draft-ietf-mpls-ldp-end-of-lib-00.txt   draft-ietf-mpls-ldp-end-of-lib-01.txt 
Network Working Group Rajiv Asati MPLS Working Group Rajiv Asati
Internet Draft Cisco Systems Internet Draft Cisco Systems
Intended status: Standards Track Intended status: Standards Track
Expires: January 2009 Pradosh Mohapatra Expires: March 2009 Pradosh Mohapatra
Cisco Systems Cisco Systems
Bob Thomas Bob Thomas
Cisco Systems
Emily Chen Emily Chen
Huawei Technologies Huawei Technologies
July 5, 2008 September 15, 2008
LDP End-of-LIB LDP End-of-LIB
draft-ietf-mpls-ldp-end-of-lib-00.txt draft-ietf-mpls-ldp-end-of-lib-01.txt
Status of this Memo Status of this Memo
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aware have been or will be disclosed, and any of which he or she aware have been or will be disclosed, and any of which he or she
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BCP 79. BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
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This Internet-Draft will expire on January 5, 2007. This Internet-Draft will expire on March 15, 2007.
Copyright Notice Copyright Notice
Copyright (C) The IETF Trust (2008). Copyright (C) The IETF Trust (2008).
Abstract Abstract
There are situations following LDP session establishment where it There are situations following Label Distribution Protocol (LDP)
would be useful for an LDP speaker to know when its peer has session establishment where it would be useful for an LDP speaker to
advertised all of its labels. These include session establishment know when its peer has advertised all of its labels. The LDP
when LDP-IGP sync is in use, as well as session re-establishment specification provides no mechanism for an LDP speaker to notify a
following loss of an LDP session when LDP graceful restart is in use. peer when it has completed its initial label advertisements to that
The LDP specification [RFC5036] provides no mechanism for an LDP peer. This document specifies means for an LDP speaker to signal
speaker to notify a peer when it has completed its initial label completion of its initial label advertisements following session
advertisements to that peer. This document specifies means for an establishment.
LDP speaker to signal completion of its initial label advertisements
following session establishment.
Conventions used in this document
In examples, "C:" and "S:" indicate lines sent by the client and
server respectively.
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].
Table of Contents Table of Contents
1. Introduction...................................................3 1. Introduction...................................................2
2. Specification Language.........................................3 2. Specification Language.........................................3
3. Unrecognized Notification Capability...........................4 3. Unrecognized Notification Capability...........................3
4. Signaling Completion of Label Advertisement....................4 4. Signaling Completion of Label Advertisement....................4
5. Usage Guidelines...............................................5 5. Usage Guidelines...............................................5
5.1. IGP-Sync..................................................6 5.1. IGP-Sync..................................................5
5.2. LDP Graceful Restart......................................6 5.2. LDP Graceful Restart......................................6
5.3. Wildcard Label Request....................................7 5.3. Wildcard Label Request....................................7
5.4. Missing Expected End-of-LIB Notifications.................7 5.4. Missing Expected End-of-LIB Notifications.................7
6. Security Considerations........................................7 6. Security Considerations........................................7
7. IANA Considerations............................................8 7. IANA Considerations............................................7
8. Acknowledgments................................................8 8. Acknowledgments................................................8
9. References.....................................................9 9. References.....................................................9
9.1. Normative References......................................9 9.1. Normative References......................................9
9.2. Informative References....................................9 9.2. Informative References....................................9
Author's Addresses...............................................10 Author's Addresses...............................................10
Intellectual Property Statement..................................10 Intellectual Property Statement..................................10
Disclaimer of Validity...........................................11 Disclaimer of Validity...........................................11
1. Introduction 1. Introduction
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RFC5036 implicitly assumes that new Status Codes will be defined over RFC5036 implicitly assumes that new Status Codes will be defined over
the course of time. However, it does not explicitly define the the course of time. However, it does not explicitly define the
behavior of an LDP speaker which does not understand the Status Code behavior of an LDP speaker which does not understand the Status Code
in a Notification message. To avoid backward compatibility issues 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 [LDPCap]
at session establishment time for informing a peer that an LDP at session establishment time for informing a peer that an LDP
speaker is capable of handling a Notification message that carries an speaker is capable of handling a Notification message that carries an
unrecognized Status Code. unrecognized Status Code.
Copyright (C) The IETF Trust (2008). This version of this MIB module
is part of RFC XXXX; see the RFC itself for full legal notices.
2. Specification Language 2. Specification Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
3. Unrecognized Notification Capability 3. Unrecognized Notification Capability
An LDP speaker MAY include a Capability Parameter [LDPCap] in the An LDP speaker MAY include a Capability Parameter [LDPCap] in the
Initialization message to inform a peer that it ignores Notification Initialization message to inform a peer that it ignores Notification
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Upon receiving a Notification with an unrecognized Status Code an LDP Upon receiving a Notification with an unrecognized Status Code an LDP
speaker MAY generate a console or system log message for trouble speaker MAY generate a console or system log message for trouble
shooting purposes. shooting purposes.
