MPLS Working Group G. Swallow, Ed. Internet-Draft Cisco Systems, Inc. Intended status: Standards Track A. Fulignoli, Ed. Expires: October 28, 2011 Ericsson M. Vigoureux, Ed. Alcatel-Lucent S. Boutros Cisco Systems, Inc. D. Ward Juniper Networks, Inc. April 26, 2011 MPLS Fault Management OAM draft-ietf-mpls-tp-fault-04 Abstract This draft specifies OAM messages to indicate service disruptive conditions for MPLS Transport Profile (MPLS-TP) Label Switched Paths (LSPs). The notification mechanism employs a generic method for a service disruptive condition to be communicated to a Maintenance End Point (MEP). An MPLS Operation, Administration, and Maintenance (OAM) channel is defined along with messages to communicate various types of service disruptive conditions. 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 October 28, 2011. Swallow, et al. Expires October 28, 2011 [Page 1] Internet-Draft MPLS Fault Management OAM April 2011 Copyright Notice Copyright (c) 2011 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 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. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 2. MPLS Fault Management Messages . . . . . . . . . . . . . . . . 4 2.1. MPLS-TP Alarm Indication Signal . . . . . . . . . . . . . 5 2.1.1. MPLS-TP Link Down Indication . . . . . . . . . . . . . 5 2.2. MPLS-TP Lock Report . . . . . . . . . . . . . . . . . . . 6 3. MPLS Fault Management Channel . . . . . . . . . . . . . . . . 6 4. MPLS Fault Management Message Format . . . . . . . . . . . . . 7 4.1. Fault Management Message TLVs . . . . . . . . . . . . . . 8 4.1.1. Interface Identifier TLV . . . . . . . . . . . . . . . 9 4.1.2. Global Identifier . . . . . . . . . . . . . . . . . . 10 4.1.3. International Carrier Code . . . . . . . . . . . . . . 10 5. Sending and Receiving Fault Management Messages . . . . . . . 10 5.1. Sending a Fault Management Message . . . . . . . . . . . . 10 5.2. Clearing a FM Indication . . . . . . . . . . . . . . . . . 11 5.3. Receiving a FM Indication . . . . . . . . . . . . . . . . 11 6. Minimum Implementation Requirements . . . . . . . . . . . . . 11 7. Security Considerations . . . . . . . . . . . . . . . . . . . 12 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 8.1. Pseudowire Associated Channel Type . . . . . . . . . . . . 12 8.2. MPLS Fault OAM Message Type Registry . . . . . . . . . . . 12 8.3. MPLS Fault OAM TLV Registry . . . . . . . . . . . . . . . 13 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13 9.1. Normative References . . . . . . . . . . . . . . . . . . . 13 9.2. Informative References . . . . . . . . . . . . . . . . . . 14 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14 Swallow, et al. Expires October 28, 2011 [Page 2] Internet-Draft MPLS Fault Management OAM April 2011 1. Introduction In traditional transport networks, circuits such as T1 lines are provisioned on multiple switches. When a disruption occurs on any link or node along the path of such a transport circuit, OAM are generated which may in turn suppress alarms and/or activate a backup circuit. The MPLS Transport Profile (MPLS-TP) provides mechanisms to emulate traditional transport circuits. Therefore a Fault Management (FM) capability must be defined for MPLS. This capability is being defined to meet the MPLS-TP requirements as defined in RFC 5654 [1], and the MPLS-TP Operations, Administration and Maintenance Requirements as defined in RFC 5860 [2]. However, this mechanism is intended to be applicable to other aspects of MPLS as well. Two broad classes of service disruptive conditions are identified. 1. Defect: the situation in which the density of anomalies has reached a level where the ability to perform a required function has been interrupted. 