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Re: comments on ID-draft-bernstein-ccamp-gmpls-vcat-lcas
Thanks for the clarifications, see in-line for responses.
OK, I have added my response [hvh2] and sipped the parts
where we agree.
Is Fixed synonymous with no-LCAS ?
[hvh] No, not necessarily, in this case the client signal will
not change its bandwidth. LCAS can be used for resilience.
[tw] Accepted that this is possible. However I still think the reader
could be forgiven for assuming that Fixed = non-LCAS-capable and Dynamic
= LCAS-capable; so perhaps this needs to be clarified in the text.
[hvh2] OK that can be done.
If so, then in the Fixed co-routed scenario, there can be no graceful
degradation in the event of a failure.
[tw] I have a typo here is should say Fixed diversely-routed instead of
[hvh] a mis-connection is also a failure
[tw] but a mis-connection won't cause a hit, since this will occur at
set-up, but I agree that if LCAS is present then graceful degradation
can be achieved in the event of a signal degrade.
[hvh2] I don't agree, mis-connections can also occur after set-up,
e.g. when a crossconnect is wrongly provisioned and changed
an existing connection.
A hitless decrease can
in certain circumstances, be achieved by using a signal degrade to
trigger the LCAS remove operation.
[hvh] how do you provision/achieve a signal degrade?
[tw] G.806 clause 10.1.1.2 shows "P-Xv_AI_TSD = P_AI[1.. XMR]_TSD"
and "P-Xv/P-X-L_A_Sk_MI_TSDEnable" as inputs to the "LCAS-capable
virtual concatenated path adaptation sink function P-Xv/P-X-L_A_Sk", and
the text says "The MI_TSDEnable input controls whether the sink function
uses AI_TSD[i] indications as contributors for signalling defective
members back to the LCAS source function (MI_TSDEnable = true) or
whether it ignores AI_TSD[i] indications altogether (MI_TSDEnable =
[hvh2] this is the enabling of the TSD to be a trigger. What I dis
mean is that it is impossible to force a signal degrade (e.g.
by introducing bit errors on purpose).
Maybe we should only mention that hitless decrease is guaranteed
when a member is removed (and LCAS is enabled).
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
[hvh] graceful degradation is a feature of LCAS, it is not necessary
to mention it here explicitly
[tw] It's equally (if not more) relevant to mention it here than in
the fixed scenario.
[hvh2] see my previous comment
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.
[hvh] mentioning only one of the LCAS states will create confusion
and is irrelevant to GMPLS
[tw] OK so take out the mention of the DNU state (18.104.22.168) and IDLE
(22.214.171.124). In fact perhaps 126.96.36.199 could be combined with 188.8.131.52 as
4.1.3 Permanent removal of a VCG member
A VCG member can be permanently removed from the VCG either following a
temporary removal (due to a failure) or as the result of a management
The LCAS in-band signaling step is taken first to take the component out
of the group, either the temporary removal or as the result of a
[hvh2] good suggestion
This permanent removal procedure is only applicable to
[hvh] the paragraph replaced by the latter sentence contains more
relevant detail and should be kept intact.
[tw] The introduction to section 4 states that it (section 4) is "in
support of the LCAS procedure". So I don't quite see how the sentence
that I deleted is relevant to LCAS since it deals with the "VCAT only"
[hvh2] you missed the word "and" in quoting, so section 4 describes
extentions for diversely routed paths and (extentions) in
support of LCAS". So the detail given in the paragraph is
relevant for making the distinction between VCAT with and
Cheers, and have a nice weekend, Huub.
Always remember that you are unique...just like everyone else...