4. Signaling Completion of Label Advertisement 4. Signaling Completion of Label Advertisement
An LDP speaker MAY signal completion of its label advertisements to a An LDP speaker MAY signal completion of its label advertisements to a
peer by means of a Notification message, if its peer had advertised peer by means of a Notification message, if its peer had advertised
the Unrecognized Notification capability during session the Unrecognized Notification capability during session
establishment. The LDP speaker MAY send the Notification message (per establishment. The LDP speaker MAY send the Notification message (per
FEC Type) to a peer even if the LDP speaker had no Label bindings to FEC Type) to a peer even if the LDP speaker had zero Label bindings
advertise. to advertise to that peer.
Such a Notification message MUST carry: Such a Notification message MUST carry:
- A status TLV with TLV E- and F-bits set to zero that carries an - A status TLV with TLV E- and F-bits set to zero that carries an
"End-of-LIB" Status Code. "End-of-LIB" Status Code.
- A FEC TLV with the Typed Wildcard FEC Element [TypedWC] that - A FEC TLV with the Typed Wildcard FEC Element [TypedWC] that
identifies the FEC type for which initial label advertisements identifies the FEC type for which initial label advertisements
have been completed. In terms of Section 3.5.1 of RFC5036, have been completed. In terms of Section 3.5.1 of RFC5036,
this TLV is an "Optional Parameter" of the Notification this TLV is an "Optional Parameter" of the Notification
message. message.
An LDP speaker MUST NOT send a Notification which carries a Status 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 TLV with the End-of-LIB Status Code to a peer unless the peer had
advertised the Unrecognized Notification capability during session advertised the Unrecognized Notification capability during session
establishment. establishment.
This applies to both non-directed and directed LDP peers. This applies to any LDP peers discovered via either basic discovery
or extended discovery mechanism (per section 2.4 of [RFC5036]).
5. Usage Guidelines 5. Usage Guidelines
The FECs known to an LDP speaker and the labels the speaker has bound 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 to those FECs may change over the course of time. This makes
determining when an LDP speaker has advertised "all" of its label determining when an LDP speaker has advertised "all" of its label
bindings for a given FEC type an issue. Ultimately, this bindings for a given FEC type an issue. Ultimately, this
determination is a judgement call the LDP speaker makes. The determination is a judgement call the LDP speaker makes. The
following guidelines may be useful. following guidelines may be useful.
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Ordered); Ordered);
- The set of FEC's to which the speaker has bound local labels; - The set of FEC's to which the speaker has bound local labels;
- Configuration settings which may constrain which label bindings - Configuration settings which may constrain which label bindings
the speaker may advertise to peers; the speaker may advertise to peers;
the speaker can determine the set of bindings for a given FEC type the speaker can determine the set of bindings for a given FEC type
that it is permitted to advertise to a given peer. that it is permitted to advertise to a given peer.
IGP-Sync, LDP Graceful Restart, and the response to a Wildcard Label LDP-IGP Sync, LDP Graceful Restart, and the response to a Wildcard
Request [TypedWC] are situations that would benefit from End-of-LIB Label Request [TypedWC] are situations that would benefit from End-
Notification. In these situations, after an LDP speaker completes of-LIB Notification. In these situations, after an LDP speaker
its label binding advertisements to a peer, it should send the peer completes its label binding advertisements to a peer, sending an End-
an End-of-LIB Notification. The following subsections cover each of of-LIB Notification to the peer makes their outcome deterministic.
these situations in turn. The following subsections further explain each of these situations
one by one.
5.1. IGP-Sync 5.1. LDP-IGP Sync
LDP-IGP Sync is a mechanism directly connected LDP speakers may use The LDP-IGP Synchronization [LDPSync] specifies a mechanism by which
to delay using the link connecting them for IP traffic until the directly connected LDP speakers may delay the use of the link between
labels required to support IP over MPLS traffic on the link have been them, for transit IP traffic forwarding until the labels required to
learned. support IP over MPLS traffic forwarding have been distributed and
installed.
Without an End-of-LIB Notification the speaker must rely on some 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 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 bindings. The heuristic chosen could cause LDP to signal the IGP too
soon in which case the likelihood that traffic will be dropped soon in which case the likelihood that traffic will be dropped
increases, or too late in which case traffic is kept on sub-optimal increases, or too late in which case traffic is kept on sub-optimal
paths longer than necessary. paths longer than necessary.
Following session establishment with a directly connected peer that Following session establishment, with a directly connected peer that
has advertised the Unrecognized Notification capability, an LDP has advertised the Unrecognized Notification capability, an LDP
speaker using LDP-IGP Sync may send the peer an End-of-LIB speaker using LDP-IGP Sync may send the peer an End-of-LIB
Notification after it completes advertisement of its IP label Notification after it completes advertisement of its IP label
bindings to the peer. Similarly, the LDP speaker may use the End-of- bindings to the peer. Similarly, the LDP speaker may use the End-of-
LIB Notification received from a directly connected peer to determine LIB Notification received from a directly connected peer to determine
when the peer has completed advertisement of its label bindings for when the peer has completed advertisement of its label bindings for
IP prefixes. After receiving the notification, the speaker should IP prefixes. After receiving the notification, the LDP speaker
consider LDP to be fully operational for the link and signal the IGP should consider LDP to be fully operational for the link and signal
to start advertising the link with normal cost. the IGP to start advertising the link with normal cost.