2. Lock: an administrative status in which it is expected that only test traffic, if any, and OAM (dedicated to the LSP) can be sent on an LSP. Within the Defect class, a further category, Fault is identified. A fault is the inability of a function to perform a required action. A fault is a persistent defect. This document specifies an MPLS OAM channel called an "MPLS-OAM Fault Management (FM)" channel. A single message format and a set of procedures are defined to communicate service disruptive conditions from the location where they occur to the endpoints of LSPs which are affected by those conditions. Multiple message types and flags are used to indicate and qualify the particular condition. Corresponding to the two classes of service disruptive conditions listed above, two messages are defined to communicate the type of condition. These are known as: Alarm Indication Signal (AIS) Lock Report (LKR) 1.1. Terminology ACH: Associated Channel Header ASN: Autonomous System Number Swallow, et al. Expires October 28, 2011 [Page 3] Internet-Draft MPLS Fault Management OAM April 2011 CC: Continuity Check FM: Fault Management GAL: Generic Associated Channel Label LOC: Loss of Continuity LSP: Label Switched Path LSR: Label Switching Router MEP: Maintenance End Point MIP: Maintenance Intermediate Point MPLS: Multi-Protocol Label Switching MPLS-TP: MPLS Transport Profile OAM: Operations, Administration and Maintenance P2MP: Point to Multi-Point P2P: Point to Point PSC: Protection State Coordination PW: Pseudowire TLV: Type Length Value TTL: Time To Live 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 RFC 2119 [3]. 2. MPLS Fault Management Messages This document defines messages to indicate service disruptive conditions. Two messages are defined, Alarm Indication Signal, and Lock Report. These semantics of the individual messages are described in subsections below. Swallow, et al. Expires October 28, 2011 [Page 4] Internet-Draft MPLS Fault Management OAM April 2011 Fault Management messages are carried in-band by using the Associated Channel Header (ACH) and Generic Associated Channel Label (GAL) as defined in RFC5586 [4]. To facilitate recognition and delivery of Fault Management messages, the Fault Management Channel is identified by a unique ACH codepoint. Fault OAM messages are generated by intermediate nodes where an LSP is switched. When a server layer, (e.g. a link) used by the LSP fails, the intermediate node sends Fault Management messages using the LSP's Fault associated channel back to the endpoint of the LSP. Strictly speaking, when a server MEP detects a service disruptive condition, Fault Management messages are generated by the convergence server-to-client adaptation function. The messages are sent to the client MEPs by inserting them into the affected LSPs in the direction opposite to the detecting MEP's peer server MEP(s). The message is sent periodically until the condition is cleared. 2.1. MPLS-TP Alarm Indication Signal The MPLS-TP Alarm Indication Signal (AIS) message is generated in response to detecting defects in the server layer. The AIS message SHOULD be sent as soon as the condition is detected, that is before any determination has been made as to whether the condition is persistent and therefore fatal. For example, an AIS message may be sent during a protection switching event and would cease being sent (or cease being forwarded by the protection switch selector) if the protection switch was successful in restoring the link. The primary purpose of the AIS message is to suppress alarms in the MPLS-TP layer network above the level at which the defect occurs. When the Link Down Indication is set, the AIS message MAY be used to trigger recovery mechanisms. 2.1.1. MPLS-TP Link Down Indication The LDI flag is set in response to detecting a fatal failure in the server layer. The LDI flag MUST NOT be set until the defect has been determined to be fatal. The LDI flag MUST be set if the defect has been determined to be fatal. For example during a protection switching event the LDI flag is not set. However if the protection switch was unsuccessful in restoring the link within the expected repair time, the LDI flag MUST be set. The setting of the LDI flag can be predetermined based on the protection state. If the Server Layer is protected and both the working and protection paths are available, both the active and standby MEPs should be programmed to send AIS with LDI clear upon detecting a defect condition. If the Server Layer is unprotected or Swallow, et al. Expires October 28, 2011 [Page 5] Internet-Draft MPLS Fault Management OAM April 2011 the Server Layer is protected but only the active path is available, the active MEP should be programmed