[c-nsp] how "fast" is L2TP "fast switching" under 12.3T?

[Alex Rubenstein]

> Here is something you can do to eliminate the UDP problem, set the MTU on
> the PPPoE link to 1452, now you are going to guaranty that no fragmentation
> is not happening. I have not been brave enough to try this, since I don't
> know what will stop working :-) If you try this, let me know how it works.


This is not a guarantee at all. Assume for a moment:

(windows host)---ethernet----(soho-router)---pppoeoatm----(ISP router)


While the ISP router during the ppp negotiation phase will tell the 
soho-router a MTU/MRU of whatever you ask (1400, 1452 or whatever), the 
windows host has no idea what going on regarding the MTU there.

You are making the assumption that PMTUD works, and, well, thats a wild 
assumption.




-- Alex Rubenstein, AR97, K2AHR, alex at nac.net, latency, Al Reuben --
--    Net Access Corporation, 800-NET-ME-36, http://www.nac.net   --