| MPLS | W. George, Ed. |
| Internet-Draft | Time Warner Cable |
| Intended status: Informational | C. Pignataro, Ed. |
| Expires: February 26, 2015 | Cisco |
| August 25, 2014 |
Gap Analysis for Operating IPv6-only MPLS Networks
draft-ietf-mpls-ipv6-only-gap-02
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 not intended to highlight a particular vendor's implementation (or lack thereof) in the context of IPv6-only MPLS functionality, but rather to focus on gaps in the standards defining the MPLS suite.
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IPv6 is an integral part of modern network deployments. At the time when this document was written, the majority of these IPv6 deployments were using dual-stack implementations, where IPv4 and IPv6 are supported equally on many or all of the network nodes, and single-stack primarily referred to IPv4-only devices. Dual-stack deployments provide a useful margin for protocols and features that are not currently capable of operating solely over IPv6, because they can continue using IPv4 as necessary. However, as IPv6 deployment and usage becomes more pervasive, and IPv4 exhaustion begins driving changes in address consumption behaviors, there is an increasing likelihood that many networks will need to start operating some or all of their network nodes either as primarily IPv6 (most functions use IPv6, a few legacy features use IPv4), or as IPv6-only (no IPv4 provisioned on the device). This transition toward IPv6-only operation exposes any gaps where features, protocols, or implementations are still reliant on IPv4 for proper function. To that end, and in the spirit of RFC 6540's [RFC6540] recommendation that implementations need to stop requiring IPv4 for proper and complete function, this document reviews the Multi-Protocol 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 and networks that are primarily IPv6 (hereafter referred to as IPv6-primary). This document is not intended to highlight a particular vendor's implementation (or lack thereof) in the context of IPv6-only MPLS functionality, but rather to focus on gaps in the standards defining the MPLS suite.
This section discusses some drivers for ensuring that MPLS completely supports IPv6-only operation. It is not intended to be a comprehensive discussion of all potential use cases, but rather a discussion of one use case to provide context and justification to undertake such a gap analysis.
IP convergence is continuing to drive new classes of devices to begin communicating via IP. Examples of such devices could include set top boxes for IP Video distribution, cell tower electronics (macro or micro cells), infrastructure Wi-Fi Access Points, and devices for machine to machine (M2M) or Internet of Things applications. In some cases, these classes of devices represent a very large deployment base, on the order of thousands or even millions of devices network-wide. The scale of these networks, coupled with the increasingly overlapping use of RFC 1918 [RFC1918] address space within the average network, and the lack of globally-routable IPv4 space available for long-term growth begins to drive the need for many of the endpoints in this network to be managed solely via IPv6. Even if these devices are carrying some IPv4 user data, it is often encapsulated in another protocol such that the communication between the endpoint and its upstream devices can be IPv6-only without impacting support for IPv4 on user data. As the number of devices to manage increases, the operator is compelled to move to IPv6. Depending on the MPLS features required, it is plausible to assume that the (existing) MPLS network will need to be extended to these IPv6-only devices.
Additionally, as the impact of IPv4 exhaustion becomes more acute, more and more aggressive IPv4 address reclamation measures will be justified. Many networks are likely to focus on preserving their remaining IPv4 addresses for revenue-generating customers so that legacy support for IPv4 can be maintained as long as necessary. As a result, it may be appropriate for some or all of the network infrastructure, including MPLS Label Switch Routers (LSRs) and Label Edge Routers (LERs), to have its IPv4 addresses reclaimed and transition toward IPv6-only operation.
This gap analysis aims to answer the question, "what fails when one attempts to use MPLS features on a network of IPv6-only devices?" The baseline assumption for this analysis is that some endpoints as well as Label Switch Routers (Provider Edge (PE) and Provider (P) routers) only have IPv6 transport available, and need to support the full suite of MPLS features defined as of the time of this document's writing at parity with the support on an IPv4 network. This is necessary whether they are enabled via Label Distribution Protocol (LDP) RFC 5036 [RFC5036], Resource Reservation Protocol Extensions for MPLS Traffic Engineering (RSVP-TE) RFC 3209 [RFC3209], or Border Gateway Protocol (BGP) RFC 3107 [RFC3107], and whether they are encapsulated in MPLS RFC 3032 [RFC3032], IP RFC 4023 [RFC4023], Generic Routing Encapsulation (GRE) RFC 4023 [RFC4023], or Layer 2 Tunneling Protocol Version 3 (L2TPv3) RFC 4817 [RFC4817]. It is important when evaluating these gaps to distinguish between user data and control plane data, because while this document is focused on IPv6-only operation, it is quite likely that some amount of the user payload data being carried in the IPv6-only MPLS network will still be IPv4.
