[55920] in North American Network Operators' Group
Re: VoIP over IPsec
daemon@ATHENA.MIT.EDU (Charlie Clemmer)
Mon Feb 17 10:54:12 2003
Date: Mon, 17 Feb 2003 09:53:11 -0600
To: "Stephen Sprunk" <stephen@sprunk.org>
From: Charlie Clemmer <cclemmer@nexgennetworks.com>
Cc: <nanog@merit.edu>
In-Reply-To: <006401c2d655$abb5d560$93b58742@ssprunk>
Errors-To: owner-nanog-outgoing@merit.edu
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At 01:24 AM 2/17/2003 -0600, Stephen Sprunk wrote:
>Unfortunately, IOS can introduce jitter when encrypting packets. To
>mitigate this, you can apply QOS, with a strict priotiy queue for the VoIP
>packets and the "qos pre-classify" feature. Your mileage will vary
>depending on the CPU power of the router, the traffic levels, and whether
>you're using hardware encryption.
Stephen, I know this is outside of Charles' original inquiry, but I'm not
familiar with this "qos pre-classify" feature. Since we would be encrypting
voice traffic ... at what point would you classify it? If I classify it
before it goes into the tunnel and gets encrypted, would that
classification last once it's encrypted? If we try to classify after it's
been encrypted, how can we tell it's voice traffic? It seems to me that
jitter from both the actual encryption process as well as that associated
with basic serialization would be the potential death of VoIP in this
scenario, but I'm not sure mechanisms available to help resolve that risk.
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