QoS on isdn line

geo_2008_ · ‎01-29-2009

Hello,

I have an isdn line as a backup with the following policy

policy-map backup

class preced-5

priority 45

class preced-4

bandwidth remaining percent 30

class preced-3

bandwidth remaining percent 30

class preced-2

bandwidth remaining percent 20

class preced-1

bandwidth remaining percent 10

class class-default

bandwidth remaining percent 10

I can see drops at the critical class even when the offered rate is 1000 or 5000bps, while it should allow untill 45Kbps.

Virtual-Access1

Service-policy output: backup

Class-map: preced-5 (match-any)

354 packets, 252724 bytes

30 second offered rate 1000 bps, drop rate 1000 bps

Match: ip precedence 5

354 packets, 252724 bytes

30 second rate 1000 bps

Queueing

Strict Priority

Output Queue: Conversation 40

Bandwidth 45 (kbps) Burst 1125 (Bytes)

(pkts matched/bytes matched) 354/252724

(total drops/bytes drops) 141/156991

Class-map: preced-5 (match-any)

268 packets, 189684 bytes

30 second offered rate 3000 bps, drop rate 3000 bps

Match: ip precedence 5

268 packets, 189684 bytes

30 second rate 3000 bps

Queueing

Strict Priority

Output Queue: Conversation 40

Bandwidth 45 (kbps) Burst 1125 (Bytes)

(pkts matched/bytes matched) 268/189684

(total drops/bytes drops) 114/130919

chuckwirth · ‎02-02-2009

It should allow an /average/ of 45kbps. If your traffic is bursty you are going to see drops even though the 30 second offered rate is low.

If you are putting Voice into your LLQ make sure you are provisioning for the layer 3 header as well as the traffic. This will be about 80kbps for a standard G.711 call and 24kbps for a single G.729 call.

You may want to change the interface to

if#max-reserved-bandwidth 90

This shouldn't be affecting your problem, but it could eliminate any problems with the default-class percent versus the other non-priority classes.