[e2e] number of flows per unit time in routers

[Clark Gaylord]

Yann Berthier wrote:

>   I would be tempted to say that uni-directional applications (which
>   are quite the minority for many networks) are just a special case of
>   bi-directional flows, with 'back' fields (number of bytes, packets
>   and so on) filled with zeros. Now that doesn't change the fact that
>   what is exported by routers is uni-directional ;), and that some
>   post-processing work is needed to match the in and out part of a
>   bi-directional flow. And i know no collector doing this job, so it
>   would have to be done after the flows have been stored on disk, which
>   seems to me rather sub optimal.
>   
>   Btw, there is now a draft for a bi-directional support in IPFIX:
>   http://www.rfc-editor.org/internet-drafts/draft-boschi-ipfix-biflow-01.txt
>  
>

For most useful analysis, both sides of a bi-directional flow are 
useful, but routing, traffic patterns, etc, are not necessarily 
symmetric either.   So flows are fundamentally unidirectional with 
bi-dir a function of synthesis.

Pedantry happens.

--ckg