Network Working Group D. King (Ed.) Internet Draft A. Farrel (Ed.) Updates: 3471, 6205 (if approved) Old Dog Consulting Category: Standards Track Y. Li (Ed.) Expires: 25 August 2013 Nanjing University F. Zhang ZTE R. Casellas CTTC 25 February 2013 Generalized Labels for the Flexi-Grid in Lambda-Switch-Capable (LSC) Label Switching Routers draft-farrkingel-ccamp-flexigrid-lambda-label-05.txt Abstract GMPLS supports the description of optical switching by identifying entries in fixed lists of switchable wavelengths (called grids) through the encoding of lambda labels. Work within the ITU-T Study Group 15 has defined a finer granularity grid, and the facility to flexibly select different widths of spectrum from the grid. This document defines a new GMPLS lambda label format to support this flexi-grid. This document updates RFC 3471 and RFC 6205 by introducing a new label format. Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html Farrel and King Expires August 2013 [Page 1] draft-farrkingel-ccamp-flexigrid-lambda-label-05.txt February 2013 Copyright Notice Copyright (c) 2012 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. 1. Introduction As described in [RFC3945], GMPLS extends MPLS from supporting only Packet Switching Capable (PSC) interfaces and switching to also support four new classes of interfaces and switching that include Lambda Switch Capable (LSC). A functional description of the extensions to MPLS signaling needed to support this new class of interface and switching is provided in [RFC3471]. [RFC3471] states that wavelength labels "only have significance between two neighbors" (Section 3.2.1.1); global wavelength semantics are not considered. [RFC6205] defines a standard lambda label format that has a global semantic and which is compliant with both the Dense Wavelength Division Multiplexing (DWDM) grid [G.694.1] and the Coarse Wavelength Division Multiplexing (CWDM) grid [G.694.2]. The terms DWDM and CWDM are defined in [G.671]. A flexible grid network selects its data channels as arbitrarily assigned pieces of the spectrum. Mixed bitrate transmission systems can allocate their channels with different spectral bandwidths so that the channels can be optimized for the bandwidth requirements of the particular bit rate and modulation scheme of the individual channels. This technique is regarded as a promising way to improve the network utilization efficiency and fundamentally reduce the cost of the core network. The "flexi-grid" has been developed within the ITU-T Study Group 15 to allow selection and switching of pieces of the optical spectrum chosen flexibly from a fine granularity grid of wavelengths with variable spectral bandwidth [G.694.1]. This document updates the Farrel and King Expires August 2013 [Page 2] draft-farrkingel-ccamp-flexigrid-lambda-label-05.txt February 2013 definition of GMPLS lambda labels provided in [RFC6205] to support the flexi-grid. This document relies on [G.694.1] for the definition of the optical data plane and does not make any updates to the work of the ITU-T in that regard. The encoding specified in this document will be communicated to the ITU-T for comment before publication as an RFC. 1.1. 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 [RFC2119]. 2. Overview of Flexi-Grid [G.694.1] extends DWDM fixed grids as defined in [G.694.1] to add support for flexible grids. The basis of the work is to allow a data channel to be formed from an abstract grid anchored at 193.1 THz and selected on a channel spacing of 6.25 GHz with a variable slot width measured in units of 12.5 GHz. Individual allocations may be made on this basis from anywhere in the spectrum, subject to allocations not overlapping. [G.694.1] provides clear guidance on the support of flexible grid by implementations in Section 2 of Appendix I: The flexible DWDM grid defined in clause 7 has a nominal central frequency granularity of 6.25 GHz and a slot width granularity of 12.5 GHz. However, devices or applications that make use of the flexible grid may not have to be capable of supporting every possible slot width or position. In other words, applications may be defined where only a subset of the possible slot widths and positions are required to be supported. For example, an application could be defined where the nominal central frequency granularity is 12.5 GHz (by only requiring values of n that are even) and that only requires slot widths as a multiple of 25 GHz (by only requiring values of m that are even). Farrel and King Expires August 2013 [Page 3] draft-farrkingel-ccamp-flexigrid-lambda-label-05.txt February 2013 3. Fixed Grid Lambda Label Encoding [RFC6205] defines an encoding for a global semantic for a DWDM label based