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Versions: 00 01 02 03

Network Working Group                                              X. Xu
Internet-Draft                                                    Huawei
Intended status: Standards Track                             G. Shepherd
Expires: July 12, 2018                                             Cisco
                                                         January 8, 2018


                   Encapsulating Non-MPLS-BIER in UDP
                draft-xu-bier-non-mpls-encap-over-udp-02

Abstract

   Bit Index Explicit Replication (BIER) is a new multicast forwarding
   paradigm which doesn't require an explicit tree-building protocol nor
   intermediate routers to maintain any multicast state.  BIER has two
   types of encapsulation formats: one is MPLS-BIER encapsulation, the
   other is non-MPLS-BIER encapsulation.  This document proposes a
   mechanism of encapsulating non-MPLS-BIER packets over UDP tunnels.

Status of This Memo

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   This Internet-Draft will expire on July 12, 2018.

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   the Trust Legal Provisions and are provided without warranty as
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   2
   3.  Encapsulation in UDP  . . . . . . . . . . . . . . . . . . . .   3
   4.  Processing Procedures . . . . . . . . . . . . . . . . . . . .   4
   5.  Congestion Considerations . . . . . . . . . . . . . . . . . .   5
   6.  Applicability Statements  . . . . . . . . . . . . . . . . . .   5
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   5
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     10.1.  Normative References . . . . . . . . . . . . . . . . . .   6
     10.2.  Informative References . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   Bit Index Explicit Replication (BIER) [RFC8279] is a new multicast
   forwarding paradigm which doesn't require an explicit tree-building
   protocol nor intermediate routers to maintain any multicast state.
   As described in Section 6.9 of [RFC8279], a BFR may need to tunnel a
   BIER packet over a certain kind of tunnel, e.g., UDP tunnel.

   [I-D.ietf-bier-mpls-encapsulation] defines two types of BIER
   encapsulation formats: one is MPLS-BIER encapsulation, the other is
   non-MPLS-BIER encapsulation.  MPLS-BIER packets can be transported
   over UDP tunnels by using the MPLS-in-UDP encapsulation as described
   in [RFC7510] . This document proposes a mechanism of encapsulating
   non-MPLS-BIER packets over UDP tunnels.

1.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

2.  Terminology

   This memo makes use of the terms defined in [RFC8279]and
   [I-D.ietf-bier-mpls-encapsulation].






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3.  Encapsulation in UDP

   Non-MPLS-BIER-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 = TBD1       |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |           UDP Length          |        UDP Checksum           |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               |
       ~                    Non-MPLS-BIER Packet                       ~
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
              Figure 1: Non-MPLS-BIER-in-UDP Encapsulation Format

      Source Port of UDP:

         This field contains a 16-bit entropy value that is generated by
         the encapsulator to uniquely identify a flow.  What constitutes
         a flow is locally determined by the encapsulator and therefore
         is outside the scope of this document.  What algorithm is
         actually used by the encapsulator to generate an entropy value
         is outside the scope of this document.  For example, the 20-bit
         entropy value contained in the BIER header could actually be
         transformed to a 16- bit value and then be filled into this
         field.

         In case the tunnel does not need entropy, this field of all
         packets belonging to a given flow SHOULD be set to a randomly
         selected constant value so as to avoid packet reordering.

         To ensure that the source port number is always in the range
         49152 to 65535 (Note that those ports less than 49152 are
         reserved by IANA to identify specific applications/protocols)
         which may be required in some cases, instead of calculating a
         16-bit hash, the encapsulator SHOULD calculate a 14-bit hash
         and use those 14 bits as the least significant bits of the
         source port field while the most significant two bits SHOULD be
         set to binary 11.  That still conveys 14 bits of entropy
         information which would be enough as well in practice.

      Destination Port of UDP:







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         This field is set to a value (TBD1) allocated by IANA to
         indicate that the UDP tunnel payload is a non-MPLS-BIER packet.

      UDP Length:



         The usage of this field is in accordance with the current UDP
         specification [RFC0768].

