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RFC 7439

Gap Analysis for Operating IPv6-Only MPLS Networks

Pages: 28
Informational
Errata
Part 2 of 2 – Pages 13 to 28
First   Prev   None

Top   ToC   RFC7439 - Page 13   prevText

3.4. MPLS Operations, Administration, and Maintenance (MPLS OAM)

For MPLS LSPs, there are primarily three OAM mechanisms: Extended ICMP [RFC4884] [RFC4950], LSP Ping [RFC4379], and Bidirectional Forwarding Detection (BFD) for MPLS LSPs [RFC5884]. For MPLS Pseudowires, there is also Virtual Circuit Connectivity Verification (VCCV) [RFC5085] [RFC5885]. Most of these mechanisms work in pure
Top   ToC   RFC7439 - Page 14
   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; RFC 4379 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 address-family mismatches exist and is not specific to MPLS.
   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 an 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. 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 [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.
Top   ToC   RFC7439 - Page 15
   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. Label Switched Path Ping (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, 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 [IPv4-MAPPED] 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 [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 [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: o LSP Ping is operating in traceroute mode over 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.
Top   ToC   RFC7439 - Page 16
   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 behavior in certain IPv6-specific scenarios.  For
   example, RFC 4379 defines the K value as 28 octets when the 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 and unclear mapping from the
   LSR Router ID to Downstream IP Address.

3.4.3. Bidirectional Forwarding Detection (BFD)

The BFD specification for MPLS LSPs [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 [RFC5085] can carry IPv4 or IPv6 OAM packets (see Sections 5.1.1 and 5.2.1 of RFC 5085), and VCCV for BFD [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.

3.4.5. MPLS Transport Profile (MPLS-TP) OAM

As with MPLS-TP, MPLS-TP OAM [RFC6371] does not require 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. Although not required, MPLS-TP can use IP. Gap: None. MPLS-TP OAM does not require IP.
Top   ToC   RFC7439 - Page 17

3.5. MIB Modules

RFC 3811 [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], the GMPLS-TE MIB specification [RFC4802] and the FRR extension [RFC6445]. "Definitions of Textual Conventions (TCs) for Multiprotocol Label Switching (MPLS) Management" [MPLS-TC] tries to resolve this gap by marking this textual convention as obsolete. The other MIB specifications for LSR [RFC3813], LDP [RFC3815], and TE [RFC4220] have support for both IPv4 and IPv6. Lastly, RFC 4990 [RFC4990] discusses how to handle IPv6 sources and destinations in the MPLS and GMPLS-TE MIB modules. In particular, Section 8 of RFC 4990 [RFC4990] describes a method of defining or monitoring an LSP tunnel using the MPLS-TE and GMPLS-TE MIB modules, working around some of the limitations in RFC 3811 [RFC3811]. Gap: Minor; Section 8 of RFC 4990 [RFC4990] describes a method to handle IPv6 addresses in the MPLS-TE [RFC3812] and GMPLS-TE [RFC4802] MIB modules. Work underway to update RFC 3811 via [MPLS-TC], may also need to update RFC 3812, RFC 4802, and RFC 6445, which depend on it.

4. Gap Summary

This document 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 that 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 documents 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.
Top   ToC   RFC7439 - Page 18
              Identified Gaps in MPLS for IPv6-Only Networks

   +---------+---------------------------------------+-----------------+
   |   Item  |                  Gap                  |   Addressed in  |
   +---------+---------------------------------------+-----------------+
   |   LDP   |   LSP mapping, LDP identifiers, LDP   |    [LDP-IPv6]   |
   | S.3.2.1 | discovery, LDP session establishment, |                 |
   |         |     next-hop address, and LDP TTL     |                 |
   |         |                security               |                 |
   +---------+---------------------------------------+-----------------+
   |   mLDP  |    Inherits gaps from LDP, RFC 6512   |     Inherits    |
   | S.3.2.2 |               [RFC6512]               |   [LDP-IPv6],   |
   |         |                                       |    additional   |
   |         |                                       |    fixes TBD    |
   +---------+---------------------------------------+-----------------+
   |  GMPLS  | RFC 6370 [RFC6370] Node ID derivation |       TBD       |
   | S.3.2.6 |                                       |                 |
   +---------+---------------------------------------+-----------------+
   |  L2VPN  |     RFC 6074 [RFC6074] discovery,     |       TBD       |
   | S.3.3.1 |               signaling               |                 |
   +---------+---------------------------------------+-----------------+
   |  L3VPN  |  RFC 4659 [RFC4659] does not define a |       TBD       |
   | S.3.3.2 |          method for 4PE/4VPE          |                 |
   +---------+---------------------------------------+-----------------+
   |   OAM   |  RFC 4379 [RFC4379] No IPv6 multipath |    [IPv6-RAO]   |
   |  S.3.4  |     support, no IPv6 RAO, possible    |                 |
   |         |     dropped messages in IP version    |                 |
   |         |                mismatch               |                 |
   +---------+---------------------------------------+-----------------+
   |   MIB   |   RFC 3811 [RFC3811] no IPv6 textual  |    [MPLS-TC]    |
   | Modules |               convention              |                 |
   |  S.3.5  |                                       |                 |
   +---------+---------------------------------------+-----------------+

