The MPLS-OPS Archive

["Eric Osborne" <eosborne@cisco.com>]

On Fri, 7 May 2004 15:18:28 +0100, Mark Gibson <Mark.Gibson@cramer.com>  
wrote:

> I'm attempting to understand how RSVP-TE signalled MPLS-TE tunnels and  
> CoS
> on MPLS networks interwork on Cisco gear (at the moment).
>
> As I understand it, an RSVP-reserved tunnel causes a fair queue to be
> created each time a reservation is created, proportional to the size of  
> the
> bandwidth signalled and is essentially flow-based (the flow being the
> tunnel)

This is true with traditional RSVP (for multicast, etc) but not for TE.   
In TE, the RSVP reservation is purely control-plane, and there's no  
forwarding-plane interaction.

>
> With MPLS-DS I can set up CB-WFQ at each PE and P router for each class.
>
> My question is this:  If I set up CB-WFQ to include a best-effort class  
> and
> then signal an RSVP-TE tunnel, does its reservation get made in the BE  
> chunk
> of the CB-WFQ?  Or does it create its own fair queue as before?
>

An RSVP reservation for TE is just control plane; any forwarding-plane  
traffic treatment you do has to come from diffserv.

>
> In the same vein, without using GB-trunks and configuring sub-pools, how  
> do
> I integrate MPLS CoS and TE tunnels?  Can I create a tunnel (with or  
> without
> a reservation), create a route map that maps packets on to this tunnel  
> and
> assign them an EXP bit with a p-map and have that priority served across  
> the
> length of the tunnel?

Today, you can do this with policy routing (PBR), and, to a limited  
extent, by playing games with stuff like BGP next-hop.

>
> It seems theoretically possible to do this from the RFCs, providing that  
> the
> reservation made at the RSVP-TE layer is just a control plane  
> reservation. I
> note that RFC3564 talks about integrating Class Type and setup/hold  
> priority
> in RSVP-TE signalling but I see no reference to an implementation that
> supports this.   I'd like to understand how CoS level reservation in an  
> MPLS
> network is put into practice.

In this regard, think of a TE tunnel like a GRE tunnel, in that the GRE  
tunnel doesn't reserve anything from the network that carries it.  Don't  
take the analogy too far, or your head will hurt, though. :)



eric

>
> Cheers
>
> Mark
>
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