Thus spake "Mathew Lodge" <[EMAIL PROTECTED]> > At 03:48 PM 4/10/2002 +0100, Peter Galbavy wrote: > >Why ? > > > >I am still waiting (after many years) for anyone to explain to me > >the issue of buffering. It appears to be completely unneccesary > >in a router. > > Well, that's some challenge but I'll have a go :-/ > > As far as I can tell, the use of buffering has to do with traffic > shaping vs. rate limiting. If you have a buffer on the interface, > you are doing traffic shaping -- whether or not your vendor calls > it that. ... If you have no queue or a very small queue ... This is > rate limiting.
Well, that's implicit shaping/policing if you wish to call it that. It's only common to use those terms with explicit shaping/policing, i.e. when you need to shape/police at something other than line rate. > except for the owner of the routers who wanted to know why > they had to buy the more expensive ATM card (i.e. why > couldn't the ATM core people couldn't put more buffering on > their ATM access ports). The answer here lies in ATM switches being designed primarily for carriers (and by people with a carrier mindset). Carriers, by and large, do not want to carry unfunded traffic across their networks and then be forced to buffer it; it's much easier (and cheaper) to police at ingress and buffer nothing. It would have been nice to see a parallel line of switches (or cards) with more buffers. However, anyone wise enough to buy those was wise enough to ditch ATM altogether :) S
