.3
The IEEE (Institute of Electrical and Electronic Engineers) standard that defines the CSMA/CD media-access method and the physical and data link layer specifications of a local area network. Among others, it includes 10BASE2, 10BASE5, 10BASE-FL and 10BASE-T Ethernet implementations.
Internet
A series of interconnected local, regional, national and international networks, linked using TCP/IP. Internet links many government, university and research sites. It provides E-mail, remote login and file transfer services.
Internetworking
General term used to describe the industry composed of products and technologies used to link networks together.
IP Address
See Network Address.
IPX
Internetwork Packet eXchange, a NetWare protocol similar to IP (Internet Protocol).
ISDN
(Integrated Services Digital Network): All digital service provided by telephone companies. Provides 144K bps over a single phone line (divided in two 64K bps "B" channels and one 16K bps "D" channel).
ISO Layered Model
The International Standards Organization (ISO) sets standards for computers and communications. Its Open Systems Interconnection (OSI) reference model specifies how dissimilar computing devices such as Network Interface Cards (NICs), bridges and routers exchange data over a network. The model consists of seven layers. From lowest to highest, they are: Physical, Data Link, Network, Transport, Session, Presentation and Application. Each layer performs services for the layer above it.
Jabber
Network error caused by an interface card placing corrupted data on the network. Or, an error condition due to an Ethernet node transmitting longer packets than allowed.
Kbps
Kilobits per second.
Kermit
A popular file transfer and terminal emulation program.
LAN
Local Area Network, a data communications system consisting of a group of interconnected computers, sharing applications, data and peripherals. The geographical area is usually a building or group of buildings.
LAT
Local Area Transport, a Digital Equipment Corporation proprietary network communication protocol. The protocol is based on the idea of a relatively small, known number of hosts on a local network sending small network packets at regular intervals. LAT will not work on a wide area network scale, as TCP/IP does.
Latency
The delay incurred by a switching or bridging device between receiving the frame and forwarding the frame.
Layer
In networks, layers refer to software protocol levels comprising the architecture, with each layer performing functions for the layers above it.
Line Speed
Expressed in bps, the maximum rate at which data can reliably be transmitted over a line using given hardware.
Load Balancing
Shifting a user job from a more heavily loaded resource to a less loaded resource.
Local Network Interconnect (LNI)
A Port Multiplier, or concentrator supporting multiple active devices or communications controllers, either used standalone or attached to standard Ethernet cable.
LocalTalk
Apple Computer's proprietary 230 Kbps baseband network protocol. It uses the CSMA/CD access method over unshielded twisted pair wire.
Logical Link
A temporary connection between source and destination nodes, or between two processes on the same node.
LPD
Line Printer Daemon, a process on Berkeley spooler implementations that provides LPR support.
LPR
The LPR command is used to queue print jobs on Berkeley queuing systems.
MAU
Medium Attachment Unit, a device used to convert signals from one Ethernet medium to another.
Mbps
Megabits per second.
MIB
Management Information Base, a database of network parameters used by SNMP and CMIP (Common Management Information Protocol) to monitor and change network device settings. It provides a logical naming of all information resources on the network that are pertinent to the network's management.
MII
Media Independent Interface, New standard developed for Fast Ethernet in IEEE 802.3u specification. The Fast Ethernet equivalent to the AUI in 10 Mbps Ethernet, allowing different types of Fast Ethernet media to be connected to a Fast Ethernet device via a common interface.
MJ
Modular Jack. A jack used for connecting voice cables to a faceplate, as for a telephone.
MMJ
Modified Modular Jack. These are the 6-pin connectors used to connect serial terminal lines to terminal devices. MMJs can be distinguished from the similar RJ12 jacks by having a side-locking tab, rather than a center-mounted one.
Modem
A modulator-demodulator device for changing transmission signals from digital to analog for
transmission over phone lines. Used in pairs, one is required at each end of the line.
MOP
Maintenance Operations Protocol, a DEC protocol used for remote communications between hosts and servers.
Multicast
A multicast is a message that is sent out to multiple devices on the network by a host.
Multilink PPP
The ability of a dialup device to allocate more than one channel of bandwidth to a particular connection. Generally, this is termed to be the ability of an ISDN device to bond two B-channels together into a single data pipe, but some vendors can perform the same function with asychronous dial-up connections over modems by having a second connection initiated to support the additional bandwidth requirements.
Multiplexer
A device that allows several users to share a single circuit. It funnels different data streams into a single stream. At the other end of the communications link, another multiplexer reverses the process by splitting the data stream back into the original streams.
Multiplexing
Transmitting multiple signals simultaneously on a single channel.
Multiport Repeater
A repeater, either standalone or connected to standard Ethernet cable, for interconnecting up to eight Thinwire Ethernet segments.
Name Server
Software that runs on network hosts charged with translating (or resolving) text-style names into numeric IP addresses.
NCP
Network Control Program, a program run on VMS machines to configure local network hardware and remote network devices.
NetWare
A Novell developed Network Operating System (NOS). Provides file and printer sharing among networks of Personal Computers (PCs). Each NetWare network must have at least one file server, and access to other resources is dependent on connecting to and logging into the file server. The file server controls user logins and access to other network clients, such as user PCs, print servers, modem/fax servers, disk/file servers, etc.
NetBIOS/NetBEUI
Microsoft's networking protocols for its LAN Manager and Windows NT products.
Network
An interconnected system of computers that can communicate with each other and share files, data and resources.
Network Address
Every node on a network has one or more addresses associated with it, including at least one fixed hardware address such as "ae-34-2c-1d-69-f1" assigned by the device's manufacturer. Most nodes also have protocol specific addresses assigned by a network manager.
Network Management
Administrative services for managing a network, including configuring and tuning, maintaining network operation, monitoring network performance, and diagnosing network problems.
NIC
Network Interface Card, an adapter card that is inserted into a computer, and contains the necessary software and electronics to enable the station to communicate over the network.
Node
Any intelligent device connected to the network. This includes terminal servers, host computers, and any other devices (such as printers and terminals) that are directly connected to the network. A node can be thought of as any device that has a "hardware address."
NOS
Network Operating System, the software for a network that runs in a file server and controls access to files and other resources from multiple users. It provides security and administrative tools. Novell's NetWare, Banyan's VINES and IBM's LAN Server are NOS examples.
Open System Interconnect (OSI)
See "ISO."
Packet
A series of bits containing data and control information, including source and destination node addresses, formatted for transmission from one node to another.
PAP
(Password Authentication Protocol) Authentication scheme for PPP links. A password can be specified for both devices on a remote link. Failure to authenticate will result in a dropped connection prior to start of data transmission.
Physical Address
An address identifying a single node.
Physical Layer
Layer 1, the bottom layer of the OSI model, is implemented by the physical channel. The Physical layer insulates Layer 2, the Data Link layer, from medium-dependent physical characteristics such as baseband, broadband or fiber-optic transmission. Layer 1 defines the protocols that govern transmission media and signals.
Point-to-Point
A circuit connecting two nodes only, or a configuration requiring a separate physical connection between each pair of nodes.
Port
The physical connector on a device enabling the connection to be made.
Port Multiplier
A concentrator providing connection to a network for multiple devices.
PostScript
A printer/display protocol developed by Adobe Corp. PostScript is an actual printing and programming language to display text and graphics. Unlike line/ASCII printers, which print character input verbatim, PostScript printers accept and interpret an entire PostScript page before printing it.
PPP
Point-to-Point Protocol. The successor to SLIP, PPP provides router-to-router and host-to-network connections over both synchronous and asynchronous circuits.
Print Server
A dedicated computer that manages printers and print requests from other nodes on the network.
PROM
Programmable ROM, a read-only memory whose data content can be altered.
Protocol
Any standard method of communicating over a network.
Remote Access
Access to network resources not located on the same physical Ethernet. (Physical Ethernet here refers to an entire site network topology.)
Remote Control
Form of remote access where a device dialing in assumes control of another network node - all keystrokes on the remote are translated into keystrokes on the network node. Used primarily with IPX protocol.
Remote Node
Form of remote access where the device dialing in acts as a peer on the target network. Used with both IP and IPX protocols.
Repeater
A repeater is a network device that repeats signals from one cable onto one or more other cables, while restoring signal timing and waveforms.
Ring
A network topology in which the nodes are connected in a closed loop. Data is transmitted from node to node around the loop, always in the same direction.
RMON
SNMP-based standard for reporting various network conditions. RMON has 10 different management groups which provide detailed information about a network.
Rlogin
Rlogin is an application that provides a terminal interface between UNIX hosts using the
TCP/IP network protocol. Unlike Telnet, Rlogin assumes the remote host is (or behaves like) a UNIX machine
ROM
Read-Only Memory, a memory device that retains its information even when power to it is removed. A ROM version of a network device does not need to download, since the ROM contains the entire executable code and thus never needs to reload it. Frequently the ROM is provided as "flash ROM", which can be reprogrammed by downloading if the user chooses.
Router
Device capable of filtering/forwarding packets based upon data link layer information. Whereas a bridge or switch may only read MAC layer addresses to filter, routers are able to read data such as IP addresses and route accordingly.
RTEL
Lantronix's "reverse Telnet" software allows hosts using TCP/IP to establish a session with a device attached to a terminal server port.
Server
A computer that provides resources to be shared on the network, such as files (file server) or
terminals (terminal server).
Session
A connection to a network service.
Shared Ethernet
Ethernet configuration in which a number of segments are bound together in a single collision domain. Hubs produce this type of configuration where only one node can transmit at a time.
SLIP
Serial Line Internet Protocol, a protocol for running TCP/IP over serial lines.
SNA
Systems Network Architecture. IBM's layered protocols for mainframe communications.
SNMP
Simple Network Management Protocol, allows a TCP/IP host running an SNMP application to query other nodes for network-related statistics and error conditions. The other hosts, which provide SNMP agents, respond to these queries and allow a single host to gather network statistics from many other network nodes.
Source Code
Programs in an uncompiled or unassembled form.
Spanning Tree
An algorithm used by bridges to create a logical topology that connects all network segments, and ensures that only one path exists between any two stations.
Store and Forward
Technique for examining incoming packets on an Ethernet switch or bridge whereby the whole packet is read before forwarding or filtering takes place. Store and forward is a slightly slower process than cut-through, but it does ensure that all bad or misaligned packets are eliminated from the network by the switching device.
SPX
Sequential Packet exchange. Novell's implementation of SPP (Sequential Packet Protocol).
SQE
Ethernet-defined signal quality test function, frequently called "heartbeat."
Switch
Multiport Ethernet device designed to increase network performance by allowing only essential traffic on the attached individual Ethernet segments. Packets are filtered or forwarded based upon their source and destination addresses.
T-Connector
A T-shaped device with two female and one male BNC connectors.
