Re: [PWE3] Re: I-D ACTION:draft-ash-avt-ecrtp-over-mpls-protocol- 00.txt

[Curtis Villamizar <curtis at workhorse.fictitious.org>]

In message <4030C043.3030509@cisco.com>, Stewart Bryant writes:
> 
> 
> 4 and 6 will be preallocated, so that they do not get trodden on.
> 
> We need to find out if there is any use of 5, 7, 8 and 9. I.e.
> are there any routers in the Internet that carry IP versions
> 5, 7, 8 or 9 over MPLS. If there are, we need to include them
> in the registry as pre-allocated values. If not, then a
> new implementation would need to operate under the rules
> proposed below (i.e. run under 0, 1 or their own value).
> 
> The IESG would advise IANA on the usage of this registry.
> 
> - Stewart


For all pracical purposes 7, 8 and 9 are not used at all, over MPLS or
otherwise.  These are left overs from the competing proposals to
replace IPv4.  The decision was made to go with IPv6.  Since then none
of them have been used.  It would be reasonable for IESG/IANA to
declare these values as having been temporarily assigned for protocol
experiments which are long ago over and available for reclaim, but
apparently they are choosing not to do so.  There is (or was at some
point) some use of 5 (ST-II).  Use of ST-II may have disappeared, but
I'm uncertain of that.

IESG does have a very good point in that what these are being used for
is not IP version numbers where the other 20 bytes are also an IP
header.  That IPv4 and IPv6 values are reserved in the new registry to
allow the largest single contributor of traffic to be placed in MPLS
without a shim is good, and not breaking very widespread current usage
is good.  If you reserve any number for "other IP version" then an IP
packet with 5, 7, 8 and 9 or any new assignments of IP versions could
be carried with a shim.

Curtis

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