Hi Brian,
>The draft is intended to allow several *simultaneous* usage scenarios to
>coexist. Yours is one of them. Diffserv is another. RSVP, and potentially
>NSIS and the recent RSVP2 proposals are others.
I don't believe the draft achieves this goal, and I don't personally
believe that we should even be trying to achieve this goal.
No amount of hand-waving or careful wording will make the load
balancing and diffserv uses of the flow label compatible with one
another.
Load balancing routers want to make balancing decisions based on the
value of the flow label field, with no other signaling required. A
very simple mechanism (such as hashing the flow label field) will
allow load balancing routers to consistently send packets from a
single flow over the same path. This offers a couple of big advantages:
- It reduces packet reordering, potentially resulting in
significant performance increases.
- It makes the PMTU mechanism work better, since packets
for a single connection will take a consistent
path.
But, for this simple mechanism to work, load balancing routers have to
be able to rely on the fact that the flow label will label a _flow_
(one direction of a TCP, UDP or SCTP connection).
Your proposal says that, instead of containing a flow label, the flow
label field may be used to hold a diffserv traffic class, or some sort
of NSIS value, or other yet-to-be-defined values...
If this is the case, how are the load balancing routers supposed to know
whether or not the flow label actually contains a flow label?
Certainly, we don't want load balancing routers performing their balancing
operations based upon the traffic class of each packet, or whatever values
have been inserted in the field by other, yet-to-be-defined mechanisms.
Margaret
--------------------------------------------------------------------
IETF IPng Working Group Mailing List
IPng Home Page: http://playground.sun.com/ipng
FTP archive: ftp://playground.sun.com/pub/ipng
Direct all administrative requests to [EMAIL PROTECTED]
--------------------------------------------------------------------
