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Keywords: Flexible-grid, Flexible optical grid, Optical network, Optical trail, Optical LSP, GMPLS, WDM, PCE, spectrum reservation, flexible spectrum
Internet Engineering Task Force (IETF) F. Zhang
Request for Comments: 7792 X. Zhang
Category: Standards Track Huawei
ISSN: 2070-1721 A. Farrel
Old Dog Consulting
O. Gonzalez de Dios
Telefonica
D. Ceccarelli
Ericsson
March 2016
RSVP-TE Signaling Extensions in Support of Flexi-Grid
Dense Wavelength Division Multiplexing (DWDM) Networks
Abstract
This memo describes the extensions to the Resource Reservation
Protocol - Traffic Engineering (RSVP-TE) signaling protocol to
support Label Switched Paths (LSPs) in a GMPLS-controlled network
that includes devices using the flexible optical grid.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc7792.
Zhang, et al. Standards Track [Page 1]
RFC 7792 Flexi-Grid RSVP-TE Signaling Extensions March 2016
Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction ....................................................3
2. Terminology .....................................................3
2.1. Conventions Used in This Document ..........................3
3. Requirements for Flexible-Grid Signaling ........................4
3.1. Slot Width .................................................4
3.2. Frequency Slot .............................................5
4. Protocol Extensions .............................................6
4.1. Traffic Parameters .........................................6
4.1.1. Applicability to Fixed-Grid Networks ................7
4.2. Generalized Label ..........................................7
4.3. Signaling Procedures .......................................7
5. IANA Considerations .............................................8
5.1. Class Types for RSVP Objects ...............................8
6. Manageability Considerations ....................................8
7. Security Considerations .........................................8
8. References ......................................................9
8.1. Normative References .......................................9
8.2. Informative References .....................................9
Acknowledgments ...................................................11
Contributors ......................................................11
Authors' Addresses ................................................12
Zhang, et al. Standards Track [Page 2]
RFC 7792 Flexi-Grid RSVP-TE Signaling Extensions March 2016
1. Introduction
[G.694.1] defines the Dense Wavelength Division Multiplexing (DWDM)
frequency grids for Wavelength Division Multiplexing (WDM)
applications. A frequency grid is a reference set of frequencies
used to denote allowed nominal central frequencies that may be used
for defining applications that utilize WDM transmission. The channel
spacing is the frequency spacing between two allowed nominal central
frequencies. All of the wavelengths on a fiber use different central
frequencies and occupy a designated range of frequencies.
Fixed-grid channel spacing is selected from 12.5 GHz, 25 GHz, 50 GHz,
100 GHz, and integer multiples of 100 GHz. Additionally, [G.694.1]
defines "flexible grids", also known as "flexi-grid". The terms
"frequency slot" (i.e., the frequency range allocated to a specific
channel and unavailable to other channels within a flexible grid) and
"slot width" (i.e., the full width of a frequency slot in a flexible
grid) are introduced in [G.694.1] to define a flexible grid.
[RFC7698] defines a framework and the associated control-plane
requirements for the GMPLS-based [RFC3945] control of flexi-grid DWDM
networks.
[RFC6163] provides a framework for GMPLS and Path Computation Element
(PCE) control of Wavelength Switched Optical Networks (WSONs), and
[RFC7689] describes the requirements and protocol extensions for
signaling to set up Label Switched Paths (LSPs) in WSONs.
This document describes the additional requirements and protocol
extensions to Resource Reservation Protocol - Traffic Engineering
(RSVP-TE) [RFC3473] to set up LSPs in networks that support the
flexi-grid.
2. Terminology
For terminology related to flexi-grid, please refer to [RFC7698] and
[G.694.1].
2.1. Conventions Used in This Document
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].
Zhang, et al. Standards Track [Page 3]
RFC 7792 Flexi-Grid RSVP-TE Signaling Extensions March 2016
3. Requirements for Flexible-Grid Signaling
The architecture for establishing LSPs in a flexi-grid network is
described in [RFC7698].
