-----Original Message-----
From: Tom Petch <nwnetworks@dial.pipex.com>
Sent: May 9, 2006 3:43 AM
To: Adrian Farrel <adrian@olddog.co.uk>, ccamp@ops.ietf.org,
tnadeau@cisco.com
Cc: joan cucchiara <jcucchiara@mindspring.com>
Subject: Freeform labels
Hi Tom,
I am confused about freeform labels. I am not familiar with them
from other
contexts and so am not clear how significant they are but ...
(draft-ietf-ccamp-gmpls-)tc-mib under GmplsFreeformLabelTC
references RFC3471
which would be a good place to read about them except I can see no
mention of
them there. They appear in tc-mib, lsr-mib and te-mib - they are
used as worked
examples which is what attracted my attention - but I cannot find
them anywhere
else in the (G)MPLS library. I think that more description is
needed somewhere.
The GmplsFreeformLabelTC is also used in the GMPLS-LABEL-STD-MIB
(gmplsLabelFreeform in the
gmplsLabelTable). I believe given the purpose of this particular
MIB table and also within the context of the other objects in this
table, that the intent of GmplsFreeformLabelTC is fairly well
described.
Why does GmplsFreeformLabelTC give size limits of 0 and 64? Can
they really be
0-length? I have no problem with an SMI object having zero length
as long as
the entity being modeled by it can have zero length but is that
meaningful here?
And why 64? ok, a lot more than 32-bit but 64 sounds arbitrary (in
which case, I
think that worth saying); or does 64 octet relate to some other
well known
address formats (IPv6 anyone?).
The length of 64 was thought by the authors to be more than enough
for the purpose
of this label. I also questioned this during the MIB Dr. review,
but currently label
lengths in the MPLS/GMPLS wgs are 4 octets, so 64 seems reasonable.
0 length is used if this object does not contain a label, so it is
not the actual label
that is 0 length, but when the object has not label.
When GmplsFreeformLabelTC says 'not defined in any RFC', I think
it sums it up
too well:-(
Yes, this is a MIB convention only.
So the use of gmplsFreeformLabel(3) everywhere except in the
formal definition
where it appears (I assume) as gmplsFreeformGeneralizedLabel(3)
seems about
right as does the descripttion
Good catch. I probably should have caught this during the MIB Dr.
reviews.
Tom N. could you change this during the IESG/RFC reviews.