Frame Relay Voice-Adaptive Traffic Shaping and Fragmentation

Before the introduction of this new feature, Frame Relay adaptive shaping could be used to reduce the sending rate when a network was congested. Because the adaptive shaping mechanism was triggered by network congestion, voice traffic might already have been delayed by the time the sending rate was reduced. The Frame Relay Voice-Adaptive Traffic Shaping and Fragmentation feature helps to ensure voice quality by adjusting the rate of traffic based on the presence of voice on the PVC.

Frame Relay voice-adaptive traffic shaping and fragmentation

• Prevents delay of voice packets when network congestion occurs by reducing the traffic rate to the minimum committed information rate (minCIR) and turning on fragmentation when voice packets are present on a PVC.
• Maximizes utilization of the PVC by increasing the traffic rate to committed information rate (CIR) when voice packets are not present.
• Reduces CPU utilization by turning off fragmentation when there are no voice packets present.

Frame Relay voice-adaptive traffic shaping enables a router to reduce the PVC sending rate to the minCIR whenever packets (usually voice) are detected in the low latency queueing priority queue or H.323 call setup signaling packets are present. When there are no packets in the priority queue and signaling packets are not present for a configured period of time, the router increases the PVC sending rate from minCIR to CIR to maximize throughput.

Note	Although the priority queue is generally used for voice traffic, Frame Relay voice-adaptive traffic shaping will respond to any packets (voice or data) in the priority queue.

Frame Relay voice-adaptive traffic shaping can be used at the same time as other types of adaptive traffic shaping. For example, if both Frame Relay voice-adaptive traffic shaping and adaptive shaping based on interface congestion are configured, the router will reduce the sending rate to minCIR if there are packets in the priority queue or the interface queue size exceeds the configured threshold.

Frame Relay voice-adaptive traffic shaping can be used in conjunction with or independently of voice-adaptive fragmentation.

Frame Relay voice-adaptive fragmentation enables a router to fragment large data packets whenever packets (usually voice) are detected in the low latency queueing priority queue or H.323 call setup signaling packets are present. When there are no packets in the priority queue for a configured period of time and signaling packets are not present, fragmentation is stopped.

Note	Although the priority queue is generally used for voice traffic, Frame Relay voice-adaptive fragmentation will respond to any packets (voice or data) in the priority queue.

Frame Relay voice-adaptive fragmentation can be used in conjunction with or independent of voice-adaptive traffic shaping.

To use voice-adaptive fragmentation, you must also have end-to-end fragmentation configured in a map class or on the interface.

1.    enable

2.    configure terminal

3.    policy-map policy-map

4.    class class-name

5.    priority bandwidth-kbps

6.    exit

7.    class class-name

8.    bandwidth bandwidth-kbps

9.    end

1.    enable

2.    configure terminal

3.    policy-map policy-map

4.    class class-default

5.    shape [average | peak] mean-rate [[burst-size] [excess-burst-size]]

6.    shape adaptive mean-rate-lower-bound

7.    shape fr-voice-adapt [deactivation seconds]

8.    Service-policy policy-map-name

9.    end

1.    enable

2.    configure terminal

3.    map-class frame-relay map-class-name

4.    frame-relay fragment fragment_size

5.    service-policy output policy-map-name

6.    end

1.    enable

2.    configure terminal

3.    interface type number

4.    encapsulation frame-relay

5.    frame-relay fragmentation voice-adaptive [deactivation seconds

6.    frame-relay fragment fragment-size end-to-end

7.    frame-relay interface-dlci dlci [ietf | cisco] [voice-cir cir]

8.    class name

9.    end

1.    enable

2.    show policy-map [policy-map]

3.    show policy-map interface interface-name [dlci dlci] [input | output]

4.    show frame-relay pvc [interface interface] [dlci] [64-bit]

The following examples show the configuration of Frame Relay voice-adaptive traffic shaping and fragmentation. The first example shows end-to-end fragmentation configured in a map class that is associated with PVC 100. In the second example, end-to-end fragmentation is configured directly on the interface.

With both example configurations, priority-queue packets or H.323 call setup signaling packets destined for PVC 100 will result in the reduction of the sending rate from CIR to minCIR and the activation of FRF.12 end-to-end fragmentation. If signaling packets and priority-queue packets are not detected for 50 seconds, the sending rate will increase to CIR and fragmentation will be deactivated.

interface serial0
 encapsulation frame-relay
 frame-relay fragmentation voice-adaptive deactivation 50
 frame-relay interface-dlci 100
  class voice_adaptive_class
! 
map-class frame-relay voice_adaptive_class
 frame-relay fragment 80 
 service-policy output shape
class-map match-all voice
 match access-group 102
class-map match-all data
 match access-group 101
policy-map vats
 class voice
  priority 10
 class data
  bandwidth 10  
policy-map shape
 class class-default
  shape average 60000
  shape adaptive 30000
  shape fr-voice-adapt deactivation 50
  service-policy vats

interface serial0
 encapsulation frame-relay
 frame-relay fragmentation voice-adaptive deactivation 50
 frame-relay interface-dlci 100
  class voice_adaptive_class
  frame-relay fragment 80 end-to-end
!
map-class frame-relay voice_adaptive_class
 service-policy output shape
      
class-map match-all voice
 match access-group 102
class-map match-all data
 match access-group 101    
      
policy-map vats
 class voice
  priority 10
 class data
  bandwidth 10 
policy-map shape
 class class-default
  shape average 60000
  shape adaptive 30000
  shape fr-voice-adapt deactivation 50
  service-policy vats