CCAMP Working Group S. Belotti Internet-Draft P. Grandi Intended status: Informational Alcatel-Lucent Expires: January 9, 2011 D. Ceccarelli D. Caviglia Ericsson F. Zhang D. Li Huawei Technologies July 08, 2010 Information model for G.709 Optical Transport Networks (OTN) draft-bccg-ccamp-otn-g709-info-model-01 Abstract The recent revision of ITU-T recommendation G.709 [G.709-v3] has introduced new fixed and flexible ODU containers in Optical Transport Networks (OTNs), enabling optimized support for an increasingly abundant service mix. This document provides a model of information needed by the routing process in OTNs to support Generalized Multiprotocol Label Switching (GMPLS) control of all currently defined ODU containers both at sub- lambdas and lambda level granularity. 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 January 9, 2011. Copyright Notice Copyright (c) 2010 IETF Trust and the persons identified as the document authors. All rights reserved. Belotti, et al. Expires January 9, 2011 [Page 1] Internet-Draft Information model for G.709 OTN July 2010 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 . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. OSPF requirements overview . . . . . . . . . . . . . . . . . . 3 3. G.709 Digital Layer TE Information and Requirement Analysis . 5 3.1. Tributary Slot type . . . . . . . . . . . . . . . . . . . 7 3.2. Signal type . . . . . . . . . . . . . . . . . . . . . . . 7 3.3. Unreserved Resources . . . . . . . . . . . . . . . . . . . 8 3.4. Maximum LSP Bandwidth . . . . . . . . . . . . . . . . . . 9 3.5. Distinction between link multiplexing capacity and link rate capacity . . . . . . . . . . . . . . . . . . . . 9 3.6. Priority Support . . . . . . . . . . . . . . . . . . . . . 10 3.7. Multi-stage multiplexing . . . . . . . . . . . . . . . . . 10 4. Security Considerations . . . . . . . . . . . . . . . . . . . 11 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11 7.1. Normative References . . . . . . . . . . . . . . . . . . . 11 7.2. Informative References . . . . . . . . . . . . . . . . . . 12 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12 Belotti, et al. Expires January 9, 2011 [Page 2] Internet-Draft Information model for G.709 OTN July 2010 1. Introduction An Opaque OSPF (Open Shortest Path First) LSA (Link State Advertisements) carrying application-specific information can be generated and advertised to other nodes following the flooding procedures defined in [RFC5250]. Three types of opaque LSA are defined, i.e. type 9 - link-local flooding scope, type 10 - area- local flooding scope, type 11 - AS flooding scope. Traffic Engineering(TE) LSA using type 10 opaque LSA is defined in [RFC3630] for TE purpose. This type of LSA is composed of a standard LSA header and a payload including one top-level TLV and possible several nested sub-TLVs. [RFC3630]defines two top-level TLVs: Router Address TLV and Link TLV; and nine possible sub-TLVs for the Link TLV, used to carry link related TE information. The Link type sub- TLVs are enhanced by [RFC4203] in order to support GMPLS networks and related specific link information. In GMPLS networks each node generates TE LSAs to advertise its TE information and capabilities (link-specific or node-specific)through the network. The TE information carried in the LSAs are collected by the other nodes of the network and stored into their local Traffic Engineering Databases (TED). In a GMPLS enabled G.709 Optical Transport Networks (OTN), routing is fundamental in order to allow automatic calculation of routes for ODUk LSPs signaled via RSVP-TE protocol. The recent revision of ITU-T Recommendation G.709 [G709-V3] has introduced new fixed and flexible ODU containers that augment those specified in foundation OTN. As a result, it is necessary to provide OSPF routing protocol extensions to allow Generalized MPLS (GMPLS) control of all currently defined ODU containers, in support of sub-lambda and lambda level routing granularity. This document provides a model of information needed by the routing process in OTNs to support Generalized Multiprotocol Label Switching (GMPLS) control of all currently defined ODU containers both at sub- lambdas and lambda level granularity. OSPF requirements are defined in [OTN-FWK], while protocol extensions are defined in [OTN-OSPF]. 