[mpls] MSRP discussion

[Huub van Helvoort <[e-mail]>]

All,

In:

> Below are the *_preliminary_* minutes taken during IETF92 MPLS sessions.

I noticed the following discussion:

> Liang Geng’s (China Mobile) presentation on MSRP:

> - Eric Osborne said that this draft needs some discussion as to why the
> existing RFC(s) are inadequate.
> - Loa asked if this observation applies to both this draft and Kireeti’s
> draft.
> - Eric said that – in his opinion – Kireeti’s draft already provides
> enough info to distinguish its applicability.

Section 2.3 of draft-cheng-mpls-tp-shared-ring-protection
describes the Configuration Complexity.

I will try to provide some more details:

Suppose a ring with N nodes.
---------------------------
Applying RFC6974 means that from every ring-node a linear
protection configuration has to be provisioned with every other
node in the ring, i.e. with (N-1) other nodes.
This means that in every node there will be (N-1) instances of
the PSC protocol.
In order to detect faults and to transport the PSC OAM each
instance shall have a MEP on the working path and a MEP on the
protection path. (A MEP == co-located so_MEP and sk_MEP).
This means that every ring-node should have the capability to
support (N-1) * 2 MEPs.

Applying draft-cheng-mpls-tp-shared-ring-protection means that
in every ring-node there will be a single instance of the MSRP
protocol.
In order to detect faults and to transport the MSRP OAM each
instance (e.g. in node N) shall have a MEP on the working path
and a MEP on the protection path to node (N-1) and also to
node (N+1).
This means that every ring-node should have the capability to
support 2 * 2 MEPs.

Suppose a ring with N nodes, and one node has to be added:
---------------------------------------------------------
Applying RFC6974 means that every existing ring-node has to
be updated: a new PSC protocol instance created, and 2 MEPs
instantiated.
In the new node N PSC instances have to be created and
N * 2 MEPs instanciated.

Applying draft-cheng-mpls-tp-shared-ring-protection means that
in every existing ring-node the ring-map has to be extended.
In the new node a single MSRP instance has to be created and
4 MEPs instantiated.
Note that the 4 MEPs have to be instantiated anyway to be able
to monitor the links with the adjacent ring-nodes, so in fact
only the MSRP OAM has to be enabled.

Regards, Huub.


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