Internet DRAFT - draft-george-mpls-ipv6-only-gap
draft-george-mpls-ipv6-only-gap
Internet Engineering Task Force W. George, Ed.
Internet-Draft Time Warner Cable
Intended status: Informational C. Pignataro, Ed.
Expires: September 25, 2014 Cisco
March 24, 2014
Gap Analysis for Operating IPv6-only MPLS Networks
draft-george-mpls-ipv6-only-gap-05
Abstract
This document reviews the 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.
Status of This Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on September 25, 2014.
Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
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include Simplified BSD License text as described in Section 4.e of
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Use Case . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Gap Analysis . . . . . . . . . . . . . . . . . . . . . . . . 4
3.1. MPLS Data Plane . . . . . . . . . . . . . . . . . . . . . 4
3.2. MPLS Control Plane . . . . . . . . . . . . . . . . . . . 5
3.2.1. LDP . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.2.2. Multipoint LDP . . . . . . . . . . . . . . . . . . . 5
3.2.3. RSVP- TE . . . . . . . . . . . . . . . . . . . . . . 6
3.2.3.1. IGP . . . . . . . . . . . . . . . . . . . . . . . 6
3.2.3.2. RSVP-TE-P2MP . . . . . . . . . . . . . . . . . . 7
3.2.3.3. RSVP-TE Fast Reroute (FRR) . . . . . . . . . . . 7
3.2.4. Controller, PCE . . . . . . . . . . . . . . . . . . . 7
3.2.5. BGP . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.2.6. GMPLS . . . . . . . . . . . . . . . . . . . . . . . . 8
3.3. MPLS Applications . . . . . . . . . . . . . . . . . . . . 8
3.3.1. L2VPN . . . . . . . . . . . . . . . . . . . . . . . . 8
3.3.1.1. EVPN . . . . . . . . . . . . . . . . . . . . . . 9
3.3.2. L3VPN . . . . . . . . . . . . . . . . . . . . . . . . 9
3.3.2.1. 6PE/4PE . . . . . . . . . . . . . . . . . . . . . 10
3.3.2.2. 6VPE/4VPE . . . . . . . . . . . . . . . . . . . . 10
3.3.2.3. BGP Encapsulation SAFI . . . . . . . . . . . . . 10
3.3.2.4. NG-MVPN . . . . . . . . . . . . . . . . . . . . . 10
3.3.3. MPLS-TP . . . . . . . . . . . . . . . . . . . . . . . 12
3.4. MPLS OAM . . . . . . . . . . . . . . . . . . . . . . . . 12
3.4.1. Extended ICMP . . . . . . . . . . . . . . . . . . . . 12
3.4.2. LSP Ping . . . . . . . . . . . . . . . . . . . . . . 13
3.4.3. BFD OAM . . . . . . . . . . . . . . . . . . . . . . . 14
3.4.4. Pseudowire OAM . . . . . . . . . . . . . . . . . . . 14
3.4.5. MPLS-TP OAM . . . . . . . . . . . . . . . . . . . . . 15
3.5. MIBs . . . . . . . . . . . . . . . . . . . . . . . . . . 15
4. Gap Summary . . . . . . . . . . . . . . . . . . . . . . . . . 15
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 16
6. Contributing Authors . . . . . . . . . . . . . . . . . . . . 16
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18
8. Security Considerations . . . . . . . . . . . . . . . . . . . 18
9. Informative References . . . . . . . . . . . . . . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 24
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1. Introduction
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. 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.
2. Use Case
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 at least 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
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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 possible. As a
result, it may be appropriate for some or all of the network
infrastructure, including MPLS LSRs and LERs, to have its IPv4
addresses reclaimed and transition toward IPv6-only operation.
3. Gap Analysis
This gap analysis aims to answer the question, "what breaks 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 (PE and 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.
3.1. MPLS Data Plane
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.
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In the case where an IPv4 prefix is resolved over an IPv6 LSP, an
IPv6 Explicit Null label cannot immediately preceed an IPv4 packet.
Gap: None.
3.2. MPLS Control Plane
3.2.1. LDP
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 TTL security RFC 5082
[RFC5082] and RFC 6720 [RFC6720].