2. OSPF requirements overview OTN serves as the convergence layer for transporting a wide range of services, including those whose bit rates do not allow efficient usage of the entire bandwidth associated with a single lambda. In such a case OTN allows aggregation (and recovery) of traffic to Belotti, et al. Expires January 9, 2011 [Page 3] Internet-Draft Information model for G.709 OTN July 2010 support optimization of overall network bandwidth allocation; i.e., OTN allows the aggregated service rate to be decoupled from the OTN line system capacity. The heterogeneous multiplexing hierarchy additionally supports various network architectures, including those optimized to minimize stranded capacity, minimize managed entities, support carrier's carrier scenarios, and/or enable ODU0/ODUflex traffic to transit a region of the network that does not support these capabilities. Thus, it is necessary to define a scalable control plane solution that is able to fully exploit OTN flexibility (both in terms of architecture, aggregation and survivability). [Ed note] (could be part of Framework but for the moment can provide introduction to the overview). In this scope, Section 5.3 of the [draft-fwk] provides a set of functional routing requirements. These requirements are summarized below : - Support for link multiplexing capability advertisement: The routing protocol has to be able to carry information regarding the capability of an OTU link to support different type of ODUs - Support for TS granularity advertisement: Each ODUj can be multiplexed into an OTUk using different TS granularities. For example, ODU1 can be multiplexed into ODU2 with either 2.5Gbps TS granularity or 1.25G TS granularity. The routing protocol should be capable of carrying the TS granularity supported by the ODU interface. - Support of any ODUk and ODUflex: The routing protocol must be capable of carrying the required link bandwidth information for performing accurate route computation for any of the fixed rate ODUs as well as ODUflex. - Support for differentiation between link multiplexing capacity and link rate capacity - Support different priorities for resource reservation. How many priorities levels should be supported depends on operator policies. Therefore, the routing protocol should be capable of supporting either no priorities or up to 8 priority levels as defined in [RFC4202]. - Support link bundling either at the same line rate or different line rates (e.g. 40G and 10G). Bundling links at different rates makes the control plane more scalable and permits better Belotti, et al. Expires January 9, 2011 [Page 4] Internet-Draft Information model for G.709 OTN July 2010 networking flexibility. 3. G.709 Digital Layer TE Information and Requirement Analysis The digital OTN layered structure is comprised of digital path layer networks (ODU) and digital section layer networks (OTU). An OTU section layer supports one ODU path layer as client and provides monitoring capability for the OCh. An ODU path layer may transport a heterogeneous assembly of ODU clients Some types of ODUs (i.e., ODU1, ODU2, ODU3, ODU4) may assume either a client or server role within the context of a particular networking domain. ITU-T G.872 amendment 2 provides two tables defining mapping and multiplexing capabilities of OTNs, which are reproduced below. +--------------------+--------------------+ | ODU client | OTU server | +--------------------+--------------------+ | ODU 0 | - | +--------------------+--------------------+ | ODU 1 | OTU 1 | +--------------------+--------------------+ | ODU 2 | OTU 2 | +--------------------+--------------------+ | ODU 2e | - | +--------------------+--------------------+ | ODU 3 | OTU 3 | +--------------------+--------------------+ | ODU 4 | OTU 4 | +--------------------+--------------------+ | ODU flex | - | +--------------------+--------------------+ Figure 1: OTN mapping capability Belotti, et al. Expires January 9, 2011 [Page 5] Internet-Draft Information model for G.709 OTN July 2010 +=================================+=========================+ | ODU client | ODU server | +---------------------------------+-------------------------+ | 1,25 Gbps client | | +---------------------------------+ ODU 