Network Working Group A. Takacs Internet-Draft B. Gero Intended status: Experimental Ericsson Expires: May 8, 2008 November 5, 2007 GMPLS RSVP-TE Ethernet OAM Extensions draft-takacs-ccamp-rsvp-te-eth-oam-ext-00 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 May 8, 2008. Copyright Notice Copyright (C) The IETF Trust (2007). Takacs & Gero Expires May 8, 2008 [Page 1] Internet-Draft GMPLS RSVP-TE Ethernet OAM Extensions November 2007 Abstract The GMPLS controlled Ethernet Label Switching (GELS) work is extending GMPLS RSVP-TE to support the establishment of Ethernet LSPs. Ethernet Connectivity Fault Management (CFM) specifies an adjunct OAM flow to check connectivity in Ethernet networks. CFM can be also used with Ethernet LSPs for fault detection and triggering recovery mechanisms. This memo proposes experimental extensions to GMPLS RSVP-TE to support the setup of the associated CFM OAM entities for point-to-point bidirectional Ethernet LSPs. Note that the extensions defined may be applicable to other fault detection mechanisms that use periodic Hello messages, e.g., BFD, as well. Subsequent versions of the ID will consider the possibility of general OAM extensions not limiting the applicability to Ethernet OAM. Takacs & Gero Expires May 8, 2008 [Page 2] Internet-Draft GMPLS RSVP-TE Ethernet OAM Extensions November 2007 Requirements Language 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 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.1. Motivations and asumptions . . . . . . . . . . . . . . . . 4 1.2. Ethernet OAM operation overview . . . . . . . . . . . . . 5 1.3. Scope of the extension . . . . . . . . . . . . . . . . . . 7 2. GMPLS RSVP-TE Extensions . . . . . . . . . . . . . . . . . . . 8 2.1. Ethernet CFM TLV . . . . . . . . . . . . . . . . . . . . . 9 2.2. Monitoring Disabled - Admin_Status bit . . . . . . . . . . 10 2.3. Error handling . . . . . . . . . . . . . . . . . . . . . . 11 3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 4. Security Considerations . . . . . . . . . . . . . . . . . . . 13 5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 14 6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16 Intellectual Property and Copyright Statements . . . . . . . . . . 17 Takacs & Gero Expires May 8, 2008 [Page 3] Internet-Draft GMPLS RSVP-TE Ethernet OAM Extensions November 2007 1. Introduction Ethernet Connectivity Fault Management (CFM) defines an adjunct connectivity monitoring OAM flow to check the liveliness of Ethernet networks [IEEE-CFM]. With Provider Backbone Bridging Traffic Engineering (PBB-TE) [IEEE-PBBTE] Ethernet networks will support explicitly-routed Ethernet connections. CFM can be used to track the liveliness of PBB-TE connections and detect data plane failures. In IETF the GMPLS controlled Ethernet Label Switching (GELS) work is extending the GMPLS control plane to support the establishment of point-to-point PBB-TE data plane connections. We refer to GMPLS established PBB-TE connections as Ethernet LSPs. GELS enables the application of MPLS-TE and GMPLS provisioning and recovery features in Ethernet networks. MPLS OAM requirements are described in [RFC4377]. It provides requirements to create consistent OAM functionality for MPLS networks. The GMPLS OAM requirements are described in [GMPLS-OAM]. GMPLS OAM is based on the MPLS OAM requirements [RFC4377], in addition it also considers the existing OAM techniques in non-packet networks. This memo discusses the basic aspects of Ethernet OAM and specifies RSVP-TE extensions addressing OAM requirements for Ethernet networks. 1.1. Motivations and asumptions The following list is an excerpt of MPLS OAM requirements documented in [RFC4377]. Only a few requirements are discussed that bear a direct relevance to the discussion set forth in this memo and which also motivated the extensions specified in this document. 1. It is desired to support the automation of LSP defect detection. It is especially important in cases where large numbers of LSPs might be tested. 