On 01/09/2011 15:37, Yaakov Stein wrote:
Stewart
Was this email meant to address my email to the IETF discussion list
(from Tues 16 Aug)
or just the discussion on MPLS and PWE lists ?
It does to SOME extent, as it leaves open the possibility of the GAL
not being at BoS;
but it does not rule out that possibility either.
Indeed, but a draft would need to make the case for it to be anywhere
other than BOS. The only case that I can think of at the moment is
where a FAT label is being used, but that is out of scope in this draft and
would need to be resolved in the draft describing the co-existance
of the two labels.
However, you did not address my other final comment that a PW that
starts in an MPLS-TP domain,
can easily leak into a non-TP domain.
What does one do then ?
That is a general issue rather than a TP issue.
When you get to the PW label and you would find that it was not BOS.
If you you are not running FAT that that is a detectable.
If you are running FAT the presence of the GAL (which is not an
allowed FAT label) is also a detectable.
(My email also identified a wording issue and what I consider to be a
completely inaccurate
explanation of what the draft is trying to accomplish.)
"architectures appropriate"
Seems to have the word "as" missing. I will add an editors note.
You say:
"Bottom of stack has been the label position of the PW label for many years,
and this position is mandated by multiple RFCs, e.g. 3985 and 4447
Note that the PW label must always
be at the bottom of the packet's label stack."
That is no longer true with the introduction of FAT.
Then you say:
"Present PW implementations receiving the PW label with stack bit cleared,
and a GAL at the bottom position will choke and, at best, discard the packet.
At worst, the GAL may coincide with a legitimate PW label, and the customer
will be
flooded with garbage."
Your first case is sort of correct - the packet should be silently
discarded as it was clearly not intended for that PW - but it had
better not choke as this would be an attack vector.
You second case cannot happen because a GAL is a reserved label and
a reserved label can never be a legitimate PW label.
Stewart
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