TCP/IP
Transmission Control Protocol (TCP) and Internet Protocol (IP) are the standard network protocols in UNIX environments. They are almost always implemented and used together and called TCP/IP.
Telnet
Telnet is an application that provides a terminal interface between hosts using the TCP/IP network protocol. It has been standardized so that "telnetting" to any host should give one an interactive terminal session, regardless of the remote host type or operating system. Note that this is very different from the LAT software, which allows only local network access to LAT hosts only.
10BASE2
Ethernet running on thin coax network cable.
10BASE5
Ethernet running on Thickwire network cable.
10BASE-T
Ethernet running on unshielded twisted pair (UTP) cable. Note that 10BASE-T is a point-to-point network media, with one end of the cable typically going to a repeater/hub and the other to the network device.
Terminal Server
A concentrator that facilitates communication between hosts and terminals.
Terminator
Used on both ends of a standard Ethernet or Thinwire Ethernet segment, this special connector provides the 50 ohm termination resistance needed for the cable.
TFTP
Trivial File Transfer Protocol. On computers that run the TCP/IP networking software, TFTP is used to quickly send files across the network with fewer security features than FTP.
Thickwire
Half-inch diameter coax cable.
Thinwire
Thin coaxial cable similar to that used for television/video hookups.
Throughput
The amount of data transmitted between two points in a given amount of time, e.g., 10 Mbps.
Token
The character sequence or frame, passed in sequence from node to node, to indicate that the node controlling it has the right to transmit for a given amount of time.
Token Ring
Developed by IBM, this 4 or 16 Mbps network uses a ring topology and a token-passing access method.
Topology
The arrangement of the nodes and connecting hardware that comprises the network. Types include ring, bus, star and tree.
Transceiver
The actual device that interfaces between the network and the local node. The term generally refers to any connector, such as a MAU, that actively converts signals between the network and
the local node.
Transceiver Cable
Cable that attaches a device either to a standard or thin coax Ethernet segment.
Twisted-Pair Cable
Inexpensive, multiple-conductor cable comprised of one or more pairs of 18 to 24 gauge copper strands. The strands are twisted to improve protection against electromagnetic and radio frequency interference. The cable, which may be either shielded or unshielded, is used in low-speed communications, as telephone cable. It is used only in baseband networks because of its narrow bandwidth.
Unix
A multitasking, multiuser computer operating system developed by AT&T. Several versions exist, e.g., the Berkeley version.
UTP
Unshielded twisted pair, one or more cable pairs surrounded by insulation. UTP is commonly used as telephone wire.
Wide Area Network (WAN)
A network using common carrier transmission services for transmission of data over a large geographical area.
Workgroup Switching
Configuration in which a number of users are connected to an Ethernet network via a switch. Switching allows each user to get greater throughput than would be available through a hub.
X.25 Gateway Access Protocol
Allows a node not directly connected to a public data network to access the facilities of that network through an intermediary gateway node. X.25 is the protocol standard governing packet-switched networks.
regards,
GAZZALI...
AppleTalk
A communications protocol developed by Apple Computer to allow networking between Macintoshes. All Macintosh computers have a LocalTalk port, running AppleTalk over a 230K bps serial line. AppleTalk also runs over Ethernet (EtherTalk) and Token Ring (TokenTalk)
Auto-Negotiate
Clause 28 of the IEEE 802.3u standard specifies a MAC sublayer for the identification of the speed and duplex mode of connection being supported by a device. Support of this feature is optional for individual vendors.
Auto-sense
Ability of a 10/100 Ethernet device to interpret the speed or duplex mode of the attached device and to adjust to that rate. Official term is Auto-Negotiation in Clause 28 of the IEEE 802.3u standard.
AUI
Attachment Unit Interface. A 15-pin shielded, twisted pair Ethernet cable used (optionally) to connect between network devices and a MAU.
Autobaud
Automatic determination and matching of transmission speed.
AWG
American Wire Gauge. A system that specifies wire size. The gauge varies inversely with the wire diameter size.
Backbone
The main cable in a network.
Bandwidth on Demand
Feature that allows a remote access device to initiate a second connection to a particular site to increase the amount of data transferred to that site to increase the desired threshold. The network manager configuring the remote access server will specify a number of bits or a percentage of connection bandwidth threshold which will trigger the secondary connection. Multilink PPP is an emerging standard to allow this feature to be interoperable, but right now the only way to ensure correct operation is to use devices on both end from the same vendor.
Baseband LAN
A LAN that uses a single carrier frequency over a single channel. Ethernet, Token Ring and Arcnet LANs use baseband transmission.
Baud
Unit of signal frequency in signals per second. Not synonymous with bits per second since signals can represent more than one bit. Baud equals bits per second only when the signal represents a single bit.
Binaries
Binary, machine readable forms of programs that have been compiled or assembled. As opposed to Source language forms of programs.
Binary
Characteristic of having only two states, such as current on and current off. The binary number system uses only ones and zeros.
Bitronics
Specification for parallel printing which allows bidirectional communication on a Centronics-type interface. Pioneered by Hewlett-Packard, mainly used for postscript printers.
Bit
The smallest unit of data processing information. A bit (or binary digit) assumes the value of either 1 or 0.
BNC
A standardized connector used with Thinnet and coaxial cable.
BOOTP
A TCP/IP network protocol that lets network nodes request configuration information from a
BOOTP "server" node.
bps
Bits per second, units of transmission speed.
Bridge
A networking device that connects two LANs and forwards or filters data packets between them, based on their destination addresses. Bridges operate at the data link level (or MAC-layer) of the OSI reference model, and are transparent to protocols and to higher level devices like routers.
Broadband
A data transmission technique allowing multiple high-speed signals to share the bandwidth of a single cable via frequency division multiplexing.
Broadband Network
A network that uses multiple carrier frequencies to transmit multiplexed signals on a single cable. Several networks may coexist on a single cable without interfering with one another.
Brouter
A device that routes specific protocols, such as TCP/IP and IPX, and bridges other protocols, thereby combining the functions of both routers and bridges.
Bus
A LAN topology in which all the nodes are connected to a single cable. All nodes are considered equal and receive all transmissions on the medium.
Byte
A data unit of eight bits.
Channel
The data path between two nodes.
CHAP
(Challenge Handshake Authentication Protocol) Authentication scheme for PPP where the password not only is required to begin connection but also is required during the connection - failure to provide correct password during either login or challenge mode will result in disconnect.
Coaxial Cable
An electrical cable with a solid wire conductor at its center surrounded by insulating materials and an outer metal screen conductor with an axis of curvature coinciding with the inner conductor - hence "coaxial." Examples are standard Ethernet cable and Thinwire Ethernet cable.
Collision
The result of two network nodes transmitting on the same channel at the same time. The transmitted data is not usable.
Collision Detect
A signal indicating that one or more stations are contending with the local station's transmission. The signal is sent by the Physical layer to the Data Link layer on an Ethernet/IEEE 802.3 node.
Communication Server
A dedicated, standalone system that manages communications activities for other computers.
Console
The terminal used to configure network devices at boot (start-up) time.
Crosstalk
Noise passed between communications cables or device elements.
Cut-through
Technique for examining incoming packets whereby an Ethernet switch looks only at the first few bytes of a packet before forwarding or filtering it. This process is faster than looking at the whole packet, but it also allows some bad packets to be forwarded.
CSMA/CD
Carrier Sense Multiple Access with Collision Detection is the Ethernet media access method. All network devices contend equally for access to transmit. If a device detects another device's signal while it is transmitting, it aborts transmission and retries after a brief pause.
Data Link
A logical connection between two nodes on the same circuit.
Data Link Layer
Layer 2 of the seven-layer OSI reference model for communication between computers on networks. This layer defines protocols for data packets and how they are transmitted to and from each network device. It is a medium-independent, link-level communications facility on top of the Physical layer, and is divided into two sublayers: medium-access control (MAC) and logical-link control (LLC).
DECnet?
Digital Equipment Corporation (DEC) proprietary network architecture, a system for networking computers. It runs on point-to-point, X.25 and Ethernet networks.
Dial on Demand
When a router detects the need to initiate a dial-up connection to a remote network, it does so automatically according to pre-defined parameters set by the network manager.
Dialback
A security feature that ensures people do not log into modems that they shouldn't have access to. When a connection is requested, the system checks the user name for validity, then "dials back" the number associated with that user name.
Distributed Processing
A system in which each computer or node in the network performs its own processing and manages some of its data while the network facilitates communications between the nodes.
Domain Name
A domain name is a text name appended to a host name to form a unique host name across internets.
Download
The transfer of a file or information from one network node to another. Generally refers to transferring a file from a "big" node, such as a computer, to a "small" node, such as a terminal server or printer.
End Node
A node such as a PC that can only send and receive information for its own use. It cannot route and forward information to another node.
Ethernet
The most popular LAN technology in use today. The IEEE standard 802.3 defines the rules for configuring an Ethernet network. It is a 10 Mbps, CSMA/CD baseband network that runs over thin coax, thick coax, twisted pair or fiber optic cable.
EtherTalk
Apple Computer's protocol for Ethernet transmissions.
FDDI
Fiberoptic Data Distribution Interface. A cable interface capable of transmitting data at 100 Mbps. Originally specified for fiber lines, FDDI can also operate over twisted-pair cable for short
distances.
Fiber-Optic Cable
A transmission medium composed of a central glass optical fiber cable surrounded by cladding and an outer protective sheath. It transmits digital signals in the form of modulated light from a laser or LED (light-emitting diode).
File Server
A computer that stores data for network users and provides network access to that data.
Filtering
Process whereby an Ethernet switch or bridge reads the contents of a packet and then finds that the packet does not need to be forwarded, and drops it. A filtering rate is the rate at which a device can receive packets and drop them without any loss of incoming packets or delay in processing.
Firmware
Alterable programs in semipermanent storage, e.g., some type of read-only or flash reprogrammable memory.
Forwarding
Process whereby an Ethernet switch or bridge reads the contents of a packet and then passes that packet on to the appropriate attached segment. A forwarding rate is the time that it takes the device to execute all of the steps.
Flash ROM
See ROM.
Framing
Dividing data for transmission into groups of bits, and adding a header and a check sequence to form a frame.
FTP
File Transfer Protocol, a TCP/IP protocol for file transfer.
Full-Duplex
Independent, simultaneous two-way transmission in both directions, as opposed to half-duplex transmission.
Gateway
A device for interconnecting two or more dissimilar networks. It can translate all protocol levels from the Physical layer up through the Applications layer of the OSI model, and can therefore interconnect entities that differ in all details.
Hardware Address
See Network Address.
Header
The initial part of a data packet or frame containing identifying information such as the source of the data, its destination, and length.
Heartbeat
Ethernet defined SQE signal quality test function.
Hertz (Hz)
A frequency unit equal to one cycle per second.
Host
Generally a node on a network that can be used interactively, i.e., logged into, like a computer.
