LDP

Multi-Topology Routing (MTR) is a technology that enables service differentiation within an IP network. The Flexible Algorithm (FA) is another mechanism for creating a sub-topology within a topology using defined topology constraints and computation algorithms. In order to deploy Multipoint LDP (mLDP) in a network that supports MTR, FA, or other methods of signaling non-default IGP Algorithms (IPAs), mLDP is required to become topology and algorithm aware. This document specifies extensions to mLDP to support the use of MTR/IPAs such that, when building multipoint Label Switched Paths (LSPs), the LSPs can follow a particular topology and algorithm. This document updates RFC 7307 by allocating eight bits from a previously reserved field to be used as the "IPA" field.

This document describes a YANG data model for the Multiprotocol Label Switching (MPLS) Label Distribution Protocol (LDP). The model also serves as the base model to define the Multipoint LDP (mLDP) model.

The YANG modules in this document conform to the Network Management Datastore Architecture (NMDA).

A Segment Routing (SR) node steers a packet through a controlled set of instructions, called segments, by prepending the packet with an SR header. A segment can represent any instruction, topological or service based. SR allows enforcing a flow through any topological path while maintaining per-flow state only at the ingress node to the SR domain.

The Segment Routing architecture can be directly applied to the MPLS data plane with no change in the forwarding plane. This document describes how Segment Routing MPLS operates in a network where LDP is deployed and in the case where SR-capable and non-SR-capable nodes coexist.

This document specifies a mechanism to signal Point-to-Multipoint (P2MP) Pseudowire (PW) trees using LDP. Such a mechanism is suitable for any Layer 2 VPN service requiring P2MP connectivity over an IP or MPLS-enabled PSN. A P2MP PW established via the proposed mechanism is root initiated. This document updates RFC 7385 by reassigning the reserved value 0xFF to be the wildcard transport tunnel type.

This document specifies extensions to the Label Distribution Protocol (LDP) to support the creation of Label Switched Paths (LSPs) for Maximally Redundant Trees (MRTs). A prime use of MRTs is for unicast and multicast IP/LDP Fast Reroute, which we will refer to as "MRT-FRR".

The sole protocol extension to LDP is simply the ability to advertise an MRT Capability. This document describes that extension and the associated behavior expected for Label Switching Routers (LSRs) and Label Edge Routers (LERs) advertising the MRT Capability.

MRT-FRR uses LDP multi-topology extensions, so three multi-topology IDs have been allocated from the MPLS MT-ID space.

Recent Targeted Label Distribution Protocol (tLDP) applications, such as remote Loop-Free Alternates (LFAs) and BGP auto-discovered pseudowires, may automatically establish a tLDP session with any Label Switching Router (LSR) in a network. The initiating LSR has information about the targeted applications to administratively control initiation of the session. However, the responding LSR has no such information to control acceptance of this session. This document defines a mechanism to advertise and negotiate the Targeted Application Capability (TAC) during LDP session initialization. As the responding LSR becomes aware of targeted applications, it may establish a limited number of tLDP sessions for certain applications. In addition, each targeted application is mapped to LDP Forwarding Equivalence Class (FEC) elements to advertise only necessary LDP FEC label bindings over the session. This document updates RFC 7473 for enabling advertisement of LDP FEC label bindings over the session.

Layer 2 services (such as Frame Relay, Asynchronous Transfer Mode, and Ethernet) can be emulated over an MPLS backbone by encapsulating the Layer 2 Protocol Data Units (PDUs) and then transmitting them over pseudowires (PWs). It is also possible to use pseudowires to provide low-rate Time-Division Multiplexed and Synchronous Optical NETworking circuit emulation over an MPLS-enabled network. This document specifies a protocol for establishing and maintaining the pseudowires, using extensions to the Label Distribution Protocol (LDP). Procedures for encapsulating Layer 2 PDUs are specified in other documents.

This document is a rewrite of RFC 4447 for publication as an Internet Standard.