2. In particular some LSPs may require automated ingress-LSR to egress-LSR testing functionality, while others may not. 3. Mechanisms are required to coordinate network responses to defects. Such mechanisms may include alarm suppression, translating defect signals at technology boundaries, and synchronising defect detection times by setting appropriately bounded detection timeframes. Generally, the frequency of OAM execution must be set properly, to achieve the OAM requirements. When periodic messages are used for liveliness check of LSPs the frequency of messages must be set Takacs & Gero Expires May 8, 2008 [Page 4] Internet-Draft GMPLS RSVP-TE Ethernet OAM Extensions November 2007 properly fulfilling the requirements of the service and/or meeting the detection time boundaries posed by possible congruent connectivity check operations of higher layer applications. Furthermore, for consistent measurement of Service Level Agreements (SLAs) it may be required that measurement points agree on a common probing rate to avoid measurement problems. In order for Ethernet LSPs to provide reliable service delivery, data plane fault detection mechanisms are needed to trigger recovery actions. Note that if lower layer fault detection (or protection) mechanisms (such as those supported by SONET/SDH) are available, we may rely on them and alleviate the need for frequent OAM message exchanges for liveliness checks of Ethernet LSPs. However, when - for example - Ethernet is deployed over a WDM optical layer that does not provide the SONET/SDH protection characteristics, failure detection and recovery must be solved in the Ethernet layer. We assume that in networks where PBB-TE and GELS will be deployed the default LSP path fault detection mechanism will be based on CFM Connectivity Check Message (CCM) flows. Fast fault detection and recovery are key to reliable service delivery. However, there is a trade-off between fast fault detection and signalling and processing overhead of connectivity monitoring flows. Today, networks are providing transport of multiple service types each with special requirements on quality of service including the requirements on recovery. To balance the tradeoff between fast detection and overhead it is essential that fault detection and recovery are matching the requirements of the supported service, as highlighted in [RFC3469]. For example, while business services may require sub-second protection switching best effort Internet traffic may rely on slower (in the order of seconds) restoration mechanisms. These different requirements are reflected in the frequency of connectivity monitoring packets that are needed to be exchanged over the Ethernet LSP supporting a particular service type. We assume that - for a network operator to be able to balance the trade-off in fast failure detection and overhead - it will be beneficial to configure the frequency of CCM messages on a per Ethernet-LSP basis. Additionally, to simplify network management and reduce the risk (and impact) of misconfiguration, it is desirable to use Ethernet LSP signaling to configure CFM at both ends of the LSP. 1.2. Ethernet OAM operation overview For the purposes of this document, we only discuss Ethernet OAM [IEEE-CFM] aspects that are relevant for the connectivity monitoring of bidirectional point-to-point PBB-TE connections. In the Takacs & Gero Expires May 8, 2008 [Page 5] Internet-Draft GMPLS RSVP-TE Ethernet OAM Extensions November 2007 discussions we assume that the two directions of the bidirectional PBB-TE connection use the same path to allow proper operation of the Link Trace and Loopback Ethernet OAM functionality. Note that the basic operation of CFM Connectivity Check is similar to the operation of Bidirectional Forwarding Detection (BFD). At both ends of the bidiretional point-to-point PBB-TE connection one Maintenance Endpoint (MEP) is configured. Each MEP is provisioned among others with its local VLAN ID (VID) and MAC address and the VID and MAC address of the remote endpoint on witch the remote MEP is configured. MEPs exchange Connectivity Check Messages (CCMs) periodically with fixed intervals. Eight distinct intervals are defined in [IEEE-CFM]: +---+--------------------+-----------------+ | # | CCM Interval (CCI) | 3 bit reference | +---+--------------------+-----------------+ | 0 | No CCMs | 000 | | | | | | 1 | 3 1/3 ms | 001 | | | | | | 2 | 10 ms | 010 | | | | | | 3 | 100 ms | 011 | | | | | | 4 | 1 s | 100 | | | | | | 5 | 10 s | 101 | | | | | | 6 | 1 min | 110 | | | | | | 7 | 10 min | 111 | +---+--------------------+-----------------+ Table 1: CCM interval encoding If 3 consecutive CCM messages are not received by one of the MEPs it declares a connectivity failure and signals the failure in subsequent CCM messages by setting the Remote Defect Indicator (RDI) bit. If a MEP receives a CCM message with RDI set it immediately declares failure. The detection of a failure may trigger protection switching mechanisms or my be signalled to a management system. However, what happens once a failure is detected is out of the scope of this document. Takacs & Gero Expires May 8, 2008 [Page 6] Internet-Draft GMPLS RSVP-TE Ethernet OAM Extensions November 2007 1.3. Scope of the extension Although the setup of both unidirectional and bidirectional Ethernet LSPs is feasible, due to the symmetric bidirectional connectivity requirement of CFM, we only consider bidirectional point-to-point Ethernet LSPs. The applicability for multipoint LSPs are for further study. The signalling of MEP identification parameters such as Maintenance Association name (MA name) and MEP ID is left for further study. Note that in addition to Connectivity Check, which is the focus of this memo, CFM defines Link Trace and Loopback mechanisms as well. The proposed extension automatically creates the MEPs and associates them to the LSP. Once the MEPs are created the Link Trace and Loopback functionality is available for on demand OAM actions. Whether additional parameters besides those specified in the next sections are required (or are beneficial) to support Link Trace and/or Loopback is for further study. In addition parameters needed to support measurement of Service Level Agreements (SLAs) is also left for further study. Hence additional parameters may be defined in subsequent versions of this document. Note that the extensions defined may be applicable to other fault detection mechanisms that use periodic Hello messages, e.g., BFD, as well. Takacs & Gero Expires May 8, 2008 [Page 7] Internet-Draft GMPLS RSVP-TE Ethernet OAM Extensions November 2007 2. GMPLS RSVP-TE Extensions To simplify the configuration of connectivity monitoring, when an Ethernet LSP is signalled the associated MEPs should be automatically established. Further more, GMPLS signalling should be able to enable/disable connectivity monitoring of a particular Ethernet LSP. To configure MEPs some parameters must be provided to the Ethernet OAM functions. First, the desired CCM interval must be specified by the management system based on service requirements or operator policy. Second, the MEPs must be aware of their own and the reachability parameters of the remote MEP, in order CCM messages can be sent and received. That is, when configuring a MEP, the CCM interval, local MAC address and VID over which data plane traffic and CCM messages are received, and the remote side MAC address and VID with which data plane traffic and CCM messages are sent must be known. The Ethernet Label as defined in [Fedyk-GELS] consists of the Destination MAC address (DA-MAC) and VID. Hence the necessary reachability parameters for the MEPs can be obtained form Ethernet Labels. Assuming the procedures described in [Fedyk-GELS] for bidirectional Ethernet LSP establishment the MEP configuration should be as follows. When the RSVP-TE signalling is initiated for the bidirectional Ethernet LSP the local node creates the Upstream Label from its MAC address and locally selected VID and generates the Path message. Once the remote node receives the Path message it can use the Upstream Label to extract the reachability information of the initiator. Then it determines the MAC address and VID it would like to use to receive traffic. These parameters determine the reachability information of the local MEP. This in turn is used to construct the Ethernet Label to be put into the Resv message. The only information that is missing to setup the MEP, is the CCM interval, which is signalled in a new TLV (the Ethernet CFM TLV) as specified in this memo. Using this information the MEP can be configured on the node. Once the Resv message successfully arrives to the initiator it can extract the remote side reachability information from the Ethernet Label whereby this node has also obtained all the information needed to establish the MEP. Once the