Network Working Group Y. Li Internet-Draft ZTE Intended status: Standards Track R. Casellas Expires: September 9, 2012 CTTC Y. Wang CATR March 8, 2012 Link Management Protocol Extensions for Grid Property Negotiation draft-li-ccamp-grid-property-lmp-01 Abstract The recent updated version of ITU-T [G.694.1] has introduced the flexible-grid DWDM technique, which provides a new tool that operators can implement to provide a higher degree of network optimization than is possible with fixed-grid systems. This document describes the extensions to the Link Management Protocol (LMP) to negotiate link grid property between the adjacent DWDM nodes before the link is brought up. 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/. 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." This Internet-Draft will expire on September 9, 2012. 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 Li, et al. Expires September 9, 2012 [Page 1] Internet-Draft LMP for grid property March 2012 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 1.1. Conventions Used in This Document . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 4 3.1. Flexi-fixed Grid Nodes Interworking . . . . . . . . . . . 4 3.2. Flexible-Grid Capability Negotiation . . . . . . . . . . . 5 3.3. Problem Summary . . . . . . . . . . . . . . . . . . . . . 6 4. LMP extensions . . . . . . . . . . . . . . . . . . . . . . . . 6 4.1. Grid Property Subobject . . . . . . . . . . . . . . . . . 6 5. Messages Exchange Procedure . . . . . . . . . . . . . . . . . 8 5.1. Flexi-fixed Grid Nodes Messages Exchange . . . . . . . . . 8 5.2. Flexible Nodes Messages Exchange . . . . . . . . . . . . . 9 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 7. Security Considerations . . . . . . . . . . . . . . . . . . . 10 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10 8.1. Normative references . . . . . . . . . . . . . . . . . . . 10 8.2. Informative References . . . . . . . . . . . . . . . . . . 11 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11 Li, et al. Expires September 9, 2012 [Page 2] Internet-Draft LMP for grid property March 2012 1. Introduction The recent updated version of ITU-T [G.694.1] has introduced the flexible-grid DWDM technique, which provides a new tool that operators can implement to provide a higher degree of network optimization than is possible with fixed-grid systems. A flexible- grid network supports allocating an arbitrary spectral slot to a channel. Mixed bitrate transmission systems can allocate their channels with different spectral bandwidths/slot widths so that they can be optimized for the bandwidth requirements of the particular bitrate and modulation scheme of the individual channels. This technique is regarded to be a promising way to improve the spectrum utilization efficiency and fundamentally reduce the cost of the core network. During the practical deployment procedure, fixed-grid optical nodes will be gradually replaced by flexible nodes. This will lead to an interworking problem between fixed-grid DWDM and flexible-grid DWDM nodes. Additionally, even two flexible-grid optical nodes may have different grid properties, leading to link property conflict. Therefore, this document describes the extensions to the Link Management Protocol (LMP) to negotiate a link grid property between two adjacent DWDM nodes before the link is brought up. 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 RFC 2119 [RFC2119]. 2. Terminology For the flexible DWDM grid, the allowed frequency slots have a nominal central frequency (in THz) defined by: 193.1 + n * 0.00625 where n is a positive or negative integer including 0 and 0.00625 is the nominal central frequency granularity in THz and a slot width defined by: 12.5 * m where m is a positive integer and 12.5 is the slot width granularity in GHz. Any combination of frequency slots is allowed as long as no two slots overlap. Li, et al. Expires September 9, 2012 [Page 3] Internet-Draft LMP for grid property March 2012 In this contribution, some other definitions are listed below: Grid granularity: Grid granularity includes two elements: nominal central frequency granularity and slot width granularity. The value of slot width granularity is always configured to be twice of the central frequency granularity, so that the spectral resources can be allocated without leaving any gaps. Therefore, when grid granularity appears alone, we just refer to the nominal central frequency granularity. Tuning range: In this draft we just refer to the tuning range of the spectral bandwidth or slot width. Channel spacing: In traditional fixed-grid network, the adjacent channel spacing is constant. While for the flexible-grid network, the adjacent channel spacing is determined by the two central frequencies. 