Many transport services require that user traffic, in the form of Pseudowires (PWs), be delivered via either a single co-routed bidirectional tunnel or two unidirectional tunnels that share the same routes. This document defines an optional extension to the Label Distribution Protocol (LDP) that enables the binding between PWs and the underlying Traffic Engineering (TE) tunnels. The extension applies to both single-segment and multi-segment PWs.

This document supports the solution put forth in "An Architecture for IP/LDP Fast Reroute Using Maximally Redundant Trees (MRT-FRR)" (RFC 7812) by defining the associated MRT Lowpoint algorithm that is used in the Default MRT Profile to compute both the necessary Maximally Redundant Trees with their associated next hops and the alternates to select for MRT-FRR.

This document defines the architecture for IP and LDP Fast Reroute using Maximally Redundant Trees (MRT-FRR). MRT-FRR is a technology that gives link-protection and node-protection with 100% coverage in any network topology that is still connected after the failure.

This document describes procedures to support node protection for Point-to-Multipoint and Multipoint-to-Multipoint Label Switched Paths (P2MP and MP2MP LSPs) that have been built by the Multipoint Label Distribution Protocol (mLDP). In order to protect a node N, the Point of Local Repair (PLR) Label Switching Router (LSR) of N must learn the Merge Point (MPT) LSR(s) of node N such that traffic can be redirected to them in case node N fails. Redirecting the traffic around the failed node N depends on existing Point-to-Point (P2P) Label Switched Paths (LSPs). The pre-established LSPs originate from the PLR LSR and terminate on the MPT LSRs while bypassing LSR N.

The Label Distribution Protocol (LDP) specification defines procedures to exchange label bindings over either IPv4 or IPv6 networks, or both. This document corrects and clarifies the LDP behavior when an IPv6 network is used (with or without IPv4). This document updates RFCs 5036 and 6720.

There is no capability negotiation done for Label Distribution Protocol (LDP) applications that set up 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 the 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 been advertised over the established LDP session.

When IP multicast trees created by Protocol Independent Multicast - Sparse Mode (PIM-SM) in Any-Source Multicast (ASM) mode need to pass through an MPLS domain, it may be desirable to map such trees to Point-to-Multipoint Label Switched Paths (P2MP LSPs). This document describes how to accomplish this in the case where such P2MP LSPs are established using Label Distribution Protocol (LDP) Extensions for P2MP and Multipoint-to-Multipoint LSPs: Multipoint LDP (mLDP).

Many service providers offer "BGP/MPLS IP VPN" service to their customers. Existing IETF standards specify the procedures and protocols that a service provider uses in order to offer this service to customers who have IP unicast and IP multicast traffic in their VPNs. It is also desirable to be able to support customers who have MPLS multicast traffic in their VPNs. This document specifies the procedures and protocol extensions that are needed to support customers who use the Multipoint LDP (mLDP) as the control protocol for their MPLS multicast traffic. Existing standards do provide some support for customers who use mLDP, but only under a restrictive set of circumstances. This document generalizes the existing support to include all cases where the customer uses mLDP, without any restrictions. This document updates RFC 6514.

There are scenarios in which an IP multicast tree traverses an MPLS domain. In these scenarios, it can be desirable to convert the IP multicast tree "seamlessly" into an MPLS Multipoint Label Switched Path (MP-LSP) when it enters the MPLS domain, and then to convert it back to an IP multicast tree when it exits the MPLS domain. Previous documents specify procedures that allow certain kinds of IP multicast trees (either Source-Specific Multicast trees or Bidirectional Multicast trees) to be attached to an MPLS Multipoint Label Switched Path (MP-LSP). However, the previous documents do not specify procedures for attaching IP Any-Source Multicast trees to MP-LSPs, nor do they specify procedures for aggregating multiple IP multicast trees onto a single MP-LSP. This document specifies the procedures to support these functions. It does so by defining "wildcard" encodings that make it possible to specify, when setting up an MP- LSP, that a set of IP multicast trees, or a shared IP multicast tree, should be attached to that MP-LSP. Support for non-bidirectional IP Any-Source Multicast trees is subject to certain applicability restrictions that are discussed in this document. This document updates RFCs 6826 and 7246.