0 | | - | | +=================================+=========================+ | 2,5 Gbps client | | +---------------------------------+ ODU 1 | | ODU 0 | | +=================================+=========================+ | 10 Gbps client | | +---------------------------------+ ODU 2 | | ODU0,ODU1,ODUflex | | +=================================+=========================+ | 10,3125 Gbps client | | +---------------------------------+ ODU 2e | | - | | +=================================+=========================+ | 40 Gbps client | | +---------------------------------+ ODU 3 | | ODU0,ODU1,ODU2,ODU2e,ODUflex | | +=================================+=========================+ | 100 Gbps client | | +---------------------------------+ ODU 4 | |ODU0,ODU1,ODU2,ODU2e,ODU3,ODUflex| | +=================================+=========================+ Figure 2: OTN multiplexing capability How an ODUk connection service is transported within an operator network is governed by operator policy. For example, the ODUk connection service might be transported over an ODUk path over an OTUk section, with the path and section being at the same rate as that of the connection service (see Table 1). In this case, an entire lambda of capacity is consumed in transporting the ODUk connection service. On the other hand, the operator might leverage sub-lambda multiplexing capabilities in the network to improve infrastructure efficiencies within any given networking domain. In this case, ODUk multiplexing may be performed prior to transport over various rate ODU servers (as per Table 2) over associated OTU sections. From the perspective of multiplexing relationships, a given ODUk may play different roles as it traverses various networking domains. Belotti, et al. Expires January 9, 2011 [Page 6] Internet-Draft Information model for G.709 OTN July 2010 As detailed in [OTN-FWK], client ODUk connection services can be transported over: o Case A) one or more wavelength sub-networks connected by optical links or o Case B) one or more ODU links (having sub-lambda and/or lambda bandwidth granularity) o Case C) a mix of ODU links and wavelength sub-networks. This document only considers the TE information needed for ODU path computation. The following sections list and analyze each type of data that needs to be advertised in order to support path computation. 3.1. Tributary Slot type ITU-T recommendations define two types of TS but each link can only support a single type at a given time. The rules to be followed when selecting the TS to be used are: - if both ends of a link can support both 2.5Gbps TS and 1.25Gbps TS, then the link will work with 1.25Gbps TS. - If one end can support the 1.25Gbps TS, and another end the 2.5Gbps TS, the link will work with 2.5Gbps TS In addition, the bandwidth accounting depends on the type of TS. Therefore, the type of the TS should be known during LO ODUk path computation. Currently such information is not provided by the routing protocol. 3.2. Signal type [RFC 4328] allows advertising foundation G.709 (single TS type) without the capability of providing precise information about bandwidth specific allocation. For example, in case of link bundling, dividing the unreserved bandwidth by the MAX LSP bandwidth it is not possible to know the exact number of LSPs at MAX LSP bandwidth size that can be set up. (see example fig. 3) The lack of spatial allocation heavily impacts the restoration process, because the lack of information of free resources highly increases the number of crank-backs affecting network convergence time. Belotti, et al. Expires January 9, 2011 [Page 7] Internet-Draft Information model for G.709 OTN July 2010 Moreover actual tools provided by OSPF-TE only allow advertising signal types with fixed bandwidth and implicit hierarchy (e.g. SDH/ SONET networks) or variable bandwidth with no hierarchy (e.g. packet switching networks) but do not provide the means for advertising networks with mixed approach (e.g. ODUflex CBR and ODUflex packet). For example, advertising ODU0 as MIN LSP bandwidth and ODU4 as MAX LSP bandwidth it is not possible to state whether the advertised link supports ODU4 and ODUflex or ODU4, ODU3, ODU2, ODU1, ODU0 and ODUflex. Such ambiguity is not present in SDH networks where the hierarchy is implicit and