Network Working Group Fatai Zhang Internet Draft Dan Li Category: Standards Track Huawei D. Ceccarelli D. Caviglia Ericsson Guoying Zhang CATR P.Grandi S.Belotti Alcatel-Lucent Expires: October 2011 April 6, 2011 Link Management Protocol (LMP) extensions for G.709 Optical Transport Networks draft-zhang-ccamp-gmpls-g709-lmp-discovery-04.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 October 6, 2011. Abstract Recent progress of the Optical Transport Network (OTN) has introduced new signal types (i.e., ODU0, ODU4, ODU2e and ODUflex) and new Tributary Slot granularity (1.25Gbps). Zhang Expires October 2011 [Page 1] draft-zhang-ccamp-gmpls-g.709-lmp-discovery-04.txt April 2011 Since equipments deployed prior to recently defined ITU-T recommendations only support 2.5 Gbps Tributary Slot granularity and ODU1, ODU2 and ODU3 containers, the compatibility problem should be considered. In addition, a Higher Order ODU (HO ODU) link may not support all the types of Lower Order ODU (LO ODU) signals defined by the new OTN standard because of the limitation of the devices at the two ends of a link. In these cases, the control plane is required to run the capability discovering functions for the evolutive OTN. This document describes the extensions to the Link Management Protocol (LMP) needed to discover the capability of HO ODU link, including the granularity of Tributary Slot to be used and the LO ODU signal types that the link can support. 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]. Table of Contents 1. Introduction ................................................. 3 2. Terminology .................................................. 3 3. Overview of the Evolutive G.709 .............................. 4 3.1. Data Plane Backward Compatibility ....................... 5 4. Link Capability Discovery Requirements ....................... 5 4.1. Discovering the Granularity of the TS ................... 5 4.2. Discovering the Supported LO ODU Signal Types ........... 6 5. Extensions: LMP Link Summary Message ......................... 7 5.1. Message Extension ....................................... 7 5.1.1. LinkSummary Message ................................ 8 5.1.2. LinkSummaryAck Message ............................. 8 5.1.3. LinkSummaryNack Message ............................ 8 5.2. Object Definitions ...................................... 8 5.3. Procedures ............................................. 10 6. Security Considerations ..................................... 12 7. IANA Considerations ......................................... 12 8. Acknowledgments ............................................. 12 9. References .................................................. 12 9.1. Normative References ................................... 12 9.2. Informative References ................................. 12 10. Authors' Addresses ......................................... 13 11. Contributors ............................................... 14 Zhang Expires October 2011 [Page 2] draft-zhang-ccamp-gmpls-g.709-lmp-discovery-04.txt April 2011 1. Introduction The Link Management Protocol (LMP) defined in [RFC4204] is being developed as part of the Generalized MPLS (GMPLS) protocol suite to manage Traffic Engineering (TE) links. Recently, great progress has been made for the Optical Transport Networking (OTN) technologies in ITU-T. New ODU containers (i.e., ODU0, ODU4, ODU2e and ODUflex) and a new Tributary Slot (TS) granularity (1.25Gbps) have been introduced by the [G709-V3], enhancing the flexibility of OTNs. With the evolution and deployment of G.709 technology, the backward compatibility problem requires to be considered. In data plane, the equipment supporting 1.25Gbps TS can combine the specific Tributary Slots together (e.g., combination of TS#i and TS#i+4 on a HO ODU2 link) so that it can interwork with other equipments which support 2.5Gbps TS. From the control plane point of view, it is necessary to discover which type of TS is supported at both ends of a link, so that it can choose and reserve the TS resources correctly in this link for the connection. Additionally, the requirement of discovering the signal types of Lower Order ODU (LO ODU) that can be supported by a Higher Order ODU (HO ODU) should be taken into account. Equipment at one end of a HO ODU link may