ATM (was Re: too many routes

Richard Irving rirving at
Sat Sep 13 15:43:10 UTC 1997

On Fri, 12 Sep 1997, Vadim Antonov wrote:

> Actually, 4000 miles is a very reasonable estimate for a cross-country

> path physical length.  That's why i took it as such without much
> arguments.

 I am thinking it may be, we are getting together timings, and people
are reporting the runs. The calculations are getting lower as we go.
It is starting to look 30 ish. I agree this is not as significant as
I thought it was going to be.... However, it is interesting to close in
on. ;)

> >      This implies that 39% of the actual timing is overhead.
> Hey, did you ever measure delay on a real cross-country fiber?
> Did you compare that with pings between attached routers?
> (Hint: i used to work for a long distance carrier).

 I do. And have for a while. That doesn't mean anything one way or

Why don't we knock off the I am , I was, and I will be's and lets get
answer from data coming in. ;) This thread has been joined by some
interesting people. All of which humble me, to be sure. (not that it is
difficult thing ;)

 The interesting thing is, most of these people are interested enough,
that the data is coming in... I suspect, we may be able to
get to a "reasonably" accurate ratio, but it should be interesting.

 Aren't you curious ?
 Or, do you have current data ? If so , post it.

> 74 ms you quoted is actally a nice RTT, for a loaded network
> particularly.  The first SprintLink's DS-3 between DC and
> Stockton, CA had 80 ms (that's clearline, w/o any routers in the

  We have one down into the mid 60's now. Check the archive.

> Now, would you care to explain how 0.3ms delay per router can
> make things worse, considering that the average number of
> _backbone_ hops for inter-provider trace is about 6?

 At each juncture , layer 3, exists an opportunity for routing
interaction. This is "for better" or "for worse". The better, is not
I am concerned with....

 If indeed a router, participating in full tables, only introduces .3 ms

delay, on a median, then the market bodes well.. But, I am
concerned with the "distribution of the curve" so to speak. How -wide-
it.... How do we narrow it ?

> --vadim

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