flexible containers like ODUFlex do not exist. The issue could be resolved by declaring 1 ISCD for each signal type actually supported by the link. Supposing for example to have an equivalent ODU2 unreserved bandwidth in a TE-link (with bundling capability) distributed on 4 ODU1, it would be advertised via the ISCD in this way: MAX LSP Bw: ODU1 MIN LSP Bw: ODU1 - Maximum Reservable Bandwidth (of the bundle) set to ODU2 - Unreserved Bandwidth (of the bundle) set to ODU2 Moreover with the current IETF solutions, ([RFC4202], [RFC4203]) as soon as no bandwidth is available for a certain signal type it is not advertised into the related ISCD, losing also the related capability until bandwidth is freed. In conclusion, the OSPF-TE extensions defined in [RFC4203] require a different ISCD per signal type in order to advertise each supported container. This motivates attempting to look for a more optimized solution, without proliferations of the number of ISCD advertised. With respect to link bundling, the utilization of the ISCD as it is, would not allow precise advertising of spatial bandwidth allocation information unless using only one component link per TE link. 3.3. Unreserved Resources Unreserved resources need to be advertised per priority and per signal type in order to allow the correct functioning of the restoration process. [RFC4203] only allows advertising unreserved resources per priority, this leads not to know how many LSPs of a specific signal type can be restored. As example it is possible to consider the scenario depicted in the following figure. Belotti, et al. Expires January 9, 2011 [Page 8] Internet-Draft Information model for G.709 OTN July 2010 +------+ component link 1 +------+ | +------------------+ | | | component link 2 | | | N1 +------------------+ N2 | | | component link 3 | | | +------------------+ | +------+ +---+--+ Figure 3: Concurrent path computation Suppose to have a TE link comprising 3 ODU3 component links with 32TSs available on the first one, 24TSs on the second, 24TSs on the third and supporting ODU2 and ODU3 signal types. The node would advertise a TE link unreserved bandwidth equal to 80 TSs and a MAX LSP bandwidth equal to 32 TSs. In case of restoration the network could try to restore 2 ODU3 (64TSs) in such TE-link while only a single ODU3 can be set up and a crank-back would be originated. In more complex network scenarios the number of crank-backs can be much higher. 3.4. Maximum LSP Bandwidth Maximum LSP bandwidth is currently advertised in the common part of the ISCD and advertised per priority, while in OTN networks it is only required for ODUflex advertising. This leads to a significant waste of bits inside each LSA. 3.5. Distinction between link multiplexing capacity and link rate capacity As mentioned earlier, to enable optimization of overall network bandwidth allocation, it is necessary to decouple the connection service rate from the OTN link rate capacity, so as to support sub- lambda switching agility. Thus, it is needed to provide the possibility to separately advertise the bandwidth available at lambda granularity from the bandwidth available at sub-lambda granularity. For example consider a bundle link consisting of 5 OTU4 and 4 OTU3, no support for ODUflex. The bandwidth advertised at full lambda granularity should be : -5 Full-lambda ODU4 -4 Full-lambda ODU3 The bandwidth advertised at sub-lambda granularity should be: Belotti, et al. Expires January 9, 2011 [Page 9] Internet-Draft Information model for G.709 OTN July 2010 -10 sub-lambda ODU3 (they are all from OTU4 link) -66 sub-lambda ODU2 (5x10 ODU2 from 5xODU4 + 4x4 ODU2 from 4xODU3) -264 sub-lambda ODU1 (5x40 ODU1 from 5xODU4 + 4x16 ODU1 from 4xODU3) - 528 sub-lambda ODU0 (5x80 ODU0 from 5xODU4 + 4x32 ODU0 from 4xODU3) The ability to distinguish between link rate capacity and link multiplexing capacity is already a requirement as per [OTN-FWK]. As discussed in Section 3.2, [RFC4203] could achieve this distinction by advertising different bandwidths for full lambda and sub-lambda signal granularities. However, this approach implies the usage of multiple ISCDs and therefore it is not efficient. For example a link with link rate capacity OTU3 and multiplexing capacity ODU1, ODU2 and ODU3, [RFC4203] could require