5.2. LDP Graceful Restart 5.2. LDP Graceful Restart
LDP Graceful Restart helps reduce the loss of MPLS traffic caused by LDP Graceful Restart [RFC3478] helps to reduce the loss of MPLS
the restart of a router's LDP component. It defines procedures that traffic caused by the restart of a router's LDP component. It
allow routers capable of preserving MPLS forwarding state across the defines procedures that allow routers capable of preserving MPLS
restart to continue forwarding MPLS traffic for a pre-agreed upon forwarding state across the restart to continue forwarding MPLS
period using forwarding state installed prior to the restart. traffic using forwarding state installed prior to the restart for a
configured time period.
During that period the restarting router and its peers consider the The current behavior without End-of-LIB Notification is as follows:
preserved forwarding state to be usable but stale until it is the restarting router and its peers consider the preserved forwarding
refreshed by receipt of new label advertisements following re- state to be usable but stale until it is refreshed by receipt of new
establishment of new LDP sessions. When the period elapses any label advertisements following re-establishment of new LDP sessions
or until the time period expires. When the time period expires, any
remaining stale forwarding state is removed by the router. remaining stale forwarding state is removed by the router.
Receipt of the End-of-LIB Notification from a peer in an LDP Graceful Receiving End-of-LIB Notification from a peer in an LDP Graceful
Restart scenario enables an LDP speaker to stop using stale Restart scenario enables an LDP speaker to stop using stale
forwarding information learned from that peer and to recover the forwarding information learned from that peer and to recover the
resources it requires without having to wait until the timeout resources it requires without having to wait until the time period
occurs. expiry. The time period expiry can still be used if the End-of-LIB-
Notification message is not received.
5.3. Wildcard Label Request 5.3. Wildcard Label Request
When an LDP speaker receives a Label Request message for a Typed When an LDP speaker receives a Label Request message for a Typed
Wildcard FEC (e.g. a particular FEC element type) from a peer it Wildcard FEC (e.g. a particular FEC element type) from a peer it
determines the set of bindings, it is permitted to advertise the peer determines the set of bindings, it is permitted to advertise the peer
for the FEC type specified by the request. Assuming the peer had for the FEC type specified by the request. Assuming the peer had
advertised the Unrecognized Notification capability at session advertised the Unrecognized Notification capability at session
initialization time, the speaker should send the peer an End-of-LIB initialization time, the speaker should send the peer an End-of-LIB
Notification for the FEC type when it completes advertisement of the Notification for the FEC type when it completes advertisement of the
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specification and described in [RFC5036] apply to signaling the End- specification and described in [RFC5036] apply to signaling the End-
of-LIB condition as described in this document. of-LIB condition as described in this document.
7. IANA Considerations 7. IANA Considerations
This draft introduces a new LDP Status Code and a new LDP Capability This draft introduces a new LDP Status Code and a new LDP Capability
both of which require IANA assignment. both of which require IANA assignment.
8. Acknowledgments 8. Acknowledgments
The authors would like to thank Ina Minei, Alia Atlas, Yakov Rekhter The authors would like to thank Ina Minei, Alia Atlas, Yakov Rekhter,
and Luyuan Fang for their valuable feedback and contribution. Loa Andersson and Luyuan Fang for their valuable feedback and
contribution.
This document was prepared using 2-Word-v2.0.template.dot. This document was prepared using 2-Word-v2.0.template.dot.
9. References 9. References
9.1. Normative References 9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
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Cisco Systems, Cisco Systems,
7025-6 Kit Creek Rd, RTP, NC, 27709-4987 7025-6 Kit Creek Rd, RTP, NC, 27709-4987
Email: rajiva@cisco.com Email: rajiva@cisco.com
Pradosh Mohapatra Pradosh Mohapatra
Cisco Systems, Cisco Systems,
3750 Cisco Way, San Jose, CA, 95134 3750 Cisco Way, San Jose, CA, 95134
Email: pmohapat@cisco.com Email: pmohapat@cisco.com
Bob Thomas Bob Thomas
Cisco Systems, Email: bobthomas@alum.mit.edu
1414 Massachusetts Ave, Boxborough, MA, 01719
Email: rhthomas@cisco.com
Emily Chen Emily Chen
Huawei Technologies Huawei Technologies
No.5 Street, Shangdi Information, Haidian, Beijing, China No.5 Street, Shangdi Information, Haidian, Beijing, China
Email: chenying220@huawei.com Email: chenying220@huawei.com
Intellectual Property Statement Intellectual Property Statement
The IETF takes no position regarding the validity or scope of any The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to Intellectual Property Rights or other rights that might be claimed to
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