Network working group                                             X. Xu
Internet Draft                                                   Huawei
Category: Standard Track                                       N. Sheth
                                                                L. Yong
                                                           C. Pignataro
                                                                 Y. Fan
                                                          China Telecom

Expires: December 2013                                     June 9, 2013

                         Encapsulating MPLS in UDP



   Existing technologies to encapsulate Multi-Protocol Label Switching
   (MPLS) over IP are not adequate for efficient load balancing of MPLS
   application traffic, such as MPLS-based Layer2 Virtual Private
   Network (L2VPN) or Layer3 Virtual Private Network (L3VPN) traffic
   across IP networks. This document specifies additional IP-based
   encapsulation technology, referred to as MPLS-in-User Datagram
   Protocol (UDP), which can facilitate the load balancing of MPLS
   application traffic across IP networks.

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on December 9, 2013.

Xu, et al.            Expires December 9, 2013                [Page 1]

Internet-Draft          Encapsulating MPLS in UDP             June 2013

Copyright Notice

   Copyright (c) 2013 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
   Provisions Relating to IETF Documents
   ( in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Conventions used in this document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in RFC-2119 [RFC2119].

Table of Contents

   1. Introduction ................................................ 3
      1.1. Existing Technologies .................................. 3
      1.2. Motivations for MPLS-in-UDP Encapsulation .............. 4
   2. Terminology ................................................. 4
   3. Encapsulation in UDP ........................................ 4
   4. Processing Procedures ....................................... 5
   5. Applicability ............................................... 6
   6. Security Considerations ..................................... 6
   7. IANA Considerations ......................................... 6
   8. Acknowledgements ............................................ 6
   9. References .................................................. 7
      9.1. Normative References ................................... 7
      9.2. Informative References ................................. 7
   Authors' Addresses ............................................. 8

Xu, et al.            Expires December 9, 2013                [Page 2]

Internet-Draft          Encapsulating MPLS in UDP             June 2013

1. Introduction

   To fully utilize the bandwidth available in IP networks and/or
   facilitate recovery from a link or node failure, load balancing of
   traffic over Equal Cost Multi-Path (ECMP) and/or Link Aggregation
   Group (LAG) across IP networks is widely used. In effect, most
   existing core routers in IP networks are already capable of
   distributing IP traffic flows over ECMP paths and/or LAG based on the
   hash of the five-tuple of User Datagram Protocol (UDP)[RFC768] and
   Transmission Control Protocol (TCP) packets (i.e., source IP address,
   destination IP address, source port, destination port, and protocol).

   In practice, there are some scenarios for Multi-Protocol Label
   Switching (MPLS) applications (e.g., MPLS-based Layer2 Virtual
   Private Network (L2VPN) or Layer3 Virtual Private Network (L3VPN))
   where the MPLS application traffic needs to be transported through
   IP-based tunnels, rather than MPLS tunnels. For example, MPLS-based
   L2VPN or L3VPN technologies may be used for interconnecting
   geographically dispersed enterprise data centers or branch offices
   across IP Wide Area Networks (WAN) where enterprise own router
   devices are deployed as L2VPN or L3VPN Provider Edge (PE) routers. In
   this case, efficient load balancing of the MPLS application traffic
   across IP networks is very desirable.

1.1. Existing Technologies

   With existing IP-based encapsulation methods for MPLS applications,
   such as MPLS-in-IP and MPLS-in-Generic Routing Encapsulation (GRE)
   [RFC4023] or even MPLS-in-Layer Two Tunneling Protocol - Version 3
   (L2TPv3)[RFC4817], distinct customer traffic flows between a given PE
   router pair would be encapsulated with the same IP-based tunnel
   headers prior to traversing the core of the IP WAN. Since the
   encapsulated traffic is neither TCP nor UDP traffic, for many
   existing core routers which could only perform hash calculation on
   fields in the IP headers of those tunnels (i.e., source IP address,
   destination IP address), it would be hard to achieve a fine-grained
   load balancing of these traffic flows across the network core due to
   the lack of adequate entropy information.

   [RFC5640] describes a method for improving the load balancing
   efficiency in a network carrying Softwire Mesh service over L2TPv3
   and GRE encapsulation. However, this method requires core routers to
   be capable of performing hash calculation on the "load-balancing"
   field contained in the tunnel encapsulation headers (i.e., the
   Session ID field in the L2TPv3 header or the Key field in the GRE

Xu, et al.            Expires December 9, 2013                [Page 3]

Internet-Draft          Encapsulating MPLS in UDP             June 2013

   header), which means a non-trivial change to the date plane of many
   existing core routers.

