Some additional information on the use of the IPv6 flow label with
"Diffserv" is in:

 draft-conta-diffserv-ipv6-fl-classifier-01.txt

submitted to the "diffserv" WG.

Alex

Brian E Carpenter wrote:
> 
> Margaret,
>
> For diffserv it's in the MIB (queued up at the RFC
> Editor). [...] For diffserv, the flow label is the only field available
> as an ISP-independent QOS flag, so (unlike the traffic class)
> it needs to survive ISP boundaries.
> 
>   Brian
> 
> Margaret Wasserman wrote:
> >
> > >No. The immutability property is necessary for both of the
> > >existing QOS standards, and is necessary for any QOS mechanism
> > >that doesn't require an explicit chain of SLAs along the entire
> > >path (an unlikely scenario in a dynamically routed internet).
> >
> > If immutability would make the flow label field useful for
> > diffserv and intserv, then I have no objection to it being
> > immutable.  I think that making intserv/diffserv more useful
> > and/or efficient would be a fine use for the flow lable.
> >
> > Could we get a draft that explains how the flow label would be
> > used for diffserv/intserv?  One that justifies the need for
> > immutability?
> >
> > Assuming that immutability would actually make the flow
> > label more useful for diffserv/intserv, I would accept the
> > minor changes to the base IPv6 spec (adding immutability) that
> > Tony sent.  But, I have not seen any draft that would make this
> > single change.
> >
> > The current draft (in the subject) says a lot more
> > than this.  First, it recaps parts of the IPv6 Appendix,
> > without really making it clear what parts of that Appendix
> > it is (and is not) intending to standardize.
> >
> > The draft also states that a given source/desination/FL
> > combination will uniquely identify a flow.  This is not
> > true -- some knowledge of lifetimes, or some restrictions
> > against flow label re-use would be needed to make this
> > true.
> >
> > Anyway, how a flow is identified shouldn't be defined as
> > part of the base IPv6 specification.  Each signalling
> > (or other flow management) mechanism should define how
> > flows are identified for its use -- and this may differ
> > for different mechanisms.
> >
> > So -- what I'd like to see:
> >
> >          - A draft that explains how the flow label
> >                  would be used for intserv and/or
> >                  diffserv that explains what properties
> >                  are necessary for that use (i.e.
> >                  length, immutability, values, etc.)
> >          - A draft that proposes the simple change
> >                  to the IPv6 spec that Tony sent.
> >
> > Do you think that is reasonable?
> >
> > Margaret
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