Gap: Major, update to RFC 5036 in progress that should close this
gap.
3.2.2. Multipoint LDP
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:
1. LDP Control plane: Since mLDP uses the LDP control plane to
discover and establish sessions with the peer, it shares the same
gaps as LDP with regards to control plane (discovery, transport,
and session establishment) in an IPv6-only network.
2. Multipoint (MP) FEC Root address: mLDP defines its own MP FECs
and rules, different from LDP, to map MP LSPs. mLDP MP FEC
contains a Root Address field which is an IP address in IP
networks. The current specification allows specifying Root
address according to AFI and hence covers both IPv4 or IPv6 root
addresses, requiring no extension to support IPv6-only MP LSPs.
The root address is used by each LSR participating in an MP LSP
setup such that root address reachability is resolved by doing a
table lookup against root address to find corresponding upstream
neighbor(s). This will pose a problem if an MP LSP traverses
IPv4-only and IPv6-only nodes in a dual-stack network on the way
to the root node.
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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
Assume R1 to be a leaf node for an P2MP LSP rooted at R6 (root node).
R1 uses R6's IPv4 address as the Root address in MP FEC. As the MP
LSP signaling proceeds from R1 to R6, the MP LSP setup will fail on
the first IPv6-only transit/branch LSRs (R3) when trying to find IPv4
root address reachability. 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 the 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 the
procedures similar to RFC6512. The translation of root address on
borders of IPv4 or IPv6 islands will also be needed for recursive
FECs and procedures defined in RFC6512.
Gap: Major, update in progress for LDP via LDP-IPv6
[I-D.ietf-mpls-ldp-ipv6], may need additional updates to RFC6512.
3.2.3. RSVP- TE
Resource Reservation Protocol Extensions for MPLS Traffic Engineering
(RSVP-TE) RFC 3209 [RFC3209] defines a set of procedures &
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
3.2.3.1. IGP
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.
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Gap: None
3.2.3.2. RSVP-TE-P2MP
RFC4875 [RFC4875] describes extensions to RSVP-TE for the setup of
point-to-multipoint (P2MP) LSPs in MPLS and GMPLS with support for
both IPv4 and IPv6.
Gap: None
3.2.3.3. RSVP-TE Fast Reroute (FRR)
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
3.2.4. Controller, PCE
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.
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3.2.5. BGP
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.
3.2.6. GMPLS
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-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.
3.3. MPLS Applications
3.3.1. L2VPN
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
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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 NLRI, and should not exceed 12 bytes (to
differentiate its AFI/SAFI 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 SAII and
TAII, which are limited to 32-bit (AII Type=1) at the moment.
RFC 6073 [RFC6073] defines the new LDP PW Switching Point PE TLV,
which supports IPv4 and IPv6.
Gap: Minor. RFC6074 needs to be updated.
3.3.1.1. EVPN
EVPN [I-D.ietf-l2vpn-evpn] is still a work in progress. As such, it
is out of scope for this gap analysis. Instead, the authors of that
draft need to ensure that it supports IPv6-only operation, or if it
cannot, identify dependencies on underlying gaps in MPLS protocol(s)
that must be resolved before it can support IPv6-only operation.
3.3.2. L3VPN
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:
1. Connecting IPv6 islands over IPv6-only MPLS network
2. Connecting IPv4 islands over IPv6-only MPLS network
Both use cases require mapping an IP packet to an IPv6-signaled LSP.
RFC4364 defines a VPN-IPv4 address family, but not a VPN-IPv6 address
family. RFC 4659 [RFC4659] corrects this oversight. Also, Section 5
of RFC 4364 [RFC4364] assumes that the BGP next-hop contains exactly
32 bits. This text should be generalized to include 128 bit next-
hops as well. Section 3.2.1.1 of RFC 4659 [RFC4659] does actually
specifies a 128-bit BGP next-hop.
