для Cisco Cisco IOS Software Release 12.2(8)T
ATM Software Segmentation and Reassembly (SAR)
ATM Software Segmentation and Reassembly (SAR)
100
Cisco IOS Release 12.2(8)T
Glossary
AAL—ATM adaptation layer. Service-dependent sublayer of the data link layer. The AAL accepts data
from different applications and presents it to the ATM layer in the form of 48-byte ATM payload
segments. AALs consist of two sublayers: CS and SAR. AALs differ on the basis of the
source-destination timing used, whether they use CBR or VBR, and whether they are used for
connection-oriented or connectionless mode data transfer. At present, the four types of AAL
recommended by the ITU-T are AAL1, AAL2, AAL3/4, and AAL5.
from different applications and presents it to the ATM layer in the form of 48-byte ATM payload
segments. AALs consist of two sublayers: CS and SAR. AALs differ on the basis of the
source-destination timing used, whether they use CBR or VBR, and whether they are used for
connection-oriented or connectionless mode data transfer. At present, the four types of AAL
recommended by the ITU-T are AAL1, AAL2, AAL3/4, and AAL5.
AAL2—ATM adaptation layer 2. One of four AALs recommended by the ITU-T. AAL2 is used for
connection-oriented services that support a variable bit rate, such as some isochronous video and voice
traffic.
connection-oriented services that support a variable bit rate, such as some isochronous video and voice
traffic.
ATM—Asynchronous Transfer Mode. International standard for cell relay in which multiple service
types (such as voice, video, or data) are conveyed in fixed-length (53-byte) cells. Fixed-length cells
allow cell processing to occur in hardware, thereby reducing transit delays. ATM is designed to take
advantage of high-speed transmission media such as E3, SONET, and T3.
types (such as voice, video, or data) are conveyed in fixed-length (53-byte) cells. Fixed-length cells
allow cell processing to occur in hardware, thereby reducing transit delays. ATM is designed to take
advantage of high-speed transmission media such as E3, SONET, and T3.
Backhaul
—
A scheme where telephony signaling is reliably transported from a gateway to a Media
Gateway Controller across a packet switched network.
BGW—see Business Gateway
Business Gateway—An xGCP media gateway which is a business customer premises equipment that
has connection(s) to the VoIP network as well as connection(s) to the user’s telephony equipment
(typically a PBX, a corporate LAN or WAN). Such gateways are used to eliminate or reduce the need for
individual medium (voice, data, and so forth) connectivity.
has connection(s) to the VoIP network as well as connection(s) to the user’s telephony equipment
(typically a PBX, a corporate LAN or WAN). Such gateways are used to eliminate or reduce the need for
individual medium (voice, data, and so forth) connectivity.
CA—see Call Agent
Call Agent—An intelligent entity in an IP telephony network which handles call control in an MGCP
model Voice over IP network.
model Voice over IP network.
CAS—channel associated signaling. A form of signaling that the circuit state is indicated by one or more
bits of signaling status sent repetitively and associated with that specific circuit. CAS is used on a T1
line. With CAS, a signaling element is dedicated to each channel in the T1 frame. This type of signaling
is sometimes called Robbed Bit Signaling (RBS) because a bit is taken out (or robbed) from the user's
data stream to provide signaling information to and from the switch.
bits of signaling status sent repetitively and associated with that specific circuit. CAS is used on a T1
line. With CAS, a signaling element is dedicated to each channel in the T1 frame. This type of signaling
is sometimes called Robbed Bit Signaling (RBS) because a bit is taken out (or robbed) from the user's
data stream to provide signaling information to and from the switch.
CBR—constant bit rate. QoS class defined by the ATM Forum for ATM networks. CBR is used for
connections that depend on precise clocking to ensure undistorted delivery.
connections that depend on precise clocking to ensure undistorted delivery.
CCS—common channel signaling. A signaling system used in telephone networks that separates
signaling information from user data. A specified channel is exclusively designated to carry signaling
information for all other channels in the system.
signaling information from user data. A specified channel is exclusively designated to carry signaling
information for all other channels in the system.
CID—channel identifier
CLASS—Custom Local Area Subscriber Services, usually referred to as “Custom Calling” features
Codec—Coder-decoder. Device that typically uses pulse code modulation to transform analog signals
into a digital bit stream and digital signals back into analog signals. In Voice over ATM, it specifies the
voice coder rate of speech for a dial peer.
into a digital bit stream and digital signals back into analog signals. In Voice over ATM, it specifies the
voice coder rate of speech for a dial peer.
Dial peer—An addressable call endpoint. In Voice over ATM, there are two kinds of dial peers: POTS
and VoATM.
and VoATM.
DS-0—digital signal level 0. Framing specification used in transmitting digital signals over a single
channel at 64-kbps on a T1 facility. A 64-K B-channel on an E1 or T1 WAN interface.
channel at 64-kbps on a T1 facility. A 64-K B-channel on an E1 or T1 WAN interface.