                       Table 1: IPv6-Only MPLS Gaps

5. 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. However, follow-on work recommended by this gap analysis will need to address any effects that the use of IPv6 in their modifications may have on security.
Top   ToC   RFC7439 - Page 19

6. References

6.1. Normative References

[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6) Specification", RFC 2460, December 1998, <http://www.rfc-editor.org/info/rfc2460>. [RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y., Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack Encoding", RFC 3032, January 2001, <http://www.rfc-editor.org/info/rfc3032>. [RFC3107] Rekhter, Y. and E. Rosen, "Carrying Label Information in BGP-4", RFC 3107, May 2001, <http://www.rfc-editor.org/info/rfc3107>. [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, <http://www.rfc-editor.org/info/rfc3209>. [RFC3471] Berger, L., "Generalized Multi-Protocol Label Switching (GMPLS) Signaling Functional Description", RFC 3471, January 2003, <http://www.rfc-editor.org/info/rfc3471>. [RFC3473] Berger, L., "Generalized Multi-Protocol Label Switching (GMPLS) Signaling Resource ReserVation Protocol-Traffic Engineering (RSVP-TE) Extensions", RFC 3473, January 2003, <http://www.rfc-editor.org/info/rfc3473>. [RFC3811] Nadeau, T. and J. Cucchiara, "Definitions of Textual Conventions (TCs) for Multiprotocol Label Switching (MPLS) Management", RFC 3811, June 2004, <http://www.rfc-editor.org/info/rfc3811>. [RFC4023] Worster, T., Rekhter, Y., and E. Rosen, "Encapsulating MPLS in IP or Generic Routing Encapsulation (GRE)", RFC 4023, March 2005, <http://www.rfc-editor.org/info/rfc4023>. [RFC4379] Kompella, K. and G. Swallow, "Detecting Multi-Protocol Label Switched (MPLS) Data Plane Failures", RFC 4379, February 2006, <http://www.rfc-editor.org/info/rfc4379>.
Top   ToC   RFC7439 - Page 20
   [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,
              <http://www.rfc-editor.org/info/4659>.

   [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,
              <http://www.rfc-editor.org/info/rfc4817>.

   [RFC5036]  Andersson, L., Minei, I., and B. Thomas, "LDP
              Specification", RFC 5036, October 2007,
              <http://www.rfc-editor.org/info/rfc5036>.

   [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, <http://www.rfc-editor.org/info/rfc6074>.

   [RFC6370]  Bocci, M., Swallow, G., and E. Gray, "MPLS Transport
              Profile (MPLS-TP) Identifiers", RFC 6370, September 2011,
              <http://www.rfc-editor.org/info/rfc6370>.

   [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,
              <http://www.rfc-editor.org/info/rfc6512>.

6.2. Informative References

[EVPN] Sajassi, A., Aggarwal, R., Bitar, N., Isaac, A., and J. Uttaro, "BGP MPLS Based Ethernet VPN", Work in Progress, draft-ietf-l2vpn-evpn-11, October 2014. [IPv4-MAPPED] Metz, C. and J. Hagino, "IPv4-Mapped Addresses on the Wire Considered Harmful", Work in Progress, draft-itojun-v6ops- v4mapped-harmful-02, October 2003. [IPv6-RAO] Raza, K., Akiya, N., and C. Pignataro, "IPv6 Router Alert Option for MPLS OAM", Work in Progress, draft-raza-mpls- oam-ipv6-rao-02, September 2014. [LDP-IPv6] Asati, R., Manral, V., Papneja, R., and C. Pignataro, "Updates to LDP for IPv6", Work in Progress, draft-ietf- mpls-ldp-ipv6-14, October 2014.
Top   ToC   RFC7439 - Page 21
   [LOOPBACK-PREFIX]
              Smith, M., "A Larger Loopback Prefix for IPv6", Work in
              Progress, draft-smith-v6ops-larger-ipv6-loopback-prefix-
              04, February 2013.