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. RFC4364 must be updated, and RFC4659 may need to be
updated to explicitly cover use case #2. (Discussed in further
detail below)
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3.3.2.1. 6PE/4PE
RFC 4798 [RFC4798] defines 6PE, which defines how to interconnect
IPv6 islands over a Multiprotocol Label Switching (MPLS)-enabled IPv4
cloud. However, use case 2 is doing the opposite, and thus could
also be referred to as 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.
3.3.2.2. 6VPE/4VPE
RFC 4659 [RFC4659] defines 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 4VPE, but the RFC does not explicitly
discuss this use.
Gap: Minor. RFC4659 may need to be updated to explicitly cover use
case #2
3.3.2.3. BGP Encapsulation SAFI
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.
3.3.2.4. NG-MVPN
RFC 6513 [RFC6513] defines the procedure to provide multicast service
over MPLS VPN backbone for the customers. The procedure involves the
below set of protocols:
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3.3.2.4.1. PE-CE Multicast Routing Protocol
RFC 6513 [RFC6513] explains the use of PIM as 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.
3.3.2.4.2. P-Tunnel Instantiation
RFC 6513 [RFC6513] explains the use of the below tunnels:
o RSVP-TE P2MP LSP
o PIM Tree
o mLDP P2MP LSP
o mLDP MP2MP LSP
o Ingress Replication
Gap: Gaps in RSVP-TE P2MP LSP and mLDP P2MP and MP2MP LSP are covered
in previous sections.
PIM Tree and Ingress Replication are out of the scope of this
document.
3.3.2.4.3. PE-PE Multicast Routing Protocol
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.
Gap: Any gaps in PIM or BGP as PE-PE Multicast Routing protocol are
outside the scope of this document
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3.3.3. MPLS-TP
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.
Gap: None.
3.4. MPLS OAM
For MPLS LSPs, there are primarily three OAM mechanisms: Extended
ICMP RFC 4884 [RFC4884] RFC 4950 [RFC4950], LSP Ping RFC 4379
[RFC4379], and BFD for MPLS LSPs RFC 5884 [RFC5884]. For MPLS
Pseudowires, there is also Virtual Circuit Connectivity Verification
(VCCV) RFC 5085 [RFC5085] RFC 5885 [RFC5885]. All of these
mechanisms work in pure IPv6 environments. The next subsections
cover these in detail.
Gap: Major. RFC4379 needs to be updated for 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.
3.4.1. Extended ICMP
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
IPv6-only infrastructure.
Assume the following:
o the path between two IPv4 only hosts contains an MPLS LSP
o the two routers that terminate the LSP run dual stack
o the LSP interior routers run IPv6 only
o the LSP is signaled over IPv6
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.
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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.
3.4.2. LSP Ping
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 later specified for IPv6
in RFC 6829 [RFC6829].
The multipath information includes also IPv6 encodings (see
Section 3.3.1 of RFC 4379).
Additionally, LSP Ping packets are UDP packets over both IPv4 and
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
ECMPs, 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].
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:
o LSP Ping is operating in traceroute mode over an MPLS LSP
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o the two routers that terminate the LSP run dual stack
o the LSP interior routers run IPv6 only
o the LSP is signaled over IPv6
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.
3.4.3. BFD OAM
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.
3.4.4. Pseudowire OAM
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.
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3.4.5. MPLS-TP OAM
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.
Gap: None.
3.5. MIBs
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
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, may also need to update
RFC3812, RFC4802, and RFC6445, which depend on it.
4. Gap Summary
This draft has reviewed a wide variety of MPLS features and protocols
to determine their suitability for use on IPv6-only 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.
