< draft-ietf-mpls-ldp-end-of-lib-03.txt   draft-ietf-mpls-ldp-end-of-lib-04.txt >
MPLS 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: July 2009 Pradosh Mohapatra Expires: Feb 2010 Pradosh Mohapatra
Cisco Systems Cisco Systems
Bob Thomas
Emily Chen Emily Chen
Huawei Technologies Huawei Technologies
January 14, 2009 Bob Thomas
LDP End-of-LIB August 28, 2009
draft-ietf-mpls-ldp-end-of-lib-03.txt
Signaling LDP Label Advertisement Completion
draft-ietf-mpls-ldp-end-of-lib-04.txt
Status of this Memo Status of this Memo
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Abstract Abstract
There are situations following Label Distribution Protocol (LDP) There are situations following Label Distribution Protocol (LDP)
session establishment where it would be useful for an LDP speaker to session establishment where it would be useful for an LDP speaker to
know when its peer has advertised all of its labels. The LDP know when its peer has advertised all of its labels. The LDP
specification provides no mechanism for an LDP speaker to notify a specification provides no mechanism for an LDP speaker to notify a
peer when it has completed its initial label advertisements to that peer when it has completed its initial label advertisements to that
peer. This document specifies means for an LDP speaker to signal peer. This document specifies means for an LDP speaker to signal
completion of its initial label advertisements following session completion of its initial label advertisements following session
establishment. establishment.
Table of Contents Table of Contents
1. Introduction...................................................3 1. Introduction...................................................3
2. Specification Language.........................................3 2. Specification Language.........................................3
3. Unrecognized Notification Capability...........................3 3. Unrecognized Notification Capability...........................4
4. Signaling Completion of Label Advertisement....................4 4. Signaling Completion of Label Advertisement....................4
5. Usage Guidelines...............................................5 4.1. Missing Expected End-of-LIB Notifications.................5
5.1. LDP-IGP Sync..............................................6 5. Usage Guidelines...............................................6
5.2. LDP Graceful Restart......................................6 5.1. LDP-IGP Sync..............................................7
5.3. Wildcard Label Request....................................7 5.2. LDP Graceful Restart......................................7
5.4. Missing Expected End-of-LIB Notifications.................7 5.3. Wildcard Label Request....................................8
6. Security Considerations........................................7 6. Security Considerations........................................8
7. IANA Considerations............................................8 7. IANA Considerations............................................8
8. Acknowledgments................................................8 8. Acknowledgments................................................9
9. References.....................................................9 9. References....................................................10
9.1. Normative References......................................9 9.1. Normative References.....................................10
9.2. Informative References....................................9 9.2. Informative References...................................10
Author's Addresses...............................................10 Author's Addresses...............................................11
1. Introduction 1. Introduction
There are situations following LDP session establishment where it There are situations following LDP session establishment where it
would be useful for an LDP speaker to know when its peer has 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 advertised all of the labels from its Label Information Base (LIB).
using LDP-IGP synchronization procedures [LDPSync], it would be For example, when an LDP speaker is using LDP-IGP synchronization
useful for the speaker to know when its peer has completed procedures [RFC5443], it would be useful for the speaker to know when
advertisement of its IP label bindings. Similarly, after an LDP its peer has completed advertisement of its IP label bindings.
session is re-established when LDP Graceful Restart [RFC3478] is in Similarly, after an LDP session is re-established when LDP Graceful
effect, it would be helpful for each peer to signal the other after Restart [RFC3478] is in effect, it would be helpful for each peer to
it has advertised all its label bindings. signal the other after it has advertised all its label bindings.
The LDP specification [RFC5036] provides no mechanism for an LDP The LDP specification [RFC5036] provides no mechanism for an LDP
speaker to notify a peer when it has completed its initial label speaker to notify a peer when it has completed its initial label
advertisements to that peer. advertisements to that peer.
This document specifies use of a Notification message with the "End- This document specifies use of a Notification message with the "End-
of-LIB" Status Code for an LDP speaker to signal completion of its of-LIB" Status Code for an LDP speaker to signal completion of its
label advertisements following session establishment. label advertisements following session establishment.
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 [RFC5561]
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.
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 [RFC5561] in the
Initialization message to inform a peer that it ignores Notification Initialization message to inform a peer that it ignores Notification
Messages that carry a Status TLV with a non-fatal Status Code unknown Messages that carry a Status Type-Length-Value (TLV) with a non-fatal
to it. Status Code unknown to it.
The Capability Parameter for the Unrecognized Notification capability The Capability Parameter for the Unrecognized Notification capability
is a TLV with the following format: is a TLV with the following format:
0 1 2 3 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 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 | |U|F| Unrecog Notif (IANA) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|S| Reserved | |S| Reserved |
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
Figure 1 Unrecognized Notification Capability format Figure 1 Unrecognized Notification Capability format
Where: Where:
U and F bits: Should be set 1 and 0 respectively as per section 4 U and F bits: MUST be 1 and 0 respectively as per section 3 of LDP
of LDP Capabilities [LDPCap]. Capabilities [RFC5561].
Unrecog Notif: TLV code point to be assigned by IANA. 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 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 that conforms to this specification SHOULD signal
peer by means of a Notification message, if its peer had advertised completion of its label advertisements to a peer by means of a
the Unrecognized Notification capability during session Notification message, if its peer has advertised the Unrecognized
establishment. The LDP speaker MAY send the Notification message (per Notification capability during session establishment. The LDP speaker
FEC Type) to a peer even if the LDP speaker had zero Label bindings SHOULD send the Notification message (per Forwarding Equivalence
to advertise to that peer. 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: Such a Notification message MUST carry:
- A status TLV (with TLV E- and F-bits set to zero) that carries - 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). an "End-of-LIB" Status Code (value to be assigned by IANA).