This document reviews the Multiprotocol Label Switching (MPLS) protocol suite in the context of IPv6 and identifies gaps that must be addressed in order to allow MPLS-related protocols and applications to be used with IPv6-only networks. This document is intended to focus on gaps in the standards defining the MPLS suite, and is not intended to highlight particular vendor implementations (or lack thereof) in the context of IPv6-only MPLS functionality.

In the data plane, MPLS fully supports IPv6, and MPLS labeled packets can be carried over IPv6 packets in a variety of encapsulations. However, support for IPv6 among MPLS control-plane protocols, MPLS applications, MPLS Operations, Administration, and Maintenance (OAM), and MIB modules is mixed, with some protocols having major gaps. For most major gaps, work is in progress to upgrade the relevant protocols.

The label advertising behavior of an LDP speaker for a given Forwarding Equivalence Class (FEC) is governed by the FEC type and not necessarily by the LDP session's negotiated label advertisement mode. This document updates RFC 5036 to make that fact clear. It also updates RFCs 3212, 4447, 5918, 6388, and 7140 by specifying the label advertisement mode for all currently defined LDP FEC types.

RFC 4762 describes a mechanism to remove or unlearn Media Access Control (MAC) addresses that have been dynamically learned in a Virtual Private LAN Service (VPLS) instance for faster convergence on topology changes. The procedure also removes MAC addresses in the VPLS that do not require relearning due to such topology changes. This document defines an enhancement to the MAC address withdraw procedure with an empty MAC list (RFC 4762); this enhancement enables a Provider Edge (PE) device to remove only the MAC addresses that need to be relearned. Additional extensions to RFC 4762 MAC withdraw procedures are specified to provide an optimized MAC flushing for the Provider Backbone Bridging (PBB) VPLS specified in RFC 7041.

This document introduces a new optional Cryptographic Authentication TLV that LDP can use to secure its Hello messages. It secures the Hello messages against spoofing attacks and some well-known attacks against the IP header. This document describes a mechanism to secure the LDP Hello messages using Hashed Message Authentication Code (HMAC) with the National Institute of Standards and Technology (NIST) Secure Hash Standard family of algorithms.

Multi-Topology (MT) routing is supported in IP networks with the use of MT-aware IGPs. In order to provide MT routing within Multiprotocol Label Switching (MPLS) Label Distribution Protocol (LDP) networks, new extensions are required.

This document describes the LDP protocol extensions required to support MT routing in an MPLS environment.

An IP Multicast Distribution Tree (MDT) may traverse both label switching (i.e., Multiprotocol Label Switching, or MPLS) and non-label switching regions of a network. Typically, the MDT begins and ends in non-MPLS regions, but travels through an MPLS region. In such cases, it can be useful to begin building the MDT as a pure IP MDT, then convert it to an MPLS Multipoint Label Switched Path (MP-LSP) when it enters an MPLS-enabled region, and then convert it back to a pure IP MDT when it enters a non-MPLS-enabled region. Other documents specify the procedures for building such a hybrid MDT, using Protocol Independent Multicast (PIM) in the non-MPLS region of the network, and using Multipoint Label Distribution Protocol (mLDP) in the MPLS region. This document extends those procedures to handle the case where the link connecting the two regions is a Virtual Routing and Forwarding (VRF) table link, as defined in the "BGP IP/MPLS VPN" specification. However, this document is primarily aimed at particular use cases where VRFs are used to support multicast applications other than multicast VPN.

This document introduces a hub and spoke multipoint (HSMP) Label Switched Path (LSP), which allows traffic from root to leaf through point-to-multipoint (P2MP) LSPs and also leaf to root along the reverse path. That means traffic entering the HSMP LSP from the application/customer at the root node travels downstream to each leaf node, exactly as if it were traveling downstream along a P2MP LSP to each leaf node. Upstream traffic entering the HSMP LSP at any leaf node travels upstream along the tree to the root, as if it were unicast to the root. Direct communication among the leaf nodes is not allowed.