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Identifed gaps in MPLS for IPv6-only networks
+---------+--------------------------+------------------------------+
| Item | Gap | Addressed in |
+---------+--------------------------+------------------------------+
| LDP | LSP mapping, LDP | LDP-IPv6 |
| S.3.2.1 | identifiers, LDP | [I-D.ietf-mpls-ldp-ipv6] |
| | discovery, LDP session | |
| | establishment, next hop | |
| | address and LDP TTL | |
| | security | |
+---------+--------------------------+------------------------------+
| GMPLS | RFC6370 [RFC6370] Node | TBD |
| S.3.2.6 | ID derivation | |
+---------+--------------------------+------------------------------+
| L2VPN | RFC 6074 [RFC6074] | TBD |
| S.3.3.1 | discovery, signaling | |
+---------+--------------------------+------------------------------+
| L3VPN | RFC 4364 [RFC4364] BGP | TBD |
| S.3.3.2 | next-hop, define method | |
| | for 4PE/4VPE | |
+---------+--------------------------+------------------------------+
| OAM | RFC 4379 [RFC4379] no | TBD |
| S.3.4 | IPv6 multipath support, | |
| | possible dropped | |
| | messages in IP version | |
| | mismatch | |
+---------+--------------------------+------------------------------+
| MIBs | RFC 3811 [RFC3811] no | 3811bis |
| S.3.5 | IPv6 textual convention | [I-D.manral-mpls-rfc3811bis] |
+---------+--------------------------+------------------------------+
Table 1: IPv6-only MPLS Gaps
5. Acknowledgements
The authors wish to thank Andrew Yourtchenko, Loa Andersson, David
Allan, Mach Chen, Mustapha Aissaoui, and Mark Tinka for their
detailed reviews, as well as Brian Haberman, Joel Jaeggli, and Adrian
Farrell for their comments.
6. Contributing Authors
The following people have contributed text to this draft:
Rajiv Asati
Cisco Systems
7025 Kit Creek Road
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Research Triangle Park, NC 27709
US
Email: rajiva@cisco.com
Kamran Raza
Cisco Systems
2000 Innovation Drive
Ottawa, ON K2K-3E8
CA
Email: skraza@cisco.com
Ronald Bonica
Juniper Networks
2251 Corporate Park Drive
Herndon, VA 20171
US
Email: rbonica@juniper.net
Rajiv Papneja
Huawei Technologies
2330 Central Expressway
Santa Clara, CA 95050
US
Email: rajiv.papneja@huawei.com
Dhruv Dhody
Huawei Technologies
Leela Palace
Bangalore, Karnataka 560008
IN
Email: dhruv.ietf@gmail.com
Vishwas Manral
Hewlett-Packard, Inc.
19111 Pruneridge Ave.
Cupertino, CA 95014
US
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Email: vishwas.manral@hp.com
Nagendra Kumar
Cisco Systems, Inc.
7200 Kit Creek Road
Research Triangle Park, NC 27709
US
Email: naikumar@cisco.com
7. IANA Considerations
This memo includes no request to IANA.
8. Security Considerations
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.
9. Informative References
[I-D.ietf-l2vpn-evpn]
Sajassi, A., Aggarwal, R., Bitar, N., Isaac, A., and J.
Uttaro, "BGP MPLS Based Ethernet VPN", draft-ietf-l2vpn-
evpn-06 (work in progress), March 2014.
[I-D.ietf-l3vpn-mvpn-mldp-nlri]
Wijnands, I., Rosen, E., and U. Joorde, "Encoding mLDP
FECs in the NLRI of BGP MCAST-VPN Routes", draft-ietf-
l3vpn-mvpn-mldp-nlri-04 (work in progress), December 2013.
[I-D.ietf-l3vpn-mvpn-pe-ce]
Patel, K., Rekhter, Y., and E. Rosen, "BGP as an MVPN PE-
CE Protocol", draft-ietf-l3vpn-mvpn-pe-ce-00 (work in
progress), October 2013.
[I-D.ietf-mpls-ldp-ipv6]
Asati, R., Manral, V., Papneja, R., and C. Pignataro,
"Updates to LDP for IPv6", draft-ietf-mpls-ldp-ipv6-12
(work in progress), February 2014.
[I-D.itojun-v6ops-v4mapped-harmful]
Metz, C. and J. Hagino, "IPv4-Mapped Addresses on the Wire
Considered Harmful", draft-itojun-v6ops-v4mapped-
harmful-02 (work in progress), October 2003.
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[I-D.manral-mpls-rfc3811bis]
Manral, V., Tsou, T., Will, W., and F. Fondelli,
"Definitions of Textual Conventions (TCs) for
Multiprotocol Label Switching (MPLS) Management", draft-
manral-mpls-rfc3811bis-03 (work in progress), June 2013.