3. Problem Statement 3.1. Flexi-fixed Grid Nodes Interworking +---+ +---+ +---+ +---+ +---+ | A |---------| B |=========| C |=========| D +--------+ E | +---+ +---+ +---+ +---+ +---+ Figure 1 ^ ^ ^ ^ ------->|<----50GHz---->|<----50GHz---->|<----50GHz---->|<------ ..... | | | | ..... +-------+-------+-------+-------+-------+--------+------+-------+- n=-2 -1 0 1 2 Fixed channel spacing of 50 GHz (Node C) ^ ^ ^ ^ | | | | --------+---------------+---------------+---------------+--------- ..... | n=-8, m=4 | n=0, m=4 | n=8, m=4 | ..... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- n=-16 -14 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 14 16 |_| Flexi-grid (Nodes B,D) 6.25 GHz Central frequency granularity=6.25 GHz Slot width granularity=12.5 GHz Li, et al. Expires September 9, 2012 [Page 4] Internet-Draft LMP for grid property March 2012 Figure 2 Figure 1 shows an example of interworking between flexible and fixed- grid nodes. Nodes A, B, D, E support flexible-grid. All these nodes can support frequency slots with a central frequency granularity of 6.25 GHz and slot width granularity of 12.5 GHz. Given the flexibility in flexible-grid nodes, it is possible to configure the nodes in such a way that the central frequencies and slot width parameters are backwards compatible with the fixed DWDM grids (adjacent flexible frequency slots with channel spacing of 8*6.25 and slot width of 4*12.5 GHz is equivalent to fixed DWDM grids with channel spacing of 50 GHz). As node C can only support the fixed-grid DWDM property with channel spacing of 50 GHz, to establish a LSP through node B,C,D, the links between B to C and C to D must set to align with the fixed-grid values. This link grid property must be negotiated before establishing the LSP. 3.2. Flexible-Grid Capability Negotiation +---+ +---+ | F +------------| G | +---+ +---+ +------------------+-------------+-----------+ | Unit (GHz) | Node F | Node G | +------------------+-------------+-----------+ | Grid granularity | 6.25 (12.5) | 12.5 (25) | +------------------+-------------+-----------+ | Tuning range | [12.5, 100] | [25, 200] | +------------------+-------------+-----------+ Figure 3 The updated version of ITU-T [G.694.1] has defined the flexible-grid with 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 be able to support every possible slot width. In other words, applications may be defined where different grid granularity can be supported. Taking node F as an example, an application could be defined where the nominal central frequency granularity is 12.5 GHz requiring slot widths being multiple of 25 GHz . Therefore the link between two optical nodes with different grid granularity must be configured to align with the larger of both granularities. Besides, different nodes may have different slot width tuning ranges. For example, in figure 3, node F can only support slot width with tuning change from 12.5 to 100 GHz, Li, et al. Expires September 9, 2012 [Page 5] Internet-Draft LMP for grid property March 2012 while node G supports tuning range from 25 GHz to 200 GHz. The link property of slot width tuning range for the link between F and G should be chosen as the range intersection, resulting in a range from 25 GHz to 100 GHz. 3.3. Problem Summary In summary, in a DWDM Link between two nodes, the following properties can be negotiated: o Grid capability (channel spacing) --- Between fixed-grid and flexible-grid nodes. o Grid granularity --- Between two flexible-grid nodes. o Slot width tuning range--- Between two flexible-grid nodes. 