An optical-spectrum LSP occupies a specific frequency slot, i.e., a
range of frequencies. The process of computing a route and the
allocation of a frequency slot is referred to as "Routing and
Spectrum Assignment" (RSA). [RFC7698] describes three architectural
approaches to RSA: combined RSA, separated RSA, and distributed SA.
The first two approaches are referred to as "centralized SA", because
routing (i.e., path determination) and spectrum assignment (i.e.,
selection of frequency slots) are both performed by a centralized
entity prior to the signaling procedure.
In the case of centralized SA, the assigned frequency slot is
specified in the RSVP-TE Path message during LSP setup. In the case
of distributed SA, the slot width of the flexi-grid LSP is specified
in the Path message, allowing the network elements to select the
frequency slot to be used when they process the RSVP-TE messages.
If the capability to switch or convert the whole optical spectrum
allocated to an optical-spectrum LSP is not available at some nodes
along the path of the LSP, the LSP is subject to the Optical
"spectrum continuity constraint" as described in [RFC7698].
The remainder of this section states the additional requirements for
signaling in a flexi-grid network.
3.1. Slot Width
The slot width is an end-to-end parameter representing how much
frequency resource is requested for a flexi-grid LSP. It is the
equivalent of optical bandwidth, although the amount of bandwidth
associated with a slot width will depend on the signal encoding.
Different LSPs may request different amounts of frequency resource in
flexible-grid networks, so the slot width MUST be carried in the
signaling message during LSP establishment. This enables the nodes
along the LSP to know how much frequency resource has been requested
(in a Path message) and how much has been allocated (by a
Resv message) for the LSP.
Zhang, et al. Standards Track [Page 4]
RFC 7792 Flexi-Grid RSVP-TE Signaling Extensions March 2016
3.2. Frequency Slot
The frequency slot information identifies which part of the frequency
spectrum is allocated on each link for an LSP in a flexi-grid
network.
This information MUST be present in a Resv message to indicate,
hop by hop, the central frequency of the allocated resource. In
combination with the slot width indicated in a Resv message (see
Section 3.1), the central frequency carried in a Resv message
identifies the resources reserved for the LSP (known as the
frequency slot).
The frequency slot can be represented by two parameters, as follows:
Frequency slot = [(central frequency) - (slot width)/2] ~
[(central frequency) + (slot width)/2]
As is common with other resource identifiers (i.e., labels) in GMPLS
signaling, it must be possible for the head-end node, when sending a
Path message, to suggest or require the central frequency to be used
for the LSP. Furthermore, for bidirectional LSPs, the Path message
MUST be able to specify the central frequency to be used for
reverse-direction traffic.
As described in [G.694.1], the allowed frequency slots for the
flexible DWDM grid have a nominal central frequency (in THz),
defined by:
193.1 + n * 0.00625
where n is zero or a positive or negative integer.
The slot width (in GHz) is defined as:
12.5 * m
where m is a positive integer.
It is possible that an implementation supports only a subset of the
possible slot widths and central frequencies. For example, an
implementation can be built that is
1. limited to have a nominal central frequency granularity of
12.5 GHz, by only allowing values of n that are even, and
2. further limited to only support slot widths of 25 GHz, by only
allowing values of m that are even.
Zhang, et al. Standards Track [Page 5]
RFC 7792 Flexi-Grid RSVP-TE Signaling Extensions March 2016
Further details can be found in [RFC7698].
4. Protocol Extensions
This section defines the extensions to RSVP-TE signaling for GMPLS
[RFC3473] to support flexible-grid networks.
4.1. Traffic Parameters
In RSVP-TE, the SENDER_TSPEC object in the Path message indicates the
requested resource reservation. The FLOWSPEC object in the Resv
message indicates the actual resource reservation. As described in
Section 3.1, the slot width represents how much frequency resource is
requested for a flexi-grid LSP. That is, it describes the end-to-end
traffic profile of the LSP. Therefore, the traffic parameters for a
flexi-grid LSP encode the slot width.
This document defines new Class Types (C-Types) for the SENDER_TSPEC
and FLOWSPEC objects to carry Spectrum-Switched Optical Network
(SSON) traffic parameters:
SSON SENDER_TSPEC: Class = 12, C-Type = 8.
