Michael Thomas wrote:
> ... snip
> > What doesn't work is if there may be non-zero values in
> the flow label > that actually don't label flows. How is a
> load-balancing or load-spreading > router supposed to know
> that this isn't a flow label?
>
> Er, well, it _doesn't_. I guess I just don't
> attach any special meaning to the word "flow";
> that is, a flow is whatever the host says is a
> flow. If it's bizarre, then well, why should
> the router care? Again, other than maybe gaming
> fair queuing algorithms[*], why do routers
> actually care about what constitutes the
> sematics of the flow? It's really in the host's
> best interest to be network friendly, right? To
> give routers information which increases the
> probability of forwarding its packets in the
> manner it hopes for, right?
>
> ... snip
> Er, but the flow label *is* an element of a
> packet classifier, or rather perhaps a
> replacement for the current method of classifying
> packets. I thought as far as routers are
> concerned, flow label were opaque and that no
> internal semantics were visible.
>
Mike is right, as far as middle-boxes are concerned the FL is opaque
unless they have been given specific state to believe otherwise. There
is no reason a load-spreader would have a problem with frequent reuse,
or even all nodes deciding to use the same value for HTTP as long as it
is basing its decisions on the Src/Dst/FL rather than just the FL.
I do have comments on the text. I would like to see the following
changed from:
4. Flow Labeling Requirements
(4) The source SHOULD assign each new transport connection (e.g.
TCP, SCTP) to a new flow.
to:
(4) The source SHOULD assign each unrelated transport connection (e.g.
TCP, SCTP) to a new flow.
This would keep it from conflicting with (3).
5. Flow State Establishment Requirements
...
To enable co-existence of different methods in IPv6 nodes, the
methods MUST meet the following basic requirements:
...
(3) The IPv6 node facility keeping track of the Flow Label and the
associated Source and Destination Addresses MUST be utilized
when assigning Flow Label values to new flows (see section 4
above).
That wording seems awkward, how about:
(3) The IPv6 source node MUST provide a facility for keeping track
of the Flow Label values associated with particular Source and
Destination Addresses for use when assigning Flow Label to new flows
(see section 4 above).
Tony
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