Subject: RE: [bmwg] Is the BMWG a proper home for this I-D?

From: [email-masked]
Date: Wed, 14 Apr 2004 18:28:31 -0400

Both of these proposed definitions are incomplete.  Convergence does not
occur until the traffic is correctly routed out the correct interface, which
means in today's routers the FIB must be updated in an ASIC at the line
card.  Remember - SP customers do not observe route table changes due to
cvonvergence, they observe traffic loss.

Scott

-----Original Message-----
From: Russ White [mailto:[email-masked]]
Sent: Wednesday, April 14, 2004 3:50 PM
To: Howard C. Berkowitz
Cc: [email-masked]
Subject: Re: [bmwg] Is the BMWG a proper home for this I-D?

But reachability doesn't always imply convergence (?). In other words, you
may reachability along some suboptimal path, and the routing protocol could
still be churning away finding the best path through some other direction.
So, that's why it's important to define convergence as "when all the
routers in the network have found (and agree on) the best path through the
network," or "when the destination is reachable."

I'm okay with both definitions, but it's important to define which meaning
you're using when you discuss a specific testing procedure.

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From: Russ White <[email-masked]>
Date: Wed, 14 Apr 2004 18:33:34 -0400 (Eastern Daylight Time)

> occur until the traffic is correctly routed out the correct interface,
> which means in today's routers the FIB must be updated in an ASIC at the
> line card.  Remember - SP customers do not observe route table changes
> due to cvonvergence, they observe traffic loss.

Well, that's the difference between a benchmark in a lab and in the real
world, I'd think. In a lab, when evaluating a particular implementation, I
can care very much more about actual total rp convergence than about
dropped packets. You have dissect a frog as well as observe it to
understand it, you can't just ask "how far does it jump," or "how fast."

IMHO, the concept of convergence is very flexible, and we should define
within the context of the document at hand, rather than trying to nail down
a specific definition of the word.

:-)

Russ

__________________________________
[email-masked] CCIE <>< Grace Alone

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From: Russ White <[email-masked]>
Date: Wed, 14 Apr 2004 18:33:34 -0400 (Eastern Daylight Time)

:-)

Russ

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From: "Howard C. Berkowitz" <[email-masked]>
Date: Wed, 14 Apr 2004 20:49:57 -0400

At 6:28 PM -0400 4/14/04, [email-masked] wrote:
>card.

You are making an assumption here about the platform: that it 
contains both control and forwarding planes. As the best-known 
exception to this, consider an RSD-type route server.  I suppose one 
could say it forwards self-generated updates, but it certainly 
doesn't forward user traffic or have any meaningful sort of FIB.

It's also plausible to speak of even more distributed routing 
architectures, where one control plane instance (perhaps with 
failover) controls many forwarding instances.  While it's outside 
BMWG scope (I thinK), there are some interesting further 
complications introduced by MPLS.

>Remember - SP customers do not observe route table changes due to
>convergence, they observe traffic loss.

User-oriented performance, I would suggest, is an entirely different 
beast than benchmarking, or even inter-provider measurement. Network 
eons ago (1980-ish), I worked on the ANSI X3.102 and X3.141 standards 
for specifying performance with respect to end users. The 
architecture of these measurements was subsequently absorbed into 
then-CCITT X.140, and specific measurements for circuit- and 
packet-switched services in the X.130 series.

User-oriented performance parameters, however, were truly independent 
of the underlying transmission system. The other documents described 
measurement techniques for specific systems, mostly using what we 
call black box testing.

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From: "Howard C. Berkowitz" <[email-masked]>
Date: Wed, 14 Apr 2004 20:49:57 -0400