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The Frame Relay IP RTP Priority feature provides a strict priority queueing scheme on a Frame Relay permanent virtual circuit (PVC) for delay-sensitive data such as voice. Voice traffic can be identified by its Real-Time Transport Protocol (RTP) port numbers and classified into a priority queue configured by the frame-relayiprtpprioritycommand. The result of using this feature is that voice is serviced as strict priority in preference to other nonvoice traffic.
This feature extends the functionality offered by the iprtppriority command by supporting Frame Relay PVCs. This feature allows you to specify a range of User Datagram Protocol (UDP) ports whose voice traffic is guaranteed strict priority service over any other queues or classes using the same output interface. Strict priority means that if packets exist in the priority queue, they are dequeued and sent first--that is, before packets in other queues are dequeued.
The strict priority queueing scheme allows delay-sensitive data such as voice to be dequeued and sent first--that is, before packets in other queues are dequeued. Delay-sensitive data is given preferential treatment over other traffic. This process is performed on a per-PVC basis, rather than at the interface level.
Related Features and Technologies
The Frame Relay IP RTP Priority feature is related to the following features:
IP RTP Priority
Class-based weighted fair queueing (CBWFQ)
Weighted fair queueing (WFQ)
Quality of Service Solutions Configuration Guide
, Cisco IOS Release 12.0
Quality of Service Solutions Command Reference
, Cisco IOS Release 12.0
Class-Based Weighted Fair Queueing
IP RTP Priority
Cisco 1600 series
Cisco 2500 series
Cisco 2600 series
Cisco 3600 series
Cisco 3800 series
Cisco 4000 series (Cisco 4000, 4000-M, 4500, 4500-M, 4700, 4700-M)
Cisco 5200 series
Cisco 7000 series
Cisco 7200 series
Cisco 7500 series
This feature runs on the platforms listed. However, it is most useful on voice supported platforms, such as the Cisco 2600 series, Cisco 3600 series, Cisco 7200 series, and Cisco 7500 Route Switch Processor (RSP) series.
Supported Standards and MIBs and RFCs
No new or modified MIBs are supported by this feature.
Frame Relay traffic shaping (FRTS) and Frame Relay Fragmentation (FRF.12) must be configured before the Frame Relay IP RTP Priority feature is used.
To reserve a strict priority queue on a Frame Relay PVC for a set of RTP packet flows belonging to a range of UDP destination ports, use the following command in map-class configuration mode.
Because the frame-relayiprtppriority command gives absolute priority over other traffic, it should be used with care. In the event of congestion, if the traffic exceeds the configured bandwidth, then all the excess traffic is dropped.
The following example first configures the Frame Relay map class called
voip and then applies the map class to PVC 100 to provide strict priority
service to matching RTP packets:
map-class frame-relay voip
frame-relay cir 256000
frame-relay bc 2560
frame-relay be 600
frame-relay mincir 256000
no frame-relay adaptive-shaping
frame-relay fragment 250
frame-relay ip rtp priority 16384 16380 210
ip address 10.10.10.10 255.0.0.0
no ip directed-broadcast
no ip mroute-cache
frame-relay interface-dlci 100
frame-relay ip rtp header-compression
frame-relay intf-type dce
In this example, RTP packets on PVC 100 with UDP ports in the range
16384 to 32764 will be matched and given strict priority service.