not support to transport some types of LO ODU signals (e.g., may not support the ODUflex). In this case, this HO ODU link should not be selected for those types of LO ODU connections. From the perspective of control plane, it is necessary to discover the capability of a HO ODUk or OTUk link including the granularity of TS to be used and the LO ODU signal types that the link can support. Note that LO ODU type information can be, in principle, discovered by routing. Since in certain case, routing is not present (e.g. UNI case) we need to extend link management protocol capabilities to cover this aspect. Obviously, in case of routing presence, the discovering procedure by LMP could also be optional. This document extends the LMP and describes the solution of discovering HO ODU link capability. 2. Terminology 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]. Zhang Expires October 2011 [Page 3] draft-zhang-ccamp-gmpls-g.709-lmp-discovery-04.txt April 2011 3. Overview of the Evolutive G.709 The traditional OTN standard [ITUT-G709] describes the optical transport hierarchy (OTH) and introduces three ODU signal types (i.e., ODU1, ODU2 and ODU3). The ODUj can be mapped into one or more Tributary Slots (with a granularity of 2.5Gbps) of OPUk where j j) signal can be depicted as follows: - ODU0 into ODU1 multiplexing (with 1,25Gbps TS granularity) - ODU0, ODU1, ODUflex into ODU2 multiplexing (with 1.25Gbps TS granularity) - ODU1 into ODU2 multiplexing (with 2.5Gbps TS granularity) - ODU0, ODU1, ODU2, ODU2e and ODUflex into ODU3 multiplexing (with 1.25Gbps TS granularity) - ODU1, ODU2 into ODU3 multiplexing (with 2.5Gbps TS granularity) - ODU0, ODU1, ODU2, ODU2e, ODU3 and ODUflex into ODU4 multiplexing (with 1.25Gbps TS granularity) Zhang Expires October 2011 [Page 4] draft-zhang-ccamp-gmpls-g.709-lmp-discovery-04.txt April 2011 3.1. Data Plane Backward Compatibility Equipment supporting a 1.25Gbps TS structure for OPU2 or OPU3 must be backward compatible with equipment which supports only the 2.5G TS structure. Specific Tributary Slots must be combined together (e.g., combination of TS#i and TS#i+4 on a HO ODU2 link) for the LO ODU at one end of the HO ODU link which supports the 1.25Gbps TS structure, so that the LO ODU can be carried on the HO ODU link correctly. In the following example, suppose that the two ends of an ODU2 or ODU3 link support different TS structure, where node A supports the 1.25Gbps TS structure, while node B supports the 2.5Gbps TS, as shown in the figure below: +-----+ +-----+ | | | | | A +-------ODU2/ODU3 link-------+ B | | | | | +-----+ +-----+ (Support 1.25G TS) (Support 2.5G TS) - In case of ODU1 multiplexing into ODU2, node A maps the ODU1 into the TS#i and TS#i+4 (where i<=4) (with the granularity of 1.25Gbps) of OPU2, so that node B can retrieve the ODU1 from the TS#i (with the granularity of 2.5Gbps) of the OPU2, and vice versa. - In case of ODU1 multiplexing into ODU3, node A maps the ODU1 into the TS#i and TS#i+16 (where i<=16) (with the granularity of 1.25Gbps) of OPU3, so that node B can retrieve the ODU1 from the TS#i (with the granularity of 2.5Gbps) of the OPU3, and vice versa. - In case of ODU2 multiplexing into ODU3, node A maps the ODU2 into the TS#a/TS#a+16, TS#b/TS#b+16, TS#c/TS#c+16 and TS#d/TS#d+16 (where a | | | A +-------ODU2 link-------+ B | | | <------------- | | +-----+ Resv +-----+ (Support 2.5G TS) (Support 1.25G TS) Therefore, for an ODU2 or ODU3 link, in order to reserve TS resources correctly for a LO ODU connection, the control plane of the two ends MUST know which granularity the other end can support before creating the LO ODU connection. 4.2. Discovering the Supported LO ODU Signal Types Many new ODU signal types are introduced by [G709-V3], such as ODU0, ODU4, ODU2e and ODUflex. It is possible that equipment does not always support all the LO ODU signal types introduced by [G709-V3]. If one end of a HO ODU link can not support a certain LO ODU signal type and there is no HO ODU FA LSP able to support this LO ODU signal, the HO ODU link/FA LSP can not be selected to carry such type of LO ODU connection. For example, in the following figure, if the interfaces IF1, IF2, IF8, IF7, IF5 and IF6 can support ODUflex signals, while the interfaces IF 3 and IF4 can not support ODUflex signals. In this case, if