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Information transported over frame relay is subject to greater delay and jitter than data transported over ATM or point-to-point TDM circuits. In a frame relay environment, the Committed Information Rate (CIR) must be sufficient to support peak voice traffic or some threshold for voice traffic as determined by the network administrator. Then prioritize the voice traffic. One method to prioritize voice is to enable priority queuing at both ends of the frame relay link, so that voice traffic is always processed and delivered out the WAN link first.
Maintain all voice traffic within the CIR because delivery of burst traffic is not guaranteed while delivery of CIR traffic is guaranteed. Service providers will contract to meet a customer's traffic delivery requirements within the CIR through Service Level Agreements (SLAs). Carriers usually will not contract to such an extent, or at all, for burst traffic. Burst frames--frames marked Discard Eligible (DE)--are either queued until network congestion subsides, or they are discarded entirely.
Under the best circumstances, frame relay is still inherently more susceptible to delay than ATM or TDM. Even with these recommendation implemented, expect more delay over frame relay than would be present under ATM or TDM.
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