Mailing List Archive: Route path simulator

Route path simulator

Jun 2, 1994, 7:40 AM

Post #1 of 3 (1165 views)

Sorry for the cross posting but I thought input from all these groups might
be beneficial.

I'm looking for some type of simulation program that would enable a network
manager to view the route taken by packets in a complex IP network that
utilizes more than just hop-count metrics. Imagine a 100+ node network with
link metrics ranging from 1 to 2000. The goal is to determine (quickly and
easily) the path taken by a packet from any particular source point to any
particular destination point without having to manually add up all of the
metric combinations to determine the least cost path. Another goal is to be
able to create a link failure and observe the new least cost path. Another
goal is to be allow what-if scenarios where the network manager can change
the metric on a given link(s) and see the result.

Input to the simulation could be as simple as a flat file of point-to-point
links and their associated metrics. Output could also be a character-based
flat file. Graphical I/O would be ideal. Note: I'm not particularly
interested in simulating traffic patterns with varying inter-arrival rates
so something like Bones or CACI Network-II might be overkill. Besides, I
don't even know if they can provide what I'm looking for above (can they?).
On the other hand, viewing traffic patterns might come in handy later. Hmmmmm.

Any suggestions?

Michael Fox

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Re: Route path simulator [ In reply to ]

sidhu at umbc

Jun 2, 1994, 12:24 PM

Post #2 of 3 (1142 views)

Permalink

Such a tool exists for seeing a packet path from any point to
any point in large internets. For information about this tool,
write to
telenix@access.digex.net
or call
410-750-2253

This tool has powerful features to specify scenarios and capacity
planning and management features.
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Re: Route path simulator [ In reply to ]

lazear at dockside

Jun 2, 1994, 12:46 PM

Post #3 of 3 (1135 views)

Permalink

As one approach to seeing whether a group of routers were acting
correctly, I wrote some code to trace all possible routings in
a network. The basic approach was to gather (via SNMP) all the
routing tables of all the routers (SNMPv2 GetBulk could help keep
this reasonable) and run through the routes for each subscriber
net to every other subscriber net. This presumed a backbone set
of routers and a known set of networks behind each "POP" router.

The program took less than a second on a Sparc ELC, for 30+
routers and 100+ subscriber nets. The program highlighted long
routes, loops (such as when defaults point to defaults that
point back...), and dead ends. The diameter of the network was
settable and "long" was defined as some amount above the diameter.

The intent was to discover that "reasonable" routing was
happening...there was no intent to insist on optimal routing.
The snapshot of routing tables could be a blurred one, as
dynamic routing protocols could be changing routing tables during the
period of table collection. The same effect could be achieved
by doing "traceroutes" from every subscriber network, but this
gets messy.

Overall, it was a fun exercise and the operational requirement was
that you identify where each network attached to your backbone.
Then you look at actual routing tables to see that your routing
protocols were being reasonable about service.

The program has been packaged and is available online:

ftp://aelred-3.ie.org/pub/chkrtr.tar

Enjoy and let me know any reactions to the scheme.

Walt
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