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
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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participants (3)
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lazear＠dockside.mitre.org -
Mervyn Frankel -
mfox＠wellfleet.com