Host Table
A list of TCP/IP hosts on the network along with their IP addresses.
IEEE 802.3
The IEEE (Institute of Electrical and Electronic Engineers) standard that defines the CSMA/CD media-access method and the physical and data link layer specifications of a local area network. Among others, it includes 10BASE2, 10BASE5, 10BASE-FL and 10BASE-T Ethernet implementations.
Internet
A series of interconnected local, regional, national and international networks, linked using TCP/IP. Internet links many government, university and research sites. It provides E-mail, remote login and file transfer services.
Internetworking
General term used to describe the industry composed of products and technologies used to link networks together.
IP Address
See Network Address.
IPX
Internetwork Packet eXchange, a NetWare protocol similar to IP (Internet Protocol).
ISDN
(Integrated Services Digital Network): All digital service provided by telephone companies. Provides 144K bps over a single phone line (divided in two 64K bps "B" channels and one 16K bps "D" channel).
ISO Layered Model
The International Standards Organization (ISO) sets standards for computers and communications. Its Open Systems Interconnection (OSI) reference model specifies how dissimilar computing devices such as Network Interface Cards (NICs), bridges and routers exchange data over a network. The model consists of seven layers. From lowest to highest, they are: Physical, Data Link, Network, Transport, Session, Presentation and Application. Each layer performs services for the layer above it.
Jabber
Network error caused by an interface card placing corrupted data on the network. Or, an error condition due to an Ethernet node transmitting longer packets than allowed.
Kbps
Kilobits per second.
Kermit
A popular file transfer and terminal emulation program.
LAN
Local Area Network, a data communications system consisting of a group of interconnected computers, sharing applications, data and peripherals. The geographical area is usually a building or group of buildings.
LAT
Local Area Transport, a Digital Equipment Corporation proprietary network communication protocol. The protocol is based on the idea of a relatively small, known number of hosts on a local network sending small network packets at regular intervals. LAT will not work on a wide area network scale, as TCP/IP does.
Latency
The delay incurred by a switching or bridging device between receiving the frame and forwarding the frame.
Layer
In networks, layers refer to software protocol levels comprising the architecture, with each layer performing functions for the layers above it.
Line Speed
Expressed in bps, the maximum rate at which data can reliably be transmitted over a line using given hardware.
Load Balancing
Shifting a user job from a more heavily loaded resource to a less loaded resource.
Local Network Interconnect (LNI)
A Port Multiplier, or concentrator supporting multiple active devices or communications controllers, either used standalone or attached to standard Ethernet cable.
LocalTalk
Apple Computer's proprietary 230 Kbps baseband network protocol. It uses the CSMA/CD access method over unshielded twisted pair wire.
Logical Link
A temporary connection between source and destination nodes, or between two processes on the same node.
LPD
Line Printer Daemon, a process on Berkeley spooler implementations that provides LPR support.
LPR
The LPR command is used to queue print jobs on Berkeley queuing systems.
MAU
Medium Attachment Unit, a device used to convert signals from one Ethernet medium to another.
Mbps
Megabits per second.
MIB
Management Information Base, a database of network parameters used by SNMP and CMIP (Common Management Information Protocol) to monitor and change network device settings. It provides a logical naming of all information resources on the network that are pertinent to the network's management.
MII
Media Independent Interface, New standard developed for Fast Ethernet in IEEE 802.3u specification. The Fast Ethernet equivalent to the AUI in 10 Mbps Ethernet, allowing different types of Fast Ethernet media to be connected to a Fast Ethernet device via a common interface.
MJ
Modular Jack. A jack used for connecting voice cables to a faceplate, as for a telephone.
MMJ
Modified Modular Jack. These are the 6-pin connectors used to connect serial terminal lines to terminal devices. MMJs can be distinguished from the similar RJ12 jacks by having a side-locking tab, rather than a center-mounted one.
Modem
A modulator-demodulator device for changing transmission signals from digital to analog for
transmission over phone lines. Used in pairs, one is required at each end of the line.
MOP
Maintenance Operations Protocol, a DEC protocol used for remote communications between hosts and servers.
Multicast
A multicast is a message that is sent out to multiple devices on the network by a host.
Multilink PPP
The ability of a dialup device to allocate more than one channel of bandwidth to a particular connection. Generally, this is termed to be the ability of an ISDN device to bond two B-channels together into a single data pipe, but some vendors can perform the same function with asychronous dial-up connections over modems by having a second connection initiated to support the additional bandwidth requirements.
Multiplexer
A device that allows several users to share a single circuit. It funnels different data streams into a single stream. At the other end of the communications link, another multiplexer reverses the process by splitting the data stream back into the original streams.
Multiplexing
Transmitting multiple signals simultaneously on a single channel.
Multiport Repeater
A repeater, either standalone or connected to standard Ethernet cable, for interconnecting up to eight Thinwire Ethernet segments.
Name Server
Software that runs on network hosts charged with translating (or resolving) text-style names into numeric IP addresses.
NCP
Network Control Program, a program run on VMS machines to configure local network hardware and remote network devices.
NetWare
A Novell developed Network Operating System (NOS). Provides file and printer sharing among networks of Personal Computers (PCs). Each NetWare network must have at least one file server, and access to other resources is dependent on connecting to and logging into the file server. The file server controls user logins and access to other network clients, such as user PCs, print servers, modem/fax servers, disk/file servers, etc.
NetBIOS/NetBEUI
Microsoft's networking protocols for its LAN Manager and Windows NT products.
Network
An interconnected system of computers that can communicate with each other and share files, data and resources.
Network Address
Every node on a network has one or more addresses associated with it, including at least one fixed hardware address such as "ae-34-2c-1d-69-f1" assigned by the device's manufacturer. Most nodes also have protocol specific addresses assigned by a network manager.
Network Management
Administrative services for managing a network, including configuring and tuning, maintaining network operation, monitoring network performance, and diagnosing network problems.
NIC
Network Interface Card, an adapter card that is inserted into a computer, and contains the necessary software and electronics to enable the station to communicate over the network.
Node
Any intelligent device connected to the network. This includes terminal servers, host computers, and any other devices (such as printers and terminals) that are directly connected to the network. A node can be thought of as any device that has a "hardware address."
NOS
Network Operating System, the software for a network that runs in a file server and controls access to files and other resources from multiple users. It provides security and administrative tools. Novell's NetWare, Banyan's VINES and IBM's LAN Server are NOS examples.
Open System Interconnect (OSI)
See "ISO."
Packet
A series of bits containing data and control information, including source and destination node addresses, formatted for transmission from one node to another.
PAP
(Password Authentication Protocol) Authentication scheme for PPP links. A password can be specified for both devices on a remote link. Failure to authenticate will result in a dropped connection prior to start of data transmission.
Physical Address
An address identifying a single node.
Physical Layer
Layer 1, the bottom layer of the OSI model, is implemented by the physical channel. The Physical layer insulates Layer 2, the Data Link layer, from medium-dependent physical characteristics such as baseband, broadband or fiber-optic transmission. Layer 1 defines the protocols that govern transmission media and signals.
Point-to-Point
A circuit connecting two nodes only, or a configuration requiring a separate physical connection between each pair of nodes.
Port
The physical connector on a device enabling the connection to be made.
Port Multiplier
A concentrator providing connection to a network for multiple devices.
PostScript
A printer/display protocol developed by Adobe Corp. PostScript is an actual printing and programming language to display text and graphics. Unlike line/ASCII printers, which print character input verbatim, PostScript printers accept and interpret an entire PostScript page before printing it.
PPP
Point-to-Point Protocol. The successor to SLIP, PPP provides router-to-router and host-to-network connections over both synchronous and asynchronous circuits.
Print Server
A dedicated computer that manages printers and print requests from other nodes on the network.
PROM
Programmable ROM, a read-only memory whose data content can be altered.
Protocol
Any standard method of communicating over a network.
Remote Access
Access to network resources not located on the same physical Ethernet. (Physical Ethernet here refers to an entire site network topology.)
Remote Control
Form of remote access where a device dialing in assumes control of another network node - all keystrokes on the remote are translated into keystrokes on the network node. Used primarily with IPX protocol.
Remote Node
Form of remote access where the device dialing in acts as a peer on the target network. Used with both IP and IPX protocols.
Repeater
A repeater is a network device that repeats signals from one cable onto one or more other cables, while restoring signal timing and waveforms.
Ring
A network topology in which the nodes are connected in a closed loop. Data is transmitted from node to node around the loop, always in the same direction.
RMON
SNMP-based standard for reporting various network conditions. RMON has 10 different management groups which provide detailed information about a network.
Rlogin
Rlogin is an application that provides a terminal interface between UNIX hosts using the
TCP/IP network protocol. Unlike Telnet, Rlogin assumes the remote host is (or behaves like) a UNIX machine
ROM
Read-Only Memory, a memory device that retains its information even when power to it is removed. A ROM version of a network device does not need to download, since the ROM contains the entire executable code and thus never needs to reload it. Frequently the ROM is provided as "flash ROM", which can be reprogrammed by downloading if the user chooses.
Router
Device capable of filtering/forwarding packets based upon data link layer information. Whereas a bridge or switch may only read MAC layer addresses to filter, routers are able to read data such as IP addresses and route accordingly.
RTEL
Lantronix's "reverse Telnet" software allows hosts using TCP/IP to establish a session with a device attached to a terminal server port.
Server
A computer that provides resources to be shared on the network, such as files (file server) or
terminals (terminal server).
Session
A connection to a network service.
Shared Ethernet
Ethernet configuration in which a number of segments are bound together in a single collision domain. Hubs produce this type of configuration where only one node can transmit at a time.
SLIP
Serial Line Internet Protocol, a protocol for running TCP/IP over serial lines.
SNA
Systems Network Architecture. IBM's layered protocols for mainframe communications.
SNMP
Simple Network Management Protocol, allows a TCP/IP host running an SNMP application to query other nodes for network-related statistics and error conditions. The other hosts, which provide SNMP agents, respond to these queries and allow a single host to gather network statistics from many other network nodes.
Source Code
Programs in an uncompiled or unassembled form.
Spanning Tree
An algorithm used by bridges to create a logical topology that connects all network segments, and ensures that only one path exists between any two stations.
Store and Forward
Technique for examining incoming packets on an Ethernet switch or bridge whereby the whole packet is read before forwarding or filtering takes place. Store and forward is a slightly slower process than cut-through, but it does ensure that all bad or misaligned packets are eliminated from the network by the switching device.
SPX
Sequential Packet exchange. Novell's implementation of SPP (Sequential Packet Protocol).
SQE
Ethernet-defined signal quality test function, frequently called "heartbeat."
Switch
Multiport Ethernet device designed to increase network performance by allowing only essential traffic on the attached individual Ethernet segments. Packets are filtered or forwarded based upon their source and destination addresses.
