Thus spake "Mathew Lodge" <mathew@cplane.com>
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