Chapter 8 Permanent Virtual Connections (PVCs and PVPs)
Avaya M770 ATM Switch User’s Guide 113
Managing Traffic Descriptors
A Traffic Descriptor defines the service category that will be used to transport traffic
and the bandwidth that is required. Each service category has its own set of
parameters. The M770 ATM Switch can support up to 32 different user configured
traffic descriptors for the creation of PVCs.
The M770 ATM Switch supports three service categories:
• Constant Bit Rate (CBR) traffic, such as uncompressed voice or video.
For CBR traffic you will need to specify the dedicated Peak Cell Rate (PCR) per
second. Bandwidth for CBR traffic is guaranteed for the duration of the
connection.
• Variable Bit Rate (VBR) traffic, such as compressed voice or video.
For VBR traffic you will need to specify a dedicated Peak Cell Rate (PCR), a
Sustainable Cell Rate (SCR), and a Maximum Burst Size (MBS). Bandwidth for
VBR traffic is guaranteed for the duration of the connection.
• Unspecified Bit Rate (UBR) traffic, such as broadcasts frames.
UBR connections will always be accepted but bandwidth will not be
guaranteed. This is also referred to as “best effort” traffic.
Note: When creating traffic descriptors all cell rates are specified as cells per second.
If the CLP bit is not set in the ATM cell header, it indicates high priority traffic.
Creating a CBR traffic descriptor
To create a CBR traffic descriptor, use the td setup CBR command.
Command: M15-155s8:/>td setup CBR <td_id> pcr0+1=<pcr0+1> [pcr0=<pcr0>]
Example: M15-155s8:/>td setup CBR 2 pcr0+1=64000 pcr0=48000
Parameters: <td_id> An unique identifier for this traffic descriptor.
<pcr0+1> The combined PCR for all cells regardless of whether the CLP (Cell
Loss Priority) bit is set in the ATM cell header.
<pcr0> An optional PCR for cells where the CLP bit is not set in the ATM
cell header. This PCR must be less than, or equal to, the combined
PCR.