1.2. Motivations for MPLS-in-UDP Encapsulation

   On basis of the fact that most existing core routers (i.e., P routers
   in the context of MPLS-based L2VPN or L3VPN) are already capable of
   balancing IP traffic flows over the IP networks based on the hash of
   the five-tuple of UDP packets, it would be advantageous to use MPLS-
   in-UDP encapsulation instead of MPLS-in-GRE or MPLS-in-L2TPv3 in the
   environments where the load balancing of MPLS application traffic
   across IP networks is much desired but the load balancing mechanisms
   defined in [RFC5640] have not yet been widely supported by most
   existing core routers. In this way, the default load balancing
   capability of most existing core routers as mentioned above can be
   utilized directly without requiring any change to them.

2. Terminology

   This memo makes use of the terms defined in [RFC4364] and [RFC4664].

3. Encapsulation in UDP

   MPLS-in-UDP encapsulation format is shown as follows:

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   |    Source Port = Entropy      |       Dest Port = MPLS        |
   |           UDP Length          |        UDP Checksum           |
   |                                                               |
   ~                       MPLS Label Stack                        ~
   |                                                               |
   |                                                               |
   ~                         Message Body                          ~
   |                                                               |

            Source Port of UDP

                This field contains an entropy value that is generated by
                the ingress PE router. For example, the entropy value can
                be generated by performing hash calculation on certain

Xu, et al.            Expires December 9, 2013                [Page 4]

Internet-Draft          Encapsulating MPLS in UDP             June 2013

                fields in the customer packets (e.g., the five tuple of
                UDP/TCP packets).

            Destination Port of UDP

                This field is set to a value (TBD) indicating that the
                UDP tunnel payload is a MPLS packet. As for whether the
                top label in the MPLS label stack is downstream-assigned
                or upstream-assigned, it SHOULD be determined based on
                the tunnel destination IP address. That is to say, if the
                destination IP address is a multicast address, the top
                label SHOULD be upstream-assigned, otherwise if the
                destination IP address is a unicast address, it SHOULD be

            UDP Length

                The usage of this field is in accordance with the current
                UDP specification.

            UDP Checksum

                The usage of this field is in accordance with the current
                UDP specification. To simplify the operation on egress PE
                routers, this field is RECOMMENDED to be set to zero in
                IPv4 UDP encapsulation case, and even in IPv6 UDP
                encapsulation case if appropriate[RFC6935][RFC6936].

            MPLS Label Stack

                This field contains an MPLS Label Stack as defined in

            Message Body

                This field contains one MPLS message body.

4. Processing Procedures

   This MPLS-in-UDP encapsulation causes MPLS packets to be forwarded
   through "UDP tunnels". When performing MPLS-in-UDP encapsulation by
   an ingress PE router, the entropy value would be generated by the
   ingress PE router and then be filled in the Source Port field of the
   UDP header. As such, P routers, upon receiving these UDP encapsulated
   packets, could balance these packets based on the hash of the five-
   tuple of UDP packets.

Xu, et al.            Expires December 9, 2013                [Page 5]

Internet-Draft          Encapsulating MPLS in UDP             June 2013

   Upon receiving these UDP encapsulated packets, egress PE routers
   would decapsulate them by removing the UDP headers and then process
   them accordingly.

   As for other common processing procedures associated with tunneling
   encapsulation technologies including but not limited to Maximum
   Transmission Unit (MTU) and preventing fragmentation and reassembly,
   Time to Live (TTL) and differentiated services, the corresponding
   procedures defined in [RFC4023] which are applicable for MPLS-in-IP
   and MPLS-in-GRE encapsulation formats SHOULD be followed.

5. Applicability

   Besides the MPLS-based L3VPN [RFC4364] and L2VPN [RFC4761, RFC4762]
   applications, MPLS-in-UDP encapsulation could apply to other MPLS
   applications including but not limited to 6PE [RFC4798] and PWE3

6. Security Considerations

   Just like MPLS-in-GRE and MPLS-in-IP encapsulation formats, the MPLS-
   in-UDP encapsulation format defined in this document by itself cannot
   ensure the integrity and privacy of data packets being transported
   through the MPLS-in-UDP tunnels and cannot enable the tunnel
   decapsulators to authenticate the tunnel encapsulator. In the case
   where any of the above security issues is concerned, the MPLS-in-UDP
   tunnels SHOULD be secured with IPsec in transport mode. In this way,
   the UDP header would not be visible to P routers anymore. As a result,
   the meaning of adopting MPLS-in-UDP encapsulation format as an
   alternative to MPLS-in-GRE and MPLS-in-IP encapsulation formats is
   lost. Hence, MPLS-in-UDP encapsulation format SHOULD be used only in
   the scenarios where all the security issues as mentioned above are
   not significant concerns. For example, in a data center environment,
   the whole network including P routers and PE routers are under the
   control of a single administrative entity and therefore there is no
   need to worry about the above security issues.

