Re: [RRG] Six/One Router revised 2008-07-12 - IPsec

[Christian Vogt <christian.vogt@nomadiclab.com>]

On Aug 7, 2008, Robin Whittle wrote:

> Short version:   Like my Ivip6 proposal, I think that Six/One Router
>                 requires the redefinition of the current Flow Label
>                 bits to be used for another purpose.



Hi Robin,

thanks for sharing this idea.  You are suggesting that the Bilateral/
Unilateral bit [*], which Six/One Router requires, could be taken from
the IPv6 Flow Label field.  This would be possible, right.

I was myself considering taking the bit from the Traffic Class field.
This would have two advantages:

- Some bits in this fields are still unused.

- Backwards compatibility:  The IPv6 spec states that bits from the
  Traffic Class field can be set by routers, and that hosts and
  routers must ignore bits they do not recognize.  Consequently,
  nothing would break if one of the bits were allocated for use by
  Six/One routers.

Think it makes sense?

Regarding your proposal, Robin, for flow-label-based forwarding:  A
circumstance that mitigates the disruptive impact of re-defining the
Flow Label field is that (i) use of the Flow Label field is currently
pretty rare, and that (ii) hosts not using a flow label must ignore
the field [RFC 3697] anyway.

- Christian


[*] Background info for other folks on this list:  The Bilateral/
Unilateral bit is used by Six/One routers to determine, in stateless
fashion, the mode of a packet received from the Internet core.



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