Subject: RE: GMPLS - Lable

From: "Mannie, Eric" <[email-masked]>
Date: Fri, 15 Dec 2000 18:35:57 +0100

Hi Juergen,

The label is indeed relative to a link or a virtual link (could be a
forwarding adjacency). 0 is used to encode a field (S, U, K, L or M) that is
not significant (as stated in the draft). So, if the link is a virtual VC-3
link between two SDH/SONET LSRs, the highest part of the label is set to
zero (not significant), while the lowest part indicates the time-slot
(bandwidth) (e.g. a VC-11) requested in that virtual link. In the same way,
the lowest part of a label is set to zero for an STM-1/STS-1 LSP.

Having one label per SDH/SONET "layer" (or bandwidth level), i.e. a flat
label, is not a solution, since in that case when you want to allocate a
VC-11 in an STM-1 for instance, you have to request and attribute one label
for each intermediate "bandwidth level", e.g one LSP per bandwidth level.
 
I saw that there was an editorial bug in the draft ("S=0 is invalid").
Thanks for having indicated that. I'll sent an updated version of the
section to the editor as soon as I go back to my office. I'll add also a
small text to better explain how it works.

Kind regards,

Eric

-----Original Message-----
From: Heiles Juergen
To: [email-masked]; [email-masked]
Sent: 12/11/00 1:45 PM
Subject: GMPLS - Lable

draft-ietf-mpls-generalized-signaling-01 defines a hierachical lable
field for SDH SONET (e.g. S+U+K+L+M) in order to define the specific
position of an VC in the STM-n interface signal. In my view is not the
correct approach to include the full multiplex stack down to the
interface layer in the lable.
The lable is used for the link-connection of a LSP between two LSRs. As
such it should include only information relevant to this link
connection. What is need is inforamtion aboout the position of the LSP
in the server layer only, but not in all other layers below. If a VC-12
is transported via a VC-4 link connection the time slot of the VC-12
within the VC-4 is important in order to acces the correct VC-12 at the
next VC-12 LSR. The position of the VC-4 within the STM-N signal however
is not important as it is not fixed. The VC-4 is a LSP of its own and
can be routed via VC-4 LSRs. It can change its time slot within a STM-N
signal at any VC-4 LSR. The time slot of the VC-4 within the STM-n
signal could therefore be different at the two VC-12 LSRs. This
multiplex structure should therefore be handled by hierachical LSPs
instead of a hierachical label field.

The lable inforamtion is therfore valid for a certain cleitn/server
relationship, but not for a certain interface. For a lower order VC-12
within a VC-4  the parameters KLM are required. For a VC-4 within an
STM-n signal the parameter S is required, not more not less.

Regards

Juergen

---

From: Maarten Vissers <[email-masked]>
Date: Tue, 19 Dec 2000 12:18:00 +0100

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