6MAN Participants,
During IESG evaluation, a DISCUSS position was raised on whether or
not several of the bits (4 was suggested) be reserved as a discriminator
to identify how the flow label is being used. We had a discussion in
2010 on separating the current 20 bits of flow label into sub-fields
(discussion started around this point in the mailing list archives :
http://www.ietf.org/mail-archive/web/ipv6/current/msg12031.html).
The consensus from that mailing list discussion was to not divide
the flow label for several reasons:
1. Encoding semantics was too complex to handle at line rate
2. A 16-bit flow label may be too easy to predict
3. These fields are not protected in anyway, so there is little trust in
the values set
The above reasons led to the decision to retain the flow label as a
single 20-bit field as it is currently defined in 3697bis. Since this
is a DISCUSS position, the goal of this message is to educate the IESG
on our line of thinking and allow other WG participants to chime in with
other reasons I have omitted for keeping the flow label a single entity
within the IPv6 header.
Regards,
Brian
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