CCAMP working Group G. Bernstein Internet-Draft Grotto Networking Expires: April 14, 2006 D. Caviglia Marconi R. Rabbat Fujitsu October 11, 2005 Operating Virtual concatenation (VCAT) and the Link Capacity Adjustment Scheme (LCAS) with Generalized Multi-Protocol Label Switching (GMPLS) draft-bernstein-ccamp-gmpls-vcat-lcas-01 Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of 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 14, 2006. Copyright Notice Copyright (C) The Internet Society (2005). Abstract This document describes the use of the Generalized Multi-Protocol Label Switching (GMPLS) control plane in conjunction with the Virtual Concatenation (VCAT) layer 1 inverse multiplexing mechanism and its companion Link Capacity Adjustment Scheme (LCAS) which can be used Bernstein, et al. Expires April 14, 2006 [Page 1] Internet-Draft GMPLS, VCAT and LCAS October 2005 for hitless dynamic resizing of the inverse multiplex group. These techniques apply to the Optical Transport Network (OTN), Synchronous Optical Network (SONET), Synchronous Digital Hierarchy (SDH) and Plesiochronous Digital Hierarchy (PDH) signals. Table of Contents 1. Overview of VCAT and LCAS . . . . . . . . . . . . . . . . . . 3 1.1. VCAT signals and components . . . . . . . . . . . . . . . 3 1.2. VCAT Capabilities and Limitations . . . . . . . . . . . . 3 1.3. The LCAS Protocol . . . . . . . . . . . . . . . . . . . . 4 2. Problem Statement and Current Support . . . . . . . . . . . . 5 2.1. Discovery of Enabled End Systems . . . . . . . . . . . . . 5 2.2. Client to End Point Mappings . . . . . . . . . . . . . . . 5 2.3. VCAT configuration without LCAS . . . . . . . . . . . . . 6 2.4. VCAT configuration with LCAS . . . . . . . . . . . . . . . 7 2.5. Component Signal Configuration Scenarios . . . . . . . . . 8 3. Possible Extensions to GMPLS to support additional VCAT/LCAS scenarios . . . . . . . . . . . . . . . . . . . . . 10 3.1. Mechanisms for Discovery of VCAT/LCAS . . . . . . . . . . 10 3.2. Mechanism to Support Multiple Client to End Point Mappings . . . . . . . . . . . . . . . . . . . . . . . . . 10 3.3. Support for Component Signal Configuration Scenarios . . . 10 4. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 12 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13 Intellectual Property and Copyright Statements . . . . . . . . . . 14 Bernstein, et al. Expires April 14, 2006 [Page 2] Internet-Draft GMPLS, VCAT and LCAS October 2005 1. Overview of VCAT and LCAS Virtual Concatenation (VCAT) is a standardized layer 1 inverse multiplexing technique that can be applied to OTN [6], SONET [3], SDH [2], and PDH [5] component signals. By inverse multiplexing we mean a method that combines multiple links at a particular layer into an aggregate link to achieve a commensurate increase in available bandwidth on that aggregate link. More formally, VCAT essentially combines the payload bandwidth of multiple path layer network signals (or trails) to support a single client (e.g. Ethernet) layer link. For a more detailed introduction see [1]. 1.1. VCAT signals and components In the following we will use SDH terminology rather than both SONET and SDH terminology. In SDH Virtual Concatenation (VCAT) can be applied to the following component time division multiplex (TDM) signals referred to as Virtual Containers (VCs): VC-11, VC-12, VC-2, VC-3, and VC-4 Only like component signals can be aggregated into a VCAT group. These groups are respectively known as: VC-11-Xv, VC-12-Xv, VC-2-Xv, VC-3-Xv, and VC-4-Xv. In the previous designations X is an integer running from 1 to a value N dependent upon the component type. See [2] for details. VCAT can be applied to the following PDH signals as specified in reference [5]: DS1,E1, E3, DS3. Similar to the SONET/SDH case these component signals can only be combined with like signals to produce aggregates. For some reason the virtual concatenation groups of the PDH signals were not given unique designations in [5] so we shall adopt a similar notation to the SDH VCAT signals for the permitted PDH VCAT signals that follow: DS1-Xv, E1-Xv, E3-Xv, DS3-Xv. Concatenation in the optical transport network (OTN) is realized by means of virtual concatenation of Optical Channel Payload Unit (OPU) signals. OPUk signals (k=1, 2, 3) can be concatenated into OPUk-Xv aggregates with X= 1,..., 256. See reference [6] for details. 1.2. VCAT Capabilities and Limitations VCAT performs inverse multiplexing by octet/byte de-interleaving of the encapsulated client bit stream. Hence the main limitation of any VCAT standard or implementation is the ammount of differential delay that can be accomodated between the component signals. These are summarized for the different signal types in reference [1] with details given in the respective standards documents. Bernstein, et al. Expires April 14, 2006 [Page 3] Internet-Draft GMPLS, VCAT and LCAS October 2005 1.3. The LCAS Protocol The Link Capacity Adjustment Scheme for VCAT signals is a protocol for dynamically and hitlessly changing (i.e., increasing and decreasing) the capacity of a VCAT group. LCAS also provides survivability capabilities, automatically decreasing the capacity