RE: [PWE3] PWE Service interworking

[Mark Seery <mark@mseery.com>]

Lloyd,

--- Lloyd Wood <l.wood@eim.surrey.ac.uk> wrote:
[SNIP]
> While management interworking is well defined for
> ATM/Frame Relay [FRF.8, ITU-T I.555], the mapping of
> PW
> failures to the equivalent ATM/Frame Relay OAM
> messages when
> pseudo wires are used to interconnect these
> technologies is
> not well defined.

Specifically what you essentially end up with (in the
case where the IWF is not done at the ingress point)
is service interworking occuring over a network
interworking function, which complicates the decision
process of where to map OAMs to (i.e. the far-end
service interface, the PW, the PSN,.....); probably
depends on how much transparency is desireable WRT the
intermediate cloud.

Can probably be done, but makes things interesting.
Moreover, if the interworked "technologies" have
different capabilities, then becomes even harder.

As has been noted, on some occassions, some types of
IWF can occur outside the PSN cloud, so there are some
short-term options available.

IMHO, the value of looking at above referenced
documents would be to try and glean the types of
mappings that past IWF implementors have considered;
therefore becoming a guide, and diminishing the
chances of reinventing the wheel - but as you say,
they do not cover this particular case.

In practice (in the short-term at least), I suspect
that when shipping traffic to an MPLS core, the IWF
will occur before the PW entry point; and after the PW
exit point in the reverse direction, thus avoiding the
issue all together.

Mark

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