Subject: [IMRG] Re: Discovering alternate routes between two hosts & source routing?

From: Mike Lloyd <[email-masked]>
Date: Tue, 03 Jun 2003 13:08:26 -0700

Yeggy,

Yeggy Easwaran <[email-masked]> wrote:
 > I would like to know if there is any means to discover
 > alternate routes on the internet between two hosts that are
 > connected and maybe reroute the packets along an alternate
 > route that is less lossy/congested or one that offers better
 > bandwidth than the default route. How popular/feasible is
 > source routing?  Thanks a bunch

I make technology for problems of this sort.  As others have observed, 
the available products for this tend to focus on the boundary of a 
single autonomous system.  There are economic reasons for this, but in 
the context of this list, there are also pragmatic, network-based reasons.

As others have said, source routing is not generally welcome for end to 
end control of routed paths through other peoples' networks.  If you're 
interested in network paths where source routing is viable, great, but 
few people are.

In general, what we've learned is that it's very beneficial to design 
your measurement technique and control technique to operate together, 
and in (roughly) the same place.  For example, one great choke-point to 
look at is where you hook up to your ISPs.  Sending packets up the 
various wires can be shown to have a great deal of impact on the end to 
end path, and hence on end to last mile path characteristics.

I don't want to belabour the marketing point, though.  I'm just 
suggesting that, as you think about this kind of rerouting, it's a good 
idea to first identify where in a network you can find a powerful 
control point.  (It's attractive to imagine every hop in the network 
doing this, but that's extremely hard, not least for flap control, loop 
suppression, etc, etc.)

Once you've found a control point, you need to measure alternate routes; 
as noted, source routing can sometimes be used, but doesn't cover many 
cases.  As a result, you probably need a specially configured 
measurement technique that avoids existing routing.  Here again, the 
edge of an autonomous system is a good default choice - there's a 
limited number of choices to measure.  The configuration change is not 
altogether trivial, which is another reason to limit the number of 
control points you look at.

Hope this helps shed at least some light
Mike Lloyd
CTO, RouteScience

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From: Kave Salamatian <[email-masked]>
Date: Tue, 3 Jun 2003 22:30:31 +0200

Of interest for the measurement community.

			Call for Participation!

                      INTIMATE 2003
		(INternet TraffIc MAtrices Estimation)
                   Paris, France
             http://adonis.lip6.fr/intimate2003/

The INTIMATE (INternet TraffIc MAtrices Estimation) workshop will be be held
in Paris in June 16 and 17th, 2003. INTIMATE Workshop is focused on traffic
matrices estimation techniques.  The idea behind this workshop is to bring
together people working, not just generally in network tomography, but more
specifically on traffic matrices. Because traffic matrices are the input to
most traffic engineering applications, this area is very important to
carriers and ISPs. Recent research has revealed that this problem area is
rich and raises a variety of challenging technical difficulties for
researchers. The goal of this workshop is to provide a forum for researchers
to carry on detailed discussions while sharing ideas and problems. This
workshop is by invitation only and will be limited to approximately 50
people in order to keep it small so that much discussion can take place. At
least 2 major tier-1 ISPs (Sprint, AT&T) and one historical European telco
(FT) will participate providing their perspective on applications and needs.
It will be a 2-day workshop with 2 panels and a series of invited talks. We
will cover the following topics:

.	Statistical and non-statistical estimation methods
.	Methods for generating good starting points for estimation
.	Stationary and non-stationary traffic matrices, temporal issues
.	Validation Methods and Problems
.	Modeling Assumptions
.	Scalability Issues for Estimation and Validation
.	Applications
.	Impact of errors in traffic matrix estimation on traffic

We have actually up to 14 invited speakers among the most renown networking
researchers. We target an attendance level of 50 participants.  Registration
is open NOW.  Please make hotel reservations as soon as possible.

					Kave Salamatian
				Local organiser of  INTIMATE workshop