MPLS Working Group Kamran Raza Internet Draft Sami Boutros Intended Status: Standards Track Expires: July 17, 2015 Cisco Systems, Inc. January 18, 2015 Controlling State Advertisements Of Non-negotiated LDP Applications draft-ietf-mpls-ldp-ip-pw-capability-09.txt Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and 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." 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Raza, et. al Expires July 17, 2015 [Page 1] Internet-Draft draft-ietf-mpls-ldp-ip-pw-capability January 18, 2014 Abstract There is no capability negotiation done for Label Distribution Protocol (LDP) applications that setup Label Switched Paths (LSPs) for IP prefixes or that signal Point-to-point (P2P) Pseudowires (PWs) for Layer 2 Virtual Private Networks (L2VPNs). When an LDP session comes up, an LDP speaker may unnecessarily advertise its local state for such LDP applications even when the peer session is established for some other applications like Multipoint LDP (mLDP) or Inter-Chassis Communication Protocol (ICCP). This document defines a solution by which an LDP speaker announces to its peer its disinterest in such non-negotiated applications, thus disabling the unnecessary advertisement of corresponding application state, which would have otherwise be advertised over the established LDP session. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Conventions used in this document . . . . . . . . . . . . . . . 4 3. Non-negotiated LDP applications . . . . . . . . . . . . . . . . 4 3.1. Non-interesting State . . . . . . . . . . . . . . . . . . . 4 3.1.1. Prefix-LSPs . . . . . . . . . . . . . . . . . . . . . 5 3.1.2. P2P-PWs . . . . . . . . . . . . . . . . . . . . . . . 5 4. Controlling State Advertisement . . . . . . . . . . . . . . . . 5 4.1. State Advertisement Control Capability . . . . . . . . . . 5 4.2. Capabilities Procedures . . . . . . . . . . . . . . . . . . 8 4.2.1. State Control Capability in an Initialization message . 8 4.2.2. State Control capability in a Capability message . . . 9 5. Applicability Statement . . . . . . . . . . . . . . . . . . . . 9 6. Operational Examples . . . . . . . . . . . . . . . . . . . . . 11 6.1. Disabling Prefix-LSPs and P2P-PWs on an ICCP session . . . 11 6.2. Disabling Prefix-LSPs on a L2VPN/PW T-LDP session . . . . . 11 6.3. Disabling Prefix-LSPs dynamically on an estab. LDP session 11 6.4. Disabling Prefix-LSPs on an mLDP-only session . . . . . . . 12 6.5. Disabling IPv4 or IPv6 Prefix-LSPs on a dual-stack LSR . . 12 7. Security Considerations . . . . . . . . . . . . . . . . . . . . 13 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 13 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13 9.1. Normative References . . . . . . . . . . . . . . . . . . . 13 9.2. Informative References . . . . . . . . . . . . . . . . . . 13 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 14 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14 Raza, et. al Expires July 17, 2015 [Page 2] Internet-Draft draft-ietf-mpls-ldp-ip-pw-capability January 18, 2014 1. Introduction LDP Capabilities specification [RFC5561] introduced a mechanism to negotiate LDP capabilities for a given feature between peer Label Switching Routers (LSRs). The capability mechanism insures that no unnecessary state is exchanged between peer LSRs unless the corresponding feature capability is successfully negotiated between the peers. Newly defined LDP features and applications, such as Typed Wildcard Forwarding Equivalence Class (FEC) [RFC5918], Inter-Chassis Communication Protocol [RFC7275], mLDP [RFC6388], and L2VPN Point-to- multipoint (P2MP) PW [P2MP-PW] make use of LDP capabilities framework for their feature negotiation. However, the earlier LDP application to establish LSPs for IP unicast prefixes, and application to signal L2VPN P2P PW [RFC4447] [RFC4762] allowed LDP speakers to exchange application state without any capability negotiation, thus causing unnecessary state advertisement when a given application is not enabled on one of the LDP speakers participating in a given session. For example, when bringing up and using an LDP peer session with a remote Provider Edge (PE) LSR for purely ICCP signaling reasons, an LDP speaker may unnecessarily advertise labels for IP (unicast) prefixes to this ICCP related LDP peer. Another example of unnecessary state advertisement can be cited when LDP is to be deployed in an IP dual-stack environment. For instance, an LSR that is locally enabled to setup LSPs for both IPv4 and IPv6 prefixes may advertise (address and label) bindings for both IPv4 and IPv6 address families towards an LDP peer that is interested in IPv4 bindings only. In this case, the advertisement of IPv6 bindings to the peer is unnecessary, as well as wasteful, from the point of view of LSR memory/CPU and network resource consumption. To avoid this unnecessary state advertisement and exchange, currently an operator is typically required to configure and define filtering policies on the LSR, which introduces unnecessary operational overhead and complexity for such deployments. This document defines an LDP Capabilities [RFC5561] based solution by which an LDP speaker may announce to its peer(s) its disinterest (or non-support) for state to setup IP Prefix LSPs and/or to signal L2VPN P2P PW at the time of session establishment. This capability helps in avoiding unnecessary state advertisement for such feature applications. This document also states the mechanics to dynamically disable or enable the state advertisement for such applications during the session lifetime. The non-interesting state of an application depends on the type of application and is described later in section 3.1. Raza, et. al Expires July 17, 2015 [Page 3] Internet-Draft draft-ietf-mpls-ldp-ip-pw-capability January 18, 2014 2. Conventions used in this document 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 [RFC2119]. The term "IP" in this document refers to both IPv4 and IPv6 unicast address families. 3. Non-negotiated LDP applications For the applications that existed prior to the definition of LDP Capabilities framework [RFC5561], an LDP speaker typically advertises, without waiting for any capabilities exchange and negotiation, its corresponding application state to its peers after the session establishment. These early LDP applications include: o IPv4/IPv6 Prefix LSPs Setup o L2VPN P2P FEC128 and FEC129 PWs signaling This document onward uses following shorthand terms for these earlier LDP applications: o "Prefix-LSPs": Refers to an application that sets up LDP LSPs corresponding to IP routes/prefixes by advertising label bindings for Prefix FEC (as defined in RFC-5036). o "P2P-PWs": Refers to an application that signals FEC 128 and/or FEC 129 L2VPN P2P Pseudowires using LDP (as defined in RFC-4447). To disable unnecessary state exchange for such LDP applications over an established LDP session, a new capability is being introduced in this document. This new capability controls the advertisement of application state and enables an LDP speaker to notify its peer its disinterest in the state of one or more of these "Non-negotiated" LDP applications at the time of session establishment. Upon receipt of such capability, the receiving LDP speaker, if supporting the capability, disables the advertisement of the state related to the application towards the sender of the capability. This new capability can also be sent later in a Capability message to either disable a previously enabled application's state advertisement or to enable a previously disabled application's state advertisement. 3.1. Non-interesting State A non-interesting state of a non-negotiated LDP application: - is the application state which is of a no interest to an LSR and need not be advertised to the LSR; Raza, et. al Expires July 17, 2015 [Page 4] Internet-Draft draft-ietf-mpls-ldp-ip-pw-capability January 18, 2014 - need not be advertised in any of the LDP protocol messages; - is dependent on application type and specified accordingly. 