on four fields: - Grid: used to select which grid the lambda is selected from. Values defined in [RFC6205] identify DWDM [G.694.1] and CWDM [G.694.2]. - C.S. (Channel Spacing): used to indicate the channel spacing. [RFC6205] defines values to represent spacing of 100, 50, 25 and 12.5 GHz. - Identifier: a local-scoped integer used to distinguish different lasers (in one node) when they can transmit the same frequency lambda. - n: a two's-complement integer to take either a positive, negative, or zero value. This value is used to compute the frequency as defined in [RFC6205] and based on [G.694.1]. The use of n is repeated here for ease of reading. Frequency (THz) = 193.1 THz + n * frequency granularity (THz) where the nominal central frequency granularity for the flexible grid is 0.00625 THz 4. Flexi-Label Format and Values 4.1 Flexi-Label Encoding This document defines a generalized label encoding for use in flexi- grid systems. As with the other GMPLS lambda label formats defined in [RFC3471] and [RFC6205], the use of this label format is known a priori. That is, since the interpretation of all lambda labels is determined hop-by-hop, the use of this label format requires that all nodes on the path expect to use this label format. For convenience, however, the label format is modeled on the fixed grid label defined in [RFC6205] and briefly described in Section 3. Farrel and King Expires August 2013 [Page 4] draft-farrkingel-ccamp-flexigrid-lambda-label-05.txt February 2013 Figure 1 shows the format of the Flexi-Label. It is a 64 bit label. 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Grid | C.S. | Identifier | n | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | m | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1 : The Flexi-Label Encoding This document defines a new Grid value to supplement those in [RFC6205]: +----------+---------+ | Grid | Value | +----------+---------+ |ITU-T Flex| 3 | +----------+---------+ Within the fixed grid network, the C.S. value is used to represent the channel spacing, as the spacing between adjacent channels is constant. For the flexible grid situation, this field is used to represent the nominal central frequency granularity. This document defines a new C.S. value to supplement those in [RFC6205]: +----------+---------+ | C.S(GHz) | Value | +----------+---------+ | 6.25 | 5 | +----------+---------+ The meaning of the Identifier field is maintained from [RFC6205] (see also Section 3). The meaning of n is maintained from [RFC6205] (see also Section 3). The m field is used to identify the slot width according to the formula given in [G.694.1] as follows: Slot Width (GHz) = 12.5 GHz * m The Reserved field MUST be set to zero on transmission and SHOULD be ignored on receipt. Farrel and King Expires August 2013 [Page 5] draft-farrkingel-ccamp-flexigrid-lambda-label-05.txt February 2013 An implementation that wishes to use the flexi-grid label encoding MUST follow the procedures of [RFC3473] and of [RFC3471] as updated by [RFC6205]. It MUST set Grid to 3 and C.S. to 5. It MUST set Identifier to indicate the local identifier of the laser in use as described in [RFC6205]. It MUST also set n according to the formula in Section 3 (inherited unchanged from [RFC6205]). Finally, the implementation MUST set m as described in the formula stated above. 4.2. Considerations of Bandwidth There is some overlap between the concept of bandwidth and label in many GMPLS-based systems where a label indicates a physical switching resource. This overlap is increased in a flexi-grid system where a label value indicates the slot width and so affects the bandwidth supported by an LSP. Thus the 'm' parameter is both a property of the label (i.e., it helps define exactly what is switched) and of the bandwidth. In GMPLS signaling [RFC3473], bandwidth is requested in the TSpec object and confirmed in the Flowspec object. The 'm' parameter is a parameter of the GMPLS flexi-grid label as described above and is also a parameter of the flexi-grid TSpec and Flowspec as described in [FLEXRSVP]. 