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New Member

VOIP QOS question

I will be connecting 2 sites. Each site will have a 2821 router with 2 port vwic. I want to set up a bridge between the 2 sites, and then want to bundle the T1's on each side to give them a total of 3mbps between the sites. No data will be on the wan. Voice traffic only. I will have a catalyst 3750 switch at one site, and a HP 2524 at the other site. What steps would I take to implement qos. We will be connecting to an nec pbx. Any help would be greatly appreciated.


Re: VOIP QOS question

A summary of the key QoS requirements and recommendations for Voice (bearer traffic) are:

- Voice traffic should be marked to DSCP EF per the QoS Baseline and RFC 3246.

- Loss should be no more than 1 %.

- One-way Latency (mouth-to-ear) should be no more than 150 ms.

- Average one-way Jitter should be targeted under 30 ms.

- 21-320 kbps of guaranteed priority bandwidth is required per call (depending on the sampling

rate, VoIP codec and Layer 2 media overhead).

Check out this:



New Member

Re: VOIP QOS question


1. Both sites are connected using NEC PBX? How many T1 from PBX to Voice Gateway?

2. Is your Setup look like this?

PBX --- Voice Gateway ----- Voice Gateway --- PBX

You do not need LLQ, because your WAN link is purely for voice. If you do not involve switch 3750 at the middle you do not required Classification and Marking as well. If your setting look like 2, basically no QOS require.

New Member

Re: VOIP QOS question

PBX is in one location.

PBX---switch---2821---3mbps ppp bridge to the other site. No pbx at the other site. Basically, I am looking for ios commands to issue on the 2821 router, which will be bridging, to enable qos. I have read about AutoQos but did not see the command available. I don't think it will work if traffic is being bridged anyway. Let me know what you think.

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