ATM Connections 7-37
Traffic Shaping for CBR, VBR, and UBR
Traffic Shaping for CBR, VBR, and UBR
With the introduction of traffic shaping for CBR, VBR, and UBR, the user has the option to provide
traffic shaping for these connections types on the BXM. Previously, only ABR utilized traffic
shaping. Traffic shaping involves passing CBR, VBR, or UBR traffic streams through VC queues for
scheduled rate shaping.
Traffic shaping is performed on a per port basis. When traffic shaping is enabled, all traffic exiting
the port (out to the network) is subject to VC scheduling based on the parameters configured by the
user for the connection.
Figure 7-22 shows an example of traffic shaping. In this example, port 1 is configured to perform
traffic shaping. Note that all the ATM cells regardless of class of service pass through the VC queues
before leaving the card when traffic shaping is enabled. In the example, port 2 is not configured for
traffic shaping, and only the ABR traffic with FCES (flow control external segment) passes through
the VC queues.
Figure 7-22 Traffic Shaping Example
Configuration
Traffic shaping is disabled by default. The cnfport command is used to enable and disable the
function on a per port basis. No connections should be enabled on the port prior to changing the port
traffic shaping parameter. If there are existing connections when the port is toggled, then these
connections will not be updated unless the card is reset, connections are rerouted, a switchcc occurs,
or the user modifies the connection parameters.
Traffic
shaping
enabled
Port 1
No traffic
shaping
Port 2
ABR/UBR Qbin
VBR Qbin
CBR Qbin
ABR/UBR Qbin
VBR Qbin
CBR Qbin
12150
VC queues
CBR
CBR
VBR
VBR
UBR
UBR
ABR
ABR
ABR (with FCES)