3.1.1 Prefix-LSPs For Prefix-LSPs application type, the non-interesting state refers to any state related to IP Prefix FEC (such as FEC label bindings, LDP Status). This document, however, does not classify IP address bindings (advertised via ADDRESS message) as a non-interesting state and allows the advertisement of IP Address bindings. The reason for this allowance is that an LSR typically uses peer IP address(es) to map an IP routing nexthop/address to an LDP peer for their functionality. For example, mLDP [RFC6388] uses peer's IP address(es) to determine its upstream LSR to reach Root node as well as to select forwarding interface towards its downstream LSR. Hence in an mLDP- only network, while it is desirable to disable advertisement of label bindings for IP (unicast) Prefixes, disabling advertisement of IP address bindings will break mLDP functionality. Similarly, other LDP applications may also depend on learnt peer IP address and hence this document does not put IP address binding into a non-interesting state category to facilitate such LDP applications. 3.1.2 P2P-PWs For P2P-PWs application type, the non-interesting state refers to any state related to P2P PW FEC128/FEC129 (such as FEC label bindings, MAC [address] withdrawal, and LDP PW Status). From now onward in this document, the term "state" will mean to refer to the "non-interesting state" for an application, as defined in this section. 4. Controlling State Advertisement To control advertisement of non-interesting state related to non- negotiated LDP applications defined in section 3, a new capability TLV is defined as follows. 4.1. State Advertisement Control Capability The "State Advertisement Control Capability" is a new Capability Parameter TLV defined in accordance with section 3 of LDP Capabilities specification [RFC5561]. The format of this new TLV is as follows: Raza, et. al Expires July 17, 2015 [Page 5] Internet-Draft draft-ietf-mpls-ldp-ip-pw-capability January 18, 2014 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|State Adv. Ctrl. Cap (IANA)| Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |S| Reserved | | +-+-+-+-+-+-+-+-+ | | ~ State Advertisement Control Element(s) ~ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1: Format of an "State Advertisement Control Capability" TLV The value of the U-bit for the TLV MUST be set to 1 so that a receiver MUST silently ignore this TLV if unknown to it, and continue processing the rest of the message. Whereas, The value of F-bit MUST be set to 0. Once advertised, this capability cannot be withdrawn; thus S-bit MUST be set to 1 in an Initialization and Capability message. The capability data associated with this State Advertisement Control (SAC) Capability TLV is one or more State Advertisement Control Elements, where each element indicates enabling/disabling of advertisement of non-interesting state for a given application. The format of a SAC Element is defined as follows: 0 1 2 3 4 5 6 7 +-+-+-+-+-+-+-+-+ |D| App |Unused | +-+-+-+-+-+-+-+-+ Figure 2: Format of "State Advertisement Control Element" Where: D bit: Controls the advertisement of the state specified in "App" field: 1: Disable state advertisement 0: Enable state advertisement When sent in an Initialization message, D bit MUST be set to 1. App: Defines the legacy application type whose state advertisement is to be controlled. The value of this field is defined as follows: 1: IPv4 Prefix-LSPs (LSPs for IPv4 prefixes) 2: IPv6 Prefix-LSPs (LSPs for IPv6 prefixes) 3: FEC128 P2P-PW (L2VPN PWid FEC signaling) Raza, et. al Expires July 17, 2015 [Page 6] Internet-Draft draft-ietf-mpls-ldp-ip-pw-capability January 18, 2014 4: FEC129 P2P-PW (L2VPN Generalized PWid FEC signaling) Any other value in this field MUST be treated as an error. Unused: MBZ on transmit and ignored on receipt. The "Length" field of SAC Capability TLV (in octets) is computed as following: Length (in octets) = 1 + number of SAC elements For example, if there are two SAC elements present, then the Length field is set to 3 octets. A receiver of this capability TLV can deduce the number of elements present in the TLV by using the Length field. From now onward, this document uses the term "element" to refer to a SAC Element. As described earlier, SAC Capability TLV MAY be included by an LDP speaker in an Initialization message to signal to its peer LSR that state exchange for one or more application(s) need to be disabled on the given peer session. This TLV can also be sent later in a Capability message to selectively enable or disable these applications. If there are more than one elements present in a SAC Capability TLV, the elements MUST belong to distinct app types and the an app type MUST NOT appear more than once. If a receiver receives such