Specifications

52 IBM Voice Over Frame Relay Perform Guide
• At the interface level, you can assign a percentage of the interface’s bandwidth
to circuit classes. Each circuit class contains one or more circuits.
• At the circuit level, we can define traffic class and allocate a percentage of the
circuit.
A new voice over frame relay (VoFR) class is used to identify voice packets. If the
circuit is dedicated to voice, set 100% of the circuit to the voice. If the circuit will
carry both voice and data traffic, we should configure VoFR with a higher priority
type than any other traffic. With priority queuing, each bandwidth class can be
assigned one of the following priority levels:
• Urgent
•High
•Normal
•Low
All packets assigned the urgent priority are sent first within the class. When all
Urgent packets have been transmitted, High packets are transmitted. Traffic class
definitions need to be defined if both voice and data will be multiplexed over the
same PVC. Voice should normally be given priority over any other traffic type in
the PVC. This can be defined in two different ways:
1. Assign all protocols to the same traffic class, giving voice traffic the highest
priority. This would result in two traffic classes. The LOCAL class is always
created and is used for traffic generated internally by the router, for example
RIP and PING. We will create the second class and decide which protocol is
assigned. Same-priority protocols within the class will be sent in FIFO order. A
higher-priority protocol within the class will always be sent before a
lower-priority protocol.
2. Create a super traffic class and assign voice to it. Assign the other protocol to
different traffic classes, assigning bandwidth percentages to each class as
required. The super class does not have a bandwidth percentage assigned to
it. Traffic queued in this class will be sent before data in any other traffic class.
Using multiple traffic classes allows you to give preference to high-priority
protocols.
Circuit class definitions are only necessary when the sum of the CIRs for the
circuits on the interface exceeds the access rate of the link. If the CIR total does
not exceed the access rate, then the bandwidth percentages assigned to the
circuit classes are not used CIR monitoring that will override the circuit class
bandwidth allocations. If the CIR total exceeds the access rate, then circuit
classes should be defined with those PVCs carrying voice rather than those
carrying data only.