Subject: [Ospf-wireless-design] next steps in simulation: performance metrics

From: "Henderson, Thomas R" <[email-masked]>
Date: Mon, 14 Mar 2005 19:23:19 -0800

In our previous work, we have been principally concerned with two
metrics:
- Overhead (bits/sec)
- Data delivery ratio (fraction of packets successfully delivered).
(NOTE-- delivery failure may be due to the lack of a physical path,
unlucky transmission, or lack of the forwarding tables knowing of a
viable path).

We have also been concerned with sensitivity to correct parameter
(timer) configurations, such as Hello and PushBack Interval.

In the methodology section of our report, we also described a number of
additional performance metrics:
- routing stretch (either for data or for the flooded control packets)
- load distribution
- processing or complexity of algorithm
- convergence time (how to define this?)
- stability of routing tables, neighbor sets, or relay node sets

Richard has evaluated his proposed algorithms in terms of:
- size of CDS (relative to number of nodes)
- number of adjacencies (relative to number of possible edges)
- adjacency change rate (relative to edge change rate)
- computational complexity

The recent discussion on the list included such items as:
- convergence time (or response time)
- ability to work with partial topology information
- the time (latency) required to bring up large numbers of adjacencies
when a relay node changes
- load/power sharing between nodes (as in, SI-CDS nodes may use more
power)
- sensitivity to neighbor's behavior (Acee's "hokey-pokey" effect)
- sensitivity to 2-hop neighbor information being correct/consistent

Separately, Cisco has suggested separating packet loss into a) losses
due to partitioning, and b) losses due to stale/incorrect routing
information.  However, this has historically been challenging in
wireless simulations, because links (neighbor transmission paths) are
only probabilistically present.

It may be nice to isolate the performance properties due to learning
2-hop info via Hellos vs. LSAs.

NOTE-- not all of the above can be investigated in the timeframe that we
have, so I hope that we can prioritize among the above options.

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From: Richard Ogier <[email-masked]>
Date: Wed, 16 Mar 2005 09:38:04 -0800

It just occurred to me that for some of the performance metrics,
e.g., rate of new adjacencies, you don't have to compute routes
and therefore can probably simulate a larger number of nodes!
I think this would satisfy my previous concern about not being
able to simulate larger networks, if you can simulate 100 (or more)
nodes for metrics that do not require route computation.

Richard