SSON FLOWSPEC: Class = 9, C-Type = 8.
The SSON traffic parameters carried in both objects MUST have the
format shown in Figure 1.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| m | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: The SSON Traffic Parameters
m (16 bits): a positive integer; the slot width is specified by
m * 12.5 GHz.
The Reserved bits MUST be set to zero and ignored upon receipt.
Zhang, et al. Standards Track [Page 6]
RFC 7792 Flexi-Grid RSVP-TE Signaling Extensions March 2016
4.1.1. Applicability to Fixed-Grid Networks
Note that the slot width (i.e., traffic parameters) of a fixed grid
defined in [G.694.1] can also be specified by using the SSON traffic
parameters. The fixed-grid channel spacings (12.5 GHz, 25 GHz,
50 GHz, 100 GHz, and integer multiples of 100 GHz) are also the
multiples of 12.5 GHz, so the m parameter can be used to represent
these slot widths.
Therefore, it is possible to consider using the new traffic parameter
object types in common signaling messages for flexi-grid and legacy
DWDM networks.
4.2. Generalized Label
In the case of a flexible-grid network, the labels that have been
requested or allocated as signaled in the RSVP-TE objects are encoded
as described in [RFC7699]. This new label encoding can appear in any
RSVP-TE object or sub-object that can carry a label.
As noted in Section 4.2 of [RFC7699], the m parameter forms part of
the label as well as part of the traffic parameters.
As described in Section 4.3 of [RFC7699], a "compound label",
constructed from a concatenation of the flexi-grid labels, is used
when signaling an LSP that uses multiple flexi-grid slots.
4.3. Signaling Procedures
There are no differences between the signaling procedures described
for LSP control in [RFC7698] and those required for use in a
fixed-grid network [RFC7689]. Obviously, the TSpec, FlowSpec, and
label formats described in Sections 4.1 and 4.2 are used. The
signaling procedures for distributed SA and centralized SA can be
applied.
Zhang, et al. Standards Track [Page 7]
RFC 7792 Flexi-Grid RSVP-TE Signaling Extensions March 2016
5. IANA Considerations
5.1. Class Types for RSVP Objects
This document introduces two new Class Types for existing RSVP
objects. IANA has made the following allocations from the "Resource
Reservation Protocol (RSVP) Parameters" registry using the "Class
Names, Class Numbers, and Class Types" sub-registry.
Class Number Class Name Reference
------------ ----------------------- ---------
9 FLOWSPEC [RFC2205]
Class Type (C-Type):
(8) SSON FLOWSPEC RFC 7792
Class Number Class Name Reference
------------ ----------------------- ---------
12 SENDER_TSPEC [RFC2205]
Class Type (C-Type):
(8) SSON SENDER_TSPEC RFC 7792
6. Manageability Considerations
This document makes minor modifications to GMPLS signaling but does
not change the manageability considerations for such networks.
Clearly, protocol analysis tools and other diagnostic aids (including
logging systems and MIB modules) will need to be enhanced to support
the new traffic parameters and label formats.
7. Security Considerations
This document introduces no new security considerations to [RFC3473].
See also [RFC5920] for a discussion of security considerations for
GMPLS signaling.
Zhang, et al. Standards Track [Page 8]
RFC 7792 Flexi-Grid RSVP-TE Signaling Extensions March 2016
8. References
8.1. Normative References
[G.694.1] International Telecommunication Union, "Spectral grids for
WDM applications: DWDM frequency grid", ITU-T
Recommendation G.694.1, February 2012,
<https://www.itu.int/rec/T-REC-G.694.1/en>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC3473] Berger, L., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Resource ReserVation
Protocol-Traffic Engineering (RSVP-TE) Extensions",
RFC 3473, DOI 10.17487/RFC3473, January 2003,
<http://www.rfc-editor.org/info/rfc3473>.
