Hi all,
I have read the ID-draft-bernstein-ccamp-gmpls-vcat-lcas-04.txt which I
have duplicated below in a word document and applied comments and
changes (see change bars) for your perusal. I have the following
questions and comments (also in the attached): -
Section 3.2:
Is Fixed synonymous with no-LCAS ?
If so, then in the Fixed co-routed scenario, there can be no graceful
degradation in the event of a failure.
This is more applicable to the dynamic, diversely-routed scenario (and
in fact could apply to the dynamic co-routed scenario, although this is
far more unlikely).
Regarding 'graceful degradation in the event of a failure': surely this
is a misnomer ? Graceful degradation can only be achieved if the VCG
capacity is hitlessly decreased. A full blown failure on any VCG member
will cause a hit to the traffic, albeit temporary. A hitless decrease
can in certain circumstances, be achieved by using a signal degrade to
trigger the LCAS remove operation.
Suggested text for 3.2 (partial)
Fixed, diversely routed: A fixed bandwidth VCG, transported over
at least two diversely routed subsets of member signals. In this
case, the subsets are link-disjoint over at least one link of the
route. The intent here is more efficient use of network resources
(no unique route has the required bandwidth), (note
that differential delay may be a limiting factor).
Dynamic, diversely routed: A dynamic VCAT group, transported over
at least two diversely routed subsets of member signals. The
intent here is dynamic resizing and resilience (but differential
delay may be a limiting factor). Graceful degradation is possible
in the event of a TSD (Trail Signal Degrade) on a VCG member(s)
Section 4
Typo on second line of last paragraph: VC4-7v should be VC-4-7v.
Section 4.1.3
G.7042 section 6.4 addresses VCG capacity decrease (temporary removal
due to member failure) and section 6.5 addresses VCG capacity decrease
(permanent removal). Each of these has distinct meanings and I think
that this ID should make that distinction also, or at least be more
pedantic in the use of 'removal'.
Perhaps (as far as GMPLS is concerned) there is only the need to address
the VCG capacity decrease (permanent removal), since the 'temporary
removal' is an autonomous action performed by the LCAS protocol and does
not require any management intervention.
Suggested text for 4.1.3: -
4.1.3. Decreasing VCG capacity
VCG capacity can be decreased in two ways
o Temporary removal of a VCG member(s) due to failure
o Planned permanent removal of a VCG member(s) which requires
management intervention
4.1.3.1 Temporary Removal of a VCG member
This is an autonomous action performed by the LCAS protocol whenever a
failure occurs on an active VCG member(s). The relevant VCG member will
then be in the DNU state.
There is no management intervention required to perform this operation.
This member can then be permanently removed from the VCG. (4.1.3.2)
4.1.3.2 Planned permanent removal of a VCG member
The procedure to remove a component signal is similar to that used to
add components as described in Section 4.1.2. The LCAS in-band
signaling step is taken first to take the component out of the group
as the result of a remove command from the LCAS controller; the
permanently removed member will then be in the IDLE state.
LCAS signaling is described in [ITU-T-G.7042]
In this case, the NVC value is decremented by 1 and the timeslot
identifier for the dropped component is removed from the ordered list
in the Generalized Label.
This permanent removal procedure is only applicable to
LCAS-capable-VCAT.
Best regards,
Trevor
Trevor Wilson
Nortel Networks
Belfast Lab
Tel: +44 2890 363701
ESN 751 3701
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-----Original Message-----
From: owner-ccamp@ops.ietf.org [mailto:owner-ccamp@ops.ietf.org] On
Behalf Of Adrian Farrel
Sent: 12 August 2006 15:56
To: ccamp@ops.ietf.org
Subject: Polling for new WG I-Ds
Hi,
As discussed in Montreal, we need to poll for a couple of new WG drafts.
http://www.ietf.org/internet-drafts/draft-bernstein-ccamp-gmpls-vcat-lca
s-04.txt
has been updated by the authors to provide further details and
clarification.
http://www.ietf.org/internet-drafts/draft-caviglia-ccamp-pc-and-sc-reqs-
02.txt
has been updated since the version discussed in Montreal.
http://www.ietf.org/internet-drafts/draft-ali-ccamp-mpls-graceful-shutdo
wn-04.txt
has been updated as Zafar says in his previous email.
Please send yes or no for these I-Ds.
Reasons and opinions are also welcomed.
Thanks,
Adrian
Attachment:
ID-draft bernstein.... VCAT-LCAS..TW-comments.doc
Description: ID-draft bernstein.... VCAT-LCAS..TW-comments.doc