A note about terminology: Gaps identified by this document are characterized as "Major" or "Minor". Major gaps refer to significant changes necessary in one or more standards to address the gap due to existing standards language having either missing functionality for IPv6-only operation or explicit language requiring the use of IPv4 with no IPv6 alternatives defined. Minor gaps refer to changes necessary primarily to clarify existing standards language. Usually these changes are needed in order to explicitly codify IPv6 support in places where it is either implicit or omitted today, but the omission is unlikely to prevent IPv6-only operation.
MPLS labeled packets can be transmitted over a variety of data links RFC 3032 [RFC3032], and MPLS labeled packets can also be encapsulated over IP. The encapsulations of MPLS in IP and GRE as well as MPLS over L2TPv3 support IPv6. See Section 3 of RFC 4023 [RFC4023] and Section 2 of RFC 4817 [RFC4817] respectively.
Gap: None.
Label Distribution Protocol (LDP) RFC 5036 [RFC5036] defines a set of procedures for distribution of labels between label switch routers that can use the labels for forwarding traffic. While LDP was designed to use an IPv4 or dual-stack IP network, it has a number of deficiencies that prohibit it from working in an IPv6-only network. LDP-IPv6 [I-D.ietf-mpls-ldp-ipv6] highlights some of the deficiencies when LDP is enabled in IPv6 only or dual-stack networks, and specifies appropriate protocol changes. These deficiencies are related to LSP mapping, LDP identifiers, LDP discovery, LDP session establishment, next hop address and LDP Time To Live (TTL) security RFC 5082 [RFC5082] and RFC 6720 [RFC6720].
Gap: Major, update to RFC 5036 in progress via LDP-IPv6 [I-D.ietf-mpls-ldp-ipv6] that should close this gap.
Multipoint LDP (mLDP) is a set of extensions to LDP for setting up Point to Multipoint (P2MP) and Multipoint to Multipoint (MP2MP) LSPs. These extensions are specified in RFC 6388 [RFC6388]. In terms of IPv6-only gap analysis, mLDP has two identified areas of interest:
For example, consider following setup, where R1/R6 are IPv4-only, R3/R4 are IPv6-only, and R2/R5 are dual-stack LSRs:
( IPv4-only ) ( IPv6-only ) ( IPv4-only )
R1 -- R2 -- R3 -- R4 -- R5 -- R6
Leaf Root
RFC 6512 [RFC6512] defines a recursive-FEC solution and procedures for mLDP when the backbone (transit/branch) LSRs have no route to the root. The proposed solution is defined for a BGP-free core in an VPN environment, but a similar concept can be used/extended to solve the above issue of IPv6-only backbone receiving an MP FEC element with an IPv4 address. The solution will require a border LSR (the one which is sitting on border of an IPv4/IPv6 island(s) (R2 and R5) to translate an IPv4 root address to equivalent IPv6 address (and vice vera) through procedures similar to RFC6512.
Gap: Major, update in progress for LDP via LDP-IPv6 [I-D.ietf-mpls-ldp-ipv6], may need additional updates to RFC6512.
Resource Reservation Protocol Extensions for MPLS Traffic Engineering (RSVP-TE) RFC 3209 [RFC3209] defines a set of procedures and enhancements to establish label-switched tunnels that can be automatically routed away from network failures, congestion, and bottlenecks. RSVP-TE allows establishing an LSP for an IPv4 or IPv6 prefix, thanks to its LSP_TUNNEL_IPv6 object and subobjects.