[I-D.smith-v6ops-larger-ipv6-loopback-prefix]
Smith, M., "A Larger Loopback Prefix for IPv6", draft-
smith-v6ops-larger-ipv6-loopback-prefix-04 (work in
progress), February 2013.
[RFC1918] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and
E. Lear, "Address Allocation for Private Internets", BCP
5, RFC 1918, February 1996.
[RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y.,
Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack
Encoding", RFC 3032, January 2001.
[RFC3107] Rekhter, Y. and E. Rosen, "Carrying Label Information in
BGP-4", RFC 3107, May 2001.
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, December 2001.
[RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
(TE) Extensions to OSPF Version 2", RFC 3630, September
2003.
[RFC3811] Nadeau, T. and J. Cucchiara, "Definitions of Textual
Conventions (TCs) for Multiprotocol Label Switching (MPLS)
Management", RFC 3811, June 2004.
[RFC3812] Srinivasan, C., Viswanathan, A., and T. Nadeau,
"Multiprotocol Label Switching (MPLS) Traffic Engineering
(TE) Management Information Base (MIB)", RFC 3812, June
2004.
[RFC3813] Srinivasan, C., Viswanathan, A., and T. Nadeau,
"Multiprotocol Label Switching (MPLS) Label Switching
Router (LSR) Management Information Base (MIB)", RFC 3813,
June 2004.
[RFC3815] Cucchiara, J., Sjostrand, H., and J. Luciani, "Definitions
of Managed Objects for the Multiprotocol Label Switching
(MPLS), Label Distribution Protocol (LDP)", RFC 3815, June
2004.
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[RFC4023] Worster, T., Rekhter, Y., and E. Rosen, "Encapsulating
MPLS in IP or Generic Routing Encapsulation (GRE)", RFC
4023, March 2005.
[RFC4090] Pan, P., Swallow, G., and A. Atlas, "Fast Reroute
Extensions to RSVP-TE for LSP Tunnels", RFC 4090, May
2005.
[RFC4220] Dubuc, M., Nadeau, T., and J. Lang, "Traffic Engineering
Link Management Information Base", RFC 4220, November
2005.
[RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
Networks (VPNs)", RFC 4364, February 2006.
[RFC4379] Kompella, K. and G. Swallow, "Detecting Multi-Protocol
Label Switched (MPLS) Data Plane Failures", RFC 4379,
February 2006.
[RFC4447] Martini, L., Rosen, E., El-Aawar, N., Smith, T., and G.
Heron, "Pseudowire Setup and Maintenance Using the Label
Distribution Protocol (LDP)", RFC 4447, April 2006.
[RFC4558] Ali, Z., Rahman, R., Prairie, D., and D. Papadimitriou,
"Node-ID Based Resource Reservation Protocol (RSVP) Hello:
A Clarification Statement", RFC 4558, June 2006.
[RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation
Element (PCE)-Based Architecture", RFC 4655, August 2006.
[RFC4659] De Clercq, J., Ooms, D., Carugi, M., and F. Le Faucheur,
"BGP-MPLS IP Virtual Private Network (VPN) Extension for
IPv6 VPN", RFC 4659, September 2006.
[RFC4664] Andersson, L. and E. Rosen, "Framework for Layer 2 Virtual
Private Networks (L2VPNs)", RFC 4664, September 2006.
[RFC4761] Kompella, K. and Y. Rekhter, "Virtual Private LAN Service
(VPLS) Using BGP for Auto-Discovery and Signaling", RFC
4761, January 2007.
[RFC4762] Lasserre, M. and V. Kompella, "Virtual Private LAN Service
(VPLS) Using Label Distribution Protocol (LDP) Signaling",
RFC 4762, January 2007.
[RFC4798] De Clercq, J., Ooms, D., Prevost, S., and F. Le Faucheur,
"Connecting IPv6 Islands over IPv4 MPLS Using IPv6
Provider Edge Routers (6PE)", RFC 4798, February 2007.
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[RFC4802] Nadeau, T. and A. Farrel, "Generalized Multiprotocol Label
Switching (GMPLS) Traffic Engineering Management
Information Base", RFC 4802, February 2007.
