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Re: Two Drafts for Resilience of Control Plane

igor - see in-line

ibryskin@movaz.com wrote:


Dimitri,
See in-line.


igor -

you are already going beyond the specific discussion context

1. what is a control plane partitioned LSP ?
LSPs with one or more controllers down, so there is/are partitions in 
hop-by-hop signaling


2. when you state "Suppose one or more signaling controllers managing
   some LSP went out of service leaving the LSP’s data plane intact."

   what does it mean "one or more controllers" ? what if you support
   RSVP GR ? why are you not able to recover the states ? etc.


See my response to John. There are no restarts in my example


you stated

"I think you missed my point here. "Dead" controllers in my example *do
not* come back for a considerable period of time. So there are no restarts here (graceful or not graceful) :=)"
but this is exactly issue i am pointing here below - if a controller is really DEAD (and i included here any redundant controller pair) - beside *replacing* the damaged controller and restart i don't know which kind of additional extension you are asking for in the present context ... and this is logical we are discussing control plane availability/MTBF issues rather than resiliency issues 


hence, i still miss the exact problem wrt to the control plane protocol
resilience

but i think there is another issue (which is even more important) - the
resilience mechanisms of the control plane that we have today have been
provided based on experience from the common use of the control plane
and for being resilient wrt common failures - but not for ALL use of the
control plane in ANY condition and for ALL possible failures - indeed
what you are asking here is like what shall i do when the CP is
completely down and the DP still up; it would surprise me that the CP
would be of any help in this specific condition


Believe me, CP could be still of a great help in such conditions. You need
some signaling extensions - which is why I think CP resilience is an
important topic within CCAMP - and then you can manage LSPs with control
plane gaps at least to the extend I described.





Igor



thanks,
- dimitri.

ibryskin@movaz.com wrote:



Hi,

Here is one of the problems that I’ve been thinking for a while –
control
plane partitioned LSPs. Suppose one or more signaling controllers
managing
some LSP went out of service leaving the LSP’s data plane intact. As far
as the user is concerned such LSP is perfectly healthy and operational.
Such situation could last for a considerable period of time. Do we need
to
manage such LSP via control plane? Sure, we must be capable to tear down
such LSP, perform mb4b rerouting, distribute alarms between operational
controllers, signal data plane faults and perform recovery switchover,
modify LSP status, etc. Can we do this today? No, but with some
(signaling) extensions the problem I believe is solvable. Is this some
artificial, “fabricated” problem? No, I think it is real. Does it fall
under the control plane resilience problem space? I believe it does.

Igor




I agree with Zafar and Dimitri.  If someone wanted to document the GMPLS
control plane resiliency features, as was done for GMPLS addressing,
that might be a useful activity.




-----Original Message-----
From: dimitri papadimitriou [mailto:dpapadimitriou@psg.com]
Sent: Friday, October 28, 2005 9:56 AM
To: Igor Bryskin
Cc: Zafar Ali (zali); Kim Young Hwa; ccamp@ops.ietf.org
Subject: Re: Two Drafts for Resilience of Control Plane

igor -

over time CCAMP came with a set of mechanims to improve control plane
resilience (RSVP and LMP GR upon channel/node failure) other WG


protocol



work are also usable used here OSPF GR, etc. ... on the other side,
mechanism such as link bundling have built-in resilience capabilities
and most GMPLS control plane capabilities have been designed such as


to



be independent of the control plane realisation (in-band, out-of-band,
etc.)

so indeed i share the concern of Zafar what could we do more here than
document these tools and provide our experience in using them;

now, before stating there are (potential) problems(s) arising - would
you please be more specific on what are these potential issue(s)


and/or



problems ? (not related to policy/config. - note: all the issues you
have pointed here below are simply policy/config specific but none of
them highlights a missing IP control plane resiliency feature)

thanks,
- dimitri.


Igor Bryskin wrote:




Zafar,

The problem arises when the control plane is decoupled



from the data plane. The question is do we need such



decoupling in IP networks? Consider, for example, the
situation when several parallel PSC data links bundled
together and controlled by a single control channel.
Does it mean in this case that when the control
channel fails all associated data links also fail? Do
we need to reroute in this case LSPs that use the data
links? Can we rely in this case on control plane
indications to decide whether an associated data link
is healthy or not (in other words, can we rely on RSVP
Hellos or should we use, for example, BTD)? Should we
be capable to recover control channels without
disturbing data plane? I think control plane
resilience is important for all layers. You are right,
Internet does work, however, we do need for some
reason TE and (fast) recovery in IP as much as in
other layers,don't we?

Cheers,
Igor

--- "Zafar Ali (zali)" <zali@cisco.com> wrote:





Hi All,

I am unable to understand the problem we are trying
to solve or
fabricate. My control network is IP based and IP has
proven resiliency
(Internet *does* work), why would I like to take
control plan resiliency
problem at a layer *above-IP* and complicate my
life. Did I miss
something?

Thanks

Regards... Zafar


________________________________

	From: owner-ccamp@ops.ietf.org
[mailto:owner-ccamp@ops.ietf.org]
On Behalf Of Kim Young Hwa
	Sent: Friday, October 28, 2005 6:04 AM
	To: ccamp@ops.ietf.org
	Subject: Two Drafts for Resilience of Control Plane


	Dear all,

	I posted two drafts for the resilience of control
plane.
	One is for requirements of the resilience of
control plane, the
other is for a protocol specification as a solution
of that .
	These are now available at:




http://www.ietf.org/internet-drafts/draft-kim-ccamp-cpr-reqts-01.txt




http://www.ietf.org/internet-drafts/draft-kim-ccamp-accp-protocol-00.txt



	I want your comments.

	Regards

	Young.

	===================================> >>	Young-Hwa Kim
	Principal Member / Ph.D
	BcN Research Division, ETRI
	Tel:     +82-42-860-5819
	Fax:    +82-42-860-5440
	e-mail: yhwkim@etri.re.kr
	===================================> >>


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