Subject: [PWE3] Response to PWE3 and MPLS WG concerns with G.8110.1 Amendment 1

From: Stewart Bryant <[email-masked]>
Date: Tue, 17 Jul 2007 18:37:38 +0100

I have been looking at the ITU liaison addressed to PWE3 and MPLS WGs

June 2007 ITU-T SG 15 IETF PWE3 and MPLS WGs Response to PWE3 and MPLS 
WG concerns with G.8110.1 Amendment 1

and would appreciate input to a suitable response. This liaison will be 
a topic on the PWE3 agenda.

https://datatracker.ietf.org/liaison/345/

ITU SG15 say:
"It appears that the work in the IETF is addressing some different 
requirements:
“Input from network operators indicates that the key requirements is the 
transparent carriage of the MPLS network of one party over the MPLS 
network of another party, with the constraint that the MPLS design MUST 
NOT be changed and that the solution MUST be compatible with their 
existing large base of already deployed MPLS networks.”

SB - Network operators subscribing to these lists are encouraged to 
indicate whether or not they agree with these two assumptions.

ITU SG 15 say:
"Some members of SG 15 expressed support for these requirements. 
However, the basis for the work in SG 15 has been the development of a 
packet switched network that meets all of the network operators 
transport operations requirements. "

SB - Would be interested in other peoples views on the second sentence - 
is it consistent or contradictory to the proposed constraint that the 
investment in the existing MPLS design and deployment be preserved?

ITU SG 15 say:
"The assumption we have made is that when deploying T-MPLS for this 
purpose it will be deployed on a network that is disjoint from any 
already deployed IP/MPLS network."

SB - As I said in my earlier email, I am concerned about this 
assumption, particularly as I saw a contribution that discussed 
interworking of MPLS and T-MPLS. If the assumption is a design invariant 
it should be designed into the protocol to ensure that it cannot be 
violated.

ITU SG15 say:
"Equipment developed prior to the approval of the T-MPLS Recommendations 
is not expected to comply with these Recommendations."

SB - Again as I stated earlier, I think that we need to note that we are 
not concerned about existing MPLS equipment being compliant with T-MPLS, 
but rather we are concerned that T-MPLS or any future enhancement to 
T-MPLS should not cause a conflict with the installed base of existing 
MPLS equipment, or any future IETF development of MPLS, or that it 
should inhibit some future development of MPLS.

ITU SG 15 Say:
"Our intention in developing the suite of T-MPLS Recommendations is to 
define a packet based transport network technology. The design 
objectives of T-MPLS are:
a) Follow the principles of the transport network used in other ITU-T 
defined transport technologies (e.g SDH, ATM, OTN).
b) To use the PDU and forwarding plane processes defined by the IETF for 
MPLS.
After the presentation of the Liaison Statement the following was noted:
• T-MPLS OAM mechanisms have been developed by ITU-T G.8114/Y.1373 to 
provide transport-like fault and performance monitoring capabilities 
including alarm suppression, packet loss measurements and support of 
multiple ownerships
• T-MPLS protection mechanisms have been developed by ITU-T G.8131 to 
provide transport-like protection schemes including trail and 
sub-network protection
• The separation between the data plane and the control plane is a major 
requirement in transport networks"

SB - I would be interested in the views of the operator community on how 
significant the differences between the TMPLS approach and the IETF 
approach is in these three aspects and whether they justify a whole new 
protocol suit?

What is the view of other members of the IETF?

- Stewart

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