to send AIS with LDI set upon detecting a defect condition. The receipt of an AIS message with the LDI flag set MAY be treated as the equivalent of loss of continuity (LOC) at the client layer. The choice of treatment is related to the rate at which the Continuity Check (CC) function is running. In a normal transport environment, CC is run at a high rate in order to detect a failure within 10s of milliseconds. In such an environment, the LDI flag may be ignored. AIS messages with the LDI flag set SHOULD be treated the same as any other AIS message, that is, used solely for alarm suppression. In more general MPLS environments the CC function may be running at a much slower rate. In this environment, the LDI flag enables faster switch-over upon a failure occurring along the LSP. 2.2. MPLS-TP Lock Report The MPLS-TP Lock Report (LKR) message is generated when a server layer entity has been administratively locked to communicated that condition to inform the client layer entities of that condition. When an MPLS-TP LSP is administratively locked it is not available to carry client traffic. The purpose of the LKR message is to suppress alarms in the MPLS-TP layer network above the level at which the defect occurs and to allow the clients to differentiate the lock condition from a defect condition. The primary purpose of the LKR message is to suppress alarms in the MPLS-TP layer network above the level at which the defect occurs. Like AIS with the LDI flag set, the receipt of an LKR message MAY be treated as the equivalent of loss of continuity at the client layer. 3. MPLS Fault Management Channel The MPLS Fault Management channel is identified by the ACH as defined in RFC 5586 [4] with the Channel Type set to the MPLS Fault Management (FM) code point = 0xHH. [HH to be assigned by IANA from the PW Associated Channel Type registry. Note: An early codepoint allocation has made: 0x0058 Fault OAM (TEMPORARY - expires 2011-07-16)] The FM Channel does not use ACH TLVs and MUST not include the ACH TLV header. The FM ACH Channel is shown below. Swallow, et al. Expires October 28, 2011 [Page 6] Internet-Draft MPLS Fault Management OAM April 2011 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |0 0 0 1|Version| Reserved | 0xHH Fault Management Channel | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ~ ~ MPLS Fault Management Message ~ ~ | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1: ACH Indication of the MPLS-TP Fault Management Channel The Fault Management Channel is 0xHH (to be assigned by IANA) 4. MPLS Fault Management Message Format The format of the Fault Management message is shown below. 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Vers | Resvd | Msg Type | Flags | Refresh Timer | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Total TLV Len | ~ +-+-+-+-+-+-+-+-+ TLVs ~ ~ | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2: MPLS-TP OAM Message Format Version The Version Number is currently 1. Reserved This field MUST be set to zero on transmission and ignored on receipt. Message Type The Message Type indicates the type of condition as listed in the table below. Swallow, et al. Expires October 28, 2011 [Page 7] Internet-Draft MPLS Fault Management OAM April 2011 Msg Type Description -------- ----------------------------- 0x0 Reserved 0x1 Alarm Indication Signal (AIS) 0x2 Lock Report (LKR) Refresh Timer The maximum time between successive FM messages specified in seconds. The range is 1 to 20. The value 0 is not permitted. Total TLV Length The total TLV length is the total of all included TLVs. Flags Two flags are defined. The reserved flags in this field MUST be set to zero on transmission and ignored on receipt. +-+-+-+-+-+-+-+-+ | Reserved |L|R| +-+-+-+-+-+-+-+-+ Figure 3: Flags L-flag Link Down Indication. See section Section 2.1.1 for details on setting this bit. R-flag The R-flag is normally set to zero. A setting of one indicates the removal of a previously sent FM condition. 