The MPLS WG Archive

["Mannie, Eric" <Eric.Mannie@gts.com>]

Hi Maarten,

Transport of VC-11 via a TU-12 is of course covered. We discussed it in
several earlier drafts. For instance, we proposed an extension to OSPF/IS-IS
to advertise this conversion capability per node (draft presented at the
Pittsburgh meeting).

Note that the label is used to indicate a time-slot, e.g. a VC-11 or VC-12.
Moreover, a label is local to the interface between two nodes (per MPLS
definition). It is not the label that "handles" with time-slot conversion
but the signaling and the routing protocols, and some nodes of course.

When a VC-11 is transported via a TU-12, the VC-11 is "converted" to a VC-12
(by adding fixed stuff). So, the result looks like a VC-12 (regular label).
See G.707 section 10.1.6 ("VC-11 to VC-12 conversion for transport by a
TU-12).

For instance, at the ingress interface you may have a VC-11 and at the
egress interface you may have a VC-12.

The signaling protocol (GMPLS) uses the GPID to indicate that the VC-11 is
indeed transported in a VC-12 so that an end system knows that it has to
convert the VC-12 back to a VC-11. Intermediate switches doesn't need to
know that the VC-12 is indeed a VC-11 (indeed, this is the goal).

Note finally that the issue of conversion is not the same as internetworking
between SDH and SONET. Conversion can be used in a pure SDH network where
some nodes don't allow to switch VC-11. Internetworking between SDH and
SONET has other specific problems (how do you convert bytes in the overhead
for instance).

Kind regards,

Eric

-----Original Message-----
From: Maarten Vissers [mailto:mvissers@lucent.com]
Sent: Tuesday, December 19, 2000 12:18 PM
To: Mannie, Eric
Cc: 'Heiles Juergen '; 'mpls@UU.NET '; 'ip-optical@lists.bell-labs.com '
Subject: Re: [IP-Optical] RE: GMPLS - Lable


Eric,

In SDH we are able to transport a VC-11 via a TU-12. This is an
interworking case to transport VT1.5 signals from e.g. the USA to
Europe. At the international gateway, the VT1.5 signals within STS1s are
forwarded as VC-11 signals via TU-12s within a VC-4. Upto 63 VC-11
signals can as such be transported per VC-4, or a mixture of VC-11 and
VC-12 signals (all within TU12s).

Is the lable able to handle this type of transport?

Regards,

Maarten