a malformed TLV, it SHOULD discard this TLV and continue processing rest of the message. If an LSR receives a message with a SAC capability TLV containing an element with "App" field set to a value other than defined above, the receiver MUST ignore and discard the element and continue processing the rest of the TLV. To control more than one application state, a sender LSR can either send a single capability TLV in a message with multiple elements present, or can send separate messages with capability TLV specifying one or more elements. A receiving LSR, however, MUST treat each incoming capability TLV with an element corresponding to a given application type as an update to its existing policy for the given type. To understand capability updates from an example, let us consider 2 LSRs, S (LDP speaker) and P (LDP peer), both of which support all the non-negotiated applications listed earlier. By default, these LSR will advertise state for these applications, as configured, to their peer as soon as an LDP session is established. Now assume that P receives from S a SAC capability in an Initialization message with "IPv6 Prefix-LSPs" and "FEC129 P2P-PW" applications disabled. This updates P's outbound policy towards S to advertise state related to only IPv4 Prefix-LSPs and FEC128 P2P-PW applications. Later, P receives another capability update from S via a Capability message with "IPv6 Prefix-LSPs" enabled and "FEC128 P2P-PWs" disabled. This Raza, et. al Expires July 17, 2015 [Page 7] Internet-Draft draft-ietf-mpls-ldp-ip-pw-capability January 18, 2014 results in P's outbound policy towards S to advertise both IPv4 and IPv6 Prefix-LSPs application state, and disable both FEC128 and FEC129 P2P-PWs signaling. Finally, P receives another update from S via a Capability message that specifies to disable all four non- negotiated applications state, resulting in P outbound policy towards S to block/disable state for all these applications, and only advertise state for any other application, as applicable. 4.2. Capabilities Procedures The SAC capability conveys the desire of an LSR to disable the receipt of unwanted/unnecessary state from its LDP peer. This capability is unilateral and unidirectional in nature, and a receiving LSR is not required to send a similar capability TLV in an Initialization or Capability message towards the sender of this capability. This unilateral behavior conforms to the procedures defined in the Section 6 of LDP Capabilities [RFC5561]. After this capability is successfully negotiated (i.e. sent by an LSR and received/understood by its peer), then the receiving LSR MUST NOT advertise any state related to the disabled applications towards the capability sending LSR until and unless these application states are explicitly enabled again via a capability update. Upon receipt of a capability update to disable an enabled application [state] during the lifetime of a session, the receiving LSR MUST also withdraw from the peer any previously advertised state corresponding to the disabled application. If a receiving LDP speaker does not understand the SAC capability TLV, then it MUST respond to the sender with "Unsupported TLV" notification as described in LDP Capabilities [RFC5561]. If a receiving LDP speaker does not understand or does not support an application specified in an application control element, it SHOULD silently ignore/skip such an element and continue processing rest of the TLV. 4.2.1. State Control Capability in an Initialization message LDP Capabilities [RFC5561] framework dictates that the S-bit of capability parameter in an Initialization message MUST be set to 1 and SHOULD be ignored on receipt. An LDP speaker determines (e.g. via some local configuration or default policy) if it needs to disable Prefix-LSPs and/or P2P-PWs applications with a peer LSR. If there is a need to disable, then the SAC TLV needs to be included in the Initialization message with respective SAC elements included with their D bit set to 1. Raza, et. al Expires July 17, 2015 [Page 8] Internet-Draft draft-ietf-mpls-ldp-ip-pw-capability January 18, 2014 An LDP speaker that supports the SAC capability MUST interpret the capability TLV in a received Initialization message such that it disables the advertisement of the application state towards the capability sending LSR for Prefix-LSPs and/or P2P-PWs applications if their SAC element's D bit is set to 1. 