T-Connector
A T-shaped device with two female and one male BNC connectors.
TCP/IP
Transmission Control Protocol (TCP) and Internet Protocol (IP) are the standard network protocols in UNIX environments. They are almost always implemented and used together and called TCP/IP.
Telnet
Telnet is an application that provides a terminal interface between hosts using the TCP/IP network protocol. It has been standardized so that "telnetting" to any host should give one an interactive terminal session, regardless of the remote host type or operating system. Note that this is very different from the LAT software, which allows only local network access to LAT hosts only.
10BASE2
Ethernet running on thin coax network cable.
10BASE5
Ethernet running on Thickwire network cable.
10BASE-T
Ethernet running on unshielded twisted pair (UTP) cable. Note that 10BASE-T is a point-to-point network media, with one end of the cable typically going to a repeater/hub and the other to the network device.
Terminal Server
A concentrator that facilitates communication between hosts and terminals.
Terminator
Used on both ends of a standard Ethernet or Thinwire Ethernet segment, this special connector provides the 50 ohm termination resistance needed for the cable.
TFTP
Trivial File Transfer Protocol. On computers that run the TCP/IP networking software, TFTP is used to quickly send files across the network with fewer security features than FTP.
Thickwire
Half-inch diameter coax cable.
Thinwire
Thin coaxial cable similar to that used for television/video hookups.
Throughput
The amount of data transmitted between two points in a given amount of time, e.g., 10 Mbps.
Token
The character sequence or frame, passed in sequence from node to node, to indicate that the node controlling it has the right to transmit for a given amount of time.
Token Ring
Developed by IBM, this 4 or 16 Mbps network uses a ring topology and a token-passing access method.
Topology
The arrangement of the nodes and connecting hardware that comprises the network. Types include ring, bus, star and tree.
Transceiver
The actual device that interfaces between the network and the local node. The term generally refers to any connector, such as a MAU, that actively converts signals between the network and
the local node.
Transceiver Cable
Cable that attaches a device either to a standard or thin coax Ethernet segment.
Twisted-Pair Cable
Inexpensive, multiple-conductor cable comprised of one or more pairs of 18 to 24 gauge copper strands. The strands are twisted to improve protection against electromagnetic and radio frequency interference. The cable, which may be either shielded or unshielded, is used in low-speed communications, as telephone cable. It is used only in baseband networks because of its narrow bandwidth.
Unix
A multitasking, multiuser computer operating system developed by AT&T. Several versions exist, e.g., the Berkeley version.
UTP
Unshielded twisted pair, one or more cable pairs surrounded by insulation. UTP is commonly used as telephone wire.
Wide Area Network (WAN)
A network using common carrier transmission services for transmission of data over a large geographical area.
Workgroup Switching
Configuration in which a number of users are connected to an Ethernet network via a switch. Switching allows each user to get greater throughput than would be available through a hub.
X.25 Gateway Access Protocol
Allows a node not directly connected to a public data network to access the facilities of that network through an intermediary gateway node. X.25 is the protocol standard governing packet-switched networks.
regards,
GAZZALI...
DNS - Domain Name System
In the early days of the Internet, all host names and their associated IP addresses were recorded in a single file called hosts.txt, maintained by the Network Information Centre in the USA.
Not surprisingly, as the Internet grew so did this file, and by the mid-80's it had become impractically large to distribute to all systems over the network, and impossible to keep up to date. The Internet Domain Name System (DNS) was developed as a distributed database to solve this problem. It's primary goal is to allow the allocation of host names to be distributed amongst multiple naming authorities, rather than centralised at a single point.
DNS names are constructed hierarchichally. The highest level of the hierarchy being the last component or label of the DNS address. Labels can be up to 63 characters long and are case insensitive. A maximum length of 255 characters is allowed. Labels must start with a letter and can only consist of letters, digits and hyphens. [Unfortunately some administrators construct names that start with digits. This is wrong and can easily cause problems with software that simply inspects the first character of a host address to determine whether a DNS name or an IP address has been quoted.]
Note In the early days of the Internet users in at least one country (the United Kingdom) adopted a similar scheme with the highest hierarchical level appearing first rather than last. I.e. uk.ac.wlv.scit.sun rather than sunc.scit.wlv.ac.uk. This practice is, fortunately, obsolete.
DNS addresses can be relative or fully qualified. A fully qualified address includes all the labels and is globally unique. A relative address can be converted by appending the local domain information. For example sunc.scit.wlv.ac.uk is a fully qualified name for the host sunc in the domain scit.wlv.ac.uk. Strictly there should be a stop at the end of a fully qualified name but this is often overlooked.
The final most significant label of a fully qualified name can fall into one of three classes
arpa
This is a special facility used for reverse translation, i.e. going from IP address to fully qualified domain address. If everything is properly configured a suitably framed query for 1.4.220.134.in-addr.arpa will return sunc.scit.wlv.ac.uk. Details of this will be described later.
3 letter codes
The DNS was orginally introduced in the United States of America and the final component of an address was intended to indicate the type of organisation hosting the computer. Some of the three letter final labels (edu, gov, mil) are still only used by organisations based in the USA, others can be used anywhere in the world.
The three letter codes are
code
meaning
com
Commercial. Now international.
edu
Educational.
gov
Government.
int
International Organisiation.
mil
Military.
net
Network related.
org
Miscellaneous Organisation.
Two letter codes
The final two letter codes indicate the country of origin and are defined in ISO 3166 with the minor exception that uk is used for the United Kingdom rather than gb although there are some .gb sites. [This apparently happened because the ISO committee was unaware that Northern Ireland was part of the United Kingdom but not part of Great Britain.]
The two letter code us is used by some sites in the United States of America.
In some countries there are sub-domains indicating the type of organisation such as ac.uk, co.uk, sch.uk in the United Kingdom and edu.au and com.au in Australia. Most European countries have not adopted this useful practice. A fuller discussion of the United Kingdom DNS domains is provided by To obtain a domain address it is necessary to identify the administrator of the required domain and then all that is basically necessary is to send the administrator the required code and the associated IP address and they will, if they accept the request, include the details in their databases. Conditions for acceptance vary widely between administrators, the administrators for the com and org being, apparently, quite happy to accept anything from anywhere.
A DNS server is just a computer that's running DNS software. Since most servers are Unix machines, the most popular program is BIND (Berkeley Internet Name Domain), but you can find software for the Mac and the PC as well.
DNS software is generally made up of two elements: the actual name server, and something called a resolver. The name server responds to browser requests by supplying name-to-address conversions. When it doesn't know the answer, the resolver will ask another name server for the information.
To see how it works, let's go back to the domain-name-space inverted tree.
When you type in a URL, your browser sends a request to the closest name server. If that server has ever fielded a request for the same host name (within a time period set by the administrator to prevent passing old information), it will locate the information in its cache and reply.
If the name server is unfamiliar with the domain name, the resolver will attempt to "solve" the problem by asking a server farther up the tree. If that doesn't work, the second server will ask yet another - until it finds one that knows. (When a server can supply an answer without asking another, it's known as an authoritative server.)
Once the information is located, it's passed back to your browser, and you're sent on your merry way. Usually this process occurs quickly, but occasionally it can take an excruciatingly long time (like 15 seconds). In the worst cases, you'll get a dialog box that says the domain name doesn't exist - even though you know damn well it does.
This happens because the authoritative server is slow replying to the first, and your computer gets tired of waiting so it times-out (drops the connection). But if you try again, there's a good chance it will work, because the authoritative server has had enough time to reply, and your name server has stored the information in its cache.
DNS Structure
The DNS is arranged as a hierarchy, both from the perspective of the structure of the names maintained within the DNS, and in terms of the delegation of naming authorities. At the top of the hierarchy is the root domain "." which is administered by the Internet Assigned Numbers Authority (IANA). Administration of the root domain gives the IANA the authority to allocate domains beneath the root.
The process of assigning a domain to an organisational entity is called delegating, and involves the administrator of a domain creating a sub-domain and assigning the authority for allocating sub-domains of the new domain the subdomain's administrative entity.
This is a hierarchical delegation, which commences at the "root" of the Domain Name Space ("."). A fully qualified domain name, is obtained by writing the simple names obtained by tracing the DNS hierarchy from the leaf nodes to the root, from left to right, separating each name with a stop ".", eg. fred.xxxx.edu.au. is the name of a host system (huxley) within the XXXX University (xxx), an educational (edu) institution within Australia (au).
The sub-domains of the root are known as the top-level domains, and include the edu (educational), gov (government), and com (commercial) domains. Although an organisation anywhere in the world can register beneath these three-character top level domains, the vast majority that have are located within, or have parent companies based in, the United States.
The top-level domains represented by the ISO two-character country codes are used in most other countries, thus organisations in Australia are registered beneath au.
The majority of country domains are sub-divided into organisational-type sub-domains. In some countries two character sub-domains are created (eg. ac.nz for New Zealand academic organisations), and in others three character sub-domains are used (eg. com.au for Australian commercial organisations). Regardless of the standard adopted each domain may be delegated to a separate authority.
Organisations that wish to register a domain name, even if they do not plan to establish an Internet connection in the immediate short term, should contact the administrator of the domain which most closely describes their activities.
Even though the DNS supports many levels of sub-domains, delegations should only be made where there is a requirement for an organisation or organisational sub-division to manage their own name space.
Any sub-domain administrator must also demonstrate they have the technical competence to operate a domain name server (described below), or arrange for another organisation to do so on their behalf.
Domain Name Servers
The DNS is implemented as collection of inter-communicating nameservers. At any given level of the DNS hierarchy, a nameserver for a domain has knowledge of all the immediate sub-domains of that domain.
For each domain there is a primary nameserver, which contains authoritative information regarding Internet entities within that domain. In addition Secondary nameservers can be configured, which periodically download authoritative data from the primary server.
Secondary nameservers provide backup to the primary nameserver when it is not operational, and further improve the overall performance of the DNS, since the nameservers of a domain that respond to queries most quickly are used in preference to any others. Thus, in addition to having a primary nameserver on site, each organisation should have at least one secondary on site, and another elsewhere on the Internet, preferably well connected. This is particularly important for entities with slow speed or dial-up Internet connections to reduce use of their link to support the DNS.
regards,
GAZZALI...
In the early days of the Internet, all host names and their associated IP addresses were recorded in a single file called hosts.txt, maintained by the Network Information Centre in the USA.
Not surprisingly, as the Internet grew so did this file, and by the mid-80's it had become impractically large to distribute to all systems over the network, and impossible to keep up to date. The Internet Domain Name System (DNS) was developed as a distributed database to solve this problem. It's primary goal is to allow the allocation of host names to be distributed amongst multiple naming authorities, rather than centralised at a single point.
