Subject: Flow cache sizes

From: [email-masked] (Noel Chiappa)
Date: Fri, 2 Dec 94 00:44:04 -0500

From: Curtis Villamizar <[email-masked]>

    We have seen close to 8,000 active destination host addresses in random 90
    second data samples (samples taken about 6 months ago).

This number unfortunately doesn't tell us what we want to know, in that we
don't know how many of those 8K were caused by what I call datagram traffic
(i.e. one-shots such as DNS), and how many were part of things which would be
candidates for flows. E.g., to use some totally made-up numbers, 80% of those
references could be caused by 20% of the traffic (to use the canonical random
numbers for this sort of thing :-).

    If we start routing on flow IDs and flow IDs are unique per TCP
    connection, I think we are going to have a space requirement explosion.
    That is also why I think connection oriented will eventually fail to
    scale.

This is something to be concerned about, but so far nobody has explained to me
what the bug is in the argument that the growth in the number of active
connections (i.e. ones that need to be stored in caches for acceptable
performance) through any switch will be limited by the growth in the bandwidth
through the switch.

Also, it's true that cache size will grow as the *square* of the feature size,
whereas speed goes only as the feature size, right? Doesn't this mean that
things will get better, not worse, at higher speeds? Where's the bug here?

	Noel