if a member of the VCAT group experiences a failure in the network, and increasing the capacity when the network fault is repaired. LCAS, itself, provides a mechanism for interworking between LCAS and non- LCAS VCAT end points. VCAT does not require LCAS for its operation. LCAS functionality does not overlap or conflict with GMPLS' routing or signaling functionality for the establishment of component links or entire VCAT groups. LCAS instead is used to control whether a particular component signal is actually put into service carrying traffic for the VCAT group. LCAS provides for graceful degradation of failed links by having the sink end report back the receive status of all member components. In the case of a reported member failure, the source end will stop using the component and the source end will send an LCAS message to the sink end that it is not transmitting data on that component. The worst case notification times are summarized in [1]. Bernstein, et al. Expires April 14, 2006 [Page 4] Internet-Draft GMPLS, VCAT and LCAS October 2005 2. Problem Statement and Current Support In this section we list a number of VCAT/LCAS usage scenarios and their current level of support. We will evaluate the applicability of GMPLS to these scenarios and for those scenarios that GMPLS does not currently support we describe possible GMPLS extensions in Section 3. Note the term "component" signal in the text is used as a simplified notion to the more formal concepts of VC-n, ODUk, and PDH termination function as well as VC-n, ODUk and PDH path/trail. 2.1. Discovery of Enabled End Systems Discovering VCAT: VCAT sources can only communicate with VCAT capable sinks. Hence the VCAT capabilities of a PDH, SDH, or OTN path termination points need to be known. Currently no support for discovery of VCAT or LCAS apriori, i.e., via routing information. Support for "discovery" of VCAT capability at connection establishment time via signaling, i.e., we can request VCAT connection and if the end system cannot support it,it would refuse the connection. TBD -- is there a specific error code concerning "VCAT not supported". Discovering LCAS: LCAS offers additional functionality between VCAT capable sources and sinks. Hence the LCAS capabilities of VCAT enabled path termination points can be useful to know in advance of component signal setup. Currently there is no mechanism to ask for an LCAS enabled end point nor is there a way to find out if the other end is LCAS enabled until after the connection is established. This is a problem if we specifically want hitless dynamic resizing or fast graceful degradation for a VCAT group. 2.2. Client to End Point Mappings Fixed Client to End point Mapping: Per client signal there is a VC-n-Xv circuit in which the X VC-n termination points are dedicated to this client signal. At any point in time, Y out of X VC-n termination points may be set up to carry client traffic. For example when VCAT is deployed on a Router, the VCAT group connects directly to one STM-N interface port (in absence of a HO or LO switch fabric in the router). The transport network will then split the VCAT group into two or more subgroups of components, each being routed via diverse routes. Bernstein, et al. Expires April 14, 2006 [Page 5] Internet-Draft GMPLS, VCAT and LCAS October 2005 Variable Client to End point Mapping: For a set of M client signals there are M VC-n-Xv VCAT endpoints sharing a set of N (N>M) VC-n termination points. Typically MxX > N (example: M=10, X=7, N=64); i.e. there is a kind of overbooking. Implication: must be able to accommodate multiple different sized VCAT groups at an "interface". For example an STM-64 interface can support many different VC-4-Xv groups. Implications: In both these cases we can have more than one VCAT group per GMPLS link. In general it is the responsibility of the signaling entity at the source and destination ends to choose the appropriate VC-n termination points for the VCAT group and in the case of "variable client mapping" to perform needed internal configuration. However multiple VCAT groups per GMPLS link or GMPLS addressed entity introduces an unresolvable ambiguity when disjoint connections are set up or dynamic resizing is applied since there is currently no "VCAT group identifier" in GMPLS signaling. 2.3. VCAT configuration without LCAS Base Configuration: For VCAT to operate the sink end needs to be informed of how many components are in the VCAT group. It has no other way of knowing if it is currently receiving all components intended to be in the group. Fixed sized co-routed groups are supported with current GMPLS signaling. Disjointly routed groups are not currently supported. Group Resizing: Additions or removals of components from a VCAT group without are not hitless, that is data loss will occur while the source and sink become synchronized as to the number of members in the group. Currently not supported within GMPLS. In particular, with each addition or removal of a component the sink end point needs to be told the expected number of components in the group. Failure Conditions: Failure of a component must detected external to VCAT system. The entire group