DNS names are constructed hierarchichally. The highest level of the hierarchy being the last component or label of the DNS address. Labels can be up to 63 characters long and are case insensitive. A maximum length of 255 characters is allowed. Labels must start with a letter and can only consist of letters, digits and hyphens. [Unfortunately some administrators construct names that start with digits. This is wrong and can easily cause problems with software that simply inspects the first character of a host address to determine whether a DNS name or an IP address has been quoted.]
Note In the early days of the Internet users in at least one country (the United Kingdom) adopted a similar scheme with the highest hierarchical level appearing first rather than last. I.e. uk.ac.wlv.scit.sun rather than sunc.scit.wlv.ac.uk. This practice is, fortunately, obsolete.
DNS addresses can be relative or fully qualified. A fully qualified address includes all the labels and is globally unique. A relative address can be converted by appending the local domain information. For example sunc.scit.wlv.ac.uk is a fully qualified name for the host sunc in the domain scit.wlv.ac.uk. Strictly there should be a stop at the end of a fully qualified name but this is often overlooked.
The final most significant label of a fully qualified name can fall into one of three classes
arpa
This is a special facility used for reverse translation, i.e. going from IP address to fully qualified domain address. If everything is properly configured a suitably framed query for 1.4.220.134.in-addr.arpa will return sunc.scit.wlv.ac.uk. Details of this will be described later.
3 letter codes
The DNS was orginally introduced in the United States of America and the final component of an address was intended to indicate the type of organisation hosting the computer. Some of the three letter final labels (edu, gov, mil) are still only used by organisations based in the USA, others can be used anywhere in the world.
The three letter codes are
code
meaning
com
Commercial. Now international.
edu
Educational.
gov
Government.
int
International Organisiation.
mil
Military.
net
Network related.
org
Miscellaneous Organisation.
Two letter codes
The final two letter codes indicate the country of origin and are defined in ISO 3166 with the minor exception that uk is used for the United Kingdom rather than gb although there are some .gb sites. [This apparently happened because the ISO committee was unaware that Northern Ireland was part of the United Kingdom but not part of Great Britain.]
The two letter code us is used by some sites in the United States of America.
In some countries there are sub-domains indicating the type of organisation such as ac.uk, co.uk, sch.uk in the United Kingdom and edu.au and com.au in Australia. Most European countries have not adopted this useful practice. A fuller discussion of the United Kingdom DNS domains is provided by To obtain a domain address it is necessary to identify the administrator of the required domain and then all that is basically necessary is to send the administrator the required code and the associated IP address and they will, if they accept the request, include the details in their databases. Conditions for acceptance vary widely between administrators, the administrators for the com and org being, apparently, quite happy to accept anything from anywhere.
A DNS server is just a computer that's running DNS software. Since most servers are Unix machines, the most popular program is BIND (Berkeley Internet Name Domain), but you can find software for the Mac and the PC as well.
DNS software is generally made up of two elements: the actual name server, and something called a resolver. The name server responds to browser requests by supplying name-to-address conversions. When it doesn't know the answer, the resolver will ask another name server for the information.
To see how it works, let's go back to the domain-name-space inverted tree.
When you type in a URL, your browser sends a request to the closest name server. If that server has ever fielded a request for the same host name (within a time period set by the administrator to prevent passing old information), it will locate the information in its cache and reply.
If the name server is unfamiliar with the domain name, the resolver will attempt to "solve" the problem by asking a server farther up the tree. If that doesn't work, the second server will ask yet another - until it finds one that knows. (When a server can supply an answer without asking another, it's known as an authoritative server.)
Once the information is located, it's passed back to your browser, and you're sent on your merry way. Usually this process occurs quickly, but occasionally it can take an excruciatingly long time (like 15 seconds). In the worst cases, you'll get a dialog box that says the domain name doesn't exist - even though you know damn well it does.
This happens because the authoritative server is slow replying to the first, and your computer gets tired of waiting so it times-out (drops the connection). But if you try again, there's a good chance it will work, because the authoritative server has had enough time to reply, and your name server has stored the information in its cache.
DNS Structure
The DNS is arranged as a hierarchy, both from the perspective of the structure of the names maintained within the DNS, and in terms of the delegation of naming authorities. At the top of the hierarchy is the root domain "." which is administered by the Internet Assigned Numbers Authority (IANA). Administration of the root domain gives the IANA the authority to allocate domains beneath the root.
The process of assigning a domain to an organisational entity is called delegating, and involves the administrator of a domain creating a sub-domain and assigning the authority for allocating sub-domains of the new domain the subdomain's administrative entity.
This is a hierarchical delegation, which commences at the "root" of the Domain Name Space ("."). A fully qualified domain name, is obtained by writing the simple names obtained by tracing the DNS hierarchy from the leaf nodes to the root, from left to right, separating each name with a stop ".", eg. fred.xxxx.edu.au. is the name of a host system (huxley) within the XXXX University (xxx), an educational (edu) institution within Australia (au).
The sub-domains of the root are known as the top-level domains, and include the edu (educational), gov (government), and com (commercial) domains. Although an organisation anywhere in the world can register beneath these three-character top level domains, the vast majority that have are located within, or have parent companies based in, the United States.
The top-level domains represented by the ISO two-character country codes are used in most other countries, thus organisations in Australia are registered beneath au.
The majority of country domains are sub-divided into organisational-type sub-domains. In some countries two character sub-domains are created (eg. ac.nz for New Zealand academic organisations), and in others three character sub-domains are used (eg. com.au for Australian commercial organisations). Regardless of the standard adopted each domain may be delegated to a separate authority.
Organisations that wish to register a domain name, even if they do not plan to establish an Internet connection in the immediate short term, should contact the administrator of the domain which most closely describes their activities.
Even though the DNS supports many levels of sub-domains, delegations should only be made where there is a requirement for an organisation or organisational sub-division to manage their own name space.
Any sub-domain administrator must also demonstrate they have the technical competence to operate a domain name server (described below), or arrange for another organisation to do so on their behalf.
Domain Name Servers
The DNS is implemented as collection of inter-communicating nameservers. At any given level of the DNS hierarchy, a nameserver for a domain has knowledge of all the immediate sub-domains of that domain.
For each domain there is a primary nameserver, which contains authoritative information regarding Internet entities within that domain. In addition Secondary nameservers can be configured, which periodically download authoritative data from the primary server.
Secondary nameservers provide backup to the primary nameserver when it is not operational, and further improve the overall performance of the DNS, since the nameservers of a domain that respond to queries most quickly are used in preference to any others. Thus, in addition to having a primary nameserver on site, each organisation should have at least one secondary on site, and another elsewhere on the Internet, preferably well connected. This is particularly important for entities with slow speed or dial-up Internet connections to reduce use of their link to support the DNS.
regards,
GAZZALI...
What is a Network?
A network is simply a group of two or more Personal Computers linked together.
What Types of Networks Exist?Many types of networks exist, but the most common types of networks are Local-Area Networks (LANs), and Wide-Area Networks (WANs). In a LAN, computers are connected together within a "local" area (for example, an office or home). In a WAN, computers are farther apart and are connected via telephone/communication lines, radio waves, or other means of connection.
How are Networks Categorized?Networks are usually classified using three properties: Topology, Protocol, and Architecture. Topology specifies the geometric arrangement of the network. Common topologies are a bus, ring, and star. You can check out a figure showing the three common types of network topologies here. Protocol specifies a common set of rules and signals the computers on the network use to communicate. Most networks use Ethernet, but some networks may use IBM's Token Ring protocol. We recommend Ethernet for both home and office networking. Architecture refers to one of the two major types of network architecture: Peer-to-peer or client/server. In a Peer-to-Peer networking configuration, there is no server, and computers simply connect with eachother in a workgroup to share files, printers, and Internet access. This is most commonly found in home configurations, and is only practical for workgroups of a dozen or less computers. In a client/server network, there is usually an NT Domain Controller, which all of the computers log on to.This server can provide various services, including centrally routed Internet Access, mail (including e-mail), file sharing, and printer access, as well as ensuring security across the network. This is most commonly found in corporate configurations, where network security is essential.
Now that you have a basic understanding of networks, we'll learn about the type of network most people will want to setup, a Local-Area Network.
In today?s Internet age, the corporate network is truly the lifeblood of business. As the success of any organization becomes increasingly intertwined and dependent on its network it is crucial to understand the latest in networking technology.And as device networking increases the number of things connected to networks and the Internet, rapidly making M2M (machine to machine) a reality, speed, remote management, wireless networking, reliability and the security of networked devices are all concerns that must be addressed. We have put together the following tutorials to help provide you with a solid foundation and understanding of basic networking protocols and techniques as well as serial to Ethernet/802.11 device server technology.
regards
GAZZALI...
A network is simply a group of two or more Personal Computers linked together.
What Types of Networks Exist?Many types of networks exist, but the most common types of networks are Local-Area Networks (LANs), and Wide-Area Networks (WANs). In a LAN, computers are connected together within a "local" area (for example, an office or home). In a WAN, computers are farther apart and are connected via telephone/communication lines, radio waves, or other means of connection.
How are Networks Categorized?Networks are usually classified using three properties: Topology, Protocol, and Architecture. Topology specifies the geometric arrangement of the network. Common topologies are a bus, ring, and star. You can check out a figure showing the three common types of network topologies here. Protocol specifies a common set of rules and signals the computers on the network use to communicate. Most networks use Ethernet, but some networks may use IBM's Token Ring protocol. We recommend Ethernet for both home and office networking. Architecture refers to one of the two major types of network architecture: Peer-to-peer or client/server. In a Peer-to-Peer networking configuration, there is no server, and computers simply connect with eachother in a workgroup to share files, printers, and Internet access. This is most commonly found in home configurations, and is only practical for workgroups of a dozen or less computers. In a client/server network, there is usually an NT Domain Controller, which all of the computers log on to.This server can provide various services, including centrally routed Internet Access, mail (including e-mail), file sharing, and printer access, as well as ensuring security across the network. This is most commonly found in corporate configurations, where network security is essential.
Now that you have a basic understanding of networks, we'll learn about the type of network most people will want to setup, a Local-Area Network.
In today?s Internet age, the corporate network is truly the lifeblood of business. As the success of any organization becomes increasingly intertwined and dependent on its network it is crucial to understand the latest in networking technology.And as device networking increases the number of things connected to networks and the Internet, rapidly making M2M (machine to machine) a reality, speed, remote management, wireless networking, reliability and the security of networked devices are all concerns that must be addressed. We have put together the following tutorials to help provide you with a solid foundation and understanding of basic networking protocols and techniques as well as serial to Ethernet/802.11 device server technology.
regards
GAZZALI...
Wednesday, September 20, 2006
List of TCP and UDP port numbers
TCP and UDP ports are network ports.
IANA is responsible for assigning TCP and UDP port numbers to specific uses. The port numbers are divided into three ranges: the Well Known Ports, the Registered Ports, and the Dynamic and/or Private Ports.
