Network Working Group L. Ong, Ciena
Internet-Draft A. Malis, Verizon
Intended status: Standards Track R. Theillaud, Marben Products
Expires: January 12, 2011
July 12, 2010
Optimization of GMPLS BW advertisement for SONET/SDH
draft-ong-gmpls-ason-routing-exper-02
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Abstract
IETF CCAMP WG has defined a set of extensions to OSPFv2 to support
ASON routing requirements in [RFC5787]. No extensions were defined
for bandwidth advertisement as the Interface Switching Capability
Descriptor may optionally be included for each layer of a multi-layer
link [RFC4202]. However, for some types SONET/SDH links there can be
several data plane layers supported by a single link, and as a
result a need to carry several copies of the ISCD.
This draft defines an optimization for bandwidth advertisement for
SONET/SDH that removes the need to carry multiple copies of the ISCD
sub-TLV and has been designed to be consistent with advertisement
of bandwidth for OTN.
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These formats are based on previous experience prototyping and
testing control plane for ASON networks and are proposed for
adoption as a Standards Track RFC for support of ASON routing.
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Optimization of bandwidth advertisement for SONET/SDH. . . . . 3
2.1. Requirements for Multi-layer SONET/SDH Links . . . . . . . 3
2.2. Link Component Availability Sub-TLV. . . . . . . . . . . . 4
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
4. Security Considerations . . . . . . . . . . . . . . . . . . . 6
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6
6. References. . . . . . . . . . . . . . . . . . . . . . . . . . . 6
6.1. Normative References. . . . . . . . . . . . . . . . . . . . 6
6.2. Informative References. . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7
Intellectual Property and Copyright Statements . . . . . . . . . . 7
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1. Introduction
The ITU-T defines the architecture of the Automatically Switched
Optical Network (ASON) in [G.8080].
[RFC4258] details the routing requirements for the GMPLS suite of
routing protocols to support the capabilities and functionality of
ASON control planes identified in [G.7715] and in [G.7715.1].
[RFC4652] evaluates the IETF Link State Routing Protocols against the
requirements identified in [RFC4258]. Section 7.1 of [RFC4652]
summarizes the capabilities to be provided by OSPFv2 [RFC2328] in
support of ASON routing. [RFC5787] is an Experimental RFC that
defines extensions to OSPFv2 to support these requirements. It
notes that the Interface Switching Capability Descriptor may
be included for each layer of a multi-layer link [RFC4202] to meet
ASON needs. However, for some types SONET/SDH links there can be
several data plane layers supported by a single link, and as a
result a need to carry several copies of the ISCD.
This draft defines an optimization for bandwidth advertisement for
SONET/SDH that removes the need to carry multiple copies of the ISCD
sub-TLV and has been designed to be consistent with advertisement
of bandwidth for OTN.
2. Optimization of bandwidth advertisement for SONET/SDH
2.1 Requirements for Multi-layer SONET/SDH Links
[RFC4652] notes that in the ASON context, bandwidth accounting
representations are possible, taking the form of a set of tuples
<signal_type; number of unallocated timeslots>, and that this
representation may also require definition of additional signal
types (from those defined in [RFC4606]) to represent support of
contiguously concatenated signals,
i.e., STS-(3xN)c SPE / VC-4-Nc, N = 4, 16, 64, 256.
It notes that the ISCD defined in [RFC4202] can be used to
support ASON without requiring any bandwidth accounting
change from an LSR perspective. However, the ISCD defined
in [RFC4202} must be advertised once per signal type
(identified by the Minimum Reservable Bandwidth value) in
order to provide an accurate advertisement of bandwidth
for each signal. For SONET/SDH links, it is common to support
4-5 signal types (e.g., STS-1, 3c, 12c, 48c and 192c) at once,
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and advertisement of 4-5 ISCD sub-TLVs would consume about
200 bytes as compared to 20-30 bytes for a tuple format.
Most of the ISCD bytes are required to advertise 8 levels of
priority. We believe this overhead can be reduced as (a) ASON
specifications do not identify priority as an ASON service; and
(b) TDM networks generally to not support preemption priority
and do not require 8 levels of priority.
2.2. Link Component Availability Sub-TLV
A Link Component Availability Sub-TLV is defined that carries an
indication of SONET/SDH bandwidth at multiple link component signal
types as supplementary information to the ISCD sub-TLV.
When multiple SONET/SDH signal types are advertised, a single ISCD
is given for the smallest bandwidth signal type and the LCA sub-TLV
is also advertised to provide compact bandwidth availability
advertisement for all signal types.
The type used for the sub-TLV is TBD.
