Need VOIP QOS help for Cisco 2811

[ericw]

Hello,

My eyes are crossed from reading so many docs on QOS.  I have a Cisco 2811 running CME, 10x1 connection to the Internet, SIP trunks to Callcentric running g729r8 and g711ulaw.  Phones are 7960's running SCCP.  Runs well except when someone is downloading an ISO, which happens often, then voice gets stomped on.

Please suggest a router VOIP QOS configuration that would help me with the voice quality issue.  I have auto qos on my Cisco switch already, and the trunk port on the switch is also configured to trust dscp.  I assume there is something I need to do on fastethernet0/1 which is the trunk to the switch too?

Thanks!

[Chris Deren]

Reading your description I am assuming this is single location deployment and all traffic is local and directly to the internet, if so unless you misconfigured your LAN QoS there is probably nothing you can do to fix it as the issue seems to be that the carrier is not doing any QoS over the SIP trunk connection.  Do you experience the issue for PSTN calls or internal calls (IP phone to IP phone) as well?  

[ericw]

Reading your description I am assuming this is single location deployment and all traffic is local and directly to the internet

Yes

if so unless you misconfigured your LAN QoS

That's just it, I haven't configured it at all, don't know how.

there is probably nothing you can do to fix it as the issue seems to be that the carrier is not doing any QoS over the SIP trunk connection.

As I mentioned, everything works fine unless someone is downloading an ISO and takes up all the available bandwidth.  I need a recipe/config to reserve some bandwidth at the WAN port, either statically or dynamically.

[Terry Cheema]

Hi Mate,

The issue you have is your inbound download traffic. You can/should configure your Edge router with QoS, policing/shaping/prioritizing outbound traffic from your router. This will control what goes out your router and at what rate, However, this will still not cover the inbound download traffic.

The real problem is the heavy inbound download traffic- you can police your inbound traffic but it will be of little use, as it has already traversed/used the bandwidth and you will be discarding at your entry point after it has congested your link. The little use it will have is the provider would then start throttling the TCP transmit as the packets are being dropped at your end and congestion will improve.

You can try few things:

1) Apply inbound/outbound QoS/policing.

Review this guide and specifically this chapter:

http://www.cisco.com/c/en/us/td/docs/solutions/Enterprise/WAN_and_MAN/QoS_SRND_40/QoSWAN_40.html#pgfId-129799

2) Speak to your ISP and try to work this out with them, if they are able to offer some assistance.

The above points may help to get you in a slightly better condition but the main problem is since your SIP traffic is going over the internet link and QoS markings are normally not honored over the internet.

-Terry