one ODUflex connection from A to C is requested, and there is no HO ODU FA LSP from node A to C through node B, link #1 and #2 should be excluded, link #3 and link #4 are the candidates (the possible path could be A-D-C through link #3 and link #4). Zhang Expires October 2011 [Page 6] draft-zhang-ccamp-gmpls-g.709-lmp-discovery-04.txt April 2011 +-----+ link #3 | | link #4 +-----------------+ D +-----------------+ | IF8| |IF7 | | +-----+ | | | |IF1 IF6| +--+--+ +-----+ +--+--+ | | link #1 | | link #2 | | | A +--------------+ B +--------------+ C | | |IF2 IF3| |IF4 IF5| | +-----+ +-----+ +-----+ Therefore, it is necessary for the two ends of a HO ODU link to discover which types of LO ODU can be supported by the HO ODU link. After discovering, the capability information can be flooded by IGP, so that the correct path for an ODU connection can be calculated. 5. Extensions: LMP Link Summary Message [RFC4204] defines the Link Management Protocol (LMP) which consists of four main procedures: control channel management, link property correlation, link connectivity verification, and fault management. As part of LMP, the link property correlation is used to verify the consistency of the TE and data link information on both sides of a link. This document extends the link property correlation procedure to discover the capability of both sides of a HO ODU link. The designated HO ODU overhead bytes (e.g., the GCC1 and GCC2 overhead bytes) can be used as the control channel to carry the LMP message after the HO ODU link is created. The out-of-band Data Communication Network (DCN) can also be used. 5.1. Message Extension Three messages are used for link property correlation: LinkSummary, LinkSummaryAck and LinkSummaryNack Message. This document does not change the basic procedure of LMP but just add a new subobject (HO ODU Link Capability Subobject) in the DATA_LINK object to carry the capability of one end of a HO ODU link. The formats of LinkSummary, LinkSummaryAck and LinkSummaryNack messages are defined in [RFC4204]. Zhang Expires October 2011 [Page 7] draft-zhang-ccamp-gmpls-g.709-lmp-discovery-04.txt April 2011 5.1.1. LinkSummary Message The local end of a TE link can send a LinkSummary message to the remote end to start the negotiation about the capability that the TE link can support. One new Subobject named HO ODU Link Capability Subobject in the DATA_LINK object is introduced by this document. This new subobect is used to tell the remote end of the HO ODU link which TS granularity and which LO ODU signal types that the local end can support. When the DATA_LINK object carries the new HO ODU Link Capability Subobject, the N flag SHOULD be set to 1 which means that the subobject is negotiable. 5.1.2. LinkSummaryAck Message The LinkSummaryAck message is used to tell the remote end that it has the same capability as the remote end after the LinkSummary message is received by the local end. 5.1.3. LinkSummaryNack Message The LinkSummaryNack message is used to tell the remote end that it has different capability from the remote end after the LinkSummary message is received by the local end. The LinkSummaryNack message also carries the HO ODU Link Capability Subobject in the DATA_LINK object to tell the remote end the exact capability of the HO ODU link after negotiation, i.e., the granularity of TS and the types of LO ODU that both side of the HO ODU link can support. 5.2. Object Definitions A new HO ODU Link Capability subobject type is introduced to the DATA LINK object to carry the HO ODU link capability information. The format of the new subobject is defined as follow: 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 |OD(T)Uk| T | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |A|B|C|D|E|F|G| LO ODU Flags | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Zhang Expires October 2011 [Page 8] draft-zhang-ccamp-gmpls-g.709-lmp-discovery-04.txt April 2011 Type (8 bits): The value of this subobject type is TBD. Length (8 bits): The Length field contains the total length of the subobject in bytes, including the Type and Length fields. As for RFC 4204, the Length MUST be at least 4, and MUST be a multiple of 4. Value of this field is 8. OD(T)Uk (4 bits): This field is used to indicate the HO ODU link type (in case of LO ODUj multiplexing into HO ODUk, wherein j