Network Working Group Fatai Zhang Internet-Draft Xiaobing Zi Intended status: Standards Track Huawei Ramon Casellas CTTC O. Gonzalez de Dios Telefonica D. Ceccarelli Ericsson Expires: April 24, 2012 October 24, 2011 GMPLS OSPF-TE Extensions in support of Flexible-Grid in DWDM Networks draft-zhang-ccamp-flexible-grid-ospf-ext-00.txt 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. This Internet-Draft will expire on April 24, 2012. Zhang Expires 2012 [Page 1] draft-zhang-ccamp-flexible-grid-ospf-ext-00.txt October 2011 Abstract This memo describes the OSPF-TE extensions in support of GMPLS control for flexible-grid in DWDM networks. 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]. Table of Contents 1. Introduction ................................................. 2 2. Terminology .................................................. 3 3. Requirements for Flexible-grid Routing ....................... 3 3.1. Available Frequency Ranges on the Flexible-Grid DWDM Links3 3.2. Comparison with Fixed-grid DWDM Links ................... 5 4. Extensions ................................................... 5 4.1. Available Labels Set sub-TLV ............................ 6 4.2. Examples ................................................ 7 5. IANA Considerations .......................................... 8 6. Security Considerations ...................................... 8 7. References ................................................... 8 8. Authors' Addresses .......................................... 10 1. Introduction [G.694.1v1] defines the Dense Wavelength Division Multiplexing (DWDM) frequency grids for 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. The channel spacing, i.e. the frequency spacing between two allowed nominal central frequencies could be 12.5 GHz, 25 GHz, 50 GHz, 100 GHz and integer multiples of 100 GHz as defined in [G.694.1v1]. All of the wavelengths on a fiber should use different central frequencies and occupy a fixed bandwidth of frequency. [G.FLEXIGRID], an updated version of [G.694.1v1] will be consented in December 2011 in support of flexible-grids. The terms "frequency slot (The frequency range allocated to a channel and unavailable to other channels within a flexible-grid)" and "slot width" (the full width of a frequency slot in a flexible-grid) are introduced to address flexible-grids. A channel is represented as a LSC (Lambda Zhang Expires 2012 [Page 2] draft-zhang-ccamp-flexible-grid-ospf-ext-00.txt October 2011 Switching Capable) LSP in the control plane, i.e. a LSC LSP should occupy a frequency slot on each fiber it traverses. In the case of flexible-grid, different LSC LSPs may have different slot width on a fiber, i.e. the slot width is flexible on a fiber. [WSON-OSPF] defines the OSPF-TE extensions for WSON networks, which focuses on the fixed grids of DWDM. [GEN-OSPF] defines OSPF-TE extensions in support of the general network element constraints under the control of GMPLS. This document describes the additional requirements and extensions of routing protocol brought by flexible- grid. This document uses the fiber link model which is shown in [FLEXIBLE- REQ] to describe the requirement and extensions for routing. The flexible-grid related terminologies can also refer to [FLEXIBLE-REQ]. 2. Terminology Flexible Grid: See [FLEXIBLE-REQ]. Frequency Slot Width: See [FLEXIBLE-REQ]. Frequency Range: See [FLEXIBLE-REQ]. SSON: Spectrum-Switched Optical Networks; See [FLEXIBLE-REQ]. LSC SS-LSP or flexi-LSP (Lambda Switch Capable Spectrum-Switched Label Switched Path): a control plane construct that represents a data plane connection in which the switching involves a frequency slot of a variable (flexible) slot width. The mapped client signal is transported over the slot width, using spectrum efficient modulations such as Coherent Optical Orthogonal Frequency Division Multiplexing (CO-OFDM). 3. Requirements for Flexible-grid Routing As described in [FLEXIBLE-REQ], the main changes for routing brought by flexible-grid are related to the DWDM links. 3.1. Available Frequency Ranges on the Flexible-Grid DWDM Links In the case of flexible-grids, the central frequency steps from 193.1 THz with 6.25 GHz granularity. The central frequency is calculated as follows: Central Frequency = 193.1 THz + n * 0.00625 THz Zhang Expires 2012 [Page 3] draft-zhang-ccamp-flexible-grid-ospf-ext-00.txt October 2011 Where n is a positive or negative integer including 0. Different LSC LSPs could occupy frequency slots with different slot width. The frequency slot width of a LSC LSP is defined as follows: Slot width = 0.0125 THz * m Where m is a positive integer. The frequency slot of a LSP can be determined by the slot width and central frequency as follows. Lowest frequency = (central frequency) - (slot width)/2 = (193.1 + n * 0.00625) - (0.0125 * m)/2 = (193.1 + (n - m) * 0.00625) THz; Highest frequency = (central frequency) + (slot width)/2 = (193.1 + n * 0.00625) + (0.0125 * m)/2 = (193.1 + (n + m) * 0.00625) THz; On a DWDM link, the frequency slots must not overlap with each other. However, the border frequencies of two frequency slots may be the same frequency, i.e. the highest frequency of a frequency slot may be the lowest frequency of the next frequency slot. Frequency Slot 1 Frequency Slot 2 +-----------+-----------------------+ | | | -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10 11 ...