Label Distribution Protocol (LDP) can be used to set up Point-to-Multipoint (P2MP) and Multipoint-to-Multipoint (MP2MP) Label Switched Paths. However, the specification for the Multipoint Extensions to LDP presupposes that the two endpoints of an LDP session are directly connected. The LDP base specification allows for the case where the two endpoints of an LDP session are not directly connected; such a session is known as a "Targeted LDP" session. This document provides the specification for using the LDP Multipoint Extensions over a Targeted LDP session.

Seamless MPLS design enables a single IP/MPLS network to scale over core, metro, and access parts of a large packet network infrastructure using standardized IP/MPLS protocols. One of the key goals of Seamless MPLS is to meet requirements specific to access networks including high number of devices, device position in network topology, and compute and memory constraints that limit the amount of state access devices can hold. This can be achieved with LDP Downstream-on-Demand (DoD) label advertisement. This document describes LDP DoD use cases and lists required LDP DoD procedures in the context of Seamless MPLS design.

In addition, a new optional TLV type in the LDP Label Request message is defined for fast-up convergence.

This document analyzes TCP-based routing protocols, the Border Gateway Protocol (BGP), the Label Distribution Protocol (LDP), the Path Computation Element Communication Protocol (PCEP), and the Multicast Source Distribution Protocol (MSDP), according to guidelines set forth in Section 4.2 of "Keying and Authentication for Routing Protocols Design Guidelines", RFC 6518.

Consider an IP multicast tree, constructed by Protocol Independent Multicast (PIM), that needs to pass through an MPLS domain in which Multipoint LDP (mLDP) point-to-multipoint and/or multipoint-to-multipoint Labels Switched Paths (LSPs) can be created. The part of the IP multicast tree that traverses the MPLS domain can be instantiated as a multipoint LSP. When a PIM Join message is received at the border of the MPLS domain, information from that message is encoded into mLDP messages. When the mLDP messages reach the border of the next IP domain, the encoded information is used to generate PIM messages that can be sent through the IP domain. The result is an IP multicast tree consisting of a set of IP multicast sub-trees that are spliced together with a multipoint LSP. This document describes procedures regarding how IP multicast trees are spliced together with multipoint LSPs. [STANDARDS-TRACK]

The Generalized TTL Security Mechanism (GTSM) describes a generalized use of a packet's Time to Live (TTL) (IPv4) or Hop Limit (IPv6) to verify that the packet was sourced by a node on a connected link, thereby protecting the router\'s IP control plane from CPU utilization-based attacks. This technique improves security and is used by many protocols. This document defines the GTSM use for the Label Distribution Protocol (LDP).

This specification uses a bit reserved in RFC 5036 and therefore updates RFC 5036. [STANDARDS-TRACK]

The "Typed Wildcard Forwarding Equivalence Class (FEC) Element" defines an extension to the Label Distribution Protocol (LDP) that can be used when requesting, withdrawing, or releasing all label bindings for a given FEC Element type is desired. However, a Typed Wildcard FEC Element must be individually defined for each FEC Element type. This specification defines the Typed Wildcard FEC Elements for the Pseudowire Identifier (PWid) (0x80) and Generalized PWid (0x81) FEC Element types. [STANDARDS-TRACK]

The control protocol used for constructing Point-to-Multipoint and Multipoint-to-Multipoint Label Switched Paths ("MP LSPs") contains a field that identifies the address of a "root node". Intermediate nodes are expected to be able to look up that address in their routing tables. However, this is not possible if the route to the root node is a BGP route and the intermediate nodes are part of a BGP-free core. This document specifies procedures that enable an MP LSP to be constructed through a BGP-free core. In these procedures, the root node address is temporarily replaced by an address that is known to the intermediate nodes and is on the path to the true root node. [STANDARDS-TRACK]

More that one set of mechanisms to support multicast in a layer 3 BGP/MPLS VPN has been defined. These are presented in the documents that define them as optional building blocks.