The following format is defined:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type (tbd) | Length = 8 + n*4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Switching Cap | Encoding | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|7|6|5|4|3|2|1|0| Reserved | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Signal Type | Number of Unallocated Timeslots |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Signal Type | Number of Unallocated Timeslots |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// ... //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Signal Type | Number of Unallocated Timeslots |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Note: n defines the number of signal types supported on this link,
and thus has a value greater than or equal to 1. Inherited from
[RFC4202], the Switching Capability field and the Encoding field MUST
take the following values for Sonet/SDH interfaces: Switching
Capability (8 bits)=100 (TDM). Encoding (8 bits)=5 (Sonet/SDH).
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Priority flags (8 bits): Indicate the priorities supported on the
advertised link (0 is highest and 7 is lowest). When the flag is set,
the corresponding priority is supported and for each signal type, a
"row" (i.e. signal type + unreserved bandwidth field) is included,
in order from the highest to the lowest priority.
If no priority is supported, just the 0 priority MUST be advertised.
Signal Type (8 bits) (as defined in [RFC4606]):
Value Type (Elementary Signal)
----- ------------------------
5 STS-1 SPE / VC-3 [RFC4606]
6 STS-3c SPE / VC-4 [RFC4606]
TBD STS-12c SPE/VC-4-4c
TBD STS-48c SPE/VC-4-16c
TBD STS-192c SPE/VC-4-64c
Number of Unallocated Timeslots (24 bits):
Specifies the number of identical unallocated timeslots per Signal
Type and per TE Link. As such, the initial value(s) of this TLV
indicates the total capacity in terms of number of timeslots per TE
link. The signal type included in the BW announcement is specific to
the layer link being reported and is not derived from some other
signal type (e.g. STS-48c is not announced as 16 x STS-3c).
For instance on an OC-192/STM-64 interface either the number of
STS-3c SPE/VC-4 unallocated timeslots is initially equal to 64, or
the number of STS-48c SPE/VC-4-16c unallocated timeslots is equal to
4 or even a combination of both type of signals depending on the
interface capabilities. Once one of these timeslots is occupied
either by being allocated for a connection at the same or a larger
signal type or by being blocked due to the allocation of part of
the timeslot for a connection at a smaller signal type, the number
of unallocated timeslots is decreased by the number of timeslots
this connection implies.
3. IANA Considerations
IANA will allocate codepoints for the new Link Component
Allocation sub-TLV and its associated sub-fields from the
standard range. Three new Signal Type values are needed.
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4. Security Considerations
This document defines an optimization for SONET/SDH link bandwidth
advertisement consistent with the requirements in [RFC4258] and
[RFC4652]. No additional security issues are identified.
5. Acknowledgements
The authors would like to thank the following OIF members for their
comments and support for this document:
Richard Graveman (Department of Defense)
Hans-Martin Foisel (Deutsche Telekom)
Thierry Marcot (France Telecom)
Evelyne Roch (Nortel Networks)
Jonathan Sadler (Tellabs)
Yoshiaki Sone (NTT Corporation)
Takehiro Tsuritani (KDDI R&D Laboratories)
6. References
6.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2328] Moy, J., "OSPF Version 2", RFC 2328,April 1998.
[RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
(TE) Extensions to OSPF Version 2", RFC 3630,
September 2003.
[RFC4202] Kompella, K. and Y. Rekhter, "Routing Extensions in
Support of Generalized Multi-Protocol Label Switching
(GMPLS)", RFC 4202,February 2005.
[RFC4606] Mannie, E. and D. Papadimitriou, "Generalized Multi-
Protocol Label Switching (GMPLS) Extensions for
Synchronous Optical Network (SONET) and Synchronous
Digital Hierarchy (SDH) Control", RFC 4606, August 2006.
6.2. Informative References
[RFC5787] Papadimitriou, D., "OSPFv2 Routing Protocol Extensions
for ASON Routing," RFC 5787, March 2010.
[RFC4258] Brungard, D., "Requirements for Generalized Multi-Protocol
Label Switching (GMPLS) Routing for the Automatically
Switched Optical Network (ASON)", RFC 4258, November 2005.
[RFC4652] Papadimitriou, D., L.Ong, Sadler, J., Shew, S., and D.
Ward, "Evaluation of Existing Routing Protocols against
Automatic Switched Optical Network (ASON) Routing
Requirements", RFC 4652, February 2006.
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Authors' Addresses
Lyndon Ong
Ciena
P.O.Box 308
Cupertino CA 95015
USA
Phone: +1 408 962 4929
Email: lyong@ciena.com
Andrew Malis
Verizon
117 West St.
Waltham, MA 02451
USA
Email: andrew.g.malis@verizon.com
Phone: +1 781 466 2362
Remi Theillaud
Marben Products
176 rue Jean Jaures
Puteaux 92800
France
Email: remi.theillaud@marben-products.com
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