The following list outlines the traffic-shaping techniques used with Frame Relay:
To control the access rate transmitted on a Cisco router, you can configure a peak rate to
limit outbound traffic to either the CIR or excess information rate (EIR).
You can configure BECN support on a per-VC basis, which will enable the router to then
monitor BECNs and throttle traffic based on BECN-designated packets.
Queuing can be used for support at the VC level. Priority, custom, and weighted fair queuing
(WFQ) can be used. This gives you more control over traffic flow on individual VCs.
It’s also important to understand when you would use traffic shaping with Frame Relay. The
following list explains this:
Use traffic shaping when one site, such as the corporate office, has a higher speed line (for
example, a T1), and the remote branches have slower lines (for example, 56Kbps). This
connection would cause bottlenecks on each VC and would result in poor response times
for time-sensitive traffic such as SNA and Telnet. This can cause packets to be dropped. By
using traffic shaping at the corporate office, you can improve response on each VC.
Traffic shaping is also helpful on a router with many subinterfaces. Because these subinterfaces
will use traffic as fast as the physical link allows, you can use rate enforcement on the subinterface
to match the CIR of the VC. This means you can preallocate bandwidth to each VC.
Traffic shaping can be used to throttle back transmission on a Frame Relay network that
is constantly congested. This can help prevent packet loss and is done on a per-VC basis.
Traffic shaping is used effectively if you have multiple Network layer protocols and want
to queue each protocol to allocate bandwidth effectively. Since IOS version 11.2, queuing
can be performed at the VC level.