Subject: [mpls] [Fwd: New Liaison Statement, "Clarification on the intended scope of T-MPLS"]

From: Loa Andersson <[email-masked]>
Date: Wed, 10 May 2006 14:31:44 +0200

All,

we have received the included liaison from ITU-T SG 15.

Note that we've two slightly mixed discussion, one on MPLS and
another on pseudo wires. Try to direct comments to the appropriate
working group list.

we plan to give a formal response on May 17th, comments, both on
the content of this liaison and on the T-MPLS documentation, are
welcome.

Loa and George

-------- Original Message --------
Subject: New Liaison Statement, "Clarification on the intended scope of 
T-MPLS"
Date: Thu, 04 May 2006 14:09:26 -0400
From: Greg Jones(ITU-T SG 15) <[email-masked]>
Reply-To: [email-masked]
To: George Swallow <[email-masked]>, Loa Andersson <[email-masked]>, 
Stewart Bryant <[email-masked]>, Danny McPherson <[email-masked]>
CC: Scott Bradner <[email-masked]>, Yoichi Maeda 
<[email-masked]>,   [email-masked], 
[email-masked], [email-masked],   [email-masked], 
[email-masked], [email-masked],   [email-masked]

Title: Clarification on the intended scope of T-MPLS
Submission Date: 2006-05-04
URL of the IETF Web page: 
https://datatracker.ietf.org/public/liaison_detail.cgi?detail_id=218

From: Greg Jones(ITU-T SG 15) <[email-masked]>
To: IETF MPLS WG, PWE3 WG(George Swallow <[email-masked]>, Loa 
Andersson <[email-masked]>, Stewart Bryant <[email-masked]>, Danny 
McPherson <[email-masked]>)
Cc: Scott Bradner <[email-masked]>
Yoichi Maeda <[email-masked]>
[email-masked]
[email-masked]
[email-masked]
Reponse Contact: [email-masked]
[email-masked]
Technical Contact: [email-masked]
[email-masked]
Purpose: For information
Body: Thank you for your informal feedback that has been provided on our 
previous liaison statement on T-MPLS Consented Recommendations, we also 
understand that you are in the process of developing a formal response. 
  To assist you in providing your formal response we would like to 
provide some additional clarifications on the intended application of 
T-MPLS.
Our intention in developing the suite of T-MPLS Recommendations was to 
define a packet based transport network technology.  The design 
objectives of T-MPLS were:
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 data plane processes defined by the IETF for MPLS.
T-MPLS is not intended to duplicate the functionality already provided 
by IP/MPLS.
The only client fully described in the current version of G.8110.1 is 
point to point Ethernet Virtual Connection (EVC).  It was agreed to 
revise the scope of the Recommendation and provide an appendix II 
(attached) to reflect this.  Some other key points identified were:
•	The current version of G.8110.1 only defines the bearer plane and only 
point to point trails are currently supported.  It should be noted that 
version 2 of G.8110.1 will add point to multipoint trails.
•	Any interworking with client signals (e.g. MPLS, Ethernet) will be 
client server i.e. any client OAM or control protocols will be tunneled 
transparently across the T-MPLS layer network.
•	Interworking between a client control plane and a (yet to be defined) 
T-MPLS control plane will be addressed as a part of the control plane 
architecture work.
•	The T-MPLS network provides a single hop link to the client, it is 
intended to offer a packet switched connection that has similar 
operational characteristics to a SDH network providing a PDH link 
connection, e.g. these connections must support the ability to activate 
performance monitoring and fault management.  Any PM data or failures 
will be reported to the transport operations center.
We also note your comments on the usage of the label space terminology. 
  We will work to clarify and if necessary correct this in a future 
revision.
We have also agreed to initiate work on the architecture of a control 
plane for T-MPLS.  We will use the ASON architecture to provide a 
framework to describe the problem that is to be addressed.  This does 
not imply that we will specify an ASON control plane.  Once we have 
refined our requirements we will communicate them to you for advice on 
how they may be addressed.  If the requirements cannot be met by an 
existing protocol suite we would like to work with you to develop the 
appropriate enhancements.
We will be continuing our work on T-MPLS in particular the support of 
other clients (e.g. IP/MPLS) at an interim meeting that is planned to be 
held 19-23 June in Ottawa Canada.  We will also address any comments 
that you provide in your planned liaison statement. Any urgent changes 
may be included in an amendment or corrigendum that could be consented 
in October 2006.  IETF experts are welcome to participate at this 
meeting.  Please contact [email-masked] by May 31st 2006 if you 
should wish to participate.

G.8110.1 draft Appendix II

Support of IP/MPLS LSR based networks by
T-MPLS networks supporting point-to-point EVC services
When two IP/MPLS LSRs are connected via e.g. 802.3 interfaces to a 
T-MPLS network, the T-MPLS network can provide an EVC service between 
these two LSRs (nodes LSR A and LSR B in Figure II-1) to establish an 
IP/MPLS link between these LSRs.
The IP/MPLS LSRs encapsulate their IP/MPLS packets into Ethernet frames 
with or without VLAN Tag. These Ethernet frames are then transported via 
802.3 interfaces to the T-MPLS network edge (nodes X and Y). At the 
T-MPLS network edge the Ethernet signal is treated either as an 
all-to-one EVC service or as one or more EVC and/or bundled EVC services 
of which the frames are mapped into one or more T-MPLS (PW) trails and 
then transported through the T-MPLS network.
In this network scenario the IP/MPLS routing and control plane adjacency 
is between LSR A and LSR B. The T-MPLS network elements do not 
participate in the IP/MPLS routing and control plane. A signalling 
session that requests PHP is between LSR A and LSR B (T-MPLS nodes X and 
Y are not involved).

Figure II-1/G.8110.1 – IP/MPLS via EVC over T-MPLS network
The functional model for this scenario is described in Figure II-2. The 
atomic functions in the figure are specified in Recommendations G.8021 
and G.8121.The IP/MPLS signals are carried through an IP/MPLS link 
between LSR A and LSR B supported by an ETH trail between LSR A and LSR 
B. The ETH trail is carried through a serial-compound ETH link supported 
by an ETY trail interconnecting LSR A with T-MPLS PE X, a T-MPLS (PW) 
trail interconnecting T-MPLS PE X with T-MPLS PE Y and an ETY trail 
interconnecting T-MPLS PE Y with LSR B.

<<Figure II-2/G.8110.1 – Functional Model for IP/MPLS via EVC over 
T-MPLS network>> - see attachment
Attachment(s):
      Clarification on the intended scope of T-MPLS (see this WinWord 
file for the diagrams) 
(https://datatracker.ietf.org/documents/LIAISON/file311.doc)

-- 
Loa Andersson

Principal Networking Architect
Acreo AB                           phone:  +46 8 632 77 14
Isafjordsgatan 22                  mobile: +46 739 81 21 64
Kista, Sweden                      email:  [email-masked]
                                            [email-masked]

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