Subject: RE: MPLS Performance analysis.....

From: [email-masked]
Date: Thu, 1 Jun 2000 11:59:02 -0500

> Can we now stop trying to either ressurect the disproven claim
> about lookup speeds, and also stop trying to pretend the claim
> was never made? I'd like to fall asleep at my desk again.
> 
I agree - sleep would be good. For those who need some motivations
for MPLS, read Traffic Engineering requirements and "Motivation" 
section in the framework document. There is some text on lookup 
performance, too.

Pasi

---

From: "J. Noel Chiappa" <[email-masked]>
Date: Tue, 6 Jun 2000 21:28:08 -0400

> From: "Dmitri Krioukov" <[email-masked]>

    > has any dynamic routing protocol research been done outside of the
    > distance vector and link state approaches?

That depends on what you mean by "distance vector" and "link state".

I suspect by the former you really meant "destination vector" (i.e. you get a
basically complete routing table [i.e. vector] from your neighbours), not
"distance vector" (which should properly be applied only to destination
vector routing protocols which provide only a metric, e.g. RIP). I know, the
terminology is confusing.... Note that BGP is a "destination vector" routing
protocol, but not a "distance vector" routing protocol; it's classified as a
"path vector" protocol since it provides a complete path for each listed
destination.

Same thing for "link state". That term should properly only be applied to
protocols which distribute a map to all players, then all the entities
participating, in parallel, compute complete routing tables from the map.
The path selection is hop-by-hop (i.e. each entity independently picks the
next hop for each given destination). (Note that everyone has to have
basically the same map [moulo area issues], and use the same path selection
algorithm, or the packets go in little circles.... :-) The "new" ARPANet
routing algorithm was the first LS routing algorithm; IS-IS and OSPF are both
LS algorithms.

There are also a whole class of routing architectures which distribute maps
(like LS), but which *don't* have the hop-by-hop path selection. (I've used
the term "map distribution" to cover both LS and these other architectures,
but there's no general term that I know of to over just this latter group.)
IDPR was the first one of these I know of in the Internet community, and
there are more (e.g. PNNI).

In general, I think you can slice routing protocols two ways:

i) what the data being passed around looks like; either maps (MD) or
routing tables (DV)

ii) how the path is selected; in basically one place (called "explicit"),
or in a peer distributed fashion ("hop-by-hop").

You can mix these two orthagonal axes and produce a four-way division. If
anyone knows of any good design that *doesn't* fall into one of these
categories, I'd be very interested to hear of it.

Then there are a few other wierd odds and ends; the "hot potato" algorithm
proposed (IIRC) in Baran's original paper, so-called "flooding" algorithms
(send a copy to everyone - not much of a routing algorithm, I know :-), etc,
etc.

	Noel

---

From: Bora Akyol <[email-masked]>
Date: Wed, 7 Jun 2000 11:56:46 -0700

Yakov,

It is a well known fact at this point we can make IP lookups as fast we can
do MPLS lookups.

So the lookup speed advantage of MPLS does not exist anymore which I believe
was the point that was being raised.

Bora (just catching up with my old mail)

> -----Original Message-----
> From: Yakov Rekhter [mailto:[email-masked]]
> Sent: Monday, May 29, 2000 4:14 AM
> To: [email-masked]
> Cc: [email-masked]
> Subject: Re: MPLS Performance analysis..... 
> 
> 
> Sean,
>  
> > Several people write:
> > 
> > > [lots of commentary about how wonderful MPLS is at making 
> forwarding fast]
> > 
> > You are analysing the performance of MPLS using the wrong metric.
> > I think MPLS performs exactly as intended.
> > Ipsilon basically died, and not even Nokia could revive it.
> > UUNET found a new layer-2 religion, essentially killing 
> backbone ATM.
> > Many companies are distracted from actually learning how to 
> do IP routing.
> 
> Of course, for some folks the *one and only* way to move data is by
> looking at the IP header, and executing the longest match algorithm on
> the destination address in that header (aka "destination based
> routing"). Anything else (e.g., MPLS), *regardless* of its pragmatic
> value, is viewed as "religion", "distraction", etc... 
> 
> Yakov.
>