Gap: None
RFC3630 [RFC3630] specifies a method of adding traffic engineering capabilities to OSPF Version 2. New TLVs and sub-TLVs were added in RFC5329 [RFC5329] to extend TE capabilities to IPv6 networks in OSPF Version 3.
RFC5305 [RFC5305] specifies a method of adding traffic engineering capabilities to IS-IS. New TLVs and sub-TLVs were added in RFC6119 [RFC6119] to extend TE capabilities to IPv6 networks.
Gap: None
RFC4875 [RFC4875] describes extensions to RSVP-TE for the setup of point-to-multipoint (P2MP) LSPs in MPLS and Generalized MPLS (GMPLS) with support for both IPv4 and IPv6.
Gap: None
RFC4090 [RFC4090] specifies FRR mechanisms to establish backup LSP tunnels for local repair supporting both IPv4 and IPv6 networks. Further RFC5286 [RFC5286] describes the use of loop-free alternates to provide local protection for unicast traffic in pure IP and MPLS networks in the event of a single failure, whether link, node, or shared risk link group (SRLG) for both IPv4 and IPv6.
Gap: None
The Path Computation Element (PCE) defined in RFC4655 [RFC4655] is an entity that is capable of computing a network path or route based on a network graph, and applying computational constraints. A Path Computation Client (PCC) may make requests to a PCE for paths to be computed. The PCE communication protocol (PCEP) is designed as a communication protocol between PCCs and PCEs for path computations and is defined in RFC5440 [RFC5440].
The PCEP specification RFC5440 [RFC5440] is defined for both IPv4 and IPv6 with support for PCE discovery via an IGP (OSPF RFC5088 [RFC5088], or ISIS RFC5089 [RFC5089]) using both IPv4 and IPv6 addresses. Note that PCEP uses identical encoding of subobjects as in the Resource Reservation Protocol Traffic Engineering Extensions (RSVP-TE) defined in RFC3209 [RFC3209] which supports both IPv4 and IPv6.
The extensions of PCEP to support confidentiality RFC5520 [RFC5520], Route Exclusion RFC5521, [RFC5521] Monitoring RFC5886 [RFC5886], and P2MP RFC6006 [RFC6006] have support for both IPv4 and IPv6.
Gap: None.
RFC3107 [RFC3107] specifies a set of BGP protocol procedures for distributing the labels (for prefixes corresponding to any address-family) between label switch routers so that they can use the labels for forwarding the traffic. RFC3107 allows BGP to distribute the label for IPv4 or IPv6 prefix in an IPv6 only network.
Gap: None.
RFC4558 [RFC4558] specifies Node-ID Based RSVP Hello Messages with capability for both IPv4 and IPv6. RFC4990 [RFC4990] clarifies the use of IPv6 addresses in GMPLS networks including handling in the MIB modules.
Section 5.3, second paragraph of RFC6370 [RFC6370] describes the mapping from an MPLS Transport Profile (MPLS-TP) LSP_ID to RSVP-TE with an assumption that Node_IDs are derived from valid IPv4 addresses. This assumption fails in an IPv6-only network, given that there wouldn’t be any IPv4 addresses.
Gap: Minor; Section 5.3. of RFC6370 needs to be updated.
L2VPN RFC 4664 [RFC4664] specifies two fundamentally different kinds of Layer 2 VPN services that a service provider could offer to a customer: Virtual Private Wire Service (VPWS) and Virtual Private LAN Service (VPLS). RFC 4447 [RFC4447] and RFC 4762 [RFC4762] specify the LDP protocol changes to instantiate VPWS and VPLS services respectively in an MPLS network using LDP as the signaling protocol. This is complemented by RFC 6074 [RFC6074], which specifies a set of procedures for instantiating L2VPNs (e.g. VPWS, VPLS) using BGP as discovery protocol and LDP as well as L2TPv3 as signaling protocol. RFC 4761 [RFC4761] and RFC 6624 [RFC6624] specify BGP protocol changes to instantiate VPLS and VPWS services in an MPLS network, using BGP for both discovery and signaling.