[RFC4817] Townsley, M., Pignataro, C., Wainner, S., Seely, T., and
J. Young, "Encapsulation of MPLS over Layer 2 Tunneling
Protocol Version 3", RFC 4817, March 2007.
[RFC4875] Aggarwal, R., Papadimitriou, D., and S. Yasukawa,
"Extensions to Resource Reservation Protocol - Traffic
Engineering (RSVP-TE) for Point-to-Multipoint TE Label
Switched Paths (LSPs)", RFC 4875, May 2007.
[RFC4884] Bonica, R., Gan, D., Tappan, D., and C. Pignataro,
"Extended ICMP to Support Multi-Part Messages", RFC 4884,
April 2007.
[RFC4950] Bonica, R., Gan, D., Tappan, D., and C. Pignataro, "ICMP
Extensions for Multiprotocol Label Switching", RFC 4950,
August 2007.
[RFC4990] Shiomoto, K., Papneja, R., and R. Rabbat, "Use of
Addresses in Generalized Multiprotocol Label Switching
(GMPLS) Networks", RFC 4990, September 2007.
[RFC5036] Andersson, L., Minei, I., and B. Thomas, "LDP
Specification", RFC 5036, October 2007.
[RFC5082] Gill, V., Heasley, J., Meyer, D., Savola, P., and C.
Pignataro, "The Generalized TTL Security Mechanism
(GTSM)", RFC 5082, October 2007.
[RFC5085] Nadeau, T. and C. Pignataro, "Pseudowire Virtual Circuit
Connectivity Verification (VCCV): A Control Channel for
Pseudowires", RFC 5085, December 2007.
[RFC5088] Le Roux, JL., Vasseur, JP., Ikejiri, Y., and R. Zhang,
"OSPF Protocol Extensions for Path Computation Element
(PCE) Discovery", RFC 5088, January 2008.
[RFC5089] Le Roux, JL., Vasseur, JP., Ikejiri, Y., and R. Zhang,
"IS-IS Protocol Extensions for Path Computation Element
(PCE) Discovery", RFC 5089, January 2008.
[RFC5286] Atlas, A. and A. Zinin, "Basic Specification for IP Fast
Reroute: Loop-Free Alternates", RFC 5286, September 2008.
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[RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic
Engineering", RFC 5305, October 2008.
[RFC5329] Ishiguro, K., Manral, V., Davey, A., and A. Lindem,
"Traffic Engineering Extensions to OSPF Version 3", RFC
5329, September 2008.
[RFC5440] Vasseur, JP. and JL. Le Roux, "Path Computation Element
(PCE) Communication Protocol (PCEP)", RFC 5440, March
2009.
[RFC5512] Mohapatra, P. and E. Rosen, "The BGP Encapsulation
Subsequent Address Family Identifier (SAFI) and the BGP
Tunnel Encapsulation Attribute", RFC 5512, April 2009.
[RFC5520] Bradford, R., Vasseur, JP., and A. Farrel, "Preserving
Topology Confidentiality in Inter-Domain Path Computation
Using a Path-Key-Based Mechanism", RFC 5520, April 2009.
[RFC5521] Oki, E., Takeda, T., and A. Farrel, "Extensions to the
Path Computation Element Communication Protocol (PCEP) for
Route Exclusions", RFC 5521, April 2009.
[RFC5640] Filsfils, C., Mohapatra, P., and C. Pignataro, "Load-
Balancing for Mesh Softwires", RFC 5640, August 2009.
[RFC5837] Atlas, A., Bonica, R., Pignataro, C., Shen, N., and JR.
Rivers, "Extending ICMP for Interface and Next-Hop
Identification", RFC 5837, April 2010.
[RFC5884] Aggarwal, R., Kompella, K., Nadeau, T., and G. Swallow,
"Bidirectional Forwarding Detection (BFD) for MPLS Label
Switched Paths (LSPs)", RFC 5884, June 2010.