To enable interoperability between implementations, this document defines a subset of features that is considered mandatory for a multicast BGP/MPLS VPN implementation. This will help implementers and deployers understand which L3VPN multicast requirements are best satisfied by each option. This document is not an Internet Standards Track specification; it is published for informational purposes.

This document describes procedures for distributing upstream-assigned labels for the Label Distribution Protocol (LDP). It also describes how these procedures can be used for avoiding branch Label Switching Router (LSR) traffic replication on a LAN for LDP point-to-multipoint (P2MP) Label Switched Paths (LSPs). [STANDARDS-TRACK]

This document describes extensions to the Label Distribution Protocol (LDP) for the setup of point-to-multipoint (P2MP) and multipoint-to-multipoint (MP2MP) Label Switched Paths (LSPs) in MPLS networks. These extensions are also referred to as multipoint LDP. Multipoint LDP constructs the P2MP or MP2MP LSPs without interacting with or relying upon any other multicast tree construction protocol. Protocol elements and procedures for this solution are described for building such LSPs in a receiver-initiated manner. There can be various applications for multipoint LSPs, for example IP multicast or support for multicast in BGP/MPLS Layer 3 Virtual Private Networks (L3VPNs). Specification of how such applications can use an LDP signaled multipoint LSP is outside the scope of this document. [STANDARDS-TRACK]

This document lists a set of functional requirements that served as input to the design of Label Distribution Protocol (LDP) extensions for setting up point-to-multipoint (P2MP) Label Switched Paths (LSP), in order to deliver point-to-multipoint applications over a Multiprotocol Label Switching (MPLS) infrastructure.

This work was overtaken by the protocol solution developed by the MPLS working group, but that solution did not closely follow the requirements documented here. This document is published as a historic record of the ideas and requirements that shaped the protocol work. This document defines a Historic Document for the Internet community.

RFC 5443 describes a mechanism to achieve LDP IGP synchronization to prevent black-holing traffic (e.g., VPN) when an Interior Gateway Protocol (IGP) is operational on a link but Label Distribution Protocol (LDP) is not. If this mechanism is applied to broadcast links that have more than one LDP peer, the metric increase procedure can only be applied to the link as a whole but not to an individual peer. When a new LDP peer comes up on a broadcast network, this can result in loss of traffic through other established peers on that network. This document describes a mechanism to address that use-case without dropping traffic. The mechanism does not introduce any protocol message changes. This document is not an Internet Standards Track specification; it is published for informational purposes.

The Label Distribution Protocol (LDP) specification for the Wildcard Forward Equivalence Class (FEC) element has several limitations. This document addresses those limitations by defining a Typed Wildcard FEC Element and associated procedures. In addition, it defines a new LDP capability to address backward compatibility. [STANDARDS-TRACK]

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. [STANDARDS-TRACK]

A number of enhancements to the Label Distribution Protocol (LDP) have been proposed. Some have been implemented, and some are advancing toward standardization. It is likely that additional enhancements will be proposed in the future. This document defines a mechanism for advertising LDP enhancements at session initialization time, as well as a mechanism to enable and disable enhancements after LDP session establishment. [STANDARDS-TRACK]

In certain networks, there is dependency on the edge-to-edge Label Switched Paths (LSPs) setup by the Label Distribution Protocol (LDP), e.g., networks that are used for Multiprotocol Label Switching (MPLS) Virtual Private Network (VPN) applications. For such applications, it is not possible to rely on Internet Protocol (IP) forwarding if the MPLS LSP is not operating appropriately. Blackholing of labeled traffic can occur in situations where the Interior Gateway Protocol (IGP) is operational on a link on which LDP is not. While the link could still be used for IP forwarding, it is not useful for MPLS forwarding, for example, MPLS VPN applications or Border Gateway Protocol (BGP) route-free cores. This document describes a mechanism to avoid traffic loss due to this condition without introducing any protocol changes. This memo provides information for the Internet community.