4.1. Fault Management Message TLVs TLVs are used in fault OAM to carry information that may not pertain to all messages as well as to allow for extensibility. The TLVs currently defined are the IF_ID, Global-ID, and ICC. TLVs (Type-Length-Value tuples) have the following format: Swallow, et al. Expires October 28, 2011 [Page 8] Internet-Draft MPLS Fault Management OAM April 2011 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 | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ . | . . Value . . | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 4: Fault TLV Format Type Encodes how the Value field is to be interpreted. Length Specifies the length of the Value field in octets. Value Octet string of Length octets that encodes information to be interpreted as specified by the Type field. 4.1.1. Interface Identifier TLV This TLV carries the Interface Identifier as defined in draft-ietf-mpls-tp-identifiers [5]. The Type is 0x1. The length is 0x8. 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MPLS-TP Node Identifier | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MPLS-TP Interface Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 5: Interface Identifier TLV Format Swallow, et al. Expires October 28, 2011 [Page 9] Internet-Draft MPLS Fault Management OAM April 2011 4.1.2. Global Identifier This TLV carries the Interface Identifier as defined in draft-ietf-mpls-tp-identifiers [5]. The Type is 0x2. The length is 0x4. 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MPLS-TP Global Identifier | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 6: Global Identifier TLV Format 4.1.3. International Carrier Code This TLV carries the International Carrier Code. The Type is 0x3. The length is 0x8. The value is an Octet string padded with nulls. 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | International Carrier Code | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | International Carrier Code (Cont.) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 7: International Carrier Code 5. Sending and Receiving Fault Management Messages 5.1. Sending a Fault Management Message Service disruptive conditions are indicated by sending FM messages. The message type is set to the value corresponding to the condition. The refresh timer is set to the maximum time between successive FM messages. This value MUST not be changed on successive FM messages. If the optional clearing procedures are not used, then the default value is 1. Otherwise the default value is 20. Swallow, et al. Expires October 28, 2011 [Page 10] Internet-Draft MPLS Fault Management OAM April 2011 A Global-ID TLV or an ICC TLV MAY be included. The IF_ID TLV SHOULD be included. If the R-Flag clearing procedures are to be used, the IF_ID TLV MUST be included. The message is then sent. The message MUST be refreshed two more times at an interval of one second. Further refreshes are sent according to the value of the refresh timer. Refreshing continues until the condition is cleared. 5.2. Clearing a FM Indication Ceasing to send FM messages will clear the indication after 3.5 times the Refresh Timer. To clear an indication more quickly, the following procedure is used. The R-Flag of the FM message is set to one. Other fields of the FM message SHOULD NOT be modified. The message is sent immediately and then refreshed two more times at an interval of one second. 5.3. Receiving a FM Indication When a FM message is received, a MEP examines it to ensure that that it is well formed. If the message type is unknown, the message is ignored. If the R-Flag is zero, the condition corresponding to the message type is entered. A timer is set to 3.5 times the refresh timer. If the message is not refreshed within this period, the condition is cleared. A message is considered a refresh if the message type and IF_ID match an existing condition and the R-Flag is set to zero. If the R-Flag is set to one, the MEP checks to see if a condition matching the message type and IF_ID exists. If it does, that condition is cleared. Otherwise the message is ignored. 6. Minimum Implementation Requirements At a minimum an implementation MUST support the following: 1. Sending AIS and LKR messages at a rate of 1 per second. In particular other values of the Refresh Timer and setting the R bit to value other than zero need not be supported. 