[RFC7699] Farrel, A., King, D., Li, Y., and F. Zhang, "Generalized
Labels for the Flexi-Grid in Lambda Switch Capable (LSC)
Label Switching Routers", RFC 7699, DOI 10.17487/RFC7699,
November 2015, <http://www.rfc-editor.org/info/rfc7699>.
8.2. Informative References
[RFC2205] Braden, R., Ed., Zhang, L., Berson, S., Herzog, S., and S.
Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1
Functional Specification", RFC 2205, DOI 10.17487/RFC2205,
September 1997, <http://www.rfc-editor.org/info/rfc2205>.
[RFC3945] Mannie, E., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Architecture", RFC 3945,
DOI 10.17487/RFC3945, October 2004,
<http://www.rfc-editor.org/info/rfc3945>.
[RFC5920] Fang, L., Ed., "Security Framework for MPLS and GMPLS
Networks", RFC 5920, DOI 10.17487/RFC5920, July 2010,
<http://www.rfc-editor.org/info/rfc5920>.
[RFC6163] Lee, Y., Ed., Bernstein, G., Ed., and W. Imajuku,
"Framework for GMPLS and Path Computation Element (PCE)
Control of Wavelength Switched Optical Networks (WSONs)",
RFC 6163, DOI 10.17487/RFC6163, April 2011,
<http://www.rfc-editor.org/info/rfc6163>.
Zhang, et al. Standards Track [Page 9]
RFC 7792 Flexi-Grid RSVP-TE Signaling Extensions March 2016
[RFC7689] Bernstein, G., Ed., Xu, S., Lee, Y., Ed., Martinelli, G.,
and H. Harai, "Signaling Extensions for Wavelength
Switched Optical Networks", RFC 7689,
DOI 10.17487/RFC7689, November 2015,
<http://www.rfc-editor.org/info/rfc7689>.
[RFC7698] Gonzalez de Dios, O., Ed., Casellas, R., Ed., Zhang, F.,
Fu, X., Ceccarelli, D., and I. Hussain, "Framework and
Requirements for GMPLS-Based Control of Flexi-Grid Dense
Wavelength Division Multiplexing (DWDM) Networks",
RFC 7698, DOI 10.17487/RFC7698, November 2015,
<http://www.rfc-editor.org/info/rfc7698>.
Zhang, et al. Standards Track [Page 10]
RFC 7792 Flexi-Grid RSVP-TE Signaling Extensions March 2016
Acknowledgments
This work was supported in part by the FP-7 IDEALIST project under
grant agreement number 317999.
Contributors
Ramon Casellas
CTTC
Av. Carl Friedrich Gauss n7
Castelldefels, Barcelona 08860
Spain
Email: ramon.casellas@cttc.es
Felipe Jimenez Arribas
Telefonica Investigacion y Desarrollo
Emilio Vargas 6
Madrid 28045
Spain
Email: felipej@tid.es
Yi Lin
Huawei Technologies Co., Ltd.
F3-5-B R&D Center, Huawei Base
Bantian, Longgang District
Shenzhen 518129
China
Phone: +86 755-28972914
Email: yi.lin@huawei.com
Qilei Wang
ZTE
Email: wang.qilei@zte.com.cn
Haomian Zheng
Huawei Technologies
Email: zhenghaomian@huawei.com
Zhang, et al. Standards Track [Page 11]
RFC 7792 Flexi-Grid RSVP-TE Signaling Extensions March 2016
Authors' Addresses
Fatai Zhang
Huawei Technologies
Email: zhangfatai@huawei.com
Xian Zhang
Huawei Technologies
Email: zhang.xian@huawei.com
Adrian Farrel
Old Dog Consulting
Email: adrian@olddog.co.uk
Oscar Gonzalez de Dios
Telefonica Investigacion y Desarrollo
Ronda de la Comunicacion S/N
Madrid 28050
Spain
Phone: +34 913129647
Email: oscar.gonzalezdedios@telefonica.com
Daniele Ceccarelli
Ericsson
Via A. Negrone 1/A
Genova - Sestri Ponente
Italy
Email: daniele.ceccarelli@ericsson.com
Zhang, et al. Standards Track [Page 12]