The Ports that are popular are those in the range 0–1023. On Unix-like operating systems, opening a port in this range to receive incoming connections requires administrative privileges, although this all might change. [ 0 ]
The Registered Ports are those in the range 1024–49151.
The Dynamic and/or Private Ports are those in the range 49152–65535. These ports are not used by any defined application.
IANA does not enforce this; it is simply a set of recommended uses. Sometimes ports may be used for different applications or protocols than their official IANA designation. This misuse may, for example, be by a Trojan horse, or alternatively be by a commonly used program that didn't get an IANA registered port or port range.
ICANN formed a contract with the US government on March 21, 2001, and now performs the IANA's function.
The tables below indicate a status with the following colors and tags:
Official if the application and port combination is in the IANA list of port assignments;
Unofficial if the application and port combination is not in the IANA list of port assignments; and
Conflict if the port is being used commonly for two applications or protocols.
(Common) Ports 0 to 1023
Contents
1 (Common) Ports 0 to 1023
2 (Registered) Ports 1024 to 49151
3 (Dynamic/Private) Ports 49152 to 65535
4 References
5 External links
Port/ Description/ status
0/TCP,UDP
Reserved; do not use (but is a permissible source port value if the sending
process does not expect messages in response)
Official
1/TCP,UDP TCPMUX (TCP port service multiplexer) Official
5/TCP,UDP RJE (Remote Job Entry) Official
7/TCP,UDP ECHO protocol Official
9/TCP,UDP DISCARD protocol Official
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13/TCP,UDP DAYTIME protocol Official
17/TCP,UDP QOTD (Quote of the Day) protocol Official
18/TCP,UDP Message Send Protocol Official
19/TCP,UDP CHARGEN (Character Generator) protocol Official
20/TCP,UDP FTP - data port Official
21/TCP,UDP FTP - control (command) port Official
22/TCP,UDP
SSH (Secure Shell) - used for secure logins, file transfers (scp, sftp) and port
forwarding
Official
23/TCP,UDP Telnet protocol - unencrypted text communications Official
25/TCP,UDP SMTP - used for e-mail routing between mailservers E-mails Official
26/TCP,UDP RSFTP - A simple FTP-like protocol Unofficial
35/TCP,UDP QMS Magicolor 2 printer Unofficial
37/TCP,UDP TIME protocol Official
38/TCP,UDP Route Access Protocol Official
39/TCP,UDP Resource Location Protocol Official
41/TCP,UDP Graphics Official
42/TCP,UDP Host Name Server Official
49/TCP,UDP TACACS Login Host protocol Official
53/TCP,UDP DNS (Domain Name System) Official
57/TCP MTP, Mail Transfer Protocol
67/UDP
BOOTP (BootStrap Protocol) server; also used by DHCP (Dynamic Host
Configuration Protocol)
Official
68/UDP BOOTP client; also used by DHCP Official
69/UDP TFTP (Trivial File Transfer Protocol) Official
70/TCP Gopher protocol Official
79/TCP Finger protocol Official
80/TCP HTTP (HyperText Transfer Protocol) - used for transferring web pages Official
80/TCP,UDP Skype - CONFLICT with HTTP listening ports Conflict
81/TCP Torpark - Onion routing ORport Unofficial
82/UDP Torpark - Control Port Unofficial
88/TCP Kerberos - authenticating agent Official
101/TCP HOSTNAME
107/TCP Remote Telnet Service
109/TCP POP, Post Office Protocol, version 2
110/TCP POP3 (Post Office Protocol version 3) - used for sending/retrieving E-mails Official
113/TCP
ident - old server identification system, still used by IRC servers to identify its
users
Official
115/TCP SFTP, Simple File Transfer Protocol
118/TCP,UDP SQL Services Official
119/TCP
NNTP (Network News Transfer Protocol) - used for retrieving newsgroups
messages
Official
123/UDP NTP (Network Time Protocol) - used for time synchronization Official
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137/TCP,UDP NetBIOS NetBIOS Name Service Official
138/TCP,UDP NetBIOS NetBIOS Datagram Service Official
139/TCP,UDP NetBIOS NetBIOS Session Service Official
143/TCP,UDP IMAP4 (Internet Message Access Protocol 4) - used for retrieving E-mails Official
152/TCP,UDP BFTP, Background File Transfer Program
153/TCP,UDP SGMP, Simple Gateway Monitoring Protocol
156/TCP,UDP SQL Service Official
158/TCP,UDP DMSP, Distributed Mail Service Protocol
161/TCP,UDP SNMP (Simple Network Management Protocol) Official
162/TCP,UDP SNMPTRAP Official
179/TCP BGP (Border Gateway Protocol) Official
194/TCP IRC (Internet Relay Chat) Official
201/TCP,UDP AppleTalk Routing Maintenance
209/TCP,UDP The Quick Mail Transfer Protocol
213/TCP,UDP IPX Official
218/TCP,UDP MPP, Message Posting Protocol
220/TCP,UDP IMAP, Interactive Mail Access Protocol, version 3
259/TCP,UDP ESRO, Efficient Short Remote Operations
264/TCP,UDP BGMP, Border Gateway Multicast Protocol
318/TCP,UDP TSP, Time Stamp Protocol
323/TCP,UDP IMMP, Internet Message Mapping Protocol
366/TCP,UDP SMTP, Simple Mail Transfer Protocol. ODMR, On-Demand Mail Relay
369/TCP,UDP Rpc2portmap Official
384/TCP,UDP A Remote Network Server System
387/TCP,UDP AURP, AppleTalk Update-based Routing Protocol
389/TCP,UDP LDAP (Lightweight Directory Access Protocol) Official
401/TCP,UDP UPS Uninterruptible Power Supply Official
411/TCP Direct Connect Hub port Unofficial
427/TCP,UDP SLP (Service Location Protocol) Official
443/TCP,UDP HTTPS - HTTP Protocol over TLS/SSL (encrypted transmission) Official
444/TCP,UDP SNPP, Simple Network Paging Protocol
445/TCP
Microsoft-DS (Active Directory, Windows shares, Sasser-worm, Agobot,
Zobotworm)
Official
445/UDP Microsoft-DS SMB file sharing Official
464/TCP,UDP Kerberos Change/Set password Official
465/TCP SMTP over SSL - CONFLICT with registered Cisco protocol Conflict
500/TCP,UDP Isakmp, IKE-Internet Key Exchange Official
514/TCP
rsh protocol - used to execute non-interactive commandline commands on a
remote system and see the screen return
514/UDP syslog protocol - used for system logging Official
515/TCP Line Printer Daemon protocol - used in LPD printer servers
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524/TCP,UDP
NCP (NetWare Core Protocol) is used for a variety things such as access to
primary NetWare server resources, Time Synchronization, etc.
Official
530/TCP,UDP RPC Official
531/TCP,UDP AOL Instant Messenger, IRC Unofficial
540/TCP UUCP (Unix-to-Unix Copy Protocol) Official
542/TCP,UDP
commerce (Commerce Applications) (RFC maintained by: Randy Epstein
[repstein at host.net])
Official
546/TCP,UDP DHCPv6 client
547/TCP,UDP DHCPv6 server
548/TCP AFP (Apple Filing Protocol)
554/TCP RTSP (Real Time Streaming Protocol) Official
563/TCP,UDP NNTP protocol over TLS/SSL (NNTPS) Official
587/TCP email message submission (SMTP) (RFC 2476) Official
591/TCP FileMaker 6.0 Web Sharing (HTTP Alternate, see port 80) Official
593/TCP,UDP HTTP RPC Ep Map Official
604/TCP TUNNEL
631/TCP,UDP IPP, Internet Printing Protocol
636/TCP,UDP LDAP over SSL (encrypted transmission) Official
639/TCP,UDP MSDP, Multicast Source Discovery Protocol
646/TCP LDP, Label Distribution Protocol
647/TCP DHCP Failover Protocol
648/TCP RRP, Registry Registrar Protocol
652/TCP DTCP, Dynamic Tunnel Configuration Protocol
654/TCP AODV, Ad hoc On-Demand Distance Vector
666/TCP
id Software's Doom multiplayer game played over TCP (666 is the Number of
the Beast)
Official
674/TCP ACAP, Application Configuration Access Protocol
691/TCP MS Exchange Routing Official
692/TCP Hyperwave-ISP
695/TCP IEEE-MMS-SSL
698/TCP OLSR, Optimized Link State Routing
699/TCP Access Network
700/TCP EPP, Extensible Provisioning Protocol
701/TCP LMP, Link Management Protocol.
702/TCP IRIS over BEEP
706/TCP SILC, Secure Internet Live Conferencing
711/TCP TDP, Tag Distribution Protocol
712/TCP TBRPF, Topology Broadcast based on Reverse-Path Forwarding
720/TCP SMQP, Simple Message Queue Protocol
829/TCP CMP (Certificate Management Protocol)
860/TCP iSCSI
873/TCP rsync File synchronisation protocol Official
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(Registered) Ports 1024 to 49151
901/TCP Samba Web Administration Tool (SWAT) Unofficial
981/TCP
SofaWare Technologies Remote HTTPS management for firewall devices
running embedded Checkpoint Firewall-1 software
Unofficial
989/TCP,UDP FTP Protocol (data) over TLS/SSL Official
990/TCP,UDP FTP Protocol (control) over TLS/SSL Official
991/TCP,UDP NAS (Netnews Admin System)
992/TCP,UDP Telnet protocol over TLS/SSL Official
993/TCP IMAP4 over SSL (encrypted transmission) Official
995/TCP POP3 over SSL (encrypted transmission) Official
Port Description Status
1080/tcp SOCKS proxy Official
1099/tcp RMI Registry Official
1099/udp RMI Registry Official
1176/tcp Perceptive Automation Indigo home control server Official
1194/udp OpenVPN Official
1198/tcp & udp The cajo project Free dynamic transparent distributed computing in Java Official
1214/tcp Kazaa Official
1241/tcp & udp Nessus Security Scanner Official
1223/tcp+udp TGP: "TrulyGlobal Protocol" aka "The Gur Protocol" Official
1313/tcp Xbiim (Canvii server) Port Unofficial
1337/tcp
menandmice.com DNS (not to be confused with standard DNS port).
Often used on compromised/infected computers - "1337" a "Leet speak"
version of "Elite". See unregistered use below.
