[cisco-voip] Cisco 871 - Voice over DMVPN

[Matthew Linsemier]

Hey all,

I am in the process of refreshing my Cisco 871 router configurations (5th
build now ) and I was looking for some input in regards to maintaining my
voice quality the best I can over the Internet.  I have been doing voice
over IPSec for the last 5-6 years and it seems like it never gets easier. :)

Right now we have about 35 users deployed remotely using Cisco 871W routers
and Cisco 7960 phones behind them.  They are connected to two DMVPN hubs
(for redundancy).  We have voice prioritized (among other items) within the
Tunnels and all works as expected (utilizing priority queues, qos
pre-classify, etc.).

With the increase in home user bandwidth (10 meg / 12 meg) we are starting
to notice congestion on our 6 meg Internet link when large amounts of data
is sent or received over the tunnel Interfaces, which in the end causes
congestion, which in turn effects call quality.  We utilize PacketShaper¹s
on the internet links to prioritize IPSec traffic, but when all the traffic
is IPSec traffic, there are issues.

I am looking into some possibilities of removing the voice traffic to
maintain call quality at all costs, and I have come up with a few ideas.

1. Creating two DMVPN tunnels, one that carries only voice, and the other
that carries the rest of the data, and then using the PacketShaper to
guarantee bandwidth to the DMVPN tunnel that carries voice above all other
data. 
2. Pulling the voice traffic out of the tunnel and using PhoneProxy on the
ASA¹s then utilizing PacketShaper to guarantee bandwidth to the srtp session
above all other data.

If anyone can throw out some pros and cons to either of these ideas, I would
like to hear them.  Also, if anyone knows of a better appliance for managing
QoS at the Internet level other than the PacketShaper, I would like to hear
that as well (outside of Cisco IOS QoS).

Thanks in advance,

Matt

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