   [mLDP-NLRI]
              Wijnands, I., Rosen, E., and U. Joorde, "Encoding mLDP
              FECs in the NLRI of BGP MCAST-VPN Routes", Work in
              Progress, draft-ietf-l3vpn-mvpn-mldp-nlri-10, November
              2014.

   [MPLS-TC]  Manral, V., Tsou, T., Will, W., and F. Fondelli,
              "Definitions of Textual Conventions (TCs) for
              Multiprotocol Label Switching (MPLS) Management", Work in
              Progress, draft-manral-mpls-rfc3811bis-04, September 2014.

   [PE-CE]    Patel, K., Rekhter, Y., and E. Rosen, "BGP as an MVPN
              PE-CE Protocol", Work in Progress,
              draft-ietf-l3vpn-mvpn-pe- ce-02, October 2014.

   [RFC1918]  Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and
              E. Lear, "Address Allocation for Private Internets",
              BCP 5, RFC 1918, February 1996,
              <http://www.rfc-editor.org/info/rfc1918>.

   [RFC3630]  Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
              (TE) Extensions to OSPF Version 2", RFC 3630, September
              2003, <http://www.rfc-editor.org/info/rfc3630>.

   [RFC3812]  Srinivasan, C., Viswanathan, A., and T. Nadeau,
              "Multiprotocol Label Switching (MPLS) Traffic Engineering
              (TE) Management Information Base (MIB)", RFC 3812, June
              2004, <http://www.rfc-editor.org/info/rfc3812>.

   [RFC3813]  Srinivasan, C., Viswanathan, A., and T. Nadeau,
              "Multiprotocol Label Switching (MPLS) Label Switching
              Router (LSR) Management Information Base (MIB)", RFC 3813,
              June 2004, <http://www.rfc-editor.org/info/rfc3813>.

   [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, <http://www.rfc-editor.org/info/rfc3815>.

   [RFC4090]  Pan, P., Swallow, G., and A. Atlas, "Fast Reroute
              Extensions to RSVP-TE for LSP Tunnels", RFC 4090, May
              2005, <http://www.rfc-editor.org/info/rfc4090>.
Top   ToC   RFC7439 - Page 22
   [RFC4220]  Dubuc, M., Nadeau, T., and J. Lang, "Traffic Engineering
              Link Management Information Base", RFC 4220, November
              2005, <http://www.rfc-editor.org/info/rfc4220>.

   [RFC4364]  Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
              Networks (VPNs)", RFC 4364, February 2006,
              <http://www.rfc-editor.org/info/rfc4364>.

   [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,
              <http://www.rfc-editor.org/info/rfc4447>.

   [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,
              <http://www.rfc-editor.org/info/rfc4558>.

   [RFC4655]  Farrel, A., Vasseur, J., and J. Ash, "A Path Computation
              Element (PCE)-Based Architecture", RFC 4655, August 2006,
              <http://www.rfc-editor.org/info/rfc4655>.

   [RFC4664]  Andersson, L. and E. Rosen, "Framework for Layer 2 Virtual
              Private Networks (L2VPNs)", RFC 4664, September 2006,
              <http://www.rfc-editor.org/info/rfc4664>.

   [RFC4761]  Kompella, K. and Y. Rekhter, "Virtual Private LAN Service
              (VPLS) Using BGP for Auto-Discovery and Signaling", RFC
              4761, January 2007,
              <http://www.rfc-editor.org/info/rfc4761>.

   [RFC4762]  Lasserre, M. and V. Kompella, "Virtual Private LAN Service
              (VPLS) Using Label Distribution Protocol (LDP) Signaling",
              RFC 4762, January 2007,
              <http://www.rfc-editor.org/info/rfc4762>.

   [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,
              <http://www.rfc-editor.org/info/rfc4798>.

   [RFC4802]  Nadeau, T. and A. Farrel, "Generalized Multiprotocol Label
              Switching (GMPLS) Traffic Engineering Management
              Information Base", RFC 4802, February 2007,
              <http://www.rfc-editor.org/info/rfc4802>.
Top   ToC   RFC7439 - Page 23
   [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,
              <http://www.rfc-editor.org/info/rfc4875>.

   [RFC4884]  Bonica, R., Gan, D., Tappan, D., and C. Pignataro,
              "Extended ICMP to Support Multi-Part Messages", RFC 4884,
              April 2007, <http://www.rfc-editor.org/info/rfc4884>.

