Subject: RE: Load balancing draft

From: "David Allan" <[email-masked]>
Date: Wed, 20 Nov 2002 15:26:31 -0500

George:

If you look at my post from rather late last night, I'd question the lighter
overhead assertion. This discussion is really orthogonal to the probe
frequency and is more concerned with the probe quantity/quality to determine
there is a problem. Goodness and scalability (and again my favorite "bounded
detection time") can be expressed as how authoritative a test result is in
proportion to the messages expended. Also the fewer heuristics required to
interpret the test results, the more reliable the overall system is.... 

rgds
Dave

> -----Original Message-----
> From: George Swallow [mailto:[email-masked]]
> Sent: Wednesday, November 20, 2002 11:20 AM
> To: Alia Atlas
> Cc: George Swallow; Shahram Davari; [email-masked]'; [email-masked]
> Subject: Re: Load balancing draft 
> 
> 
> > Why is it not incrementally useful?  Every LSR along the 
> path that does 
> > this decreases the cases where an OAM packet may take a 
> different route 
> > from the data packet.   It does require every LSR to implement to 
> > completely avoid OAM packets from taking different routes, but 
> > incrementally does simplify determining what happened to 
> the OAM packets as 
> > compared to the data plane packets because there are fewer 
> potential branch 
> > points.
> 
> Well if you want your CV OAM to make you pretty sure, then yes, you
> get surer as you incrementally deploy.  But most of the time you can
> be pretty sure with much lighter overhead.  So I was assuming (perhaps
> incorectly) that someone who want to send a CV OAM packet every second
> wanted to be 100% sure.
> 
> ...George
> 
> ==================================================================
> George Swallow       Cisco Systems                  (978) 497-8143
>                      250 Apollo Drive
>                      Chelmsford, Ma 01824
> 
>

---

From: George Swallow <[email-masked]>
Date: Wed, 20 Nov 2002 15:58:36 -0500

> interpret the test results, the more reliable the overall system is.... 

My only point is that if your measurement is based on the assumption
that all load-balancing is being done in a prescribed manner, then the
quality of that measurement is very much dependent on the certainty
that all of the nodes in the path are actually behaving according to
that assumption.  On node behaving differently could reroute a large
portion (or all) of the probes.  Thus the measurement could be far
from the actual behavior.  

...George

---

From: Don Fedyk <[email-masked]>
Date: Wed, 20 Nov 2002 20:13:41 -0500

George to be fair I heard Dave say  that the load balancing should not 
use certain fields which are part of the label stack. This does not 
require that balancing be done in a prescribed manner, freedom is still 
there. Instead load balancing should be correct with respect to all of 
MPLS formats  including reserved labels.

Don

---

From: George Swallow <[email-masked]>
Date: Thu, 21 Nov 2002 09:32:45 -0500

Don -

This seems to a non-sequitor.  I don't see how this comment relates to
what I wrote below.  Were you trying to answer some other message?

...George

---

From: Don Fedyk <[email-masked]>
Date: Thu, 21 Nov 2002 10:33:33 -0500

George

Let me restate. You Said "All load balancing done in prescribed manner." 
Which is certainly restrictive. The Draft for load balancing says  not 
to use certain fields. That is not the same. So I added different 
implementations for load balancing following the draft still have 
freedoms and different vendors can choose different algorithms.

Hope that makes it clear,
Don .

---

From: "Thomas D. Nadeau" <[email-masked]>
Date: Thu, 21 Nov 2002 10:58:40 -0500

>Which is certainly restrictive. The Draft for load balancing says  not to 
>use certain fields. That is not the same. So I added different 
>implementations for load balancing following the draft still have freedoms 
>and different vendors can choose different algorithms.

         Not really. If you want things to work the way the draft aspires
them to, then everyone in the MPLS domain must use the same,
predictable load balancing algorithm.  Going halfway doesn't work,
and is arguably no better than what we have today.

         --Tom

>>>>from the actual behavior.

Success is relative; the more success, the more relatives. -Anonymous