Network Working Group Qilei Wang Internet-Draft Xihua Fu Intended status: Standards Track ZTE Corporation Expires: September 1, 2012 Feb 29, 2012 OSPF extensions for support wavelength range allocation in flexible grid supported network draft-wang-ccamp-flexigrid-wavelength-range-ospf-00.txt Abstract This document addresses the requirements and routing protocol extension of wavelength range allocation in flexible grid supported network in order to help spectrum utilization in the process of path computation. Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. 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Qilei Wang & Xihua Fu Expires September 1, 2012 [Page 1] Internet-Draft wavelength range allocation Feb 2012 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Conventions used in this document . . . . . . . . . . . . . . . 4 3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 4. Extension of routing protocol . . . . . . . . . . . . . . . . . 5 4.1. Relationship with WSON . . . . . . . . . . . . . . . . . . 5 4.2. Extensions of OSPF Protocol to Support Wavelength Range Allocation . . . . . . . . . . . . . . . . . . . . . 6 4.2.1. Wavelength Range Allocation by Bitrates . . . . . . . . 6 5. Security Considerations . . . . . . . . . . . . . . . . . . . . 8 6. IANA considerations . . . . . . . . . . . . . . . . . . . . . . 8 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8 7.1. Normative References . . . . . . . . . . . . . . . . . . . 8 7.2. Informative References . . . . . . . . . . . . . . . . . . 8 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9 Qilei Wang & Xihua Fu Expires September 1, 2012 [Page 2] Internet-Draft wavelength range allocation Feb 2012 1. Introduction In the latest version of ITU-T G.694.1, a new flexible grid technology is defined. The flexible grid technology is also a dense wavelength division multiplexing and is different from traditional fixed grid technology. Difference between fixed grid technology and flexible grid technology can be found in [G.694.1], the flexible grid technology allows mixed bit rates or mixed modulation formats transmission system to allocate frequency slots with different slot widths so that they can be optimized for the bandwidth requirements of a particular bit rate and modulation scheme of the individual channels. As shown in Figure 1, there are three different channel spacing exist in one system. 25GHz 50GHz 75GHz +-------+ +---------------+ +-----------------------+ | | | | | | __|_______|_______|_______________|_______|_______________________|_ | | | | | | | | | | | | | | | | | 193 193.1 193.2 Figure 1: flexible grid wavelength utilization Traditional fixed grid doesn't allow system to allocate frequency slots with different widths, whereas flexible grid technology allows this. The situation that different slot widths exist in the flexible grid network brings much disorder. Spectrum fragments that can't be used anyone will appear in the network in the process of allocation of wavelength for a channel. And this will result in the decline of spectrum utilization rate. So in order to raise the spectrum utilization rate, spectrum utilization scheme such as scheme of wavelength assignment and use of slot position, wavelength range, can be done in advance, and this will help raise the spectrum utilization rate. More advantage can be seen in section 2. This document mainly addresses the routing protocol extension support the advertisement of wavelength range (or spectrum block) allocation information, such as the wavelength range positions and specific restriction information which are related to this wavelength range and so on. Certain policy would be involved here to help allocation wavelength range. One wavelength range can only be used for path setup with specific attributes, for example, with specific bitrates and/or modulation format. When control plane uses path computation element to setup an end-to- Qilei Wang & Xihua Fu Expires September 1, 2012 [Page 3] Internet-Draft wavelength range allocation Feb 2012 end path in flexible grid network, wavelength available information and restriction information should be considered in order to compute a suitable end-to-end path. The restriction information can be derived by path computation element through routing advertisement, and the wavelength restriction information depicted in this document should also be considered in the flexible network. 2. 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]. 