4.2.2. State Control capability in a Capability message If the LDP peer supports "Dynamic Announcement Capability" [RFC5561], then an LDP speaker may send SAC capability in a Capability message towards the peer. Once advertised, these capabilities cannot be withdrawn and hence the S-bit of the TLV MUST be set to 1 when sent in a Capability message. An LDP speaker may decide to send this TLV towards an LDP peer if one or more of its Prefix-LSPs and/or P2P-PWs applications get disabled, or if previously disabled application gets enabled again. In this case, the LDP speaker constructs the TLV with appropriate SAC element(s) and sends the corresponding capability TLV in a Capability message. Upon receipt of this TLV in a Capability message, the receiving LDP speaker reacts in the same manner as it reacts upon the receipt of this TLV in an Initialization message. Additionally, the peer withdraws/advertises the application state from/to the capability sending LDP speaker according to the capability update. 5. Applicability Statement The procedures defined in this document may result in disabling announcement of label bindings for IP Prefixes and/or P2P PW FECs, and hence should be used with caution and discretion. This document recommends that this new SAC capability and its procedures SHOULD be enabled on an LSR only via a configuration knob. This knob could either be a global LDP knob or be implemented per LDP neighbor. Hence, it is recommended that an operator SHOULD enable this capability and its associated procedures on an LSR towards a neighbor only if it is known that such bindings advertisement and exchange with the neighbor is unnecessary and wasteful. Following table summarizes a non-exhaustive list of typical LDP session types on which this new SAC capability and its procedures are expected to be applied to disable advertisement of non-interesting state: Raza, et. al Expires July 17, 2015 [Page 9] Internet-Draft draft-ietf-mpls-ldp-ip-pw-capability January 18, 2014 +===============================+================================+ | Session Type(s) | Non-interesting State | +===============================+================================+ | P2P-PW FEC128-only | IP Prefix LSPs + P2P-PW FEC129 | |-------------------------------|--------------------------------| | P2P-PW only (FEC128/129) | IP Prefix LSPs | |-------------------------------|--------------------------------| | IPv4-only on a Dual-Stack LSR | IPv6 Prefix LSPs + P2P-PW | |-------------------------------|--------------------------------| | IPv6-only on a Dual-Stack LSR | IPv4 Prefix LSPs + P2P-PW | |-------------------------------|--------------------------------| | mLDP-only | IP Prefix LSPs + P2P-PW | |-------------------------------|--------------------------------| | ICCP-only | IP Prefix LSPs + P2P-PW | +-------------------------------+--------------------------------+ It is to be noted that if an application state needs changing after session initialization (e.g. to enable previously disabled application or to disable previously enabled application), the procedures defined in this document expect LSR peers to support LDP "Dynamic Announcement" Capability to announce the change in SAC capability via LDP Capability message. However, if any of the peering LSR does not support this capability, the alternate option is to force reset the LDP session to advertise the new SAC capability accordingly during the following session initialization. Following are some more important points that an operator need to consider regarding the applicability of this new capability and associated procedures defined in this document: - An operator SHOULD disable Prefix-LSPs state on any Targeted LDP (T-LDP) session that is established for ICCP-only and/or PW-only purposes. - An operator MUST NOT disable Prefix-LSPs state on any T-LDP session that is established for remote LFA FRR [RLFA] reasons. - In a remote LFA FRR [RLFA] enabled network, it is RECOMMENDED to not disable Prefix-LSPs state on a T-LDP session even if the current session type is PW-only and/or ICCP-only. This is recommended because any remote/T-LDP neighbor