>I am not a kernel specialist, but I assume that from
>a performance point of view it would be much more performant
>to have several flows using only one socket instead of
>having a single socket for each flow?
I believe there's no performance issue here. what kind of
performace drawback do you have in mind?
I can imagine a use of multiple flow label values for single TCP/UDP
session, if:
- a single TCP session includes traffic with different characteristics,
for example, MPEG key frames (full picture) and intermediate data
(differences between Nth full picture to (N+1)th full picture)
- the application would like to enforce different RSVP characteristics
to key frames and intermediate data.
- so, application would like to label packets with key frames with flow
label X, and intermediate data with flow label Y. packets with flow
label X will have a higher priority than those with flow label Y.
i'm not sure if the above example makes sense or not.
even if the example is okay, there's absolutely no kernel performance
issue here. the reason why we use two flow label values (X and Y)
is from the applicatoin needs, not from kernel performance issues.
>An other concern is the redundancy of information in
>ports and labels.
as i noted in previous messages, the purpose of flow label value is
to provide quick lookup of L4 port pair and protocol type. so
I would say that the redundancy is expected. the redundancy is
what we really want - intermediate routers do not want to chase
extension headers to find L4 header.
itojun
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