MEPs are established the monitoring of the LSP is operational. In certain situations, e.g., maintenance, re- optimisation of LSPs, it is desirable to explicitly enable or disable the monitoring of LSPs (i.e., start/stop exchanging CC messages). To allow administrative control of LSP monitoring one bit in the Admin_Status object is used. The "Monitoring Disabled" (M) bit is allocated for this purpose. Takacs & Gero Expires May 8, 2008 [Page 8] Internet-Draft GMPLS RSVP-TE Ethernet OAM Extensions November 2007 Note that since the reachability information could be extracted form the Ethernet Labels it is an option not using any extension to support MEP configuration of Ethernet LSPs. That is, an implementation could use default parameters for CCM intervals to setup connectivity monitoring. However, we rejected this approach, as it does not provide means to set the CCM interval on a per LSP level, leaving limited possibilities to configure CFM in a way that matches the supported services' requirements. Moreover, there is no way for providing additional CFM parameters to configure other parameters of Ethernet OAM. 2.1. Ethernet CFM TLV In RSVP-TE the Flags field of the SESSION_ATTRIBUTE object is used to indicate options and attributes of the LSP. The Flags field has 8 bits and hence is limited to differentiate only 8 options. [RFC4420] defines a new object for RSVP-TE messages to allow the signalling of arbitrary attribute parameters making RSVP-TE easily extensible to support new applications. Furthermore, [RFC4420] allows options and attributes that do not need to be acted on by all Label Switched Routers (LSRs) along the path of the LSP. In particular, these options and attributes may apply only to key LSRs on the path such as the ingress LSR and egress LSR. Options and attributes can be signalled transparently, and only examined at those points that need to act on them. The LSP_ATTRIBUTES object and the LSP_REQUIRED_ATTRIBUTES objects are defined in [RFC4420] to provide means to signal LSP attributes and options in the form of TLVs. Options and attributes signalled in the LSP_ATTRIBUTES object can be passed transparently through LSRs not supporting a particular option or attribute, while the contents of the LSP_REQUIRED_ATTRIBUTES object must be examined and processed by each LSR. One TLV is defined in [RFC4420]: the Attributes Flags TLV. Since the extensions defined for CFM Continuity Check are required to be processed only by the edge nodes while internal nodes need to pass on the information transparently, the LSP_ATTRIBUTES object should be used for CFM related information signalling. We propose a new TLV, the Ethernet CFM TLV (depicted below) for supporting CFM CCM setup of Ethernet LSPs. This new TLV accommodates information on CCM interval and also leaves room for further extensions. Takacs & Gero Expires May 8, 2008 [Page 9] Internet-Draft GMPLS RSVP-TE Ethernet OAM Extensions November 2007 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 (2) (IANA) | Length (4) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | CI | Reserved (set to all 0s) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1 The type field indicates a new type: the Ethernet CFM TLV (2) (IANA to define). The length field is set to 4 bytes. CI (4 bits): CCM Interval, using the 3 bit encoding shown in Table 1. The first bit of the CI field is set to 0. The Ethernet CFM TLV is carried in the LSP_ATTRIBUTE object and is allowed in both the Path and Resv messages. The CCM interval field in the Path message is the required value to be set for the remote MEPs. The CCM interval field in the Resv message is optional and if present it is the CCM interval that was set by the remote MEP. If the Ethernet CFM TLV is not present in the Resv message this is understood as the remote MEP would have been configured with the requested CCM interval. The initiator upon receipt of the Resv message can determine whether the egress set the same interval that was requested or it used a different (slower) rate. If acceptable the ingress may set the rate received in the Resv message otherwise it initiates the tear down of the LSP. Note, both sides should use the same CCM interval. The negotiation allows accounting for the processing load posed on nodes to process CCM messages. A node can consider the current CCM load (determined by the number of active CCM flows and their respective CCM intervals) when deciding to setup a new MEP with a given CCM interval. It will be possible for a node to reject a small CCM interval request (e.g., 3.3ms) and propose a new less frequent rate for connectivity monitoring (e.g., 10ms). 