2. Support of the sending the LDI flag. 3. Receiving AIS and LKR messages with any allowed Refresh Timer value. The following items are optional to implement. Swallow, et al. Expires October 28, 2011 [Page 11] Internet-Draft MPLS Fault Management OAM April 2011 1. Support of receiving the LDI flag. 2. Support of receiving the R flag. 3. All TLVs. 7. Security Considerations Spurious fault OAM messages form a vector for a denial of service attack. However, since these messages are carried in a control channel, one would have to gain access to a node providing the service in order to effect such an attack. Since transport networks are usually operated as a walled garden, such threats are less likely. 8. IANA Considerations 8.1. Pseudowire Associated Channel Type Fault OAM requires a unique Associated Channel Type which are assigned by IANA from the Pseudowire Associated Channel Types Registry. Registry: Value Description TLV Follows Reference ----------- ----------------------- ----------- --------- 0xHHHH Fault OAM No (This Document) 8.2. MPLS Fault OAM Message Type Registry This sections details the MPLS Fault OAM TLV Registry, a new name spaces to be managed by IANA. The Type space is divided into assignment ranges; the following terms are used in describing the procedures by which IANA allocates values: "Standards Action" (as defined in RFC 5226 [6]) and "Private Use". MPLS Fault OAM Message Types take values in the range 0-255. Assignments in the range 0-251 are via Standards Action; values in the range 251-255 are for Private Use, and MUST NOT be allocated. Message Types defined in this document are: Msg Type Description -------- ----------------------------- 0x0 Reserved 0x1 Alarm Indication Signal (AIS) Swallow, et al. Expires October 28, 2011 [Page 12] Internet-Draft MPLS Fault Management OAM April 2011 0x2 Lock Report (LKR) 8.3. MPLS Fault OAM TLV Registry This sections details the MPLS Fault OAM TLV Registry, a new name spaces to be managed by IANA. The Type space is divided into assignment ranges; the following terms are used in describing the procedures by which IANA allocates values: "Standards Action" (as defined in RFC 5226 [6]), "Specification Required" and "Private Use". MPLS Fault OAM TLVs which take values in the range 0-255. Assignments in the range 0-191 are via Standards Action; assignments in the range 192-248 are made via "Specification Required"; values in the range 248-255 are for Private Use, and MUST NOT be allocated. TLVs defined in this document are: Value TLV Name ----- ------- 0 Reserved 1 Interface Identifier TLV 2 Global Identifier 3 International Carrier Code 9. References 9.1. Normative References [1] Niven-Jenkins, B., Brungard, D., Betts, M., Sprecher, N., and S. Ueno, "Requirements of an MPLS Transport Profile", RFC 5654, September 2009. [2] Vigoureux, M., Ward, D., and M. Betts, "Requirements for Operations, Administration, and Maintenance (OAM) in MPLS Transport Networks", RFC 5860, May 2010. [3] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [4] Bocci, M., Vigoureux, M., and S. Bryant, "MPLS Generic Associated Channel", RFC 5586, June 2009. [5] Bocci, M., Swallow, G., and E. Gray, "MPLS-TP Identifiers", draft-ietf-mpls-tp-identifiers-04 (work in progress), March 2011. [6] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Swallow, et al. Expires October 28, 2011 [Page 13] Internet-Draft MPLS Fault Management OAM April 2011 Considerations Section in RFCs", BCP 26, RFC 5226, May 2008. 9.2. Informative References Authors' Addresses George Swallow (editor) Cisco Systems, Inc. 300 Beaver Brook Road Boxborough, Massachusetts 01719 United States Email: swallow@cisco.com Annamaria Fulignoli (editor) Ericsson Email: annamaria.fulignoli@ericsson.com Martin Vigoureux (editor) Alcatel-Lucent Route de Villejust Nozay, 91620 France Email: martin.vigoureux@alcatel-lucent.com Sami Boutros Cisco Systems, Inc. 3750 Cisco Way San Jose, California 95134 USA Email: sboutros@cisco.com David Ward Juniper Networks, Inc. Email: dward@juniper.net Swallow, et al. Expires October 28, 2011 [Page 14] Internet-Draft MPLS Fault Management OAM April 2011 Stewart Bryant Cisco Systems, Inc. 250, Longwater Green Park, Reading RG2 6GB UK Email: stbryant@cisco.com Siva Sivabalan Cisco Systems, Inc. 2000 Innovation Drive Kanata, Ontario K2K 3E8 Canada Email: msiva@cisco.com Swallow, et al. Expires October 28, 2011 [Page 15]