Network Working Group Fatai Zhang Internet-Draft Xian Zhang Intended status: Informational Huawei Ramon Casellas CTTC O. Gonzalez de Dios Telefonica D. Ceccarelli Ericsson Expires: December 28, 2013 June 29, 2013 GMPLS OSPF-TE Extensions in support of Flexible Grid DWDM Networks draft-zhang-ccamp-flexible-grid-ospf-ext-02.txt Abstract This memo describes the OSPF-TE extensions in support of GMPLS control of networks that include devices that use the new flexible optical grid. 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 December 28, 2013. Copyright Notice Zhang Expires December 2013 [Page 1] draft-zhang-ccamp-flexible-grid-ospf-ext-02.txt June 2013 Copyright (c) 2013 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 ................................................ 2 2. Terminology ................................................. 3 2.1. Conventions Used in this Document .......................3 3. Requirements for Flexi-grid Routing ..........................3 3.1. Available Frequency Ranges.............................. 4 3.2. Application Compliance Considerations ...................5 3.3. Comparison with Fixed-grid DWDM Links ...................5 4. Extensions .................................................. 6 4.1. Available Labels Set Sub-TLV............................ 6 4.1.1. Inclusive/Exclusive Label Range ....................7 4.1.2. Inclusive/Exclusive Label Lists ....................7 4.1.3. Bitmap ............................................ 7 4.2. Extensions to Port Label Restriction sub-TLV ............7 4.3. Examples for Available Label Set Sub-TLV ................8 5. IANA Considerations ......................................... 9 6. Security Considerations...................................... 9 7. References ................................................. 10 7.1. Normative References................................... 10 7.2. Informative References................................. 10 8. Authors' Addresses ..........................................11 9. Contributors' Addresses..................................... 11 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. The channel spacing is the frequency spacing between two allowed nominal central frequencies. All of the Zhang Expires December 2013 [Page 2] draft-zhang-ccamp-flexible-grid-ospf-ext-02.txt June 2013 wavelengths on a fiber should use different central frequencies and occupy a fixed bandwidth of frequency. Fixed grid channel spacing is selected from 12.5 GHz, 25 GHz, 50 GHz, 100 GHz and integer multiples of 100 GHz. But [G.694.1] also 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 used to define a flexible grid. [FLEX-FWK] defines a framework and the associated control plane requirements for the GMPLS based 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 [WSON-OSPF] defines the requirements and OSPF-TE extensions in support of GMPLS control of a WSON. [FLEX-SIG] describes requirements and protocol extensions for signaling to set up LSPs in networks that support the flexi-grid, and this document complements [FLEX-SIG] by describing the requirement and extensions for OSPF-TE routing in a flexi-grid network. 2. Terminology For terminology related to flexi-grid, please consult [FLEX-FWK] 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]. 3. Requirements for Flexi-grid Routing The architecture for establishing LSPs in a Spectrum Switched optical Network (SSON) is described in [FLEX-FWK]. An flexi-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 RSA (Routing and Spectrum Assignment). [FLEX-FWK] describes three types of architectural approaches to RSA: combined RSA; separated RSA; and distributed SA. The first two approaches among them could be called "centralized SA" Zhang Expires December 2013 [Page 3] draft-zhang-ccamp-flexible-grid-ospf-ext-02.txt June 2013 because both routing and spectrum (frequency slot) assignment are performed by centralized entity before the signaling procedure. In the case of centralized SA, the assigned frequency slot is specified in the 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 involved network elements to select the frequency slot to be used. If the capability of switching or converting the whole optical spectrum allocated to an optical spectrum LSP is not available at nodes along the path of the LSP, the LSP is subject to the Optical "Spectrum Continuity Constraint", as described in [FLEX-FWK]. The remainder of this section states the additional extensions on the routing protocols in a flexi-grid network. That is, the additional information that must be collected and passed between nodes in the network by the routing protocols in order to enable correct path computation and signaling in support of LSPs within the network. 3.1. Available Frequency Ranges In the case of flexi-grids, the central frequency steps from 193.1 THz with 6.25 GHz granularity. The calculation method of central frequency and the frequency slot width of flexi-LSP are defined in [G.694.1]. 