[e2e] number of flows per unit time in routers

[Clark Gaylord]

Ghanwani, Anoop wrote:

>I have a very basic question -
>
>Is there industry consensus on what constitutes a flow?
>Theoretically, it could be some arbitrary bit mask being
>applied to every packet.  However, in practice people talk
>about TCP flows, UDP flows, ICMP flows, etc.  Just wondering
>if there is a comprehensive list of these anywhere.
>  
>

You could read more from the ipfix group, but basically cisco got the 
definition right with netflow.  This gets messy with non-TCP traffic, 
but what are you gonna do?  "The five-tuple" is the usual shorthand 
(dst/src address/port + protocol).  Non-port protocols either have 
something similar (a la icmp message) or ignore the port field.  Note 
that a flow is uni-directional, so some have tried to define the 
bi-directional pair, but that gets dicey since there are plenty of 
applications (e.g. multicast streaming) that are inherently 
uni-directional.  Of course, multicast is a bit of a special case anyway.

--ckg