To facilitate the establishment of Label Switched Paths (LSPs) that would span multiple IGP areas in a given Autonomous System (AS), this document describes a new optional Longest-Match Label Mapping Procedure for the Label Distribution Protocol (LDP).

This procedure allows the use of a label if the Forwarding Equivalence Class (FEC) Element matches an entry in the Routing Information Base (RIB). Matching is defined by an IP longest-match search and does not mandate an exact match. [STANDARDS-TRACK]

The architecture for Multiprotocol Label Switching (MPLS) is described in RFC 3031. A fundamental concept in MPLS is that two Label Switching Routers (LSRs) must agree on the meaning of the labels used to forward traffic between and through them. This common understanding is achieved by using a set of procedures, called a label distribution protocol, by which one LSR informs another of label bindings it has made. This document defines a set of such procedures called LDP (for Label Distribution Protocol) by which LSRs distribute labels to support MPLS forwarding along normally routed paths. [STANDARDS-TRACK]

The purpose of this memo is to document how some of the requirements specified in RFC 1264 for advancing protocols developed by working groups within the IETF Routing Area to Draft Standard have been satisfied by LDP (Label Distribution Protocol). Specifically, this report documents operational experience with LDP, requirement 5 of section 5.0 in RFC 1264. This memo provides information for the Internet community.

Multiprotocol Label Switching (MPLS), described in RFC 3031, is a method for forwarding packets that uses short, fixed-length values carried by packets, called labels, to determine packet next hops. A fundamental concept in MPLS is that two Label Switching Routers (LSRs) must agree on the meaning of the labels used to forward traffic between and through them. This common understanding is achieved by using a set of procedures, called a Label Distribution Protocol (as described in RFC 3036) , by which one LSR informs another of label bindings it has made. One such protocol, called LDP, is used by LSRs to distribute labels to support MPLS forwarding along normally routed paths. This document reports on a survey of LDP implementations conducted in August 2002 as part of the process of advancing LDP from Proposed to Draft Standard. This memo provides information for the Internet community.

This document describes a Virtual Private LAN Service (VPLS) solution using pseudowires, a service previously implemented over other tunneling technologies and known as Transparent LAN Services (TLS). A VPLS creates an emulated LAN segment for a given set of users; i.e., it creates a Layer 2 broadcast domain that is fully capable of learning and forwarding on Ethernet MAC addresses and that is closed to a given set of users. Multiple VPLS services can be supported from a single Provider Edge (PE) node.

This document describes the control plane functions of signaling pseudowire labels using Label Distribution Protocol (LDP), extending RFC 4447. It is agnostic to discovery protocols. The data plane functions of forwarding are also described, focusing in particular on the learning of MAC addresses. The encapsulation of VPLS packets is described by RFC 4448. [STANDARDS-TRACK]

Proper functioning of RFC 1191 path Maximum Transmission Unit (MTU) discovery requires that IP routers have knowledge of the MTU for each link to which they are connected. As currently specified, the Label Distribution Protocol (LDP) does not have the ability to signal the MTU for a Label Switched Path (LSP) to the ingress Label Switching Router (LSR). In the absence of this functionality, the MTU for each LSP must be statically configured by network operators or by equivalent off-line mechanisms. This document specifies experimental extensions to LDP in support of LSP MTU discovery. This memo defines an Experimental Protocol for the Internet community.

This memo defines a portion of the Management Information Base (MIB) for use with network management protocols in the Internet community. In particular, it describes managed objects for the Multiprotocol Label Switching, Label Distribution Protocol (LDP). [STANDARDS-TRACK]

The Optical Interworking Forum (OIF) has defined extensions to the Label Distribution Protocol (LDP) and the Resource ReSerVation Protocol (RSVP) for optical User Network Interface (UNI) signaling. These extensions consist of a set of new data objects and error codes. This document describes these extensions. This memo provides information for the Internet community.