the utilization of up to three different ISCDs, one for each capability. So TE-link declaring would need: 1 ISCD for ODU1 with MAX LSP BW = MIN LSP BW = ODU1 1 ISCD for ODU2 with MAX LSP BW = MIN LSP BW = ODU2 1 ISCD for ODU3 with MAX LSP BW = MIN LSP BW = ODU3 (full lambda) Maximum Reservable Bandwidth (of the TE-link) set to ODU3 Unreserved Bandwidth (of the TE-link)) set to ODU3 3.6. Priority Support The IETF foresees that up to eight priorities must be supported and that all of them have to be advertised independently on the number of priorities supported by the implementation. Considering that the advertisement of all the different supported signal types will originate large LSAs, it is advised to advertise only the information related to the really supported priorities. 3.7. Multi-stage multiplexing With reference to the [OTN-FWK] , introduction of multi-stage multiplexing implies the advertisement of cascaded adaptation capabilities together with the matrix access constraints. The structure defined by IETF for the advertisement of adaptation capabilities is ISCD/IACD as in [RFC4202] and [RFC5339]. Belotti, et al. Expires January 9, 2011 [Page 10] Internet-Draft Information model for G.709 OTN July 2010 Modifications to ISCD/IACD , if needed, are FFS. 4. Security Considerations TBD 5. IANA Considerations TBD 6. Acknowledgements The authors would like to thank Eve Varma for her precious collaboration and review. 7. References 7.1. Normative References [OTN-OSPF] D.Ceccarelli,D.Caviglia,F.Zhang,D.Li,Y.Xu,P.Grandi,S.Belot ti, "Traffic Engineering Extensions to OSPF for Generalized MPLS (GMPLS) Control of Evolutive G.709 OTN Networks", consented by ITU-T on Oct 2009. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering (TE) Extensions to OSPF Version 2", RFC 3630, September 2003. [RFC4202] Kompella, K. and Y. Rekhter, "Routing Extensions in Support of Generalized Multi-Protocol Label Switching (GMPLS)", RFC 4202, October 2005. [RFC4203] Kompella, K. and Y. Rekhter, "OSPF Extensions in Support of Generalized Multi-Protocol Label Switching (GMPLS)", RFC 4203, October 2005. [RFC4328] Papadimitriou, D., "Generalized Multi-Protocol Label Switching (GMPLS) Signaling Extensions for G.709 Optical Transport Networks Control", RFC 4328, January 2006. Belotti, et al. Expires January 9, 2011 [Page 11] Internet-Draft Information model for G.709 OTN July 2010 [RFC5250] Berger, L., Bryskin, I., Zinin, A., and R. Coltun, "The OSPF Opaque LSA Option", RFC 5250, July 2008. [RFC5339] Le Roux, JL. and D. Papadimitriou, "Evaluation of Existing GMPLS Protocols against Multi-Layer and Multi-Region Networks (MLN/MRN)", RFC 5339, September 2008. 7.2. Informative References [G.709-v1] ITU-T, "Interface for the Optical Transport Network (OTN)", G.709 Recommendation (and Amendment 1), February 2001. [G.709-v2] ITU-T, "Interface for the Optical Transport Network (OTN)", G.709 Recommendation (and Amendment 1), March 2003. [G.709-v3] ITU-T, "Rec G.709, version 3", approved by ITU-T on December 2009. [G.872-am2] ITU-T, "Amendment 2 of G.872 Architecture of optical transport networks for consent", consented by ITU-T on June 2010. [OTN-FWK] F.Zhang, D.Li, H.Li, S.Belotti, "Framework for GMPLS and PCE Control of G.709 Optical Transport Networks", work in progress draft-ietf-ccamp-gmpls-g709-framework-00, April 2010. Authors' Addresses Sergio Belotti Alcatel-Lucent Via Trento, 30 Vimercate Italy Email: sergio.belotti@alcatel-lucent.com Belotti, et al. Expires January 9, 2011 [Page 12] Internet-Draft Information model for G.709 OTN July 2010 Pietro Vittorio Grandi Alcatel-Lucent Via Trento, 30 Vimercate Italy Email: pietro_vittorio.grandi@alcatel-lucent.com Daniele Ceccarelli Ericsson Via A. Negrone 1/A Genova - Sestri Ponente Italy Email: daniele.ceccarelli@ericsson.com Diego Caviglia Ericsson Via A. Negrone 1/A Genova - Sestri Ponente Italy Email: diego.caviglia@ericsson.com Fatai Zhang Huawei Technologies F3-5-B R&D Center, Huawei Base Shenzhen 518129 P.R.China Bantian, Longgang District Phone: +86-755-28972912 Email: zhangfatai@huawei.com Dan Li Huawei Technologies F3-5-B R&D Center, Huawei Base Shenzhen 518129 P.R.China Bantian, Longgang District Phone: +86-755-28973237 Email: danli@huawei.com Belotti, et al. Expires January 9, 2011 [Page 13]