- 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 any LDP peers discovered via either basic discovery This applies to any LDP peers discovered via either basic discovery
or extended discovery mechanism (per section 2.4 of [RFC5036]). 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 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 judgment call the LDP speaker makes. The
following guidelines may be useful. following guidelines may be useful.
An LDP speaker is assumed to "know" a set of FECs. Depending on a An LDP speaker is assumed to "know" a set of FECs. Depending on a
variety of criteria, such as: variety of criteria, such as:
- The label distribution control mode in use (Independent or - The label distribution control mode in use (Independent or
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;
skipping to change at page 6, line 7 skipping to change at page 7, line 7
LDP-IGP Sync, LDP Graceful Restart, and the response to a Wildcard LDP-IGP Sync, LDP Graceful Restart, and the response to a Wildcard
Label Request [TypedWC] are situations that would benefit from End- Label Request [TypedWC] are situations that would benefit from End-
of-LIB Notification. In these situations, after an LDP speaker of-LIB Notification. In these situations, after an LDP speaker
completes its label binding advertisements to a peer, sending an End- completes its label binding advertisements to a peer, sending an End-
of-LIB Notification to the peer makes their outcome deterministic. of-LIB Notification to the peer makes their outcome deterministic.
The following subsections further explain each of these situations The following subsections further explain each of these situations
one by one. one by one.
5.1. LDP-IGP Sync 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 directly connected LDP speakers may delay the use of the link between
them, for transit IP traffic forwarding until the labels required to them, for transit IP traffic forwarding until the labels required to
support IP over MPLS traffic forwarding have been distributed and support IP over MPLS traffic forwarding have been distributed and
installed. 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
skipping to change at page 7, line 28 skipping to change at page 8, line 24
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
permitted bindings. permitted bindings.
As in the previous applications, receipt of the Notification As in the previous applications, receipt of the Notification
eliminates uncertainty as to when the peer has completed its eliminates uncertainty as to when the peer has completed its
advertisements of label bindings for the requested Wildcard FEC advertisements of label bindings for the requested Wildcard FEC
Element Type. 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 6. Security Considerations
No security considerations beyond those that apply to the base LDP No security considerations beyond those that apply to the base LDP
specification [RFC5036] and further described in [MPLSsec] apply to specification [RFC5036] and further described in [MPLSsec] apply to
signaling the End-of-LIB condition as described in this document. signaling the End-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 -
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The 'Unrecognized Notification' Capability requires a code point The 'Unrecognized Notification' Capability requires a code point
from the TLV Type name space. [RFC5036] partitions the TLV TYPE from the TLV Type name space. [RFC5036] partitions the TLV TYPE
name space into 3 regions: IETF Consensus region, First Come name space into 3 regions: IETF Consensus region, First Come
First Served region, and Private Use region. The authors First Served region, and Private Use region. The authors
recommend that a code point from the IETF Consensus range be recommend that a code point from the IETF Consensus range be
assigned to the 'Unrecognized Notification' Capability. assigned to the 'Unrecognized Notification' Capability.
8. Acknowledgments 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, The authors would like to thank Ina Minei, Alia Atlas, Yakov Rekhter,
Loa Andersson and Luyuan Fang for their valuable feedback and Loa Andersson and Luyuan Fang for their valuable feedback and
contribution. 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. 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.
[RFC5036] Andersson, L., Doolan, P., Feldman, N., Fredette, A. and [RFC5036] Andersson, L., Doolan, P., Feldman, N., Fredette, A. and
Thomas, B., "LDP Specification", RFC 5036, January 2001. Thomas, B., "LDP Specification", RFC 5036, January 2001.
[LDPCap] Thomas, B., Aggarwal, S., Aggarwal, R., Le Roux, J.L., "LDP [RFC5561] Thomas, B., Aggarwal, S., Aggarwal, R., Le Roux, J.L., "LDP
Capabilities", draft-ietf-mpls-ldp-capabilities-02, Work in Capabilities", RFC5561, May 2007.
Progress, May 2007.
[TypedWC] Thomas, B., Minei, I., "LDP Typed Wildcard FEC", draft- [TypedWC] Thomas, B., Minei, I., "LDP Typed Wildcard FEC", draft-
ietf-mpls-ldp-typed-wildcard-03, Work in Progress, March ietf-mpls-ldp-typed-wildcard-03, Work in Progress, March
2008. 2008.
9.2. Informative References 9.2. Informative References
[LDPSync] Jork, M., Atlas, A., Fang, L., "LDP IGP Synchronization", [RFC5443] Jork, M., Atlas, A., Fang, L., "LDP IGP Synchronization",
draft-ietf-mpls-ldp-igp-sync-04, Work in Progress, Dec RFC5443, Dec 2007.
2007.
[RFC3478] Leelanivas, M., Rekhter, Y., Aggarwal, R., "Graceful [RFC3478] Leelanivas, M., Rekhter, Y., Aggarwal, R., "Graceful
Restart Mechanism for Label Distribution Protocol", Restart Mechanism for Label Distribution Protocol",
February 2003. February 2003.
[MPLSsec] Fang, L., "Security Framework for MPLS and GMPLS Networks", [MPLSsec] Fang, L., "Security Framework for MPLS and GMPLS Networks",
draft-ietf-mpls-mpls-and-gmpls-security-framework-04, Work draft-ietf-mpls-mpls-and-gmpls-security-framework-06, Work
in Progress, Nov 2008. in Progress, July 13 2009.
Author's Addresses Author's Addresses
Rajiv Asati Rajiv Asati
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,
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