Official
1337/tcp WASTE Encrypted File Sharing Program
Unofficial,
Conflict
1352/tcp IBM Lotus Notes/Domino RPC Official
1387/tcp Computer Aided Design Software Inc LM (cadsi-lm ) Official
1387/udp Computer Aided Design Software Inc LM (cadsi-lm ) Official
1414/tcp IBM MQSeries Official
1433/tcp Microsoft SQL database system Official
1434/tcp Microsoft SQL Monitor Official
1434/udp Microsoft SQL Monitor Official
1494/tcp Citrix MetaFrame ICA Client Official
1521/tcp
Oracle database default listener - CONFLICT with registered use: nCube
License Manager
Unofficial,
Conflict
1533/tcp IBM Sametime IM Official
1547/tcp Laplink Official
1547/udp Laplink Official
1677/tcp Novell GroupWise clients in client/server access mode
1723/tcp Microsoft PPTP VPN Official
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1723/udp Microsoft PPTP VPN Official
1761/tcp
Novell Zenworks Remote Control utility - CONFLICT with registered use:
cft-0
Unofficial,
Conflict
1863/tcp MSN Messenger Official
1900/udp Microsoft SSDP Enables discovery of UPnP devices Official
1935/tcp Macromedia Flash Communications Server MX Official
1972/tcp InterSystems Caché Official
1972/udp InterSystems Caché Official
1984/tcp Big Brother - network monitoring tool Official
2000/udp Cisco SCCP (Skinny) Official
2000/tcp Cisco SCCP (Skinny) Official
2002/tcp [Cisco Secure Access Control Server (ACS) for Windows] Unofficial
2030 Oracle Services for Microsoft Transaction Server Unofficial
2031/tcp mobrien-chat - Mike O'Brien
2031/udp mobrien-chat - Mike O'Brien
2082/tcp
CPanel's default port - CONFLICT with registered use: Infowave Mobility
Server
Unofficial,
Conflict
2083/tcp CPanel's default port for SSL connections Unofficial
2086/tcp
WebHost Manager's default port - CONFLICT with registered use:
GNUnet
Unofficial,
Conflict
2087/tcp WebHost Manager's default port for SSL connections Unofficial
2095/tcp CPanel's default port for webmail connections Unofficial
2096/tcp CPanel's default port for webmail connections via SSL connections Unofficial
2181/tcp EForward-document transport system Official
2181/udp EForward-document transport system Official
2222/tcp DirectAdmin's default port Unofficial
2427/udp Cisco MGCP Official
2447/tcp ovwdb - OpenView Network Node Manager (NNM) daemon Official
2447/udp ovwdb - OpenView Network Node Manager (NNM) daemon Official
2710/tcp XBT Bittorrent Tracker Unofficial
2710/udp XBT Bittorrent Tracker experimental UDP tracker extension Unofficial
2809/tcp
corbaloc:iiop URL, per the CORBA 3.0.3 specification.
Also used by IBM WebSphere Application Server Node Agent
Official
2809/udb corbaloc:iiop URL, per the CORBA 3.0.3 specification. Official
2967/udp Symantec AntiVirus Corporate Edition Unofficial
3000/tcp Miralix License server Unofficial
3001/tcp Miralix Phone Monitor Unofficial
3002/tcp Miralix CSTA Unofficial
3003/tcp Miralix GreenBox API Unofficial
3004/tcp Miralix InfoLink Unofficial
3006/tcp Miralix SMS Client Connector Unofficial
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3007/tcp Miralix OM Server Unofficial
3050/udp gds_db Official
3050/tcp gds_db Official
3074/tcp/udp Xbox Live Official
3128/tcp HTTP used by web caches and the default port for the Squid cache Official
3306/tcp MySQL Database system Official
3333/tcp Network Caller ID server Unofficial
3389/tcp
Microsoft Terminal Server (RDP) officially registered as Windows Based
Terminal (WBT)
Official
3396/tcp Novell NDPS Printer Agent Official
3689/tcp DAAP Digital Audio Access Protocol used by Apple's ITunes Official
3690/tcp Subversion version control system Official
3724/tcp World of Warcraft Online gaming MMORPG Unofficial
3784/tcp Ventrilo VoIP program used by Ventrilo Official
3785/udp Ventrilo VoIP program used by Ventrilo Official
4007/TCP PrintBuzzer printer monitoring socket server Unofficial
4089/udp OpenCORE Remote Control Service Official
4089/tcp OpenCORE Remote Control Service Official
4100 WatchGuard Authentication Applet - default port Unofficial
4226/tcp Aleph One (computer game) Unofficial
4226/udp Aleph One (computer game) Unofficial
4569/udp IAX - Inter-Asterisk eXchange Unofficial
4662/tcp eMule - port often used Unofficial
4672/udp eMule - port often used Unofficial
4894/tcp LysKOM Protocol A Official
4899/tcp
RAdmin remote administration tool (program sometimes used as a Trojan
horse)
Official
5000/tcp
Universal Plug and Play (UPnP) - Windows network device
interoperability; CONFLICT with registered use: commplex-main
Unofficial,
Conflict
5001/tcp Slingbox and Slingplayer Unofficial
5003/tcp Filemaker Filemaker Pro Official
5060/tcp Session Initiation Protocol (SIP) Official
5060/udp Session Initiation Protocol (SIP) Official
5061/tcp Session Initiation Protocol (SIP) over Transport Layer Security (TLS) Official
5121 Neverwinter Nights and its mods, such as Dungeon Eternal X Unofficial
5190/tcp AOL and AOL Instant Messenger Official
5222/tcp XMPP/Jabber - client connection Official
5223/tcp XMPP/Jabber - default port for SSL Client Connection Unofficial
5269/tcp XMPP/Jabber - server connection Official
5432/tcp PostgreSQL database system Official
5500/tcp VNC remote desktop protocol - for incoming listening viewer Unofficial
5517/tcp Setiqueue Proxy server client for SETI@Home project Unofficial
List of TCP and UDP port numbers - Wikipedia, the free encyclopedia Page 7 of 9
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5631/tcp Symantec pcAnywhere Official
5800/tcp VNC remote desktop protocol - for use over HTTP Unofficial
5900/tcp ARD/VNC remote desktop protocol - regular port Unofficial
6000/tcp X11 - used between an X client and server over the network Official
6112/udp
Blizzard's Battle.net gaming service - CONFLICT with registered use:
"dtspcd" is a network daemon that accepts requests from clients to execute
commands and launch applications remotely
Unofficial,
Conflict
6346/tcp Gnutella Filesharing (FrostWire, Limewire, Bearshare, etc.) Official
6347/udp Gnutella Official
6543/udp
Jetnet - default port that Paradigm R&D Technology's Jetnet protocol
communicates on
Unofficial
6600/tcp mpd - default port that mpd listens for client connects on Unofficial
6667/tcp IRC (Internet Relay Chat) - port often used Unofficial
6668/tcp IRC (Internet Relay Chat) - port often used Unofficial
6669/tcp IRC (Internet Relay Chat) - port often used Unofficial
6881-6999/tcp,
udp
BitTorrent - full range of ports used most often Unofficial
6891-6900/tcp
& udp
MSN Messenger (File transfer) Official
6901/tcp & udp MSN Messenger (Voice) Official
6969/tcp BitTorrent tracker port - CONFLICT with registered use: acmsoda
Unofficial,
Conflict
7000/tcp Default Port for Azureus's built in HTTPS Bittorrent Tracker Unofficial
7312/udp Sibelius License Server port Unofficial
8000/tcp
iRDMI - often mistakenly used instead of port 8080 (The Internet
Assigned Numbers Authority (iana.org) officially lists this port for iRDMI
protocol)
Official
8000/tcp
Common port used for internet radio streams such as those using
SHOUTcast
Unofficial,
Conflict
8010/tcp XMPP/Jabber File transfers Unofficial
8080/tcp
HTTP Alternate (http-alt) - used when running a second web server on the
same machine (the other is in port 80), for web proxy and caching server,
or for running a web server as a non-root user. Default port for Jakarta
Tomcat.
Official
8086/tcp HELM Web Host Automation Windows Control Panel Unofficial
8087/tcp Hosting Accelerator Control Panel Unofficial
8118/tcp Privoxy web proxy - advertisements-filtering web proxy Official
8087/tcp SW Soft Plesk Control Panel Unofficial
8291/tcp
Winbox - Default port on a MikroTik RouterOS for a Windows application
used to adminster MikroTik RouterOS
Unofficial
8443/tcp SW Soft Plesk Control Panel Unofficial
8767 TeamSpeak - Default UDP Port Unofficial
9001
Tor network default port. CONFLICT with: cisco-xremote router
configuration
Unofficial,
Conflict
9535 mngsuite - Management Suite Remote Control Official
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(Dynamic/Private) Ports 49152 to 65535
By definition, no ports can be officially registered in the Dynamic Ports range.
9800
WebCT e-learning portal. CONFLICT with registered use: WebDav
Source Port
Unofficial,
Conflict
9999 Hydranode - edonkey2000 control telnet port Unofficial
10000 Webmin - web based linux admin tool
Unofficial,
Conflict
10008 Octopus Multiplexer - CROMP protocol primary port, hoople.org Official
11576 IPStor Server management communication Unofficial
11371 OpenPGP HTTP Keyserver Official
12345
NetBus - remote administration tool (often Trojan horse). Also used by
NetBuster
Unofficial
14567/udp Battlefield 1942 and mods Unofficial
15345/udp XPilot Official
16567/udp Battlefield 2 and mods Unofficial
20000 Usermin - web based user tool Official
20720/tcp Symantec i3 Web GUI server Unofficial
24842 StepMania: Online: Dance Dance Revolution Simulator Unofficial
27010 Half-Life and its mods, such as Counter-Strike Unofficial
27015 Half-Life and its mods, such as Counter-Strike Unofficial
27374 Sub7's default port. Most script kiddies do not change the default port. Unofficial
27000/udp (through 27006) id Software's QuakeWorld master server Unofficial
27500/udp (through 27900) id Software's QuakeWorld Unofficial
27888/udp Kaillera server Unofficial
27900 (through 27901) Nintendo Wi-Fi Connection Unofficial
27960/udp
(through 27969) Activision's Enemy Territory and id Software's Quake III
Arena and Quake III derived games
Unofficial
28910 Nintendo Wi-Fi Connection Unofficial
28960 Call of Duty 2 Common Call of Duty 2 port - (PC Version) Unofficial
29900 (through 29901) Nintendo Wi-Fi Connection Unofficial
29920 Nintendo Wi-Fi Connection Unofficial
31337/tcp
Back Orifice - remote administration tool (often Trojan horse) ("31337" is
the "Leet speak" version of "Elite")
Unofficial
31456-
31458/tcp
TetriNET ports (in order: irc, game, and spectating) Unofficial
regards,
Gazzali...
BASIC SHORTCUT KEYS
The below basic shortcut keys are a listing of shortcut keys that will work with almost all IBM compatible computers and software programs. It is highly recommended that all users keep a good reference of the below short cut keys and/or try to memorize the below keys. Doing so will dramatically increase your productivity.
Shortcut Keys
Description
Alt + F
File menu options in current program.
Alt + E
Edit options in current program
F1
Universal Help in almost ever Windows program.
Ctrl + A
Select all text.
Ctrl + X
Cut selected item.
Shift + Del
Cut selected item.
