From: Tim (ccie2be@nyc.rr.com)
Date: Mon Aug 21 2006 - 16:07:13 ART
Hey Elias,
Thanks kindly for that added perspective.
That's the kind of info one typically doesn't find in Cisco published
material.
Based on what little I know about MPLS that makes a lot of sense.
Thanks, Tim
_____
From: Elias Chari [mailto:elias.chari@gmail.com]
Sent: Monday, August 21, 2006 2:58 PM
To: Tim
Cc: Chris Broadway; ccielab@groupstudy.com
Subject: Re: MPLS speed -- switching vs IP routing
Hi Tim,
Just to add add a point which may interest you. With MPLS the intelligence
is pushed to the edge (PE routers) whilst your core (P routers) just does
the switching. The PE and P routers will use an IGP normally ISIS (or OSPF
in some cases) to build the Global Routing Table, which normally contains
internal network prefixes. This means that the routing table of the core can
be very small in comparison to the PE routers which will run MP-iBGP to
exchange vpnv4 routes and maintain VRFs.
The result of this is that the core is not overloaded with protocols such as
MP-iBGP, RSVP (for MPLS-TE) and large routing tables as all of that is done
at the PE level. One could argue that as less resources are consumed in the
core, it can switch traffic more efficiently.
Having said that the control and forwarding plane are separated in
distributed architectures such as the GSR 12k, however this undoubtedly
helps even in such cases.
Rgds
Elias
On 8/21/06, Tim <ccie2be@nyc.rr.com> wrote:
Hey Chris,
Thanks much.
I had a feeling that what you described was the case but it's great to have
confirmation from someone who is obviously much more knowledgeable about
this than I am.
Tim
_____
From: Chris Broadway [mailto:midatlanticnet@gmail.com
<mailto:midatlanticnet@gmail.com> ]
Sent: Monday, August 21, 2006 12:18 PM
To: Tim
Cc: ccielab@groupstudy.com
Subject: Re: MPLS speed -- switching vs IP routing
Back in the old days of using the 7500s, MPLS (tag switching) was faster
than routing due to the method of route lookups. Modern routers do not look
up routes the same, so there is really no speed diference between layer 3
and layer 2 lookups. But, when you read up on MPLS, they still state speed
is a reson to use it. The real reson to use MPLS is the services that you
would use on top of it.
-Broadway
This archive was generated by hypermail 2.1.4 : Fri Sep 01 2006 - 15:41:58 ART