Section 7: QoS (4 Points)

• Configure the Frame Relay connection between R2 and R3 such that the connection can adapt to congestion when a BECN is received from the network. Assume a 1544 kbps access rate and a CIR of 64 kbps.

If you configured this correctly as shown in Example 6-48, you have scored 2 points.

This is an application of Traffic Shaping to accommodate congestion. Notice the configuration of the traffic-shape fecn-adapt on both ends of the link. The far end will reflect received FECNs as BECNs in the Q.922 TEST RESPONSE messages.

Example 6-48. R2 and R3 traffic-shape Adaptability Configuration

 R2#sh run int s0/0 Building configuration... Current configuration : 362 bytes ! interface Serial0/0  ip address 160.10.32.2 255.255.255.252  ip helper-address 130.200.10.200  encapsulation frame-relay  ip ospf network point-to-point  traffic-shape rate 1544000 38600 38600 1000  traffic-shape adaptive 64000  traffic-shape fecn-adapt  frame-relay map ip 160.10.32.1 203 broadcast  no frame-relay inverse-arp  frame-relay lmi-type ansi end R2# ________________________________________________________________ R3#sh run int s0/0 Building configuration... Current configuration : 328 bytes ! interface Serial0/0  ip address 160.10.32.1 255.255.255.252  encapsulation frame-relay  ip ospf network point-to-point  traffic-shape rate 1544000 38600 38600 1000  traffic-shape adaptive 64000  traffic-shape fecn-adapt  frame-relay map ip 160.10.32.2 302 broadcast  no frame-relay inverse-arp  frame-relay lmi-type ansi end R3# 

• Consider VoIP to be a "critical" application. Configure PQ-CBWFQ (Priority Queueing-Class-Based Weight Fair Queueing) on R3 and R4 to guarantee a bandwidth of 256 kbps on VoIP traffic and Fair-Queue with a queue size of 32 for all other traffic types.

Class Based Weight Fair Queue (CBWFQ) with Low Latency Queue (LLQ) is used to guarantee quality to VoIP applications. This technique is what is recommended for VoIP.

If you configured this correctly as shown in Example 6-49, you have scored 2 points.

Example 6-49. R3 and R4 LLQ-CBWFQ Configuration

 R4#sh run ! class-map match-all VOICE   match input-interface Serial0/0 ! ! policy-map Class1   class VOICE     priority 256   class class-default    fair-queue 32 R4#show policy-map interface s0/1  Serial0/1   Service-policy output: Class1     Class-map: VOICE (match-all)       35 packets, 1260 bytes       5 minute offered rate 0 bps, drop rate 0 bps       Match: input-interface Serial0/0       Queueing         Strict Priority         Output Queue: Conversation 40         Bandwidth 256 (kbps) Burst 6400 (Bytes)         (pkts matched/bytes matched) 35/1260         (total drops/bytes drops) 0/0     Class-map: class-default (match-any)       410 packets, 28471 bytes       5 minute offered rate 0 bps, drop rate 0 bps       Match: any       Queueing         Flow Based Fair Queueing         Maximum Number of Hashed Queues 32         (total queued/total drops/no-buffer drops) 0/0/0 ! ! ________________________________________________________________ R3#sh run         (total queued/total drops/no-buffer drops) 0/0/0 ! class-map match-all VOICE   match input-interface Serial0/0 ! ! policy-map Class1   class VOICE     priority 256   class class-default    fair-queue 32 ! ! R3#sh run int s0/0 Building configuration... Current configuration : 358 bytes ! interface Serial0/0  ip address 160.10.32.1 255.255.255.252  service-policy output Class1  encapsulation frame-relay  end R3#sh policy-map interface s0/0  Serial0/0   Service-policy output: Class1     Class-map: VOICE (match-all)       36 packets, 1296 bytes       5 minute offered rate 0 bps, drop rate 0 bps       Match: input-interface Serial0/0       Queueing         Strict Priority         Output Queue: Conversation 40         Bandwidth 256 (kbps) Burst 6400 (Bytes)         (pkts matched/bytes matched) 36/1296         (total drops/bytes drops) 0/0     Class-map:2 class-default (match-any)       734 packets, 50212 bytes       5 minute offered rate 4000 bps, drop rate 0 bps       Match: any       Queueing         Flow Based Fair Queueing         Maximum Number of Hashed Queues 32         (total queued/total drops/no-buffer drops) 0/0