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New Member

QOS : Queuing to be done at the Edge or Distribution Layer?

Hi folks,

I have a setup which involves Avaya ip phones on Cisco infrastructure. The Cisco equipments are the catalyst 3550 (edge) and the 6500 (Distri & Core).

I'm pretty much a QOS newbie, and I've browsed through the LAN QOS and QOS best practices documentation, and I will like to know which part of the infrastructure should I apply Queuing to ? From the documentation, its either at the Edge/Distri or both. On either, is it better than the other?

appreciate any feedbacks. Thank you!

regards,

seanwy.

4 REPLIES
Super Bronze

Re: QOS : Queuing to be done at the Edge or Distribution Layer?

Hi

You would perform classification at the Edge, or perhaps use a trust-dscp model.

Queueing would be performed at any point where bandwidth may be contended - so this will probably include the edge, distribution, and core.

Regards

Aaron

Aaron Please remember to rate helpful posts to identify useful responses, and mark 'Answered' if appropriate!
New Member

Re: QOS : Queuing to be done at the Edge or Distribution Layer?

Hi Aaron,

Thank you for yr reply. It seems if I were to apply Queuing all all 3 layers, I believe the configuration will be pretty complex.

Just a side note, the Avaya IP phones are able to propagate both CoS & DSCP values. Thus, should I trust-dscp or trust-cos on the access (Edge) switch ?

much thanks!

regards,

Sean.

Blue

Re: QOS : Queuing to be done at the Edge or Distribution Layer?

if your devices send DSCP & CoS, trust is OK.

be sure to verify your QoS at the access & distribution layers at least.

if your core is sufficient, you may have no real need to worry there.

Bronze

Re: QOS : Queuing to be done at the Edge or Distribution Layer?

with my avaya ip phones i trust COS..

Example

interface FastEthernet0/5

Description to IP phone and PC

switchport mode access

switchport access vlan 10

switchport voice vlan 11

no ip address

spanning-tree portfast

mls qos trust cos

Also, for security reasons have the avaya ip phone re-write the "PC's dataport" (phones 2nd ethernet port connected to pc) to COS of 0

It's done by adding PHY2PRIO=0 in option 176 string or in 46xxsrttings script file via SET PHY2PRIO=0

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