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Friday, May 22, 2009

Computer Networking Terms

Here are some useful networking terms. (constantly updated) 


ACK - A 1 bit flag in the TCP header that indicates the acknowledgment field is valid

Acknowledgment - A notification sent from one network device to another for confirming certain events

Address pool - The range of IP addresses that can be assigned by the DHCP server

Address Resolution Protocol (ARP) - The method of finding a host's hardware address from its IPv4 network layer address

Administratively scoped address - A multicast address that is restricted to a local group or organization (IPv4)

AND - One of the three basic binary operations. The result will only yield 1 when both ANDed numbers are 1

Argument - Additional data that is provided with a command to provide information used by the execution of the command

ARP cache/table - A logical storage in a host's RAM to sore ARP entries

ARP poisoning/spoofing - A technique used to attack an Ethernet network by sending fake ARP messages to an Ethernet LAN

Asynchronous - Communication that does not use a common clock between the sender and reciever. To maintain timing, additional information is sent to sychronize the recieve circuit to the incoming data

Attenuation - The loss of communication signal on the media. This loss is due to degradation of the energy wave over time

ication - A process used to verify the identity of a person or process


Bandwidth - In networking, a measurement of the speed of bits that can be transmitted over a particular link. It is the amount of data that can be transmitted in a certain amount of time. It is usually expressed in bps (bits per second)

Best-effort - Network protocols or technologies that do not use the acknowledgment system to guarantee reliable delivery of information

Binary - A numbering system characterized by 1's and 0's

Bit - Binary digit used in the binary numbering system. Binary digits are units of information storage and communications in computing. Each bit can be either 0 or 1

Bit time - The time required to send a single bit over some transmission medium

Bridge - A device that connects multiple network segments at the data link layer of the OSI model. Predecessor of LAN switches

Bridge table - The table used by a switch or bridge that associates MAC addresses with the outgoing port. Used in forwarding/filtering decisions

Broadcast - A form of transmission where one device transmits to all devices within the network or another network

Broadcast address - An address used to represent a transmission from one device to all devices. In Ethernet, it is represented by FFFF.FFFF.FFFF

Broadcast domain - A logical network composed of all the computers and networking devices that can be reached by sending a frame to the data link layer broadcast address

Burned-in address (BIA) - The MAC address that is permanently assigned to a LAN interface or NIC. Also called UAA or universally administered address


Cache - A temporary storage where data that has been retrieved or calculated and is accessed frequently can be stored.  After the data is stored in the cache, the processes can access the copy instead of accessing the original data. A cache reduces the average access time and reduces the overhead of recalculating the data.

Carrier - A signal on the medium used to support the transmission of data. Data is "carried" over the medium by modulation (combining the data signal with the carrier signal).

Carrier sense multiple access (CSMA) - Media access methodology in which a node wishing to transmit listens for a carrier wave before trying to send. If a carrier is sensed, the node waits for the transmission in progress to finish before initiating its own transmission.

Carrier sense multiple access collision avoid (CSMA/CA) - A mechanism used to regulate the transmission of data onto a network medium. A device must first send a request to send. It is used in 802.11 WLANS (wireless LAN).

Carrier sense multiple access collision detect (CSMA/CD) - The MAC algorithm used by ethernet devices in a shared media. The protocol requires a node wishing to transmit to listen for a carrier signal before trying to send. If a collision occurs and detected, the sending node uses the backoff algorithm before retransmitting.

Channel - A communication path over a medium used to transport information from a sender to a reciever. Multiple channels can be multiplexed over a single cable.

Channel service unit/data service unit (CSU/DSU) - A device that connects a logical digital telephone loop for a WAN circuit to a serial interface on a network device, typically connecting to a router. The CSU/DSU performs physical (Layer 1) signaling on WAN circuits.

Classful Addressing - A unicast IP address that is considered to have three parts: a network part, a subnet part and a host part. The term classful refers to the fact that the classful network rules are first applied to the address, and then the rest of the address can be separated into a subnet and host part to perform subnetting. In the early days of IPv4, IP addresses were divided into five classes from Class A to E. Classful addressing is not generally practiced in current network implementations.