Nick Hilliard wrote:
Are you saying you thought a 100G Ethernet link actually consisting of 4 parallel 25G links, which is an example of "equal speed multi parallel point to point links", were relying on hashing?
this is an excellent example of what we're not talking about in this thread.
Not "we", but "you".
A 100G serdes is an unbuffered mechanism which includes a PLL, and this allows the style of clock/signal synchronisation required for the deserialised 4x25G lanes to be reserialised at the far end. This is one of the mechanisms used for packet / cell / bit spray, and it works really well.
That's why I, instead of fully shared buffer, mentioned round robin as the proper solution for the case.
This thread is talking about buffered transmission links on routers / switches on systems which provide no clocking synchronisation and not even a guarantee that the bearer circuits have comparable latencies. ECMP / hash based load balancing is a crock, no doubt about it;
See the first three lines of this mail to find that I explicitly mentioned "equal speed multi parallel point to point links" as the context for round robin. As I already told you: : In theory, you can always fabricate unrealistic counter examples : against theories by ignoring essential assumptions of the theories. you are keep ignoring essential assumptions for no good purposes. Masataka Ohta