+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--... ------------ ------------------------ ^ ^ Central F = 193.1THz Central F = 193.1375 THz Slot width = 25 GHz Slot width = 50 GHz Figure 1 - Two Frequency Slots on a link Figure 1 shows two adjacent frequency slots on a link. The highest frequency of frequency slot 1 denoted by n=2 is the lowest frequency Zhang Expires 2012 [Page 4] draft-zhang-ccamp-flexible-grid-ospf-ext-00.txt October 2011 of slot 2. In this example, it means that the frequency range from n=-2 to n=10 is occupied and is unavailable to other LSC LSPs. Hence, the available frequency ranges should be advertised for the flexible-grid DWDM links. A set of non-overlapping available frequency ranges SHOULD be disseminated in order to allow efficient resource management of Flexible-grid DWDM links and RSA procedures which are described in section 4 of [FLEXIBLE-REQ]. 3.2. Comparison with Fixed-grid DWDM Links In case of fixed-grid DWDM links, each wavelength has a pre-defined central frequency and all the wavelengths occupy the same frequency range (channel spacing). Hence all the wavelengths in the DWDM links can be identified uniquely and the status (available or not) of the wavelengths can be advertised through routing protocol. W(-2) | W(-1) | W(0) | W(1) | W(2) | ...---------+-----------+-----------+-----------+-----------+----... 50 GHz | 50 GHz | 50 GHz | 50 GHz | 50 GHz | n=-2 n=-1 n=0 n=1 n=2 ...---+-----------+-----------+-----------+-----------+----------... ^ Central F = 193.1THz Figure 2 - A Link supports Fixed Wavelengths with 50 GHz Channel Spacing Figure 2 shows a link that supports fixed-grid with 50 GHz channel spacing. The central frequencies of the wavelengths are pre-defined by 'n' and each wavelength occupies a fixed 50 GHz frequency range as described in [G.694.1v1]. Different from the fixed-grid DWDM links, the slot width of the wavelengths are flexible on a flexible-grid DWDM link as described in section 2.1, i.e., the value of m in the formula is uncertain before a frequency slot is allocated. So, the available frequency ranges instead of the specific "wavelengths" should be advertised for a flexible-grid DWDM link. 4. Extensions As described in [FLEXIBLE-REQ], the network connectivity topology constructed by the links/nodes and node capabilities are the same as Zhang Expires 2012 [Page 5] draft-zhang-ccamp-flexible-grid-ospf-ext-00.txt October 2011 WSON which can be advertised by GMPLS routing protocol (refer to section 6.2 of [RFC6163]. In case of flexible-grid, the available frequency ranges instead of the specific ''wavelengths'' should be advertised for the link, which is different from the fixed grid DWDM. This section defines the GMPLS OSPF-TE extensions in support of advertising the available frequency ranges for the flexible-grid DWDM links. 4.1. Available Labels Set sub-TLV As described in section 2.1, the available frequency ranges other than the available frequency slots should be advertised for the flexible-grid DWDM links. The Available Labels Set sub-TLV defined in [GEN-OSPF] can be re-used to advertise the available frequency ranges for the flexible-grid DWDM links. To make the encoding efficiently, the inclusive/exclusive label ranges format of Available Labels Set sub-TLV defined in [GEN-OSPF] can be used for specifying the frequency ranges of the flexible-grid DWDM links. 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |2 or 3 | Num Labels(not used) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Start Label | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | End Label | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Note that it needs multiple Available Labels Set sub-TLVs if there are multiple discontinuous frequency ranges on a link. The fields of Start Label and End Label specify the lowest frequency and highest frequency of a frequency range. The label format defined in [FLEXIBLE-SIG] shown below can be used to encode the Start Label and End 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Zhang Expires 2012 [Page 6] draft-zhang-ccamp-flexible-grid-ospf-ext-00.txt October 2011 In case of Grid=1 (ITU-T DWDM), a new value of C.S. is defined for flexible 6.25 GHz grid. If the C.S. is 6.25 GHz in an Available Labels Set sub-TLV, it means that the corresponding link supports flexible-grid and the Start Label/End Label specifies the frequency range of the link. [Editors' Note: the other formats of Label set (e.g., Inclusive/Exclusive Label Lists and Bitmap Label Set) can also be used to specify the frequency ranges for the flexible-grid DWDM links.] 