[nsp] Prioritisation of VoIP

[Vincent De Keyzer]

Tim,

thanks.

If you (or anybody else) are willing to help further, please see below...

> In general you don't need the VoIP gear to do anything other 
> than generate packets that you can recognise as being VoIP.  
> If your addressing plan is such that the phones are all in 
> their own subnets, this is easy - you can identify by IP 
> address.  Otherwise you'll have to look at ports / protocols 
> / existing markings to spot the traffic.

Indeed. And what is the best way to do this? Look for UDP/RTP? How?

> On the router, you can the classify the traffic as "VoIP" or 
> "other".  Look at CBWFQ with LLQ - the VoIP goes in the 
> "priority" (LLQ) queue, everything else goes in one or more 
> CBWFQ queues.  You'll probably want to mark (DSCP or 
> IPPrecedence) on the way out so you can tell which traffic is 
> which elsewhere in your network without having to repeat the 
> classification ACLs you used earlier.

Can you give me an example of config, or is it too long? Something like 
what do I need on the CPE, and what do I need on the access router?

Since the potential congestion is on the WAN.

> If your core's congested, you'll need to use those markings 
> in the core to affect your queueing behaviour there.
> If the LAN is congested, you'll need to look into 802.1p on 
> your L2 gear and check that the VoIP gear can mark appropriately.

Core's not congested, LAN is not congested either, so that's cool. 

> The Cisco Press "IP Quality of Service" (Srinivas Vegesna) is 
> well worth a read.

That's what I am trying to avoid by asking knowledgeable people... 

;)

V