[c-nsp] prioritize VoIP and Skype traffic in office routers

[Chuck Church]

Martin,

	It depends on your ISP connections.  If Ethernet, then it's probably
rate limited by ISP in one or both directions.  If so, plain prioritization
won't help alone, you'll need to police/shape yourself, but send the
VoIP/Skype first.  It's do-able.  If your circuits are T1 or something else
that is essentially line-rate to/from you, then prioritization alone will
work.  NBAR is good for VoIP, Skype I'm not so sure about, haven't tried it.
Changing the CEF load sharing won't have any effect.

Chuck

-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net
[mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Martin T
Sent: Wednesday, February 01, 2012 10:57 AM
To: cisco-nsp at puck.nether.net
Subject: [c-nsp] prioritize VoIP and Skype traffic in office routers

I would like to improve packet processing prioritization in case of
temporary congestions in my gateways(Cisco 1842,
C1841-ADVIPSERVICESK9-M) which are serving two small offices in different
cities. My ISP(same for both offices) does not support RSVP so I can't make
any RSVP requests. In addition, they do not support prioritization based on
DSCP or TOS field values. VoIP gateways are located in office LAN's.

So far I have came up with following ideas:

1) Process packets passing the router using CEF("ip cef" in global
configuration mode). Should I consider changing the load-sharing algorithm?
At the moment I use "universal" load-sharing algorithm for CEF.

2) Change interface queuing strategy(currently it's FIFO) for all Fast
Ethernet interfaces in gateways. There are many possibilities like Custom
Queuing, CBWFQ, Priority Queuing. "Priority Queuing" seems to be especially
appealing in this scenario- Skype and VoIP traffic would have the highest
priority and there isn't a worry that they could take all of the available
bandwidth. Any opinions here? Is Priority Queuing a smart decision here?

3) use WRED


For classifying traffic I would use NBAR for
Skype(http://www.cisco.com/en/US/docs/ios/12_4t/qos/configuration/guide/qsnb
arrm.html)
and transport layer protocol + port numbers for VoIP.

Which interface buffer queuing would be the best in described scenario? Are
all three methods reasonable?

PS if any additional information is needed, feel free to ask!

regards,
martin
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