could potentially be picked as a remote LFA PQ node. - This capability SHOULD be enabled for Prefix-LSPs in the scenarios when it is desirable to disable (or enable) advertisement of "all" the prefix label bindings. For scenarios when a "subset" of bindings need to be filtered, the existing filtering procedures pertaining to label binding announcement should be used. Raza, et. al Expires July 17, 2015 [Page 10] Internet-Draft draft-ietf-mpls-ldp-ip-pw-capability January 18, 2014 - It is allowed to use label advertisement filtering policies in conjunction with the procedures defined in this document for Prefix-LSPs. In such cases, the label bindings will be announced as per the label filtering policy for the given neighbor when Prefix-LSP application is enabled. 6. Operational Examples 6.1. Disabling Prefix-LSPs and P2P-PWs on an ICCP session Consider two PE routers, LSR1 and LSR2, which understand/support SAC capability TLV, and have an established LDP session to exchange ICCP state related to dual-homed devices connected to these LSRs. Let us assume that both LSRs are provisioned not to exchange any state for Prefix-LSPs (IPv4/IPv6) and P2P-PWs (FEC128/129) application. To indicate their disinterest in these applications, the LSRs will include a SAC capability TLV (with 4 SAC elements corresponding to these 4 applications with D bit set to 1 for each one) in the Initialization message. Upon receipt of this TLV in Initialization message, the receiving LSR will disable the advertisement of IPv4/IPv6 label bindings, as well as P2P PW FEC128/129 signaling, towards its peer after session establishment. 6.2. Disabling Prefix-LSPs on a L2VPN/PW T-LDP session Now, consider LSR1 and LSR2 have an established T-LDP session for P2P-PWs application to exchange label bindings for FEC 128/129. Given that there is no need to exchange IP label bindings amongst the PE LSRs over a PW T-LDP session in most typical deployments, let us assume that LSRs are provisioned to disable IPv4/IPv6 Prefix-LSPs application state on the given PW session. To indicate their disinterest in Prefix-LSPs application over a PW T- LDP session, the LSRs will follow/apply the same procedures as described in previous section. As a result, only P2P-PWs related state will be exchanged between these LSRs over this T-LDP session. 6.3. Disabling Prefix-LSPs dynamically on an established LDP session Assume that LSRs from previous sections were initially provisioned to exchange both Prefix-LSPs and P2P-PWs state over the session between them, and also support "Dynamic Announcement" Capability [RFC5561]. Now, assume that LSR1 is dynamically provisioned to disable (IPv4/IPv6) Prefix-LSPs over T-LDP session with LSR2. In this case, LSR1 will send SAC capability TLV in a Capability message towards LSR2 with application control elements defined for IPv4 and IPv6 Raza, et. al Expires July 17, 2015 [Page 11] Internet-Draft draft-ietf-mpls-ldp-ip-pw-capability January 18, 2014 Prefix-LSPs with D bit set to 1. Upon receipt of this TLV, LSR2 will disable Prefix-LSPs application state(s) towards LSR1 and withdraw all previously advertised application state from LSR1. To withdraw label bindings from its peer, LSR2 MAY use a single Prefix FEC Typed Wildcard Label Withdraw message [RFC5918] if the peer supports Typed Wildcard FEC capability. This dynamic disability of Prefix-LSPs application does not impact L2VPN P2P-PWs application on the given session, and both LSRs should continue to exchange PW Signaling application related state. 6.4. Disabling Prefix-LSPs on an mLDP-only session Now assume that LSR1 and LSR2 have formed an LDP session to exchange mLDP state only. In typical deployments, LSR1 and LSR2 also exchange bindings for IP (unicast) prefixes upon mLDP session, which is unnecessary and wasteful for an mLDP-only LSR. Using the procedures defined earlier, an LSR can indicate its disinterest in Prefix-LSPs application state to its peer upon session establishment time or dynamically later via LDP capabilities update. Reference to section 3.1, the peer disables the advertisement of any state related to IP Prefix FECs, but still advertises IP address bindings that are required for the correct operation of mLDP. 6.5. Disabling IPv4 or IPv6 Prefix-LSPs on a dual-stack