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Prioritisng IP traffic on Cisco

By denisobrien ·
I want to run an IP PBX (Digium / Asterisk) for local and
international calls. My Internet connection is via VSAT and very
expensive but I want to be able to have toll quality voice for 4
concurrent international calls. The IP PBX will reside on the LAN
and my serial connection will be to the VSAT. Do I prioritise on
the E0 or S0? I suspect S0 and if so, what would be the best way
to do this? (CBQ , WFQ, ) Also, anyone out theremwith
experience on Asterisk / cisco? thx in advance

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by thanetadmin In reply to Prioritisng IP traffic on ...

Well you can create an access list on cisco & divide http traffic & voice port 5060/1720 traffic on CBQ .It should work well. I use TC on Linux with HTB which is very pratcical & stable for me. get back to me in case of further issues.


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by dplewis In reply to Prioritisng IP traffic on ...

Best way of doing this - so you can apply QoS with a policy across your network (put it on your LAN switches too), rather than on a link-by-link basis is to use explicit priority marked on the packet by the priginating device. This is usually done using DiffServ Code Points. Voice is usually marked with DSCP=46 in the IP header - you'll need to check the documentation for your IP PBX and IP handsets. If you use Cisco AuotQoS feature - configurde to trust DSCP (by default it usually trusts Layer-2 802.1P markings) then it's really easy to configure. In the background it's using LLQ, by the way as this provides strict priority for the voice. Ultimately you may find voice quality stillisn't great as you won't get QoS over the Internet, nor on the inbound traffic from the iSP. Good luck...

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