On Aug 30, 2007, at 1:31 PM, Brian E Carpenter wrote:
Incidentally, RFC 2460 is clear that unknown headers should cause
the
packet to be dropped, so the transition strategy is tricky in any
case.
If, as a result of processing a header, a node is required to
proceed
to the next header but the Next Header value in the current
header is
unrecognized by the node, it should discard the packet and
send an
ICMP Parameter Problem message to the source of the packet,
with an
ICMP Code value of 1 ("unrecognized Next Header type
encountered")
and the ICMP Pointer field containing the offset of the
unrecognized
value within the original packet.
Yes, but this would only be the node addressed by the IPv6 header
- or do I read this wrongly?
Correct ... and actually I quoted the wrong text for the case of an
unknown RH number, but the result is the same - only the next-hop
router listed in the RH itself needs to understand that new RH number.
But that does create a 'consenting adults' situation; if you construct
an RHx you must know that every router listed in it understands RHx,
otherwise the packet will be dropped. That is quite a restriction on
deployment scenarios beyond experimental or local use.
Brian
Maybe this isn't a huge problem. For source routing to be
particularly useful, the sender probably wants / needs to know
something about the topology. At a minimum, the sender would
presumably need to know the addresses of the way-points to use in the
source route. Whatever mechanism / process is used to determine
these way-points could probably verify RHx support (at those
addresses) with just a little more work.
R,
Dow
So the core of the network is not affected either
way (unless explicit filtering is implemented somewhere), and only
routers of end networks that wish to participate in, say, a future
RH4
routing would need to upgrade the software.
-is
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