[c-nsp] mpls-te - dynamic latency?

[christian.macnevin at uk.bnpparibas.com]

Sadly, the prefixes aren't going to be that easy to extricate from one 
another. We have no guarantee that a given subnet
won't contain hosts who want market data / soft phone / video conf  / 
message block data as well as web and email
traffic. Hence, our best bet is a routing mechanism which can forward 
based on dscp marking.

I can't be the only one - there must be loads of people on here who can 
see a need for layer 4 routing in large networks.
Most organisations want to be able to use all the links they've paid for, 
and this gives them the chance to do it, and remove
invisible mechanisms like PBR, and potentially sidestep requirements for 
more technology like TE.





Internet
oboehmer at cisco.com

06/04/2006 16:26

To
Christian MACNEVIN
cc
cisco-nsp
Subject
RE: [c-nsp] mpls-te - dynamic latency?






christian.macnevin at uk.bnpparibas.com
<mailto:christian.macnevin at uk.bnpparibas.com> wrote on Thursday, April
06, 2006 12:22 PM:

> Not dealt with african providers before have you? :) Unfortunately,
> VSAT is a fact of life for many, and the shortage 
> of fat pipes in the big continent requires live/live configs. Much as
> I hated it at first, we gotta move on and find a way. 

I know, I know, hence the ";-)" behind my comment..

> I've been looking at the MTR stuff, and frankly it looks like a dream
> come true. Chetan tells me we're looking at 2007 for 
> the first release though, so we're going to need some black magic in
> the meantime.

sounds about right, and you need this on all platforms involved..

> Incidentally, I'd recommend a few 
> people take a look at this, because others must be suffering some of
> the same pain we are, and if this looks like a solution 
> to others as well, it'd be good if Cisco realised customers had
> interest in the availability of application-layer routing
> capabilities without the evil.

Ack, and this is where MFR could fit in (as far as I understood, don't
know too much about MTR)..

> Looking at OER, it seems like it'll still only work on destination
> prefix - ie: no layer 4 awareness. Not true? 

Right, OER modifies the RIB, hence it operates on L3.

The question is whether you have any option moving this from L4 to L3 by
using distinct prefixes/addresses for your sensitive traffic. Then you
can use routing mechanisms to steer the traffic either way (I think I
made an error mentioning PBR with TE on a PE, don't think this will
work). 

PE-PE TE tunnels with a modification of the BGP next-hop could do the
trick here. As a rough idea:
- create a new loopback address on each PE
- Full mesh of PE-PE TE-Tunnels with two path-options: #1 goes via
explit-path along the low-delay links,  #2 uses any path in case #1 is
not available. no autoroute, no FA, enable LDP on the tunnel
- statically route the loopback to the tunnel
- set the BGP next-hop for the "voice" BGP prefixes to the new loopback
routed via the Tunnel. you could do this next-hop rewrite based on acl,
community, etc.. it could get more complicated if you have multi-homed
sites (you do) and you are using RRs as the new next-hop obviously
depends on which remote PE advertised the prefix..

                 oli



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