--- 1/draft-ietf-mpls-ldp-end-of-lib-03.txt 2009-08-28 22:12:08.000000000 +0200 +++ 2/draft-ietf-mpls-ldp-end-of-lib-04.txt 2009-08-28 22:12:08.000000000 +0200 @@ -1,194 +1,235 @@ MPLS Working Group Rajiv Asati Internet Draft Cisco Systems Intended status: Standards Track -Expires: July 2009 Pradosh Mohapatra +Expires: Feb 2010 Pradosh Mohapatra Cisco Systems - Bob Thomas - Emily Chen Huawei Technologies - January 14, 2009 + Bob Thomas - LDP End-of-LIB - draft-ietf-mpls-ldp-end-of-lib-03.txt + August 28, 2009 + + Signaling LDP Label Advertisement Completion + draft-ietf-mpls-ldp-end-of-lib-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. + provisions of BCP 78 and BCP 79. This document may contain material + from IETF Documents or IETF Contributions published or made publicly + available before November 10, 2008. The person(s) controlling the + copyright in some of this material may not have granted the IETF + Trust the right to allow modifications of such material outside the + IETF Standards Process. Without obtaining an adequate license from + the person(s) controlling the copyright in such materials, this + document may not be modified outside the IETF Standards Process, and + derivative works of it may not be created outside the IETF Standards + Process, except to format it for publication as an RFC or to + translate it into languages other than English. 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 14, 2009. + This Internet-Draft will expire on Feb 28, 2010. Copyright Notice Copyright (c) 2009 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. + Provisions Relating to IETF Documents in effect on the date of + publication of this document (http://trustee.ietf.org/license-info). + Please review these documents carefully, as they describe your rights + and restrictions with respect to this document. Abstract There are situations following Label Distribution Protocol (LDP) session establishment where it would be useful for an LDP speaker to know when its peer has advertised all of its labels. The LDP specification provides no mechanism for an LDP speaker to notify a peer when it has completed its initial label advertisements to that peer. This document specifies means for an LDP speaker to signal completion of its initial label advertisements following session establishment. Table of Contents 1. Introduction...................................................3 2. Specification Language.........................................3 - 3. Unrecognized Notification Capability...........................3 + 3. Unrecognized Notification Capability...........................4 4. Signaling Completion of Label Advertisement....................4 - 5. Usage Guidelines...............................................5 - 5.1. LDP-IGP Sync..............................................6 - 5.2. LDP Graceful Restart......................................6 - 5.3. Wildcard Label Request....................................7 - 5.4. Missing Expected End-of-LIB Notifications.................7 - 6. Security Considerations........................................7 + 4.1. Missing Expected End-of-LIB Notifications.................5 + 5. Usage Guidelines...............................................6 + 5.1. LDP-IGP Sync..............................................7 + 5.2. LDP Graceful Restart......................................7 + 5.3. Wildcard Label Request....................................8 + 6. Security Considerations........................................8 7. IANA Considerations............................................8 - 8. Acknowledgments................................................8 - 9. References.....................................................9 - 9.1. Normative References......................................9 - 9.2. Informative References....................................9 - Author's Addresses...............................................10 + 8. Acknowledgments................................................9 + 9. References....................................................10 + 9.1. Normative References.....................................10 + 9.2. Informative References...................................10 + Author's Addresses...............................................11 1. Introduction There are situations following LDP session establishment where it would be useful for an LDP speaker to know when its peer has - advertised all of its labels. For example, when an LDP speaker is - using LDP-IGP synchronization procedures [LDPSync], it would be - useful for the speaker to know when its peer has completed - advertisement of its IP label bindings. Similarly, after an LDP - session is re-established when LDP Graceful Restart [RFC3478] is in - effect, it would be helpful for each peer to signal the other after - it has advertised all its label bindings. + advertised all of the labels from its Label Information Base (LIB). + For example, when an LDP speaker is using LDP-IGP synchronization + procedures [RFC5443], it would be useful for the speaker to know when + its peer has completed advertisement of its IP label bindings. + Similarly, after an LDP session is re-established when LDP Graceful + Restart [RFC3478] is in effect, it would be helpful for each peer to + signal the other after it has advertised all its label bindings. The LDP specification [RFC5036] provides no mechanism