LSR In IP dual-stack scenarios, LSR2 may advertise unnecessary state (e.g. IPv6 prefix label bindings) towards peer LSR1 corresponding to IPv6 Prefix-LSPs application once a session is established mainly for exchanging state for IPv4. The similar scenario also applies when advertising IPv4 Prefix-LSPs state on a session meant for IPv6. The SAC capability and its procedures defined in this document can help to avoid such unnecessary state advertisement. Consider IP dual-stack environment where LSR2 is enabled for Prefix- LSPs application for both IPv4 and IPv6, but LSR1 is enabled for (or interested in) only IPv4 Prefix-LSPs. To avoid receiving unwanted state advertisement for IPv6 Prefix-LSPs application from LSR2, LSR1 can send SAC capability with element for IPv6 Prefix-LSPs with D bit set to 1 in the Initialization message towards LSR2 at the time of session establishment. Upon receipt of this capability, LSR2 will disable all IPv6 label binding advertisement towards LSR1. If IPv6 Prefix-LSPs application is later enabled on LSR1, LSR1 can update the capability by sending SAC capability in a Capability message towards LSR2 to enable this application dynamically. Raza, et. al Expires July 17, 2015 [Page 12] Internet-Draft draft-ietf-mpls-ldp-ip-pw-capability January 18, 2014 7. Security Considerations The proposal introduced in this document does not introduce any new security considerations beyond that already apply to the base LDP specification [RFC5036] and [RFC5920]. 8. IANA Considerations This document defines a new LDP capability parameter TLV. IANA is requested to assign the lowest available value after 0x0500 from "TLV Type Name Space" in the "Label Distribution Protocol (LDP) Parameters" registry as the new code point for the new LDP capability TLV code point. +-----+---------------------+---------------+-----------------------+ |Value| Description | Reference |Notes/Registration Date| +-----+---------------------+---------------+-----------------------+ | TBA | State Advertisement | This document | | | | Control Capability | | | +-----+---------------------+---------------+-----------------------+ 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., Ed., Minei, I., Ed., and B. Thomas, Ed., "LDP Specification", RFC 5036, October 2007, . [RFC5561] Thomas, B., Raza, K., Aggarwal, S., Aggarwal, R., and JL. Le Roux, "LDP Capabilities", RFC 5561, July 2009, . 9.2 Informative References [RFC4447] Martini, L., Ed., Rosen, E., El-Aawar, N., Smith, T., and G. Heron, "Pseudowire Setup and Maintenance Using the Label Distribution Protocol (LDP)", RFC 4447, April 2006, . [RFC4762] Lasserre, M., Ed., and V. Kompella, Ed., "Virtual Private LAN Service (VPLS) Using Label Distribution Protocol (LDP) Signaling", RFC 4762, January 2007, . [RFC5918] Asati, R., Minei, I., and B. Thomas, "Label Distribution Protocol (LDP) 'Typed Wildcard' Forward Equivalence Class (FEC)", RFC 5918, August 2010, . [RFC5920] Fang, L., Ed., "Security Framework for MPLS and GMPLS Networks", RFC 5920, July 2010, . [RFC6388] Wijnands, IJ., Ed., Minei, I., Ed., Kompella, K., and B. Thomas, "Label Distribution Protocol Extensions for Point- to-Multipoint and Multipoint-to-Multipoint Label Switched Paths", RFC 6388, November 2011, . [RFC7275] Martini, L., Salam, S., Sajassi, A., Bocci, M., Matsushima, S., and T. Nadeau, "Inter-Chassis Communication Protocol for Layer 2 Virtual Private Network (L2VPN) Provider Edge (PE) Redundancy", RFC 7275, June 2014, . [P2MP-PW] Martini, L. et. al, "Signaling Root-Initiated Point-to- Multipoint Pseudowires using LDP", draft-ietf-pwe3-p2mp- pw-04.txt, Work in Progress, March 2012. [RLFA] Bryant, S., Filsfils, C., Previdi, S., Shand, M., So, N., "Remote LFA FRR", draft-ietf-rtgwg-remote-lfa-10, Work in Progress, January 2015. 10. Acknowledgments The authors would like to thank Eric Rosen and Alexander Vainshtein for their review and valuable comments. We also acknowledge Karthik Subramanian and IJsbrand Wijnands for bringing up mLDP use case. Authors' Addresses Kamran Raza Cisco Systems, Inc., 2000 Innovation Drive, Ottawa, ON K2K-3E8, Canada. E-mail: skraza@cisco.com Sami Boutros Cisco Systems, Inc. 3750 Cisco Way, San Jose, CA 95134, USA. E-mail: sboutros@cisco.com Raza, et. al Expires July 17, 2015 [Page 14]