7. IANA Considerations

   One UDP destination port number indicating MPLS needs to be allocated
   by IANA.

8. Acknowledgements

   Thanks to Shane Amante, Dino Farinacci, Keshava A K, Ivan Pepelnjak,
   Eric Rosen, Andrew G. Malis, Kireeti Kompella, Marshall Eubanks,
   George Swallow, Loa Andersson, Ross Callon, Vivek Kumar, Weiguo Hao,

Xu, et al.            Expires December 9, 2013                [Page 6]

Internet-Draft          Encapsulating MPLS in UDP             June 2013

   Zhenxiao Liu and Xing Tong for their valuable comments and
   suggestions on this document. Thanks to Daniel King, Gregory Mirsky
   and Eric Osborne for their valuable reviews on this document.

9. References

9.1. Normative References

   [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
             Requirement Levels", BCP 14, RFC 2119, March 1997.

9.2. Informative References

   [RFC4364] Rosen, E and Y. Rekhter, "BGP/MPLS IP Virtual Private
             Networks (VPNs)", RFC 4364, February 2006.

   [RFC4664] Andersson, L. and Rosen, E. (Editors),"Framework for Layer
             2 Virtual Private Networks (L2VPNs)", RFC 4664, Sept 2006.

   [RFC4023] Worster, T., Rekhter, Y., and E. Rosen, "Encapsulating MPLS
             in IP or GRE", RFC4023, March 2005.

   [RFC4817] M. Townsley, C. Pignataro, S. Wainner, T. Seely and J.
             Young, "Encapsulation of MPLS over Layer 2 Tunneling
             Protocol Version 3, March 2007.

   [RFC5640] Filsfils, C., Mohapatra, P., and C. Pignataro, "Load-
             Balancing for Mesh Softwires", RFC 5640, August 2009.

   [RFC5332] Eckert, T., Rosen, E., Aggarwal, R., and Y. Rekhter, "MPLS
             Multicast Encapsulations", RFC 5332, August 2008.

   [RFC4798] J Declerq et al., "Connecting IPv6 Islands over IPv4 MPLS
             using IPv6 Provider Edge Routers (6PE)", RFC4798, February

   [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.

   [RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y.,
             Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack
             Encoding", RFC 3032, January 2001.

Xu, et al.            Expires December 9, 2013                [Page 7]

Internet-Draft          Encapsulating MPLS in UDP             June 2013

   [RFC768]  Postel, J., "User Datagram Protocol", STD 6, RFC 768,
             August 1980.

   [RFC6935] Eubanks, M., Chimento, P., and M. Westerlund, "UDP
             Checksums for Tunneled Packets", RFC6935,
             Feburary 2013.

   [RFC6936] Fairhurst, G. and M. Westerlund, "Applicability Statement
             for the use of IPv6 UDP Datagrams with Zero Checksums",
             RFC6936, Feburary 2013.

   [IP-in-UDP] Xu, etc, "Encapsulating IP in UDP", draft-xu-softwire-ip-
             in-udp-01 (work in progress), February 2013.

Authors' Addresses

   Xiaohu Xu
   Huawei Technologies
   Beijing, China
   Phone: +86-10-60610041

   Nischal Sheth
   Juniper Networks
   1194 N. Mathilda Ave
   Sunnyvale, CA 94089

   Lucy Yong
   Huawei USA
   5340 Legacy Dr.
   Plano TX75025
   Phone: 469-277-5837

   Carlos Pignataro
   Cisco Systems
   7200-12 Kit Creek Road
   Research Triangle Park, NC 27709

   Yongbing Fan
   China Telecom
   Guangzhou, China.
   Phone: +86 20 38639121

Xu, et al.            Expires December 9, 2013                [Page 8]

Internet-Draft          Encapsulating MPLS in UDP             June 2013

   Zhenbin Li
   Huawei Technologies,
   Beijing, China
   Phone: +86-10-60613676

Xu, et al.            Expires December 9, 2013                [Page 9]