is rendered inoperable until source takes the failed component out of service and sink end is notified to take component out of service. Currently not supported within GMPLS. The source needs to be told what component has failed and remove it from service, then the sink must be told to also remove it from service. Bernstein, et al. Expires April 14, 2006 [Page 6] Internet-Draft GMPLS, VCAT and LCAS October 2005 2.4. VCAT configuration with LCAS Base Configuration: Sink end (and source end) are first configured with the value of "Y" (the number of components), and more specifically which of the X (e.g. VC-n) access points (and thus (VC-n) termination functions) are allocated to the VCAT group with Y (VC-n) components. LCAS then detects automatically which of those Y (VC-n) components is carrying actual traffic and puts them into service for the group. Currently both co-routed and disjointly routed VCAT groups can be supported if there is no VCAT group ambiguity. Component Addition: When a new component signal has to be added to a VCAT group the following procedure applies. 1. Configure the adaptation source/sink functions and change the number of components, Y, to Y+1 by identifying which of the X-Y (e.g. VC-n) access points currently outside the group is added to the group; 2. The new component is created, e.g., the cross-connections are establish along the components path. 3. As soon as LCAS protocol information exchange is finished, i.e., the state NORM is reached, client traffic is sent on the added component. This procedure does not affect the already established LCAS members, that is, client traffic is not sent on the new component until the LCAS procedure is complete; This can be supported within GMPLS if, after GMPLS has successfully established a potential new component, the source end LCAS is (internally) told to add it to the group. Component Removal: When a component is removed the following procedure applies: 1. LCAS protocol is used to remove the component from the group, that is, incoming traffic client data is transmitted on the other VCAT component(s) to assure that the procedure is not traffic affecting 2. Configure the adaptation source/sink functions and change the number of components Y to Y-1; i.e. remove the VC-n access point from the group. Bernstein, et al. Expires April 14, 2006 [Page 7] Internet-Draft GMPLS, VCAT and LCAS October 2005 3. The component connection can be, if needed, removed from the transport network. This can be supported within GMPLS if, before GMPLS tears down a component, LCAS is told (local to source end) to remove the component from service in the group. Component Failure: When a component fails, the LCAS sink detects the failure (how this is done is outside the scope of this ID) and informs the source of this failure via the member status (MST) information. The source then: 1. Takes the failed component out of service and if necessary rearranges the sequencing of the VCAT group. 2. Informs the sink about the component removed from service and any re-arranging of the VCAT group. When the failed component is repaired, LCAS can automatically add the repaired component back to the group, or alternatively a new component can be added to bring the group back to its original size. Note that component failure is not hitless, but note the fast notification times of [BernDiegoRabbat]. Currently supported since no action required of GMPLS. 2.5. Component Signal Configuration Scenarios Here we use the term "group" to refer to the entire VCAT group and the terminology "set" and "subset" to refer to the collection of potential VCAT group member signals. Note that all assesments of whether a scenario is curretly supported assumes either (a) a single VCAT group per GMPLS addressable entity, or (b) a mechanism is in place to disambiguate multiple VCAT groups (see Section 2.2). Fixed, Co-routed: A fixed bandwidth VCAT group, transported over a co-routed set of member signals. This is the case where the intended bandwidth of the VCAT group does not change and all member signals follow a similar route. The intent here is the capability to allocate the "right" amount of bandwidth. Currently supported in GMPLS. Fixed, Disjoint: A fixed bandwidth VCAT group, transported over at least two disjointly routed subsets of member signals. The intent here is additional resilience and graceful degradation in the case of failure. Bernstein, et al. Expires April 14, 2006 [Page 8] Internet-Draft GMPLS, VCAT and LCAS October 2005 If LCAS is present this scenario is supported under GMPLS. Not supported without LCAS since we need two-way communications of some type between source and sink to coordinate which members are to be used in the group in a failure scenario. Dynamic, Co-routed: A dynamic VCAT group (bandwidth can be increased or decreased via the addition or removal of member signals), transported over a co-routed set of members. Intent here is dynamic sizing of bandwidth. If LCAS present this scenario is currently supported by GMPLS. Implications: LCAS is needed for hitless resizing. Note before LCAS can do its part of getting traffic over the modified VCAT group, the two VCAT/LCAS endpoints