5. Manageability Considerations This document introduces no new elements for management. That is, labels can continue to be used in the same way by the GMPLS protocols and where those labels were treated as opaque quantities with local or global significance, no change is needed to the management systems. However, this document introduces some changes to the nature of a label that may require changes to management systems. Firstly, systems that handle lambda labels as 32 bit quantities need to be updated to process the 64 bit labels described in this document even if the labels are treated as opaque quantities. Furthermore, although management systems that can handle lambda labels as defined in [RFC6205] can continue to process the fields defined in RFC 6205 as before, they have to handle new legal values of some of those fields (Grid = 3 and C.S. = 5), and they have to be aware of the new 'm' field. Farrel and King Expires August 2013 [Page 6] draft-farrkingel-ccamp-flexigrid-lambda-label-05.txt February 2013 6. Security Considerations [RFC6205] notes that the definition of a new label encoding does not introduce any new security considerations to [RFC3471] and [RFC3473]. That statement applies equally to this document. For a general discussion on MPLS and GMPLS-related security issues, see the MPLS/GMPLS security framework [RFC5920]. 7. IANA Considerations IANA maintains the "Generalized Multi-Protocol Label Switching (GMPLS) Signaling Parameters" registry that contains several subregistries. 7.1. Grid Subregistry IANA is requested to allocate a new entry in this subregistry as follows: Value Grid Reference ----- ------------------------- ---------- 3 ITU-T Flex [This.I-D] 7.2. DWDM Channel Spacing Subregistry IANA is requested to allocate a new entry in this subregistry as follows: Value Channel Spacing (GHz) Reference ----- ------------------------- ---------- 5 6.25 [This.I-D] 8. Acknowledgments Very many thanks to Lou Berger for discussions of labels of more than 32 bits. Many thanks to Sergio Belotti, Pietro Vittorio Grandi, and Fatai Zhang for their support of this work. Special thanks to the Vancouver 2012 Pool Party for discussions and rough consensus: Dieter Beller, Ramon Casellas, Daniele Ceccarelli, Oscar Gonzalez de Dios, Iftekhar Hussain, Cyril Margaria, Lyndon Ong, and Fatai Zhang. The authors would like to thank Ben Niven-Jenkins for inspiring the choice of filename for this document. Farrel and King Expires August 2013 [Page 7] draft-farrkingel-ccamp-flexigrid-lambda-label-05.txt February 2013 9. References 9.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC3471] Berger, L., Ed., "Generalized Multi-Protocol Label Switching (GMPLS) Signaling Functional Description", RFC 3471, January 2003. [RFC3473] Berger, L., Ed., "Generalized Multi-Protocol Label Switching (GMPLS) Signaling Resource ReserVation Protocol- Traffic Engineering (RSVP-TE) Extensions", RFC 3473, January 2003. [RFC6205] Otani, T., and Li, D., "Generalized Labels for Lambda- Switch-Capable (LSC) Label Switching Routers", RFC 6205, October 2011. [G.694.1] ITU-T Recommendation G.694.1 (revision 2), "Spectral grids for WDM applications: DWDM frequency grid", February 2012. 9.2. Informative References [RFC3945] Mannie, E., Ed., "Generalized Multi-Protocol Label Switching (GMPLS) Architecture", RFC 3945, October 2004. [RFC5920] Fang, L., Ed., "Security Framework for MPLS and GMPLS Networks", RFC 5920, July 2010. [G.671] ITU-T Recommendation G.671, "Transmission characteristics of optical components and subsystems", 2009. [G.694.2] ITU-T Recommendation G.694.2, "Spectral grids for WDM applications: CWDM wavelength grid", December 2003. [FLEXRSVP] Zhang, F., Gonzalez de Dios, O., and D. Ceccarelli, "RSVP-TE Signaling Extensions in support of Flexible Grid", draft-zhang-ccamp-flexible-grid-rsvp-te-ext, work in progress. Farrel and King Expires August 2013 [Page 8] draft-farrkingel-ccamp-flexigrid-lambda-label-05.txt February 2013 Appendix A. Flexi-Grid Example Consider a fragment of an optical LSP between node A and node B using the flexible grid. Suppose that the LSP on this hop is formed: - using the ITU-T Flexi-Grid - the nominal central freequency of the slot 193.05 THz - the nominal central frequency granularity is 6.25 GHz - the slot width is 50 GHz. In this case the label representing the switchable quantity that is the flexi-grid quantity is encoded as described in Section 4.1 with the following parameter settings. The label can be used in signaling or in management protocols to describe the LSP. Grid = 3 : ITU-T Flexi-Grid C.S. = 5 : 6.25 GHz nominal central frequency granularity Identifier = local value indicating the laser in use n = -8 : Frequency (THz) = 193.1 THz + n * frequency granularity (THz) 193.05 (THz) = 193.1 (THz) + n * 0.00625 (THz) n = (193.05-193.1)/0.00625 = -8 m = 4 : Slot Width (GHz) = 12.5 GHz * m 50 (GHz) = 12.5 (GHz) * m m = 50 / 12.5 = 4 Authors' Addresses Adrian Farrel Old Dog Consulting EMail: adrian@olddog.co.uk Daniel King (Editor) Old Dog Consulting EMail: daniel@olddog.co.uk Yao Li (Editor) Nanjing University EMail: wsliguotou@hotmail.com Farrel and King Expires August 2013 [Page 9] draft-farrkingel-ccamp-flexigrid-lambda-label-05.txt February 2013 Zhang Fei ZTE EMail: zhang.fei3@zte.com.cn Ramon Casellas CTTC EMail: ramon.casellas@cttc.es Farrel and King Expires August 2013 [Page 10]