for an LDP speaker to notify a peer when it has completed its initial label advertisements to that peer. This document specifies use of a Notification message with the "End- of-LIB" Status Code for an LDP speaker to signal completion of its label advertisements following session establishment. RFC5036 implicitly assumes that new Status Codes will be defined over the course of time. However, it does not explicitly define the behavior of an LDP speaker which does not understand the Status Code in a Notification message. To avoid backward compatibility issues - this document specifies use of the LDP capability mechanism [LDPCap] + this document specifies use of the LDP capability mechanism [RFC5561] at session establishment time for informing a peer that an LDP speaker is capable of handling a Notification message that carries an unrecognized Status Code. 2. Specification 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 [RFC2119]. 3. Unrecognized Notification Capability - An LDP speaker MAY include a Capability Parameter [LDPCap] in the + An LDP speaker MAY include a Capability Parameter [RFC5561] in the Initialization message to inform a peer that it ignores Notification - Messages that carry a Status TLV with a non-fatal Status Code unknown - to it. + Messages that carry a Status Type-Length-Value (TLV) with a non-fatal + Status Code unknown to it. The Capability Parameter for the Unrecognized Notification capability is a TLV with the following format: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |U|F| Unrecog Notif (IANA) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |S| Reserved | +-+-+-+-+-+-+-+-+ Figure 1 Unrecognized Notification Capability format Where: - U and F bits: Should be set 1 and 0 respectively as per section 4 - of LDP Capabilities [LDPCap]. + U and F bits: MUST be 1 and 0 respectively as per section 3 of LDP + Capabilities [RFC5561]. Unrecog Notif: TLV code point to be assigned by IANA. - S-bit: Must be 1 (indicates that capability is being advertised). + S-bit: MUST be 1 (indicates that capability is being advertised). Upon receiving a Notification with an unrecognized Status Code an LDP speaker MAY generate a console or system log message for trouble shooting purposes. 4. Signaling Completion of Label Advertisement - An LDP speaker MAY signal completion of its label advertisements to a - peer by means of a Notification message, if its peer had advertised - the Unrecognized Notification capability during session - establishment. The LDP speaker MAY send the Notification message (per - FEC Type) to a peer even if the LDP speaker had zero Label bindings - to advertise to that peer. + An LDP speaker that conforms to this specification SHOULD signal + completion of its label advertisements to a peer by means of a + Notification message, if its peer has advertised the Unrecognized + Notification capability during session establishment. The LDP speaker + SHOULD send the Notification message (per Forwarding Equivalence + Class (FEC) Type) to a peer even if the LDP speaker had zero Label + bindings to advertise to that peer. Such a Notification message MUST carry: - A status TLV (with TLV E- and F-bits set to zero) that carries an "End-of-LIB" Status Code (value to be assigned by IANA). - A FEC TLV with the Typed Wildcard FEC Element [TypedWC] that identifies the FEC type for which initial label advertisements have been completed. In terms of Section 3.5.1 of RFC5036, this TLV is an "Optional Parameter" of the Notification message. An LDP speaker MUST NOT send a Notification which carries a Status TLV with the End-of-LIB Status Code to a peer unless the peer had advertised the Unrecognized Notification capability during session establishment. This applies to any LDP peers discovered via either basic discovery or extended discovery mechanism (per section 2.4 of [RFC5036]). +4.1. Missing Expected End-of-LIB Notifications + + There is no guarantee that an LDP speaker will receive (or send) End- + of-LIB Notification from (or to) a peer even if the LDP speaker has + signaled the 'Unrecognized Notification' capability (section 3). + + Although it is expected that an LDP speaker supporting Unrecognized + Notification Capability would support sending and receiving End-of- + LIB Notication, it is not mandatory by definition. + + Please note that this is not a concern since the LDP speaker would + simply ignore the received Notification with End-of-LIB status code + (or any status code) that is not recognized or supported, by + definition. + + To deal with the possibility of missing End-of-LIB Notifications + after the LDP session establishment, an LDP speaker MAY time out + receipt of an expected End-of-LIB Notification. An LDP speaker SHOULD + start a per-peer internal timer, called 'EOL Notification' timer (the + default value of 60 seconds is RECOMMENDED, though the value of this + timer SHOULD be configurable) immediately following the LDP session + establishment. + + This timer is reset by the subsequent label advertisement, and + stopped by the End-of-LIB Notification message. Lacking any label + advertisement from the peer, the timer would expire, resulting in the + LDP speaker to behave as if it had received the End-of-LIB + notification from the peer. + + If the End-of-LIB Notification message is received after the timer + expires, then the message SHOULD be ignored. + 