Date: Tue, 9 Apr 2002 07:13:38 +0200 From: Jesper Skriver <jesper@skriver.dk>
We're talking parallel GigE links between switches which are located close to each other.
And we're talking real life applications, which perhaps sends 100 pps in one stream, which means that you need to have ~ 10 ms different transmission delay on the individual links, before the risk of out of order packets for a given stream arise.
Hmmmm. You're right. I lost sight of the original thread... GigE inter-switch trunking at PAIX. In that case, congestion _should_ be low, and there shouldn't be much queue depth. But this _does_ bank on current "real world" behavior. If endpoints ever approach GigE speeds (of course requiring "low enough" latency and "big enough" windows)... Then again, last mile is so slow that we're probably a ways away from that happening.
IIRC, 802.3ad DOES NOT allow round robin distribution;
That is not what we're talking about, we're talking about the impact of doing it.
Yes, I was incomplete in that part. Intended point was that IEEE at least [seemingly] found round robin inappropriate for general case.
it uses hashes. Sure, hashed distribution isn't perfect.
It's broken in a IX environment where you have few src/dst pairs, and where a single src/dst pair can easily use several hundreds of Mbps, if you have a few of those going of the same link due to the hashing algorithm, you will have problems.
In the [extreme] degenerate case, yes, one goes from N links to 1 effective link.
A large IX in Europe have this exact problem on their Foundry swiches, which doesn't support round robin, and is currently forced to moving for
Can you state how many participants? With N x GigE, what sort of [im]balance is there over the N lines? Of course, I'd hope that individual heavy pairs would establish private interconnects instead of using public switch fabric, but I know that's not always { an option | done | ... }.
10 GigE due to this very fact.
I'm going to have to play with ISL RR...
/Jesper
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