Alex,

I don't agree. This restores the uncertainty that is preventing any
current usage. 

   Brian

Alex Conta wrote:
> 
> Making the field "immutable" by "default", but "mutable" when a router
> is so instructed by a flow setup and flow processing mechanism is a
> compromise that would satisfy all current and future possible cases.
> 
> Therefore I think last sentence of the first paragraph
> 
>     All routers MUST pass the field on unchanged when forwarding a
> packet.
> 
> should be something like:
> 
>     All routers MUST leave the field unchanged, by default, when
> forwarding a packet.
>     A specific flow setup/processing mechanism MAY give a "mutable"
> character to the field,
>     by requesting routers, supporting the mechanism, to change the field
> in certain ways.
>     Routers supporting such a mechanism MUST follow the steps indicated
> by the flow
>     setup and flow processing mechanism.
> 
> Alex
> 
> Brian E Carpenter wrote:
> >
> > Taking Scott's suggestion, here's another try:
> >
> > I'd like to propose the following as the
> > complete and total replacement of Section 6 of RFC 2460.
> >
> >    The 20-bit Flow Label field in the IPv6 header MAY be set by a
> >    source to uniquely label sets of packets. Nodes that do not support
> >    the Flow Label field MUST set the field to zero when originating a
> >    packet, and MUST ignore the field when receiving a packet. All routers
> >    MUST pass the field on unchanged when forwarding a packet.
> >
> >    This specification does not further define the meaning of the
> >    Flow Label.
> >
> >  [and delete Appendix A, which is unhelpful.]
> >
> >        Brian
> > --------------------------------------------------------------------
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-- 
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Brian E Carpenter 
Distinguished Engineer, Internet Standards & Technology, IBM 
On assignment at the IBM Zurich Laboratory, Switzerland
Board Chairman, Internet Society http://www.isoc.org


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