4. LMP extensions 4.1. Grid Property Subobject According to [RFC4204], the LinkSummary message is used to verify the consistency of the link property on both sides of the link before it is brought up. The LinkSummary message contains negotiable and non- negotiable DATA_LINK objects, carrying a series of variable-length data items called subobjects, which illustrate the detailed link properties. The subobjects are defined in Section 12.12.1 in [RFC4204]. To solve the problems stated in section 3, this draft extends the LMP protocol by introducing a new DATA_LINK subobject called "Grid property", allowing the grid property correlation between adjacent nodes. The encoding format of this new subobject is as follows: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Grid | C.S. | Reserved | Min | Max | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Type=TBD, Grid property type. Grid: Li, et al. Expires September 9, 2012 [Page 6] Internet-Draft LMP for grid property March 2012 The value is used to represent which grid the node/interface supports. Values defined in [RFC6205] identify DWDM [G.694.1] and CWDM [G.694.2]. The value defined in [I-D.farrkingel-ccamp-flexigrid-lambda-label] identifies flexible DWDM. +---------------+-------+ | Grid | Value | +---------------+-------+ | Reserved | 0 | +---------------+-------+ | ITU-T DWDM | 1 | +---------------+-------+ | ITU-T CWDM | 2 | +---------------+-------+ | Flexible DWDM | 3 | +---------------+-------+ | Future use | 4-7 | +---------------+-------+ C.S.: For a fixed-grid node/interface, the C.S. value is used to represent the channel spacing, as the spacing between adjacent channels is constant. For a flexible-grid node/interface, this field should be used to represent the central frequency granularity. +------------+-------+ | C.S. (GHz) | Value | +------------+-------+ | Reserved | 0 | +------------+-------+ | 100 | 1 | +------------+-------+ | 50 | 2 | +------------+-------+ | 25 | 3 | +------------+-------+ | 12.5 | 4 | +------------+-------+ | 6.25 | 5 | +------------+-------+ | Future use | 6-15 | +------------+-------+ Min & Max: The slot width tuning range the interface supports (indicated by the Li, et al. Expires September 9, 2012 [Page 7] Internet-Draft LMP for grid property March 2012 m value defined in section 2). For example, for slot width tuning range from 25 GHz to 100 GHz (with regarding to a node with slot width granularity of 12.5 GHz ), the values of Min and Max should be 2 and 8 respectively. For fixed-grid nodes, these two fields are meaningless and should be set to zeros. 5. Messages Exchange Procedure 5.1. Flexi-fixed Grid Nodes Messages Exchange To demonstrate the procedure of grid property correlation, the model shown in Figure 1 is reused. Node B starts sending messages. o After inspecting its own node/interface property, node B sends node C a LinkSummary message including the MESSAGE ID, TE_LINK ID and DATA_LINK objects. The setting and negotiating of MESSAGE ID and TE_link ID can be referenced to [RFC4204]. As node B supports flexible-grid property, the Grid and C.S. values in the grid property subobject are set to be 3 and 5 respectively. The slot width tuning range is from 12.5 GHz to 200 GHz. Meanwhile, the N bit of the DATA_LINK object is set to 1, indicating that the property is negotiable. o When node C receives the LinkSummary message from B, it checks the Grid, C.S., Min and Max values in the grid property subobject. Node C can only support fixed-grid DWDM and realizes that the flexible-grid property is not acceptable for the link. Since the receiving N bit in the DATA_LINK object is set, indicating that the Grid property of B is negotiable, node C responds to B with a LinkSummaryNack containing a new Error_code object and state that the property needs further negotiation. Meanwhile, an accepted grid property subobject (Grid=2, C.S.=2, fixed DWDM with channel spacing of 50 GHz) is carried in LinkSummaryNack message. At this moment, the N bit in the DATA_LINK object is set to 0, indicating that the grid property subobject is non-negotiable. o As the channel spacing and slot width of node B can be configured to be any integral multiples of 6.25 GHz and 12.5 GHz respectively, node B supports the fixed DWDM values announced by node C. Consequently, node B will resend the LinkSummary message carrying the grid property subobject with values of Grid=2 and C.S.=2. o Once received the LinkSummary message from node B, node C replies with a LinkSummaryACK message. After the message exchange, the link between node B and C is brought up with a fixed channel spacing of 50 GHz. Li, et al. Expires September 9, 2012 [Page 8] Internet-Draft LMP for grid property March 2012 In the above mentioned grid property correlation scenario, the node supporting a flexible-grid is the one that starts sending LMP messages. The procedure where the initiator is the fixed-grid node is as follows: o After inspecting its own interface property, Node C sends B a LinkSummary message containing a grid property subobject with Grid=2, C.S.