NAME OF I-D:
http://www.ietf.org/internet-drafts/draft-ghani-optical-rings-01.txt
SUMMARY:
Given the large installed base of ring fiber-plants and the extensive
experience operators have gained in operating SONET/SDH ring networks,
optical rings are becoming increasingly important. As such, optical
rings will play a crucial role in the migration from existing TDM-based
SONET/SDH architectures to more dynamic lightpath provisioning
paradigms. To date, various optical ring concepts have been tabled,
proposing multi-services support and mirroring the fast protection
switching capabilities of existing SONET/SDH rings. Nevertheless, the
emerging MPL(ambda)S/GMPLS framework for optical networks is largely
based upon (optical) mesh routing concepts. Clearly, there is a strong
need to formalize a more comprehensive architectural framework for
optical rings and ensure its proper integration within the emerging
MPL(ambda)S/GMPLS architecture. Along these lines, the various optical
ring schemes are summarized and their associated dynamic provisioning
concerns detailed. A key concern here is service survivability, as
implement via fast protection switching protocols. Additionally, multi-
domain and layer interworking issues are also crucial to effectively
managing larger multi-ring domains.
RELATED DOCUMENTS
P. Ashwood-Smith, et al, "Generalized MPLS-Signaling Functional
Description," Internet Draft, draft-ietf-mpls-generalized-
signaling-01.txt, November 2000.
O. Aboul-Magd, et al, "Signaling Requirements of the Optical
UNI," Internet Draft, draft-bala-mpls-optical-uni-signaling-
01.txt, November 2000.
Y. Xu, et al, "Generalized MPLS Control Plane Architecture
for Automatic Switched Transport Network," Internet Draft,
draft-xu-mpls-ipo-gmpls-arch-00.txt, November 2000.
D. Guo, et al, "Extensions to RSVP-TE for Bi-directional Optical
Path Setup," Internet Draft, draft-sorrento-rsvp-bi-osp-00.txt, July 2000.
D. Papadimitriou, "Optical Rings and Hybrid Mesh-Ring Optical
Networks," Internet Draft, draft-papadimitriou-optical-rings-00.txt,
February 2001.
M. Soulliere, "Proposed ITU-T Contribution on Transparent
OCh SPRings," T1X1 Forum, T1X1.5/2001-027, January 2001.
K. Owens, et al, "A Path Protection/Restoration Mechanism
for MPLS Networks", Internet Draft, draft-chang-mpls-path-
protection-02.txt, November 2000.
R. Bhandari, S. Sankaranarayanan, E. Varma, "High-Level
Requirements for Optical Shared Mesh Restoration," Internet Draft,
draft-bhandari-optical-restoration-00.txt, May 2001.
WHERE DOES IT FIT IN THE PICTURE OF THE SUB-IP WORK
OPT (IP Over Optical)
WHY IS IT TARGETED AT THIS WG
This document introduces the control and provisioning requirements of optical ring networks.
In reality, many optical fiberplants form ring topologies, and many ring architectures are being
studied/standardized in the ITU/T1X1. However, the commensurate control and provisioning
requirements need specific attention, and the broader integration/commonalization of control
frameworks between optical ring and mesh networks is also very important.
JUSTIFICATION
Given this large, entrenched base of ring topologies, currently many
operators are planning for a migration to equivalent dynamic optical
ring architectures. Since many operators have significant experience in
deploying and maintaining SONET/SDH rings, future optical analogs of such
rings are of great transitional value. Optical rings will allow operators
to immediately leverage their current fiber topologies and avoid lengthy
fiber-expansion costs (i.e., associated with deploying mesh networks).
Furthermore, ADM-based ring architectures are well-known for their operational
simplicity and inherently fast protection switching capabilities. Network
operators have become well-accustomed to the fast, timely recovery capabilities
provided by SONET/SDH automatic protection switching (APS) schemes.
Nevertheless, the emerging MPL(ambda)S/GMPLS framework has its origins in (mesh)
IP packet routing networks, as it stands today, is largely geared to support dynamic
optical mesh networks. Additionally, there are no control/provisioning standards
for optical rings and most offerings rely instead upon proprietary solutions.
Now given the abundance and strategic importance of ring fiber-plants, it is
crucial to extend the existing MPL(ambda)S/GMPLS framework to provision
dynamic optical ring networks. Although some may state that rings are
special cases of meshes (technically speaking), the various intricacies
of ring networks require special attention in the MPL(ambda)S/GMPLS
framework. A uniform provisioning framework will permit true optical services
provisioning across all network/geographic domains. In particular, the MPL(ambda)S/GMPLS
framework must address ring channel provisioning and protection switching functions.
Undoubtedly, optical (ring) solutions must provide equivalent, or improved, capabilities in
order to replace TDM rings in a timely manner. This draft details an architectural framework
for optical rings, representing a logical, structured evolution (expansion) from existing
SONET/SDH (TDM) ring paradigms. Optical ring equivalents of SONET/SDH protection
schemes are presented and detailed provisioning issues outlined within the context of the
broader MPL(ambda)S/GMPLS framework.