   [RFC4950]  Bonica, R., Gan, D., Tappan, D., and C. Pignataro, "ICMP
              Extensions for Multiprotocol Label Switching", RFC 4950,
              August 2007, <http://www.rfc-editor.org/info/rfc4950>.

   [RFC4990]  Shiomoto, K., Papneja, R., and R. Rabbat, "Use of
              Addresses in Generalized Multiprotocol Label Switching
              (GMPLS) Networks", RFC 4990, September 2007,
              <http://www.rfc-editor.org/info/rfc4990>.

   [RFC5082]  Gill, V., Heasley, J., Meyer, D., Savola, P., and C.
              Pignataro, "The Generalized TTL Security Mechanism
              (GTSM)", RFC 5082, October 2007,
              <http://www.rfc-editor.org/info/rfc5082>.

   [RFC5085]  Nadeau, T. and C. Pignataro, "Pseudowire Virtual Circuit
              Connectivity Verification (VCCV): A Control Channel for
              Pseudowires", RFC 5085, December 2007,
              <http://www.rfc-editor.org/info/rfc5085>.

   [RFC5088]  Le Roux, JL., Vasseur, JP., Ikejiri, Y., and R. Zhang,
              "OSPF Protocol Extensions for Path Computation Element
              (PCE) Discovery", RFC 5088, January 2008,
              <http://www.rfc-editor.org/info/rfc5088>.

   [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,
              <http://www.rfc-editor.org/info/rfc5089>.

   [RFC5286]  Atlas, A. and A. Zinin, "Basic Specification for IP Fast
              Reroute: Loop-Free Alternates", RFC 5286, September 2008,
              <http://www.rfc-editor.org/info/rfc5286>.

   [RFC5305]  Li, T. and H. Smit, "IS-IS Extensions for Traffic
              Engineering", RFC 5305, October 2008,
              <http://www.rfc-editor.org/info/rfc5305>.
Top   ToC   RFC7439 - Page 24
   [RFC5329]  Ishiguro, K., Manral, V., Davey, A., and A. Lindem,
              "Traffic Engineering Extensions to OSPF Version 3", RFC
              5329, September 2008,
              <http://www.rfc-editor.org/info/rfc5329>.

   [RFC5440]  Vasseur, JP. and JL. Le Roux, "Path Computation Element
              (PCE) Communication Protocol (PCEP)", RFC 5440, March
              2009, <http://www.rfc-editor.org/info/rfc5440>.

   [RFC5512]  Mohapatra, P. and E. Rosen, "The BGP Encapsulation
              Subsequent Address Family Identifier (SAFI) and the BGP
              Tunnel Encapsulation Attribute", RFC 5512, April 2009,
              <http://www.rfc-editor.org/info/rfc5512>.

   [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,
              <http://www.rfc-editor.org/info/rfc5520>.

   [RFC5521]  Oki, E., Takeda, T., and A. Farrel, "Extensions to the
              Path Computation Element Communication Protocol (PCEP) for
              Route Exclusions", RFC 5521, April 2009,
              <http://www.rfc-editor.org/info/rfc5521>.

   [RFC5640]  Filsfils, C., Mohapatra, P., and C. Pignataro, "Load-
              Balancing for Mesh Softwires", RFC 5640, August 2009,
              <http://www.rfc-editor.org/info/rfc5640>.

   [RFC5837]  Atlas, A., Bonica, R., Pignataro, C., Shen, N., and JR.
              Rivers, "Extending ICMP for Interface and Next-Hop
              Identification", RFC 5837, April 2010,
              <http://www.rfc-editor.org/info/rfc5837>.

   [RFC5884]  Aggarwal, R., Kompella, K., Nadeau, T., and G. Swallow,
              "Bidirectional Forwarding Detection (BFD) for MPLS Label
              Switched Paths (LSPs)", RFC 5884, June 2010,
              <http://www.rfc-editor.org/info/rfc5884>.

   [RFC5885]  Nadeau, T. and C. Pignataro, "Bidirectional Forwarding
              Detection (BFD) for the Pseudowire Virtual Circuit
              Connectivity Verification (VCCV)", RFC 5885, June 2010,
              <http://www.rfc-editor.org/info/rfc5885>.

   [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,
              <http://www.rfc-editor.org/info/rfc5886>.
Top   ToC   RFC7439 - Page 25
   [RFC5921]  Bocci, M., Bryant, S., Frost, D., Levrau, L., and L.
              Berger, "A Framework for MPLS in Transport Networks",
              RFC 5921, July 2010,
              <http://www.rfc-editor.org/info/rfc5921>.