In an IPv6-only MPLS network, use of L2VPN represents connection of Layer 2 islands over an IPv6 MPLS core, and very few changes are necessary to support operation over an IPv6-only network. The L2VPN signaling protocol is either BGP or LDP in an MPLS network, and both can run directly over IPv6 core infrastructure, as well as IPv6 edge devices. RFC 6074 [RFC6074] is the only RFC that appears to have a gap for IPv6-only operation. In its discovery procedures (section 3.2.2 and section 6), it suggests encoding PE IP address in the VSI-ID, which is encoded in Network Layer Reachability Information (NLRI), and should not exceed 12 bytes (to differentiate its AFI/SAFI (Subsequent Address Family Identifier) encoding from RFC4761). This means that PE IP address can NOT be an IPv6 address. Also, in its signaling procedures (section 3.2.3), it suggests encoding PE_addr in Source Attachment Individual Identifier (SAII) and Target Attachment Individual Identifier (TAII), which are limited to 32-bit (AII Type=1) at the moment.
RFC 6073 [RFC6073] defines the new LDP Pseudowire (PW) Switching Point PE TLV, which supports IPv4 and IPv6.
Gap: Minor. RFC6074 needs to be updated.
Ethernet VPN (EVPN) [I-D.ietf-l2vpn-evpn] defines a method for using BGP MPLS-based Ethernet VPNs. Because it can use functions in LDP and mLDP, as well as RFC 7117 [RFC7117] Multicast VPLS, it inherits gaps previously identified in LDP [LDP] and RFC 6074 [RFC6074]. Once those gaps are resolved, it should function properly on IPv6-only networks as defined.
RFC 4364 [RFC4364] defines a method by which a Service Provider may use an IP backbone to provide IP Virtual Private Networks (VPNs) for its customers. The following use cases arise in the context of this gap analysis:
Both use cases require mapping an IP packet to an IPv6-signaled LSP. RFC4364 defines Layer 3 Virtual Private Networks (L3VPNs) for IPv4 only and has references to 32-bit BGP next hop addresses. RFC 4659 [RFC4659] adds support for IPv6 on L3VPNs including 128-bit BGP next hop addresses, and discusses operation whether IPv6 is the payload or the underlying transport address family. However, RFC4659 does not formally update RFC4364, and thus an implementer may miss this additional set of standards unless it is explicitly identified independently of the base functionality defined in RFC4364. An erratum has been filed to correct this metadata problem. Further, section 1 of RFC4659 explicitly identifies use case #2 as out of scope for the document.
The authors do not believe that there are any additional issues encountered when using L2TPv3, RSVP, or GRE (instead of MPLS) as transport on an IPv6-only network.
Gap: Major. RFC4659 needs to be updated to explicitly cover use case #2. (Discussed in further detail below)
RFC 4798 [RFC4798] defines IPv6 Provider Edge (6PE), which defines how to interconnect IPv6 islands over a MPLS-enabled IPv4 cloud. However, use case 2 is doing the opposite, and thus could also be referred to as IPv4 Provider Edge (4PE). The method to support this use case is not defined explicitly. To support it, IPv4 edge devices need to be able to map IPv4 traffic to MPLS IPv6 core LSP's. Also, the core switches may not understand IPv4 at all, but in some cases they may need to be able to exchange Labeled IPv4 routes from one AS to a neighboring AS.
Gap: Major. RFC4798 covers only the "6PE" case. Use case #2 is currently not specified in an RFC.
RFC 4659 [RFC4659] defines IPv6 Virtual Private Network Extension (6VPE), a method by which a Service Provider may use its packet-switched backbone to provide Virtual Private Network (VPN) services for its IPv6 customers. It allows the core network to be MPLS IPv4 or MPLS IPv6, thus addressing use case 1 above. RFC4364 should work as defined for use case 2 above, which could also be referred to as IPv4 Virtual Private Extension (4VPE), but the RFC explicitly does not discuss this use and defines it as out of scope.
Gap: Minor. RFC4659 needs to be updated to explicitly cover use case #2
RFC 5512 [RFC5512] defines the BGP Encapsulation SAFI and the BGP Tunnel Encapsulation Attribute, which can be used to signal tunneling over a single-Address Family IP core. This mechanism supports transport of MPLS (and other protocols) over Tunnels in an IP core (including an IPv6-only core). In this context, load-balancing can be provided as specified in RFC 5640 [RFC5640].
