From: Chris Lewis (chrlewiscsco@yahoo.com)
Date: Tue Oct 04 2005 - 14:18:12 GMT-3
All:
I am aware of the following options for prioritizing voice traffic over a frame relay DLCI. Does this look complete, or can anyone add to it?
1. Creating a separate high priority queue on the interface
This requires FRF.12 (fragment in the map-class).Data packets larger than the packet size specified in the frame-relay fragment command are first enqueued to a WFQ subqueue, whereas the smaller packest go to the high priority queue. They are then dequeued and fragmented. After fragmentation, the first segment is transmitted. The remaining segments wait for the next available transmission time for that VC, as determined by the shaping algorithm. At this point, small voice packets and fragmented data packets are interleaved from other PVCs. With this interface level queueing mechanism, small data packest also get in to the priority queue on the interface if they are smaller than the fragment size.
2. This can be enhanced by adding frame-relay ip rtp priority. KNown as VoIPoFR, this classifies VoIP packets by matching on the RTP UDP port range defined in a Frame Relay map-class. All RTP traffic within this port range is enqueued to a priority queue for the VC. In addition, voice packets go into the high priority queue at the interface level. All other packets go into the non-priority queue at the interface level.
3. The generic form of using MQC to identify voice traffic, then using a policy-map to give this traffic priority treatment and applying the service-policy to a class for the DLCI
4. PIPQ configured on the interface using the interface-queue priority command and assigning a complete DLCI to the priority queue in its map-class, this of course requires one to dedicate voice to a specific DLCI.
5. Using PPP to fragment and interleave, which is pretty much like F=plain FRF.12 and assumes that packet size is enough of a differentiator to separate voice and data packets.
Chris
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