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 Zhang Expires December 2013 [Page 4] draft-zhang-ccamp-flexible-grid-ospf-ext-02.txt June 2013 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 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 flexi-LSPs. Hence, in order to clearly show which LSPs can be supported and what frequency slots are unavailable, the available frequency ranges should be advertised by the routing protocol for the flexi-grid DWDM links. A set of non-overlapping available frequency ranges should be disseminated in order to allow efficient resource management of flexi-grid DWDM links and RSA procedures which are described in section 5.7 of [FLEX-FWK]. 3.2. Application Compliance Considerations As described in [G.694.1], devices or applications that make use of the flexi-grid may not be capable of supporting every possible slot width or position (i.e., central frequency). In other words, applications or implementations 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). Hence, in order to support all possible applications and implementations the following information should be advertised for a flexi-grid DWDM link: o Central frequency granularity: a multiplier of 6.25 GHz. o Slot width granularity: a multiplier of 12.5 GHz. o Slot width range: two multipliers of 12.5GHz, each indicate the minimal and maximal slot width supported by a port respectively. The combination of slot width range and slot width granularity can be used to determine the slot widths set supported by a port. 3.3. Comparison with Fixed-grid DWDM Links In the case of fixed-grid DWDM links, each wavelength has a pre- defined central frequency and each wavelength has the same frequency range (i.e., there is a uniform channel spacing). Hence all the wavelengths on a DWDM link can be identified uniquely simply by Zhang Expires December 2013 [Page 5] draft-zhang-ccamp-flexible-grid-ospf-ext-02.txt June 2013 giving it an identifier (such as the central wavelength [RFC6205]), and the status of the wavelengths (available or not) can be advertised through a routing protocol. Figure 2 shows a link that supports a fixed-grid with 50 GHz channel spacing. The central frequencies of the wavelengths are pre-defined by values of 'n' and each wavelength occupies a fixed 50 GHz frequency range as described in [G.694.1]. W(-2) | W(-1) | W(0) | W(1) | W(2) | ...---------+-----------+-----------+-----------+-----------+----... | 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 Unlike the fixed-grid DWDM links, on a flexi-grid DWDM link the slot width of the frequency slot are flexible as described in section 2.1. That is, the value of m in the formula is uncertain before a frequency slot is actually allocated. For this reason, the available frequency slot/ranges need to be advertised for a flexi- grid DWDM link instead of the specific "wavelengths" that are sufficient for a fixed-grid link. 4. Extensions As described in [FLEX-FWK], the network connectivity topology constructed by the links/nodes and node capabilities are the same as for WSON, and can be advertised by the GMPLS routing protocols (refer to section 6.2 of [RFC6163]). In the flexi-grid case, the available frequency ranges instead of the specific "wavelengths" are advertised for the link. This section defines the GMPLS OSPF-TE extensions in support of advertising the available frequency ranges for flexi-grid DWDM links. 4.1. Available Labels Set Sub-TLV As described in section 3.1, the available frequency ranges other than the available frequency slots should be advertised for the flexi-grid DWDM links. The label encoding defined in [FLEX-LBL] is Zhang Expires December 2013 [Page 6] draft-zhang-ccamp-flexible-grid-ospf-ext-02.txt June 2013 used to encode the label field in Available Labels Set sub-TLV [GEN- Encode]. 4.1.1. Inclusive/Exclusive Label Range The inclusive/exclusive label ranges format of the Available Labels Set sub-TLV defined in [GEN-ENCODE] can be used for specifying the frequency ranges of the flexi-grid DWDM links. Note that multiple Available Labels Set sub-TLVs may be needed if there are multiple discontinuous frequency ranges on a link. 4.1.2. Inclusive/Exclusive Label Lists The inclusive/exclusive label lists format of Available Labels Set sub-TLV defined in [GEN-ENCODE] can be used for specifying the available central frequencies of flexi-grid DWDM links. 4.1.3. Bitmap The bitmap format of Available Labels Set sub-TLV defined in [GEN- ENCODE] can be used for specifying the available central frequencies of the flexi-grid DWDM links. Each bit in the bit map represents a particular central frequency with a value of 1/0 indicating whether the central frequency is in the set or not. Bit position zero represents the lowest central frequency and corresponds to the base label, while each succeeding bit position represents the next central frequency logically above the previous. 