Term
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Definition
Part of the original IEEE 802.3 standard, 10BaseT is the Ethernet specification of
10Mbps baseband that uses two pairs of twisted-pair, Category 3, 4, or 5 cabling—using one
pair to send data and the other to receive. 10BaseT has a distance limit of about 100 meters
per segment. |
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Term
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Definition
Based on the IEEE 802.3u standard, 100BaseT is the Fast Ethernet specification of
100Mbps baseband that uses UTP wiring. 100BaseT sends link pulses (containing more information
than those used in 10BaseT) over the network when no traffic is present. |
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Term
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Definition
Based on the IEEE 802.3u standard, 100BaseTX is the 100Mbps baseband Fast
Ethernet specification that uses two pairs of UTP or STP wiring. The first pair of wires receives
data; the second pair sends data. To ensure correct signal timing, a 100BaseTX segment
cannot be longer than 100 meters. |
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Term
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Definition
Used in T1 transmission facilities and sometimes called “24th channel
signaling.” Each of the 24 T1 subchannels in this procedure uses one bit of every sixth frame
to send supervisory signaling information. |
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Term
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Definition
Authentication, Authorization, and Accounting: A system developed by Cisco to
provide network security. |
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Term
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Definition
ATM Adaptation Layer: A service-dependent sublayer of the Data Link layer, which
accepts data from other applications and brings it to the ATM layer in 48-byte ATM payload
segments. CS and SAR are the two sublayers that form AALs. Currently, the four types of AAL
recommended by the ITU-T are AAL1, AAL2, AAL3/4, and AAL5. AALs are differentiated by
the source-destination timing they use, whether they are CBR or VBR, and whether they are
used for connection-oriented or connectionless mode data transmission. |
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Term
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Definition
ATM Adaptation Layer 1: One of four AALs recommended by the ITU-T, it is used for
connection-oriented, time-sensitive services that need constant bit rates, such as isochronous
traffic and uncompressed video. |
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Term
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Definition
ATM Adaptation Layer 2: One of four AALs recommended by the ITU-T, it is used
for connection-oriented services that support a variable bit rate, such as compressed voice
traffic. |
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Term
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Definition
ATM Adaptation Layer 3/4: One of four AALs (a product of two initially distinct
layers) recommended by the ITU-T, supporting both connectionless and connection-oriented
links. Its primary use is in sending SMDS packets over ATM networks. |
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Term
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Definition
ATM Adaptation Layer 5: One of four AALs recommended by the ITU-T, it is used
to support connection-oriented VBR services primarily to transfer classical IP over ATM and
LANE traffic. This least complex of the AAL recommendations uses SEAL, offering lower
bandwidth costs and simpler processing requirements but also providing reduced bandwidth
and error-recovery capacities. |
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Term
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Definition
AppleTalk Address Resolution Protocol: The protocol in an AppleTalk stack that
maps data-link addresses to network addresses. |
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Term
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Definition
Packets sent by the AARP to determine whether a given node ID is
being used by another node in a nonextended AppleTalk network. If the node ID is not in use,
the sending node appropriates that node’s ID. If the node ID is in use, the sending node will
select a different ID and then send out more AARP probe packets. |
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Term
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Definition
Asynchronous Balanced Mode: When two stations can initiate a transmission, ABM
is an HDLC (or one of its derived protocols) communication technology that supports peeroriented,
point-to-point communications between both stations. |
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Term
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Definition
Area Border Router: An OSPF router that is located on the border of one or more OSPF
areas. ABRs are used to connect OSPF areas to the OSPF backbone area. |
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Term
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Definition
One of the layers in Cisco’s three-layer hierarchical model. The access layer
provides users with access to the internetwork. |
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Term
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Definition
A link used with switches that is part of only one virtual LAN (VLAN). Trunk
links carry information from multiple VLANs. |
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Term
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Definition
A set of test conditions kept by routers that determines “interesting traffic” to
and from the router for various services on the network. |
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Term
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Definition
The manner in which network devices approach gaining access to the network
itself. |
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Term
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Definition
Defines the bandwidth rate of the circuit. For example, the access rate of a
T1 circuit is 1.544Mbps. In Frame Relay and other technologies, there may be a fractional T1
connection—256Kbps, for example—however, the access rate and clock rate are still
1.544Mbps. |
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Term
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Definition
Also known as a “network access server,” it is a communications process connecting
asynchronous devices to a LAN or WAN through network and terminal emulation
software, providing synchronous or asynchronous routing of supported protocols. |
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Term
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Definition
One of the three components in AAA. Accounting provides auditing and logging
functionalities to the security model. |
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Term
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Definition
Verification sent from one network device to another signifying that an
event has occurred. May be abbreviated as ACK.
Contrast with: NAK. |
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Term
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Definition
Allowed cell rate: A designation defined by the ATM Forum for managing ATM traffic.
Dynamically controlled using congestion control measures, the ACR varies between the minimum
cell rate (MCR) and the peak cell rate (PCR).
See also: MCR
and
PCR. |
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Term
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Definition
The mechanism used to manage a token ring. The network node with the
highest MAC address on the ring becomes the active monitor and is responsible for management
tasks such as preventing loops and ensuring that tokens are not lost. |
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Term
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Definition
In regard to an EIGRP routing table, a route will be in active state when a router
is undergoing a route convergence. |
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Term
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Definition
Used with transparent bridges to learn the hardware addresses of all devices
on a network. The switch then filters the network with the known hardware (MAC) addresses. |
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Term
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Definition
By translating network addresses from one format to another, this methodology
permits different protocols to operate interchangeably. |
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Term
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Definition
A bit combination descriptor identifying which portion of an address refers
to the network or subnet and which part refers to the host. Sometimes simply called the mask. |
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Term
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Definition
The process used for resolving differences between computer addressing
schemes. Address resolution typically defines a method for tracing Network layer (layer 3)
addresses to Data Link layer (layer 2) addresses. |
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Term
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Definition
The relationship made to exchange routing information between defined neighboring
routers and end nodes using a common media segment. |
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Term
| administrative distance (AD) |
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Definition
A number between 0 and 255 that expresses the level of trustworthiness
of a routing information source. The lower the number, the higher the integrity rating. |
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Term
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Definition
A value designated by a network administrator to rate the preference
given to a network link. It is one of four link metrics exchanged by PTSPs to test ATM network
resource availability. |
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