Beta Draft Confidential
Configuring ATM Traffic Descriptors
About TDs
ATM Services Configuration Guide for CBX 3500, CBX 500, GX 550, and B-STDX 9000
1/19/05
12-3
About TDs
To define a TD, you must select the QoS Class and TD combination to meet your
network needs. The following sections describe each of the QoS classes, as well as the
various TD parameters. For each QoS class, you can select combinations of traffic
parameters, which together form a TD.
About QoS
ATM supports four service classes to handle the various data types in a network. By
selecting the appropriate service class, you can ensure optimal network usage.
describes each service type class. The numerical value for the QoS Class
reflects the ATM Forum definitions.
Table 12-1.
QoS Classes
Type
Description
QoS
Class
Constant bit rate (CBR)
Handles digital information, such as video and
digitized voice that is represented by a
continuous bit stream. CBR traffic requires
guaranteed throughput rates and service levels.
Note: The CBR QoS class is not available on
management PVCs (MPVCs).
1
Variable bit rate real time
(VBR-RT)
For packaging special delay-sensitive
applications, such as packet video, that require
low cell delay variation (CDV) between
endpoints.
2
Variable bit rate non-real
time (VBR-NRT)
Handles packaging for transfer of long, bursty
data streams over a pre-established ATM
connection. This service is also used for short
bursty data, such as LAN traffic. CPE
protocols adjust for any delay or loss incurred
through the use of a VBR NRT service class.
3
Available bit rate/unspecified
bit rate (ABR/UBR)
Primarily used for LAN traffic. The CPE
should compensate for any delay or lost cell
traffic. This service class is intended for (but
not restricted to) use with the ATM FCP.
4
Note – If the network equipment connected to the logical port does not support QoS,
select the corresponding Unspecified class of service (CoS) type. This provides a QoS
class of zero (0).
Summary of Contents for CBX 3500
Page 888: ......