   [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, <http://www.rfc-editor.org/info/rfc6006>.

   [RFC6073]  Martini, L., Metz, C., Nadeau, T., Bocci, M., and M.
              Aissaoui, "Segmented Pseudowire", RFC 6073, January 2011,
              <http://www.rfc-editor.org/info/rfc6073>.

   [RFC6119]  Harrison, J., Berger, J., and M. Bartlett, "IPv6 Traffic
              Engineering in IS-IS", RFC 6119, February 2011,
              <http://www.rfc-editor.org/info/rfc6119>.

   [RFC6371]  Busi, I. and D. Allan, "Operations, Administration, and
              Maintenance Framework for MPLS-Based Transport Networks",
              RFC 6371, September 2011,
              <http://www.rfc-editor.org/info/rfc6371>.

   [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,
              <http://www.rfc-editor.org/info/rfc6388>.

   [RFC6445]  Nadeau, T., Koushik, A., and R. Cetin, "Multiprotocol
              Label Switching (MPLS) Traffic Engineering Management
              Information Base for Fast Reroute", RFC 6445, November
              2011, <http://www.rfc-editor.org/info/rfc6445>.

   [RFC6513]  Rosen, E. and R. Aggarwal, "Multicast in MPLS/BGP IP
              VPNs", RFC 6513, February 2012,
              <http://www.rfc-editor.org/info/rfc6513>.

   [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,
              <http://rfc-editor.org/info/rfc6514>.

   [RFC6540]  George, W., Donley, C., Liljenstolpe, C., and L. Howard,
              "IPv6 Support Required for All IP-Capable Nodes", BCP 177,
              RFC 6540, April 2012,
              <http://www.rfc-editor.org/info/rfc6540>.
Top   ToC   RFC7439 - Page 26
   [RFC6624]  Kompella, K., Kothari, B., and R. Cherukuri, "Layer 2
              Virtual Private Networks Using BGP for Auto-Discovery and
              Signaling", RFC 6624, May 2012,
              <http://www.rfc-editor.org/info/rfc6624>.

   [RFC6720]  Pignataro, C. and R. Asati, "The Generalized TTL Security
              Mechanism (GTSM) for the Label Distribution Protocol
              (LDP)", RFC 6720, August 2012,
              <http://www.rfc-editor.org/info/rfc6720>.

   [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,
              <http://www.rfc-editor.org/info/rfc6829>.

   [RFC7117]  Aggarwal, R., Kamite, Y., Fang, L., Rekhter, Y., and C.
              Kodeboniya, "Multicast in Virtual Private LAN Service
              (VPLS)", RFC 7117, February 2014,
              <http://www.rfc-editor.org/info/rfc7117>.

Acknowledgements

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 Farrel, Nobo Akiya, Francis Dupont, and Tobias Gondrom for their comments.

Contributors

The following people have contributed text to this document: Rajiv Asati Cisco Systems 7025 Kit Creek Road Research Triangle Park, NC 27709 United States EMail: rajiva@cisco.com
Top   ToC   RFC7439 - Page 27
      Kamran Raza
      Cisco Systems
      2000 Innovation Drive
      Ottawa, ON K2K-3E8
      Canada

      EMail: skraza@cisco.com


      Ronald Bonica
      Juniper Networks
      2251 Corporate Park Drive
      Herndon, VA 20171
      United States

      EMail: rbonica@juniper.net


      Rajiv Papneja
      Huawei Technologies
      2330 Central Expressway
      Santa Clara, CA 95050
      United States

      EMail: rajiv.papneja@huawei.com


      Dhruv Dhody
      Huawei Technologies
      Leela Palace
      Bangalore, Karnataka 560008
      India

      EMail: dhruv.ietf@gmail.com


      Vishwas Manral
      Ionos Networks
      Sunnyvale, CA 94089
      United States

      EMail: vishwas@ionosnetworks.com
Top   ToC   RFC7439 - Page 28
      Nagendra Kumar
      Cisco Systems, Inc.
      7200 Kit Creek Road
      Research Triangle Park, NC 27709
      United States

      EMail: naikumar@cisco.com

Authors' Addresses

Wesley George (editor) Time Warner Cable 13820 Sunrise Valley Drive Herndon, VA 20111 United States 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 United States Phone: +1-919-392-7428 EMail: cpignata@cisco.com