ZyXEL Communications SAM1316-22, User Manual

Page: 110 / 464

Chapter 14 xDSL Profiles Setup
SAM1316-22 User’s Guide
110
14.4 ATM QoS
ATM Quality of Service (QoS) mechanisms provide the best service on a per-flow
guarantee. ATM network infrastructure was designed to provide QoS. It uses fixed
cell sizes and built-in traffic management (see
Section 14.5 on page 110 ). This
allows you to fine-tune the levels of services on the priority of the traffic flow.
14.5 Traffic Shaping
Traffic shaping is an agreement between the carrier and the subscriber to regulate
the average rate and fluctuations of data transmission over an ATM network. This
agreement helps eliminate congestion, which is important for transmission of real
time data such as audio and video connections.
Note: Traffic shaping controls outgoing (downstream) traffic, not incoming (upstream).
14.5.1 ATM Traffic Classes
These are the basic ATM traffic classes defined by the ATM Forum Traffic
Management 4.0 Specification.
14.5.1.1 Constant Bit Rate (CBR)
Constant Bit Rate (CBR) is an ATM traffic class that provides fixed bandwidth. CBR
traffic is generally time-sensitive (doesn’t tolerate delay). CBR is used for
connections that continuously require a specific amount of bandwidth. Examples
of connections that need CBR would be high-resolution video and voice.
14.5.1.2 Variable Bit Rate (VBR)
The Variable Bit Rate (VBR) ATM traffic class is used with bursty connections.
Connections that use the Variable Bit Rate (VBR) traffic class can be grouped into
real time (rt-VBR) or non-real time (nrt-VBR) connections.
Add Click Add to save your changes to the SAM1316-22’s volatile
memory. The SAM1316-22 loses these changes if it is turned off or
loses power, so use the Config Save link on the navigation panel to
save your changes to the non-volatile memory when you are done
configuring.
Cancel Click Cancel to start configuring the screen again.
Table 24 Port Profile (continued)
LABEL DESCRIPTION