=2. The N bit in the DATA_LINK object is set to 0, indicating that it is non-negotiable. o As the channel spacing and slot width of node B can be configured to be any integral multiples of 6.25 GHz and 12.5 GHz respectively, node B is able to support the fixed DWDM parameters. Then, node B will make appropriate configuration and reply node C the LinkSummaryACK message. o After the message exchange, the link between node B and C is brought up with a fixed channel spacing of 50 GHz. 5.2. Flexible Nodes Messages Exchange To demonstrate the procedure of grid property correlation between to flexi-grid capable nodes, the model shown in figure 3 is reused. The procedure of grid property correlation (negotiating the grid granularity and slot width tuning range) is similar to the scenarios mentioned above. o The Grid, C.S., Min and Max values in the grid property subobject sent from node F to G are set to be 3,5,1,8 respectively. Meanwhile, the N bit of the DATA_LINK object is set to 1, indicating that the grid property is negotiable. o When node G has received the LinkSummary message from F, it will analyze the Grid, C.S., Min and Max values in the Grid property subobject. But node G can only support grid granularity of 12.5 GHz and a slotwdith tuning range from 25 GHz to 200 GHz. Considering the property of node F, node G then will respond F a LinkSummaryNack containing a new Error_code object and state that the property need further negotiation. Meanwhile, an accepted grid property subobject (Grid=3, C.S.=4, Min=1, Max=4, the slot width tuning range is set to the intersection of Node F and G) is carried in LinkSummaryNack message. Meanwhile, the N bit in the DATA_LINK object is set to 1, indicating that the grid property subobject is non-negotiable. Li, et al. Expires September 9, 2012 [Page 9] Internet-Draft LMP for grid property March 2012 o As the channel spacing and slot width of node F can be configured to be any integral multiples of 6.25 GHz and 12.5 GHz respectively, node F can support the lager granularity. The suggested slot width tuning range is acceptable for node F. In consequence, node F will resend the LinkSummary message carrying the grid subobject with values of Grid=3, C.S.=4, Min=1 and Max=4. o Once received the LinkSummary message from node F, node G replies with a LinkSummaryACK message. After the message exchange, the link between node F and G is brought up supporting central frequency granularity of 12.5 GHz and slot width tuning range from 25 GHz to 100 GHz. From the perspective of the control plane, once the links have been brought up, wavelength constraint information can be advertised and the wavelength label can be assigned hop-by-hop when establishing a LSP based on the link grid property. 6. IANA Considerations TBD 7. Security Considerations TBD 8. References 8.1. Normative references [G.694.1] International Telecommunications Union, "Spectral grids for WDM applications: DWDM frequency grid", Recommendation G.694.1, June 2002 . [G.694.2] International Telecommunications Union, "Spectral grids for WDM applications: CWDM wavelength grid", Recommendation G.694.2, December 2003 . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC4204] Lang, J., "Link Management Protocol (LMP)", RFC 4204, October 2005. Li, et al. Expires September 9, 2012 [Page 10] Internet-Draft LMP for grid property March 2012 [RFC6205] Otani, T. and D. Li, "Generalized Labels for Lambda- Switch-Capable (LSC) Label Switching Routers", RFC 6205, March 2011. 8.2. Informative References [I-D.farrkingel-ccamp-flexigrid-lambda-label] King, D., Farrel, A., Li, Y., Zhang, F., and R. Casellas, "Generalized Labels for the Flexi-Grid in Lambda-Switch- Capable (LSC) Label Switching Routers", draft-farrkingel-ccamp-flexigrid-lambda-label-01 (work in progress), October 2011. Authors' Addresses Yao Li ZTE Email: li.yao3@zte.com.cn Ramon Casellas CTTC Email: ramon.casellas@cttc.es Yu Wang China Academy of Telecom Research, MIIT No.52 Huayuan Beilu, Haidian District,Beijing,P.R. China, 100083 Email: wangyu@mail.ritt.com.cn Li, et al. Expires September 9, 2012 [Page 11]