3. Overview Concerns were expressed in ITU-T document about mixing and matching a variety of bitrates and modulation formats on a single fiber completely freedom. If flexible grid network allows completely freedom, indiscriminate positioning of the various channels with respect to each other, it is likely to lead to dramatically impaired system performance compared to a more careful choice of slot positioning / wavelength assignment. Effects like XPM (Cross-phase modulation) will appear if network allows completely freedom, indiscriminate positioning of various channels. Solution expressed by the ITU-T expert is that grouping of wavelength with the same bitrates and modulation formats is a sensible one. This document addresses the requirements and protocol extension of the grouping of wavelength with the same attributes such as bitrates and/or modulation formats. As signals of the same bitrates usually use the same modulation formation on a specific link, this document mainly pays attention to grouping of wavelength with the same bitrates and routing protocol extension is described in the next chapter. Some other advantages are also brought if operator split supported wavelength into several wavelength ranges and one wavelength range can be only used for path with specific attributes in the flexible grid network except what have been described above. Grouping of wavelength of the same bitrates would help reduce fragments. Channels in the same wavelength range with the same bitrates looks almost like fixed grid technology, and they won't generate much fragments in the path setup and release because every channel use the same slot width. It will also be convenient for operator to manage the flexible network if the operator groups the wavelength of the same bitrates. The whole wavelength that subsystems support can be partitioned into Qilei Wang & Xihua Fu Expires September 1, 2012 [Page 4] Internet-Draft wavelength range allocation Feb 2012 several wavelength ranges, and one wavelength range can only be used for paths setup with the specific bit rate. For example, a wavelength range which has a range of (m1, m2) can only be used for signal with 400Gbit/s to setup path, and m1 represents the start label of the wavelength range, m2 represents the end label of the wavelength range. Also the wavelength can be partitioned according to the bitrates and/or modulation format if it is needed in some complex scenarios, that is to say a wavelength range can only be used for signal with the specific bitrates and/or modulation format to setup path. When control plane uses path computation element to setup an end-to- end path through flexible grid network, wavelength available information and restriction information should be taken into consideration in order to compute a suitable end-to-end path. The wavelength range allocation information needs to be advertised by routing protocol in order to help the path computation. Section 4 describes the extension of OSPF routing protocol to advertise these wavelength range information in order to help with path computation. 4. Extension of routing protocol 4.1. Relationship with WSON As described in the introduction section, flexible grid is a new DWDM technology which is different from traditional fixed grid technology. It is described in newest version of ITU-T [G.694.1]. Flexible grid can make use of current WSON control plane technology to setup path, for example, routing protocol and signaling protocol. Additional extensions may be needed because of new features introduced by flexible grid. This Section addresses the routing extension of the features which is describe above base on the current WSON routing extension in IETF CCAMP. [draft-ietf-ccamp-general-constraint-encode] defines a new link sub- TLV called Port Label Restrictions sub-TLV. Descriptions about Port Label Restrictions sub-TLV in this draft are referenced here: "Port label restrictions describe the label restrictions that the network element (node) and link may impose on a port. These restrictions represent what labels may or may not be used on a link and are intended to be relatively static. More dynamic information is contained in the information on available labels. Port label restrictions are specified relative to the port in general or to a specific connectivity matrix for increased modeling flexibility" and "For example, Port Label Restrictions describes the wavelength restrictions that the link and various optical devices such as OXCs, ROADMs, and waveband multiplexers may impose on a port in WSON. Qilei Wang & Xihua Fu Expires September 1, 2012 [Page 5] Internet-Draft wavelength range allocation Feb 2012 These restrictions represent what wavelength may or may not be used on a link and are relatively static." The wavelength range allocation information described in this document can be regarded as label restrictions which are imposed by network element (node) on a port, and the network element include various optical devices such as OXCs, ROADMs and waveband multiplexers and so on. These wavelength range allocation restrictions represent what labels may or may not be used on a link or what labels can only be used for channel with specific bitrates and/or modulation format. The restrictions described in this document can be seen as relative static and can be included in Port Label Restrictions sub-TLV. 4.2. Extensions of OSPF Protocol to Support Wavelength Range Allocation Wavelength range allocation information should be known by path computation element if operators want to compute an end-to-end flexible grid network path. As described in the previous section, Port Label Restrictions sub-TLV can be used to carry this wavelength range allocation restriction information. Figure 1 is the format of Port Label Restrictions sub-TLV which is described in [draft-ietf-ccamp-general-constraint-encode] and definition of the parameters included in this sub-TLV can be found in this document. 