Gap: None.
RFC 6513 [RFC6513] defines the procedure to provide multicast service over an MPLS VPN backbone for downstream customers. It is sometimes referred to as Next Generation Multicast VPN (NG-MVPN) The procedure involves the below set of protocols:
RFC 6513 [RFC6513] explains the use of Protocol Independent Multicast (PIM) as Provider Edge-Customer Edge (PE-CE) protocol while Section 11.1.2 of RFC 6514 [RFC6514] explains the use of mLDP as PE-CE protocol.
The MCAST-VPN NLRI route-type format defined in RFC 6514 [RFC6514] is not sufficiently covering all scenarios when mLDP is used as PE-CE protocol. The issue is explained in section 2 of [I-D.ietf-l3vpn-mvpn-mldp-nlri] along with new route-type that encodes the mLDP FEC in NLRI.
Further [I-D.ietf-l3vpn-mvpn-pe-ce] defines the use of BGP as PE-CE protocol.
Gap: None.
RFC 6513 [RFC6513] explains the use of the below tunnels:
Gap: Gaps in RSVP-TE P2MP LSP [RSVP-P2MP] and mLDP [mLDP] P2MP and MP2MP LSP are covered in previous sections. There are no MPLS-specific gaps for PIM Tree or Ingress Replication and any protocol-specific gaps not related to MPLS are outside the scope of this document.
Section 3.1 of RFC 6513 [RFC6513] explains the use of PIM as PE-PE protocol while RFC 6514 [RFC6514] explains the use of BGP as PE-PE protocol.
PE-PE multicast routing is not specific to P-tunnel or to MPLS. It can be PIM or BGP with label based or PIM tree based P-Tunnels. Enabling PIM as a PE-PE multicast protocol is equivalent to running it on a non-MPLS IPv6 network, so there are not any MPLS-specific considerations, and any gaps are applicable for non-MPLS networks as well. Similarly, BGP only includes the PMSI tunnel attribute as a part of the NLRI which is inherited from P-tunnel instantiation and considered to be an opaque value. So any gaps in the Control plane (PIM or BGP) will not be specific to MPLS.
Gap: Any gaps in PIM or BGP as PE-PE Multicast Routing protocol are not unique to MPLS, and therefore are outside the scope of this document. It is included for completeness.
MPLS-TP does not require IP (see section 2 of RFC 5921 [RFC5921]) and should not be affected by operation on an IPv6-only network. Therefore this is considered out of scope for this document, but is included for completeness.
Gap: None.
For MPLS LSPs, there are primarily three Operations, Administration, and Maintenance (OAM) mechanisms: Extended ICMP RFC 4884 [RFC4884] RFC 4950 [RFC4950], LSP Ping RFC 4379 [RFC4379], and Bidirectional Forwarding Detection (BFD) for MPLS LSPs RFC 5884 [RFC5884]. For MPLS Pseudowires, there is also Virtual Circuit Connectivity Verification (VCCV) RFC 5085 [RFC5085] RFC 5885 [RFC5885]. Most of these mechanisms work in pure IPv6 environments, but there are some problems encountered in mixed environments due to address-family mismatches. The next subsections cover these gaps in detail.
Gap: Major. RFC4379 needs to be updated to better support multipath IPv6. Additionally, there is potential for dropped messages in Extended ICMP and LSP ping due to IP version mismatches. It is important to note that this is a more generic problem with tunneling when IP address family mismatches exist, and is not specific to MPLS, so while MPLS will be affected, it will be difficult to fix this problem specifically for MPLS, rather than fixing the more generic problem.
Extended ICMP to support Multi-part messages is defined in RFC 4884 [RFC4884]. This extensibility is defined generally for both ICMPv4 and ICMPv6. The specific ICMP extensions for MPLS are defined in RFC 4950 [RFC4950]. ICMP Multi-part with MPLS extensions works for IPv4 and IPv6. However, the mechanisms described in RFC 4884 and 4950 may fail when tunneling IPv4 traffic over an LSP that is supported by an IPv6-only infrastructure.