      UDP Checksum:



         For IPv4 UDP encapsulation, this field is RECOMMENDED to be set
         to zero for performance or implementation reasons because the
         IPv4 header includes a checksum and use of the UDP checksum is
         optional with IPv4.  For IPv6 UDP encapsulation, the IPv6
         header does not include a checksum, so this field MUST contain
         a UDP checksum that MUST be used as specified in [RFC0768] and
         [RFC2460] unless one of the exceptions that allows use of UDP
         zero-checksum mode (as specified in [RFC6935]) applies.

      Non-MPLS-BIER Packet:



         This field contains one non-MPLS-BIER packet.

4.  Processing Procedures

   This Non-MPLS-BIER-in-UDP encapsulation causes non-MPLS BIER packets
   to be forwarded across an IP transit core via "UDP tunnels".  While
   performing Non-MPLS-BIER-in-UDP encapsulation, an encapsulator would
   generate an entropy value and encode it in the Source Port field of
   the UDP header.  The Destination Port field is set to a value (TBD1)
   allocated by IANA to indicate that the UDP tunnel payload is a non-
   MPLS-BIER packet.  Transit routers, upon receiving these UDP
   encapsulated non-MPLS-BIER packets, could balance these packets based
   on the hash of the five-tuple of UDP packets.  Decapsulators
   receiving these UDP encapsulated non-MPLS-BIER packets MUST
   decapsulate these packets by removing the UDP header and then forward
   them accordingly.

   Similar to all other IP-based tunneling technologies, Non-MPLS-BIER-
   in-UDP encapsulation introduces overheads and reduces the effective
   Maximum Transmission Unit (MTU) size.  Non-MPLS-BIER-in-UDP
   encapsulation may also impact Time-to-Live (TTL) or Hop Count (HC)



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   and Differentiated Services (DSCP).  Hence, Non-MPLS-BIER-in-UDP MUST
   follow the corresponding procedures defined in [RFC2003].

   Encapsulators MUST NOT fragment non-MPLS-BIER packet, and when the
   outer IP header is IPv4, encapsulators MUST set the DF bit in the
   outer IPv4 header.  It is strongly RECOMMENDED that IP transit core
   be configured to carry an MTU at least large enough to accommodate
   the added encapsulation headers.  Meanwhile, it is strongly
   RECOMMENDED that Path MTU Discovery [RFC1191] [RFC1981] or
   Packetization Layer Path MTU Discovery (PLPMTUD) [RFC4821] is used to
   prevent or minimize fragmentation.

5.  Congestion Considerations

   As it's explicitly stated in the Application Statements (Section 6),
   this Non-MPLS-BIER-in-UDP encapsulation method MUST only be used
   within networks that are well-managed, therefore, congestion control
   mechanism is not needed.

6.  Applicability Statements

   This Non-MPLS-BIER-in-UDP encapsulation technology MUST only be used
   within networks which are well-managed by a service provider and MUST
   NOT be used within the Internet.  In the well-managed network,
   traffic is well-managed to avoid congestion and fragmentation on
   encapsulated packets (i.e., Non-MPLS-BIER packets) are not needed.

7.  Acknowledgements

   TBD.

8.  IANA Considerations

   One UDP destination port number indicating non-MPLS-BIER needs to be
   allocated by IANA:

      Service Name: Non-MPLS-BIER-in-UDP Transport Protocol(s):UDP
      Assignee: IESG <iesg@ietf.org>
      Contact: IETF Chair <chair@ietf.org>.
      Description: Encapsulate Non-MPLS-BIER packets in UDP tunnels.
      Reference: This document.
      Port Number: TBD1 -- To be assigned by IANA.

   One UDP destination port number indicating Non-MPLS-BIER with DTLS
   needs to be allocated by IANA:






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   Service Name: Non-MPLS-BIER-in-UDP-with-DTLS
   Transport Protocol(s): UDP
   Assignee: IESG <iesg@ietf.org>
   Contact: IETF Chair <chair@ietf.org>.
   Description: Encapsulate Non-MPLS-BIER packets in UDP tunnels with DTLS.
   Reference: This document.
   Port Number: TBD2 -- To be assigned by IANA.