4.2. Extensions to Port Label Restriction sub-TLV As described in Section 3.2, a port that supports flexi-grid may support only a restricted subset of the full flexible grid. The Port Label Restriction sub-TLV is defined in [GEN-ENCODE] and [GEN- OSPF]. It can be used to describe the label restrictions on a port. A new restriction type, the flexi-grid Restriction Type, is defined here to specify the restrictions on a port to support flexi-grid. Zhang Expires December 2013 [Page 7] draft-zhang-ccamp-flexible-grid-ospf-ext-02.txt June 2013 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 | RstType = TBA | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | C.F.G | S.W.G | Min Width | Max Width | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ MatrixID (8 bits): As defined in [GEN-ENCODE]. RstType (Restriction Type, 8 bits): Takes the value (TBD) to indicate the restrictions on a port to support flexi-grid. C.F.G (Central Frequency Granularity, 8 bits): A positive integer. Its value indicates the multiple of 6.25 GHz in terms of central frequency granularity. S.W.G (Slot Width Granularity, 8 bits): A positive integer. Its value indicates the multiple of 12.5 GHz in terms of slot width granularity. Min Width (8 bits): A positive integer. Its value indicates the multiple of 12.5 GHz in terms of the supported minimal slot width. Max Width (8 bits): A positive integer. Its value indicates the multiple of 12.5 GHz in terms of the supported maximal slot width. 4.3. Examples for Available Label Set Sub-TLV Figure 3 shows an example of available frequency range of a flexi- grid DWDM link. -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10 11 ...+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--... |--Available Frequency Range--| Figure 3 - Flexi-grid DWDM Link The symbol '+' represents the allowed nominal central frequency. The symbol "--" represents a 6.25 GHz frequency unit. The number on the top of the line represents the 'n' in the frequency calculation formula (193.1 + n * 0.00625). The nominal central frequency is 193.1 THz when n equals zero. Assume that the central frequency granularity is 6.25GHz, the label set can be encoded as follows: Zhang Expires December 2013 [Page 8] draft-zhang-ccamp-flexible-grid-ospf-ext-02.txt June 2013 Inclusive Label Range: o Start Slot = -2; o End Slot = 8. The available central frequencies (-1, 0, 1, 2, 3, 4, 5, 6, 7) can be deduced by the Inclusive Label Range, because the Central Frequency Granularity is 6.25 GHz. Inclusive Label Lists: o List Entry 1 = slot -1; o List Entry 2 = slot 0; o List Entry 3 = slot 1; o List Entry 4 = slot 2; o List Entry 5 = slot 3; o List Entry 6 = slot 4; o List Entry 7 = slot 5; o List Entry 8 = slot 6; o List Entry 9 = slot 7. Bitmap: o Base Slot = -1; o Bitmap = 111111111(padded out to a full multiple of 32 bits) 5. IANA Considerations [GEN-OSPF] defines the Port label Restriction sub-TLV of OSPF TE Link TLV. It also creates a registry of values of the Restriction Type field of that sub-TLV IANA is requested to assign a new value from that registry as follows: Value Meaning Reference TBD Flexi-grid restriction [This.I-D] 6. Security Considerations This document does not introduce any further security issues other than those discussed in [RFC3630], [RFC4203]. Zhang Expires December 2013 [Page 9] draft-zhang-ccamp-flexible-grid-ospf-ext-02.txt June 2013 7. References 7.1. Normative References [RFC2119] S. Bradner, "Key words for use in RFCs to indicate requirements levels", RFC 2119, March 1997. [G.694.1] ITU-T Recommendation G.694.1 (revision 2), "Spectral grids for WDM applications: DWDM frequency grid", February 2012. [GEN-ENCODE] Bernstein, G., Lee, Y., Li, D., and W. Imajuku, "General Network Element Constraint Encoding for GMPLS Controlled Networks", draft-ietf-ccamp-general-constraint- encode, work in progress. [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, work in progress. [RFC6205] T. Otani and D. Li, "Generalized Labels for Lambda-Switch- Capable (LSC) Label Switching Routers", RFC 6205, March 2011. [FLEX-LBL] King, D., Farrel, A. and Y. Li, "Generalized Labels for the Flexi-Grid in Lambda Switch Capable (LSC) Label Switching Routers", draft-farrkingel-ccamp-flexigrid- lambda-label, work in progress. 7.2. Informative References [RFC6163] Y. Lee, G. Bernstein and W. Imajuku, "Framework for GMPLS and Path Computation Element (PCE) Control of Wavelength Switched Optical Networks (WSONs)", RFC 6163, April 2011. [FLEX-SIG] F.Zhang et al, "RSVP-TE Signaling Extensions in support of Flexible-grid", draft-zhang-ccamp-flexible-grid-rsvp- te-ext, work in progress. [FLEX-FWK] Gonzalez de Dios, O,, Casellas R., Zhang, F., Fu, X., Ceccarelli, D., and I. Hussain, "Framework and Requirements for GMPLS based control of Flexi-grid DWDM networks', draft-ogrcetal-cammp-flexi-grid-fwk, work in progress. Zhang Expires December 2013 [Page 10] draft-zhang-ccamp-flexible-grid-ospf-ext-02.txt June 2013 [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, work in progress. 8. Authors' Addresses Fatai Zhang Huawei Technologies Email: zhangfatai@huawei.com Xian Zhang Huawei Technologies Email: zhang.xian@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 9. Contributors' Addresses Adrian Farrel Old Dog Consulting Email: adrian@olddog.co.uk Zhang Expires December 2013 [Page 11]