4.2. Examples Figure 3 shows an example of a flexible-grid DWDM link which is traversed by two LSC LSPs. Frequency Slot 1 Frequency Slot 2 ------------- ------------------- | | | | -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10 11 ...+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--... ------------- ------------------- ^ ^ Central F = 193.1THz Central F = 193.14375 THz Slot width = 25 GHz Slot width = 37.5 GHz Figure 3 - Two Frequency Slots on a Link The available frequency resource of the link could be advertised as follows: sub-TLV: o Exclusive Range 1: [Start label = 193.1 + (-2)*0.00625, End Label = 193.1 + 2*0.00625] o Exclusive Range 2: [Start label = 193.1 + 4*0.00625, End Label = 193.1 + 10*0.00625] It is noted that the central frequency denoted by n=3 is available for a LSC LSP with 12.5 GHz slot width request but unavailable for a LSC LSP with a wider slot width request. Zhang Expires 2012 [Page 7] draft-zhang-ccamp-flexible-grid-ospf-ext-00.txt October 2011 o If a LSC LSP which requires a 12.5 GHz width frequency slot is requested on this link, the central frequency denoted by n=3 is available because the corresponding frequency slot [n=2, n=4] dose not overlap the existing LSPs (the unavailable frequency ranges is [n=-2, n=2] and [n=4, n=10]). o If a LSC LSP which requires a 25 GHz width frequency slot is requested on this link, the central frequency denoted by n=3 is unavailable because the corresponding frequency slot [n=1, n=5] overlaps the unavailable central frequencies (the unavailable frequency ranges is [n=-2, n=2] and [n=4, n=10]). 5. IANA Considerations TBD. 6. Security Considerations This document does not introduce any further security issues other than those discussed in [RFC3630], [RFC4203]. 7. References [RFC2119] S. Bradner, "Key words for use in RFCs to indicate requirements levels", RFC 2119, March 1997. [G.694.1v1] ITU-T Recommendation G.694.1, Spectral grids for WDM applications: DWDM frequency grid, June 2002. [G.FLEXIGRID] Draft revised G.694.1 version 1.3, Unpublished ITU-T Study Group 15, Question 6. [WSON-PCE] Y. Lee, G. Bernstein, Jonas Martensson, T. Takeda and T. Tsuritani, "PCEP Requirements for WSON Routing and Wavelength Assignment", draft-ietf-pce-wson-routing- wavelength-05, July 2011. [WSON-SIG] G. Bernstein, Sugang Xu, Y. Lee, G. Martinelli and Hiroaki Harai, "Signaling Extensions for Wavelength Switched Optical Networks", draft-ietf-ccamp-wson- signaling-02, September 2011. [WSON-OSPF] Y. Lee and G. Bernstein, " GMPLS OSPF Enhancement for Signal and Network Element Compatibility for Wavelength Switched Optical Networks ", draft-ietf-ccamp-wson-signal- compatibility-ospf-06, September 2011. Zhang Expires 2012 [Page 8] draft-zhang-ccamp-flexible-grid-ospf-ext-00.txt October 2011 [GEN-OSPF] Fatai Zhang, Y. Lee, Jianrui Han, G. Bernstein and Yunbin Xu, " OSPF-TE Extensions for General Network Element Constraints ", draft-ietf-ccamp-gmpls-general-constraints- ospf-te-02, September 2011. [RFC6163] Y. Lee, G. Bernstein and W. Imajuku, "Framework for GMPLS and Path Computation Element (PCE) Control of Wavelength Switched Optical Networks (WSONs)t", RFC 6163, April 2011. [RFC6205] T. Otani and D. Li, "Generalized Labels for Lambda-Switch- Capable (LSC) Label Switching Routers", RFC 6205, March 2011. [FLEXIBLE-REQ] F.Zhang et al, "Requirements for GMPLS Control of Flexible-grids",draft-zhang-ccamp-flexible-grid- requirements, in progress. [FLEXIBLE-SIG] F.Zhang et al, " RSVP-TE Signaling Extensions in support of Flexible-grid",draft-zhang-ccamp-flexible-grid- rsvp-te-ext-00, in progress. Zhang Expires 2012 [Page 9] draft-zhang-ccamp-flexible-grid-ospf-ext-00.txt October 2011 8. Authors' Addresses Fatai Zhang Huawei Technologies F3-5-B R&D Center, Huawei Base Bantian, Longgang District Shenzhen 518129 P.R.China Phone: +86-755-28972912 Email: zhangfatai@huawei.com Ramon Casellas, Ph.D. CTTC Spain Phone: +34 936452916 Email: ramon.casellas@cttc.es Oscar Gonzalez de Dios Telefonica Investigacion y Desarrollo Emilio Vargas 6 Madrid, 28045 Spain Phone: +34 913374013 Email: ogondio@tid.es Daniele Ceccarelli Ericsson Via A. Negrone 1/A Genova - Sestri Ponente Italy Email: daniele.ceccarelli@ericsson.com Xiaobing Zi Huawei Technologies F3-5-B R&D Center, Huawei Base Bantian, Longgang District Shenzhen 518129 P.R.China Phone: +86-755-28973229 Email: zixiaobing@huawei.com Intellectual Property Zhang Expires 2012 [Page 10] draft-zhang-ccamp-flexible-grid-ospf-ext-00.txt October 2011 The IETF Trust takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in any IETF Document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. 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