9.  Security Considerations

   The security problems faced with the Non-MPLS-BIER-in-UDP tunnel are
   exactly the same as those faced with MPLS-in-UDP tunnel [RFC7510].
   In other words, the Non-MPLS-BIER-in-UDP tunnel as defined in this
   document by itself cannot ensure the integrity and privacy of data
   packets being transported through the Non-MPLS-BIER-in-UDP tunnel and
   cannot enable the tunnel decapsulator to authenticate the tunnel
   encapsulator.  In the case where any of the above security issues is
   concerned, the Non-MPLS-BIER-in-UDP tunnel SHOULD be secured with
   IPsec or DTLS.  IPsec was designed as a network security mechanism
   and therefore it resides at the network layer.  As such, if the
   tunnel is secured with IPsec, the UDP header would not be visible to
   intermediate routers anymore in either IPsec tunnel or transport
   mode.  As a result, the meaning of adopting the Non-MPLS-BIER-in-UDP
   tunnel as an alternative to the Non-MPLS-BIER-in-GRE or Non-MPLS-
   BIER-in-IP tunnel is lost.  By comparison, DTLS is better suited for
   application security and can better preserve network and transport
   layer protocol information.  Specifically, if DTLS is used, the
   destination port of the UDP header will be filled with a value (TBD2)
   indicating non-MPLS-BIER with DTLS and the source port can still be
   used as an entropy field for load-sharing purposes.

10.  References

10.1.  Normative References

   [I-D.ietf-bier-mpls-encapsulation]
              Wijnands, I., Rosen, E., Dolganow, A., Tantsura, J.,
              Aldrin, S., and I. Meilik, "Encapsulation for Bit Index
              Explicit Replication in MPLS and non-MPLS Networks",
              draft-ietf-bier-mpls-encapsulation-12 (work in progress),
              October 2017.

   [RFC0768]  Postel, J., "User Datagram Protocol", STD 6, RFC 768,
              DOI 10.17487/RFC0768, August 1980,
              <https://www.rfc-editor.org/info/rfc768>.






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   [RFC1191]  Mogul, J. and S. Deering, "Path MTU discovery", RFC 1191,
              DOI 10.17487/RFC1191, November 1990,
              <https://www.rfc-editor.org/info/rfc1191>.

   [RFC1981]  McCann, J., Deering, S., and J. Mogul, "Path MTU Discovery
              for IP version 6", RFC 1981, DOI 10.17487/RFC1981, August
              1996, <https://www.rfc-editor.org/info/rfc1981>.

   [RFC2003]  Perkins, C., "IP Encapsulation within IP", RFC 2003,
              DOI 10.17487/RFC2003, October 1996,
              <https://www.rfc-editor.org/info/rfc2003>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC2460]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460,
              December 1998, <https://www.rfc-editor.org/info/rfc2460>.

   [RFC4821]  Mathis, M. and J. Heffner, "Packetization Layer Path MTU
              Discovery", RFC 4821, DOI 10.17487/RFC4821, March 2007,
              <https://www.rfc-editor.org/info/rfc4821>.

   [RFC6935]  Eubanks, M., Chimento, P., and M. Westerlund, "IPv6 and
              UDP Checksums for Tunneled Packets", RFC 6935,
              DOI 10.17487/RFC6935, April 2013,
              <https://www.rfc-editor.org/info/rfc6935>.

   [RFC6936]  Fairhurst, G. and M. Westerlund, "Applicability Statement
              for the Use of IPv6 UDP Datagrams with Zero Checksums",
              RFC 6936, DOI 10.17487/RFC6936, April 2013,
              <https://www.rfc-editor.org/info/rfc6936>.

   [RFC8279]  Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A.,
              Przygienda, T., and S. Aldrin, "Multicast Using Bit Index
              Explicit Replication (BIER)", RFC 8279,
              DOI 10.17487/RFC8279, November 2017,
              <https://www.rfc-editor.org/info/rfc8279>.

10.2.  Informative References

   [RFC7510]  Xu, X., Sheth, N., Yong, L., Callon, R., and D. Black,
              "Encapsulating MPLS in UDP", RFC 7510,
              DOI 10.17487/RFC7510, April 2015,
              <https://www.rfc-editor.org/info/rfc7510>.




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Authors' Addresses

   Xiaohu Xu
   Huawei

   Email: xuxh.mail@gmail.com


   Greg Shepherd
   Cisco

   Email: gjshep@gmail.com







































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