need to be configured (Y -> Y+1 or Y -> Y-1); this requires either "communication" between the two endpoints (when one of the endpoints is configured by call/ connection controller, or simple communication of the call/ connection controller with both endpoints. Without LCAS we still need two way communications between source and sink to coordinate which members are used in the group and changes will not be hitless. Dynamic, Disjoint: A dynamic VCAT group, transported over at least two disjointly routed subsets of member signals. Intent here is dynamic resizing and resilience. Currently support and implications similar to the "dynamic, co- routed" and "fixed, disjoint" cases. Shared Pool: Two or more VCAT groups between the same source and sink who desire to share a pool of component signals between them. Each VCAT group may have a dedicated set of members, and may also obtain additional members from a "common pool" of components. Note that at any given point in time a component signal can belong to at most one VCAT group. The intent here is to allow dynamic resizing of VCAT groups via the sharing of a pool of established component signals without requiring complete circuit provisioning, i.e., only the group membership of the component signal would change. Currently not supported by GMPLS. Implications: a communications mechanism between source and sink to indicate during a "change" which group a component should now belong. Bernstein, et al. Expires April 14, 2006 [Page 9] Internet-Draft GMPLS, VCAT and LCAS October 2005 3. Possible Extensions to GMPLS to support additional VCAT/LCAS scenarios Here we look at what might be reasonable to add to GMPLS to support the interest scenarios of Section 2 that were not currently covered. 3.1. Mechanisms for Discovery of VCAT/LCAS Would like to get both VCAT and LCAS capability of end systems via routing... Would like to be able to specifically ask for LCAS capability via signaling... 3.2. Mechanism to Support Multiple Client to End Point Mappings This is a very important capability and it is very similar to one that is being proposed in the end-to-end signaling for recovery I-D. In particular the ASSOCIATION object. Note, however, since there is a rather high probability that at some point we might use VCAT/LCAS with GMPLS based protection we would really need an ASSOCIATION object type specific to VCAT. Association objects are not unique and therefore adding a new type to the Association object would make it a good candidate to support this requirement. 3.3. Support for Component Signal Configuration Scenarios TBD based on analysis of use of admin-status object. If the admin- status object is sufficient we will detail its use in this application since it is currently an optional object. 4. References [1] Bernstein, G., Caviglia, D., and R. Rabbat, "VCAT/LCAS in a Clamshell", To Be Published available at http:// www.grotto-networking.com/pages/VCAT-in-a-Clamshell-DRAFT.pdf, October 2005. [2] International Telecommunications Union, "Network node interface for the synchronous digital hierarchy (SDH)", ITU- T Recommendation G.707, December 2003. [3] American National Standards Institute, "Synchronous Optical Network (SONET) - Basic Description including Multiplex Structure, Rates, and Formats", ANSI T1.105-2001, 2001. [4] "Link capacity adjustment scheme (LCAS) for virtual concatenated signals", ITU-T Recommendation G.7042, February 2004. Bernstein, et al. Expires April 14, 2006 [Page 10] Internet-Draft GMPLS, VCAT and LCAS October 2005 [5] "Virtual concatenation of plesiochronous digital hierarchy (PDH) signals", ITU-T Recommendation G.7043, July 2004. [6] "Interfaces for the Optical Transport Network (OTN)", ITU- T Recommendation G.709, March 2003. [7] Sklower, K., Lloyd, B., McGregor, G., Carr, D., and T. Coradetti, "The PPP Multilink Protocol (MP)", RFC 1990, August 1996. [8] "Information technology - Telecommunications and information exchange between systems - Local and metropolitan area networks - Specific requirements - Part 3: Carrier sense multiple access with collision detection (CSMA/CD) access method and physical layer specifications", IEEE Standard 802.3, March 2002. [9] Bernstein, G., Rajagopalan, B., and D. Saha, "Optical Network Control: Archtecture, Protocols", Addison-Wesley, 2004. Bernstein, et al. Expires April 14, 2006 [Page 11] Internet-Draft GMPLS, VCAT and LCAS October 2005 Appendix A. Acknowledgements The authors would like to thank Maarten Vissers for extensive reviews and contributions to this draft. Bernstein, et al. Expires April 14, 2006 [Page 12] Internet-Draft GMPLS, VCAT and LCAS October 2005 Authors' Addresses Greg Bernstein Grotto Networking Phone: +1 510 573 2237 Email: gregb@grotto-networking.com Diego Caviglia Marconi Email: Diego.Caviglia@marconi.com Richard Rabbat Fujitsu Phone: +1 408 530 4537 Email: richard@us.fujitsu.com Bernstein, et al. Expires April 14, 2006 [Page 13] Internet-Draft GMPLS, VCAT and LCAS October 2005 Intellectual Property Statement The IETF 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 this 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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