Assume the following:
Now assume that one of the hosts sends an IPv4 packet to the other. However, the packet’s TTL expires on an LSP interior router. According to RFC 3032 [RFC3032], the interior router should examine the IPv4 payload, format an ICMPv4 message, and send it (over the tunnel upon which the original packet arrived) to the egress LSP. In this case, however, the LSP interior router is not IPv4-aware. It cannot parse the original IPv4 datagram, nor can it send an IPv4 message. So, no ICMP message is delivered to the source. Some specific ICMP extensions, in particular ICMP Extensions for Interface and Next-Hop Identification RFC 5837 [RFC5837] restrict the address family of address information included in an Interface Information Object to the same one as the ICMP (see Section 4.5 of RFC 5837). While these extensions are not MPLS specific, they can be used with MPLS packets carrying IP datagrams. This has no implications for IPv6-only environments.
Gap: Major. IP version mismatches may cause dropped messages. However, as noted in the previous section, this problem is not specific to MPLS.
The LSP Ping mechanism defined in RFC 4379 [RFC4379] is specified to work with IPv6. Specifically, the Target FEC Stacks include both IPv4 and IPv6 versions of all FECs (see Section 3.2 of RFC 4379). The only exceptions are the Pseudowire FECs, which are later specified for IPv6 in RFC 6829 [RFC6829]. The multipath information also includes IPv6 encodings (see Section 3.3.1 of RFC 4379).
LSP Ping packets are UDP packets over either IPv4 or IPv6 (see Section 4.3 of RFC 4379). However, for IPv6 the destination IP address is a (randomly chosen) IPv6 address from the range 0:0:0:0:0:FFFF:127/104. That is, using an IPv4-mapped IPv6 address. This is a transitional mechanism that should not bleed into IPv6-only networks, as [I-D.itojun-v6ops-v4mapped-harmful] explains. The issue is that the MPLS LSP Ping mechanism needs a range of loopback IP addresses to be used as destination addresses to exercise Equal Cost Multiple Path (ECMP), but the IPv6 address architecture specifies a single address (::1/128) for loopback. A mechanism to achieve this was proposed in [I-D.smith-v6ops-larger-ipv6-loopback-prefix].
Additionally, RFC 4379 does not define the value to be used in the IPv6 Router Alert option (RAO). For IPv4 RAO, a value of zero is used. However, there is no equivalent value for IPv6 RAO. This gap needs to be fixed to be able to use LSP Ping in IPv6 networks. Further details on this gap are captured, along with a proposed solution, in [I-D.raza-mpls-oam-ipv6-rao].
Another gap is that the mechanisms described in RFC 4379 may fail when tunneling IPv4 traffic over an LSP that is supported by IPv6-only infrastructure.
Assume the following:
Packets will expire at LSP interior routers. According to RFC 4379, the interior router must parse the IPv4 Echo Request, and then, send an IPv4 Echo Reply. However, the LSP interior router is not IPv4-aware. It cannot parse the IPv4 Echo Request, nor can it send an IPv4 Echo Reply. So, no reply is sent.
The mechanism described in RFC 4379 also does not sufficiently explain the behaviour in certain IPv6-specific scenarios. For example, RFC 4379 defines the K value as 28 octets when Address Family is set to IPv6 Unnumbered, but it doesn't describe how to carry a 32 bit LSR Router ID in the 128 bit Downstream IP Address Field.
Gap: Major. LSP ping uses IPv4-mapped IPv6 addresses, IP version mismatches may cause dropped messages, unclear mapping from LSR Router ID to Downstream IP Address.
The BFD specification for MPLS LSPs RFC 5884 [RFC5884] is defined for IPv4 as well as IPv6 versions of MPLS FECs (see Section 3.1 of RFC 5884). Additionally the BFD packet is encapsulated over UDP and specified to run over both IPv4 and IPv6 (see Section 7 of RFC 5884).
Gap: None.
The OAM specifications for MPLS Pseudowires define usage for both IPv4 and IPv6. Specifically, VCCV RFC 5085 [RFC5085] can carry IPv4 or IPv6 OAM packets (see Section 5.1.1 and 5.2.1 of RFC 5085), and VCCV for BFD RFC 5885 [RFC5885] also defines an IPv6 encapsulation (see Section 3.2 of RFC 5885).
