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Does QOS on an 828 or 837 actually achieve anything?

John,

You are thinking along the right lines, but there is more to it. Yes, you definitely want to prioritize for packets leaving your network in case you are filling up the outgoing pipe, even though you can't control the public internet. However, you can make sure that the qos is carried end to end - not obeyed by the public routers, but used by your end site. You can always reclassify the traffic when it comes in the other end, but the better solution is to use 'qos pre-classify' with the vpn tunnel. That means that the packets inside the esp packets will be assigned the qos tag. When the other end breaks down the esp packet, it will have the qos information available. Here is a good article:

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Hope that helps,

Jim

Reply to
Scooby
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We have a number of customers using VOIP through an ADSL to ADSL or SDSL to SDSL VPN, and inevitably they occasionally get sound quality problems. Am I right in thinking that implementing QOS on the 837 (ADSL) or 828 (SDSL) routers isn't going to help?

My reasoning is:

- all the public Internet routers between the two sites will ignore any QOS settings on packets I generate

- because it's a VPN the same public routers will just see ESP packets and won't even get to see any VOIP settings made by the PBXs

If I understand correctly I can use QOS on the router to control how the router prioritises packets sent from my LAN out through the ADSl or SDSL line. However if the latency problems are due to the intervening public Internet routers there is nothing I can do about it. Is this a reasonable summary?

Thanks,

John Rennie

Reply to
John Rennie

Did you turn down the tx-ring-limit on the ATM PVC?

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Especially important for low uplink speeds.

Reply to
Joop van der Velden

And from my experience, bottleneck comes up almost always at the customer's site (out. direction) since ISP's at their interconnections and backbones usually maintain enough bandwidth to satisfy all the customer's SLAs without using QoS.

So, I strongly recommend to use QoS at your outgoing links and then see if there are any improvements for your VoIP. To measure QoS results you can use Cisco IP SLA feature. It will show you RTT, jittering, one-way fixed delay, etc. for your VoIP network, so you can compare values you get before and after adding QoS. IP SLA:

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And if you are unfamiliar with QoS configuration on IOS platforms you may wish to use Cisco AutoQoS feature. See the link below:
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B.R. Igor

Reply to
Igor Mamuzic

Thanks for all the suggestions. I'll try them and see what difference it makes.

JR

Reply to
John Rennie

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