[RFC5885] Nadeau, T. and C. Pignataro, "Bidirectional Forwarding
Detection (BFD) for the Pseudowire Virtual Circuit
Connectivity Verification (VCCV)", RFC 5885, June 2010.
[RFC5886] Vasseur, JP., Le Roux, JL., and Y. Ikejiri, "A Set of
Monitoring Tools for Path Computation Element (PCE)-Based
Architecture", RFC 5886, June 2010.
[RFC5921] Bocci, M., Bryant, S., Frost, D., Levrau, L., and L.
Berger, "A Framework for MPLS in Transport Networks", RFC
5921, July 2010.
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[RFC6006] Zhao, Q., King, D., Verhaeghe, F., Takeda, T., Ali, Z.,
and J. Meuric, "Extensions to the Path Computation Element
Communication Protocol (PCEP) for Point-to-Multipoint
Traffic Engineering Label Switched Paths", RFC 6006,
September 2010.
[RFC6073] Martini, L., Metz, C., Nadeau, T., Bocci, M., and M.
Aissaoui, "Segmented Pseudowire", RFC 6073, January 2011.
[RFC6074] Rosen, E., Davie, B., Radoaca, V., and W. Luo,
"Provisioning, Auto-Discovery, and Signaling in Layer 2
Virtual Private Networks (L2VPNs)", RFC 6074, January
2011.
[RFC6119] Harrison, J., Berger, J., and M. Bartlett, "IPv6 Traffic
Engineering in IS-IS", RFC 6119, February 2011.
[RFC6370] Bocci, M., Swallow, G., and E. Gray, "MPLS Transport
Profile (MPLS-TP) Identifiers", RFC 6370, September 2011.
[RFC6371] Busi, I. and D. Allan, "Operations, Administration, and
Maintenance Framework for MPLS-Based Transport Networks",
RFC 6371, September 2011.
[RFC6388] Wijnands, IJ., Minei, I., Kompella, K., and B. Thomas,
"Label Distribution Protocol Extensions for Point-to-
Multipoint and Multipoint-to-Multipoint Label Switched
Paths", RFC 6388, November 2011.
[RFC6445] Nadeau, T., Koushik, A., and R. Cetin, "Multiprotocol
Label Switching (MPLS) Traffic Engineering Management
Information Base for Fast Reroute", RFC 6445, November
2011.
[RFC6512] Wijnands, IJ., Rosen, E., Napierala, M., and N. Leymann,
"Using Multipoint LDP When the Backbone Has No Route to
the Root", RFC 6512, February 2012.
[RFC6513] Rosen, E. and R. Aggarwal, "Multicast in MPLS/BGP IP
VPNs", RFC 6513, February 2012.
[RFC6514] Aggarwal, R., Rosen, E., Morin, T., and Y. Rekhter, "BGP
Encodings and Procedures for Multicast in MPLS/BGP IP
VPNs", RFC 6514, February 2012.
[RFC6540] George, W., Donley, C., Liljenstolpe, C., and L. Howard,
"IPv6 Support Required for All IP-Capable Nodes", BCP 177,
RFC 6540, April 2012.
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[RFC6624] Kompella, K., Kothari, B., and R. Cherukuri, "Layer 2
Virtual Private Networks Using BGP for Auto-Discovery and
Signaling", RFC 6624, May 2012.
[RFC6720] Pignataro, C. and R. Asati, "The Generalized TTL Security
Mechanism (GTSM) for the Label Distribution Protocol
(LDP)", RFC 6720, August 2012.
[RFC6829] Chen, M., Pan, P., Pignataro, C., and R. Asati, "Label
Switched Path (LSP) Ping for Pseudowire Forwarding
Equivalence Classes (FECs) Advertised over IPv6", RFC
6829, January 2013.
Authors' Addresses
Wesley George (editor)
Time Warner Cable
13820 Sunrise Valley Drive
Herndon, VA 20111
US
Phone: +1-703-561-2540
Email: wesley.george@twcable.com
Carlos Pignataro (editor)
Cisco Systems, Inc.
7200-12 Kit Creek Road
Research Triangle Park, NC 27709
US
Phone: +1-919-392-7428
Email: cpignata@cisco.com
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