2.2. Monitoring Disabled - Admin_Status bit Administrative Status Information is carried in the Admin_Status object. The Administrative Status Information is described in [RFC3471], the Admin_Status object is specified for RSVP-TE in [RFC3473]. Takacs & Gero Expires May 8, 2008 [Page 10] Internet-Draft GMPLS RSVP-TE Ethernet OAM Extensions November 2007 One bit is allocated for the administrative control of OAM monitoring. In addition to the Reflect (R) bit, 7 bits are currently occupied (assigned by IANA or temporarily in use by work in progress Internet drafts). As the 8th bit (IANA to assign) this draft introduces the Monitoring Disabled (M) bit. When this bit is set the connectivity monitoring of the LSP is disabled. 2.3. Error handling New error messages and procedures may be needed to handle failures of OAM configuration. These will be described in subsequent versions of this document. Takacs & Gero Expires May 8, 2008 [Page 11] Internet-Draft GMPLS RSVP-TE Ethernet OAM Extensions November 2007 3. IANA Considerations This document specifies a new TLV, the Ethernet CFM TLV, to be carried in the LSP_ATTRIBUTES objects in Path and Resv messages. One bit (Monitoring Disabled (M)) needs to be allocated in the Administrative Status Object. Takacs & Gero Expires May 8, 2008 [Page 12] Internet-Draft GMPLS RSVP-TE Ethernet OAM Extensions November 2007 4. Security Considerations The signalling of OAM related parameters and the automatic establishment of OAM entities introduces additional security considerations to those discussed in [RFC3473]. In particular, a network element could be overloaded, if an attacker would request liveliness monitoring, with frequent periodic messages, for a high number of LSPs, targeting a single network element. Security aspects will be covered in more detailed in subsequent versions of this document. Takacs & Gero Expires May 8, 2008 [Page 13] Internet-Draft GMPLS RSVP-TE Ethernet OAM Extensions November 2007 5. Acknowledgements The authors would like to thank Adrian Farrel, Loa Andersson and Eric Gray for their useful comments. Takacs & Gero Expires May 8, 2008 [Page 14] Internet-Draft GMPLS RSVP-TE Ethernet OAM Extensions November 2007 6. References [Fedyk-GELS] "GMPLS control of Ethernet", Internet Draft, work in progress. [GMPLS-OAM] "OAM Requirements for Generalized Multi-Protocol Label Switching (GMPLS) Networks", Internet Draft, work in progress. [IEEE-CFM] "IEEE 802.1ag, Draft Standard for Connectivity Fault Management", work in progress. [IEEE-PBBTE] "IEEE 802.1Qay Draft Standard for Provider Backbone Bridging Traffic Engineering", work in progress. [RFC3469] "Framework for Multi-Protocol Label Switching (MPLS)-based Recovery", RFC 3469, February 2003. [RFC3471] "Generalized Multi-Protocol Label Switching (GMPLS) Signaling Functional Description", RFC 3471, January 2003. [RFC3473] "Generalized Multi-Protocol Label Switching (GMPLS) Signaling Resource ReserVation Protocol-Traffic Engineering (RSVP-TE) Extensions", RFC 3473, January 2003. [RFC4377] "Operations and Management (OAM) Requirements for Multi- Protocol Label Switched (MPLS) Networks", RFC 4377, February 2006. [RFC4420] "Encoding of Attributes for Multiprotocol Label Switching (MPLS) Label Switched Path (LSP) Establishment Using Resource ReserVation Protocol-Traffic Engineering (RSVP-TE)", RFC 4420, February 2006. Takacs & Gero Expires May 8, 2008 [Page 15] Internet-Draft GMPLS RSVP-TE Ethernet OAM Extensions November 2007 Authors' Addresses Attila Takacs Ericsson Laborc u. 1. Budapest, 1037 Hungary Email: attila.takacs@ericsson.com Balazs Gero Ericsson Laborc u. 1. Budapest, 1037 Hungary Email: balazs.gero@ericsson.com Takacs & Gero Expires May 8, 2008 [Page 16] Internet-Draft GMPLS RSVP-TE Ethernet OAM Extensions November 2007 Full Copyright Statement Copyright (C) The IETF Trust (2007). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. 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