Additionally, for LSP Ping for Pseudowires, the Pseudowire FECs are specified for IPv6 in RFC 6829 [RFC6829].
Gap: None.
As with MPLS-TP, MPLS-TP OAM RFC 6371 [RFC6371] is not dependent on IP or existing MPLS OAM functions, and should not be affected by operation on an IPv6-only network. Therefore, this is out of scope for this document, but is included for completeness.
Gap: None.
RFC3811 [RFC3811] defines the textual conventions for MPLS. These lack support for IPv6 in defining MplsExtendedTunnelId and MplsLsrIdentifier. These textual conventions are used in the MPLS TE Management Information Base (MIB) specification RFC3812 [RFC3812], GMPLS TE MIB specification RFC4802 [RFC4802] and Fast ReRoute (FRR) extension RFC6445 [RFC6445]. 3811bis [I-D.manral-mpls-rfc3811bis] tries to resolve this gap by marking this textual convention as obsolete.
The other MIB specifications for LSR RFC3813 [RFC3813], LDP RFC3815 [RFC3815] and TE RFC4220 [RFC4220] have support for both IPv4 and IPv6.
Gap: Major. Work underway to update RFC3811 via 3811bis [I-D.manral-mpls-rfc3811bis], may also need to update RFC3812, RFC4802, and RFC6445, which depend on it.
This draft has reviewed a wide variety of MPLS features and protocols to determine their suitability for use on IPv6-only or IPv6-primary networks. While some parts of the MPLS suite will function properly without additional changes, gaps have been identified in others, which will need to be addressed with follow-on work. This section will summarize those gaps, along with pointers to any work in progress to address them. Note that because the referenced drafts are works in progress and do not have consensus at the time of this document's publication, there could be other solutions proposed at a future time, and the pointers in this document should not be considered normative in any way. Additionally, work in progress on new features that use MPLS protocols will need to ensure that those protocols support operation on IPv6-only or IPv6-primary networks, or explicitly identify any dependencies on existing gaps that, once resolved, will allow proper IPv6-only operation.
Identifed gaps in MPLS for IPv6-only networks
| Item | Gap | Addressed in |
|---|---|---|
| LDP S.3.2.1 | LSP mapping, LDP identifiers, LDP discovery, LDP session establishment, next hop address and LDP TTL security | LDP-IPv6 [I-D.ietf-mpls-ldp-ipv6] |
| mLDP S.3.2.2 | inherits gaps from LDP, RFC6512 [RFC6512] | inherits LDP-IPv6 [I-D.ietf-mpls-ldp-ipv6], additional fixes TBD |
| GMPLS S.3.2.6 | RFC6370 [RFC6370] Node ID derivation | TBD |
| L2VPN S.3.3.1 | RFC 6074 [RFC6074] discovery, signaling | TBD |
| L3VPN S.3.3.2 | RFC 4659 [RFC4659] define method for 4PE/4VPE | TBD |
| OAM S.3.4 | RFC 4379 [RFC4379] no IPv6 multipath support, no IPv6 RAO, possible dropped messages in IP version mismatch | IPv6 RAO for MPLS OAM [I-D.raza-mpls-oam-ipv6-rao] |
| MIBs S.3.5 | RFC 3811 [RFC3811] no IPv6 textual convention | 3811bis [I-D.manral-mpls-rfc3811bis] |
The authors wish to thank Alvaro Retana, Andrew Yourtchenko, Loa Andersson, David Allan, Mach Chen, Mustapha Aissaoui, and Mark Tinka for their detailed reviews, as well as Brian Haberman, Joel Jaeggli, Adrian Farrell, and Nobo Akiya for their comments.
The following people have contributed text to this draft:
This memo includes no request to IANA.
Changing the address family used for MPLS network operation does not fundamentally alter the security considerations currently extant in any of the specifics of the protocol or its features, however, follow-on work recommended by this gap analysis will need to address any effects of the use of IPv6 in their modifications may have on security.