Best method to do QoS for voicew on new ASA5500 platform over VPN

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Dec 13th, 2008
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We are going to use QoS on our ASA 5500 firewall to prioritorise voice traffic over a 2 mb circuit between 2 locations. (There wil also be non urgent data traffic too). Using the ASDM GUI we can use match traffic (to various criteria) and get it applied to the priority queue to ensure that it has best chance of efficient delivery. Thing is we have several choices as to how to match - by ACL on dest/source, IP addresses, TCP/UDP Port(s), DSCP, IP Prec values etc. Has anyone who has done this found the best criteria by which to match for voice (RTP)? IE on a a range of RTP valuse - or EF46 value Codepoint DSCP or whichever ? Thanks

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husycisco Sat, 12/13/2008 - 12:24
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Hello Peter,

"Has anyone who has done this found the best criteria by which to match"

In general, packets marked with dscp ef are voice packets, if I recall correct most VOIP devices mark their traffic as ef and this marking can be used in ASA if your trust boundries are configured correctly.

I usually prefer handling marking in switch that VOIP devices are connected to, create a voice vlan for them, mark this vlan's traffic as ef, then match dscp ef in routers or firewalls.


peter-net Mon, 12/15/2008 - 11:38
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Many thanks for this - the ADSL looks great for doing qos


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