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MatrixID |RestrictionType| Reserved/Parameter | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | : Additional Restriction Parameters per RestrictionType : | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2: Port Label Restrictions sub-TLV 4.2.1. Wavelength Range Allocation by Bitrates As described in section 3, signals on a single fiber with the same bitrates usually use the same modulation format, especially when the equipments come from one vendor. So here operator can allocation wavelength into several wavelength ranges by bitrates. In this section, OSPF protocol is extended to cover the wavelength range allocation information by bitrates. Qilei Wang & Xihua Fu Expires September 1, 2012 [Page 6] Internet-Draft wavelength range allocation Feb 2012 The wavelength range allocation information by bitrates is needed in the process of path computation if an end-to-end path needs to be computed by path computation element and this information SHOULD be advertised by routing protocols. Figure 3 gives a new kinds of Port Label Restrictions sub-TLV which mainly extent the Additional Restriction Parameters field to cover the wavelength ranges allocation information. The parameters in the Additional Restriction Parameters field include Bit Rate which indicates the bitrates of the specific wavelength range and (Start Label, End Label) tuple which indicates the wavelength range. 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MatrixID |RestrictionType|F| Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Bit Rate | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ : Start Label : +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ : End Label : +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 3 Definition of MatrixID and RestrictionType field can be found in the document [draft-ietf-ccamp-general-constraint-encode]. Value of RestrictionType needs to be assigned by IANA. When fixed grid network and flexible grid network exist on a single fiber, and an indication is needed to distinguish both of them. "F" bit is introduced as an indication to distinguish fixed grid (F = 0) and flexible grid (F = 1). "Bit Rate" field indicates the bitrates of the specific wavelength range. The tuple (Start Label, End Label) indicates the wavelength range, and the label encoding format can be found in [RFC6205] when used to represent fixed grid, and in [draft-farrkingel-ccamp-flexigrid-lambda-label] when used to represent flexible grid. Note: label encoding format in [RFC6205] can also be used by flexible grid, but it's an unresolved problem and needs further discussion. Qilei Wang & Xihua Fu Expires September 1, 2012 [Page 7] Internet-Draft wavelength range allocation Feb 2012 In some situation, modulation format information may also be needed to help allocation wavelength range, as signals with the same bitrates on a single fiber can use different modulation format. In this case, modulation formats information is needed to be carried in Port Label Restrictions sub-TLV. Wavelength that is supported by subsystems can be partitioned to service traditional fixed grid technology. 5. Security Considerations TBD 6. IANA considerations TBD. 7. References 7.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC6163] Lee, Y., Bernstein, G., and W. Imajuku, "Framework for GMPLS and Path Computation Element (PCE) Control of Wavelength Switched Optical Networks (WSONs)", RFC 6163, April 2011. 7.2. Informative References [G.694.1 v1] International Telecommunications Union, "Draft revised G.694.1 version 1.3". [flexible-grid-ospf-ext] Fatai Zhang, Xiaobing Zi, Ramon Casellas, O. Gonzalez de Dios, and D. Ceccarelli, "GMPLS OSPF-TE Extensions in support of Flexible-Grid in DWDM Networks", draft-zhang-ccamp-flexible-grid-ospf-ext-00.txt . [flexigrid-lambda-label] D. King, A. Farrel, Y. Li, F. Zhang, and R. Casellas, "Generalized Labels for the Flexi-Grid in Lambda-Switch- Capable (LSC) Label Switching Routers", draft-farrkingel-ccamp-flexigrid-lambda-label-01.txt . Qilei Wang & Xihua Fu Expires September 1, 2012 [Page 8] Internet-Draft wavelength range allocation Feb 2012 [super-channel-label] Iftekhar Hussain, Abinder Dhillon, Zhong Pan, Marco Sosa and Bert Basch, Steve Liu, Andrew G. Malis, "Generalized Label for Super-Channel Assignment on Flexible Grid", draft-hussain-ccamp-super-channel-label-02.txt . Authors' Addresses Qilei Wang ZTE Corporation Email: wang.qilei@zte.com.cn Xihua Fu ZTE Corporation ZTE Plaza, No.10, Tangyan South Road, Gaoxin District Xi'an 210012 P.R.China Email: fu.xihua@zte.com.cn Qilei Wang & Xihua Fu Expires September 1, 2012 [Page 9]