5. Usage Guidelines The FECs known to an LDP speaker and the labels the speaker has bound to those FECs may change over the course of time. This makes determining when an LDP speaker has advertised "all" of its label bindings for a given FEC type an issue. Ultimately, this - determination is a judgement call the LDP speaker makes. The + determination is a judgment call the LDP speaker makes. The following guidelines may be useful. An LDP speaker is assumed to "know" a set of FECs. Depending on a variety of criteria, such as: - The label distribution control mode in use (Independent or Ordered); - The set of FEC's to which the speaker has bound local labels; @@ -201,21 +242,21 @@ LDP-IGP Sync, LDP Graceful Restart, and the response to a Wildcard Label Request [TypedWC] are situations that would benefit from End- of-LIB Notification. In these situations, after an LDP speaker completes its label binding advertisements to a peer, sending an End- of-LIB Notification to the peer makes their outcome deterministic. The following subsections further explain each of these situations one by one. 5.1. LDP-IGP Sync - The LDP-IGP Synchronization [LDPSync] specifies a mechanism by which + The LDP-IGP Synchronization [RFC5443] specifies a mechanism by which directly connected LDP speakers may delay the use of the link between them, for transit IP traffic forwarding until the labels required to support IP over MPLS traffic forwarding have been distributed and installed. Without an End-of-LIB Notification, the speaker must rely on some heuristic to determine when it has received all of its peer's label bindings. The heuristic chosen could cause LDP to signal the IGP too soon in which case the likelihood that traffic will be dropped increases, or too late in which case traffic is kept on sub-optimal @@ -264,33 +305,20 @@ advertised the Unrecognized Notification capability at session initialization time, the speaker should send the peer an End-of-LIB Notification for the FEC type when it completes advertisement of the permitted bindings. As in the previous applications, receipt of the Notification eliminates uncertainty as to when the peer has completed its advertisements of label bindings for the requested Wildcard FEC Element Type. -5.4. Missing Expected End-of-LIB Notifications - - There is no guarantee that an LDP speaker will receive End-of-LIB - Notifications from a peer even if the LDP speaker has signaled its - capability. Therefore, an implementation SHOULD NOT depend on the - receipt of such a Notification. - - To deal with the possibility of missing notifications, an LDP speaker - may time out receipt of an expected End-of-LIB Notification, and if - the timeout occurs, it may behave as if it had received the - notification. If the End-of-LIB Notification message is received - after the time-out occurs, then the message should be ignored. - 6. Security Considerations No security considerations beyond those that apply to the base LDP specification [RFC5036] and further described in [MPLSsec] apply to signaling the End-of-LIB condition as described in this document. 7. IANA Considerations This draft introduces a new LDP Status Code and a new LDP Capability both of which require IANA assignment - @@ -304,60 +332,58 @@ The 'Unrecognized Notification' Capability requires a code point from the TLV Type name space. [RFC5036] partitions the TLV TYPE name space into 3 regions: IETF Consensus region, First Come First Served region, and Private Use region. The authors recommend that a code point from the IETF Consensus range be assigned to the 'Unrecognized Notification' Capability. 8. Acknowledgments + The authors would like to recognize Kamran Raza, who helped to + formulate this draft. + The authors would like to thank Ina Minei, Alia Atlas, Yakov Rekhter, Loa Andersson and Luyuan Fang for their valuable feedback and contribution. - The authors would like to recognize Kamran Raza, who helped to - formulate this draft. - This document was prepared using 2-Word-v2.0.template.dot. 9. References 9.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC5036] Andersson, L., Doolan, P., Feldman, N., Fredette, A. and Thomas, B., "LDP Specification", RFC 5036, January 2001. - [LDPCap] Thomas, B., Aggarwal, S., Aggarwal, R., Le Roux, J.L., "LDP - Capabilities", draft-ietf-mpls-ldp-capabilities-02, Work in - Progress, May 2007. + [RFC5561] Thomas, B., Aggarwal, S., Aggarwal, R., Le Roux, J.L., "LDP + Capabilities", RFC5561, May 2007. [TypedWC] Thomas, B., Minei, I., "LDP Typed Wildcard FEC", draft- ietf-mpls-ldp-typed-wildcard-03, Work in Progress, March 2008. 9.2. Informative References - [LDPSync] Jork, M., Atlas, A., Fang, L., "LDP IGP Synchronization", - draft-ietf-mpls-ldp-igp-sync-04, Work in Progress, Dec - 2007. + [RFC5443] Jork, M., Atlas, A., Fang, L., "LDP IGP Synchronization", + RFC5443, Dec 2007. [RFC3478] Leelanivas, M., Rekhter, Y., Aggarwal, R., "Graceful Restart Mechanism for Label Distribution Protocol", February 2003. [MPLSsec] Fang, L., "Security Framework for MPLS and GMPLS Networks", - draft-ietf-mpls-mpls-and-gmpls-security-framework-04, Work - in Progress, Nov 2008. + draft-ietf-mpls-mpls-and-gmpls-security-framework-06, Work + in Progress, July 13 2009. Author's Addresses Rajiv Asati Cisco Systems, 7025-6 Kit Creek Rd, RTP, NC, 27709-4987 Email: rajiva@cisco.com Pradosh Mohapatra Cisco Systems,