This document documents the consensus reached by the Multiprotocol Label Switching (MPLS) Working Group within the IETF to focus its efforts on "Resource Reservation Protocol (RSVP)-TE: Extensions to RSVP for Label- Switched Paths (LSP) Tunnels" (RFC 3209) as the MPLS signalling protocol for traffic engineering applications and to undertake no new efforts relating to "Constraint-Based LSP Setup using Label Distribution Protocol (LDP)" (RFC 3212). The recommendations of section 6 have been accepted by the IESG. This memo provides information for the Internet community.

This document describes a mechanism that helps to minimize the negative effects on MPLS traffic caused by Label Switching Router's (LSR's) control plane restart, specifically by the restart of its Label Distribution Protocol (LDP) component, on LSRs that are capable of preserving the MPLS forwarding component across the restart. The mechanism described in this document is applicable to all LSRs, both those with the ability to preserve forwarding state during LDP restart and those without (although the latter needs to implement only a subset of the mechanism described in this document). Supporting (a subset of) the mechanism described here by the LSRs that can not preserve their MPLS forwarding state across the restart would not reduce the negative impact on MPLS traffic caused by their control plane restart, but it would minimize the impact if their neighbor(s) are capable of preserving the forwarding state across the restart of their control plane and implement the mechanism described here. The mechanism makes minimalistic assumptions on what has to be preserved across restart - the mechanism assumes that only the actual MPLS forwarding state has to be preserved; the mechanism does not require any of the LDP-related states to be preserved across the restart. The procedures described in this document apply to downstream unsolicited label distribution. Extending these procedures to downstream on demand label distribution is for further study. [STANDARDS-TRACK]

Multiprotocol Label Switching (MPLS) systems will be used in core networks where system downtime must be kept to an absolute minimum. Many MPLS Label Switching Routers (LSRs) may, therefore, exploit Fault Tolerant (FT) hardware or software to provide high availability of the core networks. The details of how FT is achieved for the various components of an FT LSR, including Label Distribution Protocol (LDP), the switching hardware and TCP, are implementation specific. This document identifies issues in the LDP specification in RFC 3036, "LDP Specification", that make it difficult to implement an FT LSR using the current LDP protocols, and defines enhancements to the LDP specification to ease such FT LSR implementations. The issues and extensions described here are equally applicable to RFC 3212, "Constraint-Based LSP Setup Using LDP" (CR-LDP). [STANDARDS-TRACK]

This document provides state machine tables for ATM (Asynchronous Transfer Mode) switch LSRs. In the current LDP specification, there is no state machine specified for processing LDP messages. We think that defining a common state machine is very important for interoperability between different LDP and CR-LDP implementations. This memo provides information for the Internet community.

This document extends and clarifies the relevant portions of RFC 3031 and RFC 3036 by specifying in more detail the procedures which to be used when distributing labels to or from ATM-LSRs, when those labels represent Forwarding Equivalence Classes (FECs, see RFC 3031) for which the routes are determined on a hop-by-hop basis by network layer routing algorithms. [STANDARDS-TRACK]

A fundamental concept in MPLS is that two Label Switching Routers (LSRs) must agree on the meaning of the labels used to forward traffic between and through them. This common understanding is achieved by using a set of procedures, called a label distribution protocol, by which one LSR informs another of label bindings it has made. This document describes the applicability of a set of such procedures called LDP (for Label Distribution Protocol) by which LSRs distribute labels to support MPLS forwarding along normally routed paths. This memo provides information for the Internet community.

This document specifies the procedures for the communication of VCID values between neighboring ATM-LSRs that must occur in order to ensure this property. [STANDARDS-TRACK]

The Loader Debugger Protocol (LDP) is an application layer protocol for loading, dumping, and debugging target machines from hosts in a network environment. This RFC specifies a proposed protocol for the ARPA-Internet and DARPA research community, and requests discussion and suggestions for improvemts.