Ctrl + C
Copy selected item.
Ctrl + Ins
Copy selected item
Ctrl + V
Paste
Shift + Ins
Paste
Home
Goes to beginning of current line.
Ctrl + Home
Goes to beginning of document.
End
Goes to end of current line.
Ctrl + End
Goes to end of document.
Shift + Home
Highlights from current position to beginning of line.
Shift + End
Highlights from current position to end of line.
Ctrl + Left arrow
Moves one word to the left at a time.
Ctrl + Right arrow
Moves one word to the right at a time.
MICROSOFT WINDOWS SHORTCUT KEYS
If you're looking for shortcut keys or information about how to navigate Microsoft Windows using your keyboard instead of the mouse see document CH000791.
Shortcut Keys
Operating System
Description
Alt + Tab
3.X / 95 / 98 / NT / 2000 / XP
Switch between open applications.
Alt + Shift + Tab
3.X / 95 / 98 / NT / 2000 / XP
Switch backwards between open applications.
Alt + Print Screen
3.X / 95 / 98 / NT / 2000 / XP
Create a screen shot only for the program you are currently in.
Ctrl + Alt + Del
3.X / 95 / 98 / NT / 2000 / XP
Reboot the computer and/or bring up the Windows task manager.
Ctrl + Esc
95 / 98 / NT / 2000 / XP
Bring Up start menu.
Alt + Esc
95 / 98 / NT / 2000 / XP
Switch Between open applications on taskbar.
F2
3.X / 95 / 98 / NT / 2000 / XP
Renames selected Icon.
F3
95 / 98 / NT / 2000 / XP
Starts find from desktop.
F4
95 / 98 / NT / 2000 / XP
Opens the drive selection when browsing.
F5
95 / 98 / NT / 2000 / XP
Refresh Contents.
Alt + F4
3.X / 95 / 98 / NT / 2000 / XP
Closes Current open program.
Ctrl + F4
3.X / 95 / 98 / NT / 2000 / XP
Closes Window in Program.
Ctrl + (the '+' key on the keypad)
98 / NT / 2000 / XP
Automatically adjust the widths of all the columns in Windows explorer
Alt + Enter
95 / 98 / NT / 2000 / XP
Opens properties window of selected icon or program.
Shift + F10
95 / 98 / NT / 2000 / XP
Simulates right-click on selected item.
Shift + Del
95 / 98 / NT / 2000 / XP
Delete programs/files without throwing into the recycle bin.
Holding Shift
3.X / 95 / 98 / NT / 2000 / XP
Boot safe mode or by pass system files.
Holding Shift
95 / 98 / NT / 2000 / XP
When putting in an audio CD, will prevent CD Player from playing.
WINDOWS KEYBOARD SHORTCUTS
Below is a listing of Windows keys that can be used on computers running a Microsoft Windows operating system and using a keyboard with a Windows key. In the below list of shortcuts, the Windows key is represented by "WINKEY". If you are looking for Windows shortcut keys, see the above Microsoft Windows shortcut key section.
Shortcut Keys
Description
WINKEY + D
Brings the desktop to the top of all other windows.
WINKEY + M
Minimizes all windows.
WINKEY + SHIFT + M
Undo the minimize done by WINKEY + M and WINKEY + D.
WINKEY + E
Open Microsoft Explorer.
WINKEY + Tab
Cycle through open programs through the taskbar.
WINKEY + F
Display the Windows Search / Find feature.
WINKEY + CTRL + F
Display the search for computers window.
WINKEY + F1
Display the Microsoft Windows help.
WINKEY + R
Open the run window.
WINKEY + Pause / Break key
Open the system properties window.
WINKEY + U
Open Utility Manager.
WINKEY + L
Lock the computer (Windows XP and above only).
EXCEL SHORTCUT KEYS
See our Microsoft Excel page for additional help and information.
Shortcut Keys
Description
F2
Edit the selected cell.
F5
Goto a specific cell. For example, C6.
F7
Spell check selected text and/or document.
F11
Create chart.
Ctrl + Shift + ;
Enter the current time.
Ctrl + ;
Enter the current date.
Alt + Shift + F1
Insert New Worksheet.
Shift + F3
Open the Excel formula window.
Shift + F5
Bring up search box.
Ctrl + A
Select all contents of the worksheet.
Ctrl + B
Bold highlighted selection.
Ctrl + I
Italic highlighted selection.
Ctrl + K
Insert link.
Ctrl + U
Underline highlighted selection.
Ctrl + 5
Strikethrough highlighted selection.
Ctrl + P
Bring up the print dialog box to begin printing.
Ctrl + Z
Undo last action.
Ctrl + F9
Minimize current window.
Ctrl + F10
Maximize currently selected window.
Ctrl + F6
Switch between open workbooks / windows.
Ctrl + Page up
Move between Excel work sheets in the same Excel document.
Ctrl + Page down
Move between Excel work sheets in the same Excel document.
Ctrl + Tab
Move between Two or more open Excel files.
Alt + =
Create a formula to sum all of the above cells
Ctrl + '
Insert the value of the above cell into cell currently selected.
Ctrl + Shift + !
Format number in comma format.
Ctrl + Shift + $
Format number in currency format.
Ctrl + Shift + #
Format number in date format.
Ctrl + Shift + %
Format number in percentage format.
Ctrl + Shift + ^
Format number in scientific format.
Ctrl + Shift + @
Format number in time format.
Ctrl + Arrow key
Move to next section of text.
Ctrl + Space
Select entire column.
Shift + Space
Select entire row.
WORD SHORTCUT KEYS
See our Microsoft Word page for additional help and information.
Shortcut Keys
Description
Ctrl + A
Select all contents of the page.
Ctrl + B
Bold highlighted selection.
Ctrl + C
Copy selected text.
Ctrl + X
Cut selected text.
Ctrl + P
Open the print window.
Ctrl + F
Open find box.
Ctrl + I
Italic highlighted selection.
Ctrl + K
Insert link.
Ctrl + U
Underline highlighted selection.
Ctrl + V
Paste.
Ctrl + Y
Redo the last action performed.
Ctrl + Z
Undo last action.
Ctrl + L
Aligns the line or selected text to the left of the screen.
Ctrl + E
Aligns the line or selected text to the center of the screen.
Ctrl + R
Aligns the line or selected text to the right of the screen.
Ctrl + M
Indent the paragraph.
Ctrl + Shift + F
Change the font.
Ctrl + Shift + >
Increase selected font +1pts up to 12pt and then increases font +2pts.
Ctrl + ]
Increase selected font +1pts.
Ctrl + Shift + <>
Moves one word to the left.
Ctrl +
Moves one word to the right.
Ctrl +
Moves to the beginning of the line or paragraph.
Ctrl +
Moves to the end of the paragraph.
Ctrl + Del
Deletes word to right of cursor.
Ctrl + Backspace
Deletes word to left of cursor.
Ctrl + End
Moves the cursor to the end of the document.
Ctrl + Home
Moves the cursor to the beginning of the document.
Ctrl + Spacebar
Reset highlighted text to the default font.
Ctrl + 1
Single-space lines.
Ctrl + 2
Double-space lines.
Ctrl + 5
1.5-line spacing.
Ctrl + Alt + 1
Changes text to heading 1.
Ctrl + Alt + 2
Changes text to heading 2.
Ctrl + Alt + 3
Changes text to heading 3.
Ctrl + F1
Open the Task Pane.
F1
Open Help.
Shift + F3
Change the case of the selected text.
Shift + Insert
Paste.
F4
Repeat the last action performed (Word 2000+)
F5
Open goto window.
F7
Spell check selected text and/or document.
Shift + F7
Activate the thesaurus.
F12
Save as.
Shift + F12
Save.
Alt + Shift + D
Insert the current date.
Alt + Shift + T
Insert the current time.
Mouse Shortcuts
Description
Click, hold, and drag
Selects text from where you click and hold to the point you drag and let go.
Double-click
If double-click a word, selects the complete word.
Double-click
Double-clicking on the left, center, or right of a blank line will make the alignment of the text left, center, or right aligned.
Double-click
Double-clicking anywhere after text on a line will set a tab stop.
Triple-click
Selects the line or paragraph of the text the mouse triple-clicked.
Ctrl + Mouse wheel
Zooms in and out of document.
INTERNET EXPLORER SHORTCUT KEYS
See our Microsoft Internet Explorer page for additional help and information.
Shortcut Keys
Description
Alt + Left Arrow
Back a page.
Alt + Right Arrow
Forward a page.
F5
Refresh current page / frame.
F11
Display the current website in full screen mode. Pressing F11 again will exit this mode.
Esc
Stop page or download from loading.
Ctrl + Enter
Quickly complete an address. For example, type computerhope in the address bar and press CTRL + ENTER to get http://www.computerhope.com.
Ctrl + N
Open New browser window.
Ctrl + P
Print current page / frame.
Spacebar
Moves down a page at a time.
Shift + Spacebar
Moves up a page at a time.
FRONTPAGE SHORTCUT KEYS
See our Microsoft FrontPage page for additional help and information.
Shortcut Keys
Description
Ctrl + C
Copy selected text.
Ctrl + X
Cut selected text.
Ctrl + P
Paste selected text.
Ctrl + K
Create a hyperlink.
Ctrl + B
Bold highlighted selection.
Ctrl + I
Italic highlighted selection.
Ctrl + U
Underline highlighted selection.
Ctrl + L
Left align the text.
Ctrl + R
Right align the text.
Ctrl + E
Center the text.
Ctrl + /
Display HTML tags.
Ctrl + S
Save document.
Ctrl + Tab
Switch between open web pages.
Ctrl + Ins
Enter Line break.
Ctrl + Enter
Move cursor above or below a table.
Ctrl + Shift + B
Preview in web browser window.
Ctrl + Shift + <>
Increase font size.
Ctrl + Del
Deletes word to right of cursor.
Ctrl + Backspace
Deletes word to left of cursor.
OUTLOOK SHORTCUT KEYS
See our Microsoft Outlook page for additional help and information.
Shortcut Keys
Description
Alt + S
Send the e-mail
Ctrl + C
Copy selected text.
Ctrl + X
Cut selected text.
Ctrl + P
Paste selected text.
Ctrl + K
Complete the name and/or e-mail being typed in the e-mail address bar.
Ctrl + B
Bold highlighted selection
Ctrl + I
Italic highlighted selection
Ctrl + U
Underline highlighted selection
Ctrl + R
Reply to an e-mail.
Ctrl + F
Forward an e-mail.
Ctrl + N
Create a new e-mail.
Ctrl + Shift + A
Create a new appointment to your calendar.
Ctrl + Shift + O
Open the Outbox.
Ctrl + Shift + I
Open the Inbox.
Ctrl + Shift + K
Add a new task.
Ctrl + Shirt + C
Create a new contact.
Ctrl + Shift + J
regards,
Gazali...
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