Advice on dscp af31 please!

Unanswered Question
Sep 4th, 2007
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Hi, We have a number of VC units running on 3750's and 3560's using the following QoS policy:


class-map match-all Video_Packets

match access-group name Video_Packets


policy-map Video_Conf

class Video_Packets

set dscp af31


ip access-list extended Video_Packets

permit udp any range 17000 17310 any range 17000 17310

permit udp any range 17000 17310 any range 49000 49310

permit udp any range 49000 49310 any range 17000 17310

permit tcp any range 1700 1750 any range 3230 3235

permit tcp any range 3230 3235 any range 1700 1750

permit tcp any range 1700 1750 any gt 1024

permit tcp any gt 1024 any range 1700 1750

permit udp any host 10.xxx.xxx.xxx

permit udp any host 10.xxx.xxx.xxx


We pay our telco to provide QoS over our WAN circuits but have a doubt that they are actually tagging the packets due to the quality we are experiencing.


Using Wireshark/Ethereal can anyone tell me what to look for (If I carry out a trace) to see if the packets are being marked/tagged?


Any help appreciated.


Josh


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Hieu Cao Tue, 09/04/2007 - 16:04
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What do you see when you do "sh policy-map int xxx" and "sh access-list"? Any hits?


What kind of problem that you're experiencing?

sionjones Wed, 09/05/2007 - 00:11
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I get:


Service-policy input: Video_Conf


Class-map: Video_Packets (match-all)

0 packets, 0 bytes

offered rate 0 bps, drop rate 0 bps

Match: access-group name Video_Packets


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

0 packets, 0 bytes

offered rate 0 bps, drop rate 0 bps

Match: any

0 packets, 0 bytes

rate 0 bps


The Polycom units show packet loss and the picture is always pixelating and refreshing.

It sporadically freezes for a split second then goes out of focus.


The switch port shows no errors whatsoever.


Hope this helps?

Hieu Cao Wed, 09/05/2007 - 08:56
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Can you also post the router config where the 3750/3560 is connected?


A couple of things that you can try:


1. Change "class-map match-all Video_Packets" to "class-map match-any Viideo_Packets" so that it'll match any parameter in your access-list.


2. Take a look at your Polycom unit. I may be set at "IP Precedence 4" instead of "AF31". If so, change it in your policy-map.


3. Verify that the port speed and duplex are set to "auto" where the Polycom unit is connected in your switch port.


4. Take a look at this document: http://www.cisco.com/en/US/tech/tk1077/technologies_configuration_example09186a0080111c1b.shtml


hth




Joseph W. Doherty Wed, 09/05/2007 - 11:35
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"Using Wireshark/Ethereal can anyone tell me what to look for (If I carry out a trace) to see if the packets are being marked/tagged?"


Look for either a DSCP or IP Precedence decode in the IP packets carrying the video traffic. Ideally, off the link coming off the WAN.


PS:

If your Telco tags the traffic, why are you setting DSCP?


Besides tagging, has the Telco committed to any SLA with regards to bandwidth, latency, jitter and/or loss, for your video traffic?


Who manages the WAN routers and what type of WAN circuits are being used?

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