Bandwidth Statement on QoS

From: Guzman, Chris (Chris.Guzman@McKesson.com)
Date: Fri Aug 18 2006 - 18:29:24 ART


I have a policy which is applied to an OC-3 interface, however this port
connects to a provider and has a 50Mb SLA. I have configured LLQ and
the total bandwidth of all the class maps is 50Mb. I would expect the
policy to start dropping packet once we reach 50Mb, however this is not
happening. Am I correct in this assumption ??

It appears that the router is using the interface bandwidth of the OC-3
(155Mb) as its rate limit. The problem here is that the provider will
be dropping at 50mb in their network, so we lose control of whats
dropped.

For instance our policy will allow us to send

COS2 traffc = 30Mb/sec

COS3 traffic = 30Mb/sec

Class-default = 30Mb/sec

The provider will start dropping packets once the total rate is greater
than 50Mb. This has been verified with end to end testing.

Here is the policy..

class-map match-any BGP

 match access-group name BGP

class-map match-any COS3

 match dscp af21

 match ip precedence 2

 match protocol telnet

 match protocol ssh

 match protocol snmp

 match protocol dhcp

 match protocol dns

class-map match-any COS2

 match ip precedence 3

 match access-group name VoIP_Control

 match dscp af31

class-map match-any COS1

 match ip dscp ef

 match ip precedence 5

 match protocol rtp audio

 match access-group name VoIP

policy-map COS

 class COS1

  priority percent 40

  set ip dscp ef

 class COS2

  bandwidth percent 24

  set ip dscp af31

  service-policy BGP

 class COS3

  bandwidth percent 18

  set ip dscp af21

class class-default

  set ip dscp default

interface POS1/0

bandwidth 50000

ip address x.x.x.x.

no ip redirects

no ip proxy-arp

encapsulation ppp

load-interval 30

crc 32

pos scramble-atm

no cdp enable

max-reserved-bandwidth 90

service-policy output COS

 In this test we are sending 28Mb/sec in COS3 and 28Mbps in the default
class and we see NO DROPS ???

Service-policy output: COS

   Class-map: COS1 (match-any)

     0 packets, 0 bytes

     30 second offered rate 0 bps, drop rate 0 bps

     Match: ip dscp ef (46)

       0 packets, 0 bytes

       30 second rate 0 bps

     Match: ip precedence 5

       0 packets, 0 bytes

       30 second rate 0 bps

     Match: protocol rtp audio

       0 packets, 0 bytes

       30 second rate 0 bps

     Match: access-group name VoIP

       0 packets, 0 bytes

       30 second rate 0 bps

     Queueing

       Strict Priority

       Output Queue: Conversation 264

       Bandwidth 40 (%)

       Bandwidth 20000 (kbps) Burst 500000 (Bytes)

       (pkts matched/bytes matched) 0/0

       (total drops/bytes drops) 0/0

     QoS Set

       dscp ef

         Packets marked 0

Class-map: COS2 (match-any)

     0 packets, 0 bytes

     30 second offered rate 0 bps, drop rate 0 bps

     Match: ip precedence 3

       0 packets, 0 bytes

       30 second rate 0 bps

     Match: access-group name VoIP_Control

       0 packets, 0 bytes

       30 second rate 0 bps

     Match: dscp af31 (26)

       0 packets, 0 bytes

       30 second rate 0 bps

     Queueing

       Output Queue: Conversation 265

       Bandwidth 24 (%)

       Bandwidth 12000 (kbps) Max Threshold 64 (packets)

       (pkts matched/bytes matched) 0/0

       (depth/total drops/no-buffer drops) 0/0/0

     QoS Set

       dscp af31

         Packets marked 0

Class-map: COS3 (match-any)

     4618860 packets, 2300192280 bytes

     30 second offered rate 28665000 bps, drop rate 0 bps

     Match: dscp af21 (18)

       0 packets, 0 bytes

       30 second rate 0 bps

     Match: ip precedence 2

       4618860 packets, 2300192280 bytes

       30 second rate 28665000 bps

Match: protocol telnet

       0 packets, 0 bytes

       30 second rate 0 bps

     Match: protocol ssh

       0 packets, 0 bytes

       30 second rate 0 bps

     Match: protocol snmp

       0 packets, 0 bytes

       30 second rate 0 bps

     Match: protocol dhcp

       0 packets, 0 bytes

       30 second rate 0 bps

     Match: protocol dns

       0 packets, 0 bytes

       30 second rate 0 bps

     Queueing

       Output Queue: Conversation 266

       Bandwidth 18 (%)

       Bandwidth 9000 (kbps) Max Threshold 64 (packets)

       (pkts matched/bytes matched) 14/6972

       (depth/total drops/no-buffer drops) 0/0/0

     QoS Set

       dscp af21

         Packets marked 4630907

Class-map: class-default (match-any)

     4620167 packets, 2300271767 bytes

     30 second offered rate 28666000 bps, drop rate 0 bps

     Match: any

     QoS Set

       dscp default

         Packets marked 4647447

     Queueing

       Flow Based Fair Queueing

       Maximum Number of Hashed Queues 256

       (total queued/total drops/no-buffer drops) 0/0/0

        exponential weight: 9



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