Internet Engineering Task Force                            F. Maino, Ed.
Internet-Draft                                                     Cisco
Intended status: Standards Track                                J. Lemon
Expires: July 9, 11, 2020                                          Broadcom
                                                              P. Agarwal
                                                                D. Lewis
                                                                M. Smith
                                                         January 6, 8, 2020

                    LISP Generic Protocol Extension


   This document describes extentions to the Locator/ID Separation
   Protocol (LISP) Data-Plane, via changes to the LISP header, to
   support multi-protocol encapsulation.

Status of This Memo

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   provisions of BCP 78 and BCP 79.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Conventions . . . . . . . . . . . . . . . . . . . . . . .   3
     1.2.  Definition of Terms . . . . . . . . . . . . . . . . . . .   3
   2.  LISP Header Without Protocol Extensions . . . . . . . . . . .   3
   3.  Generic Protocol Extension for LISP (LISP-GPE)  . . . . . . .   4
   4.  Implementation and Deployment Considerations  . . . . . . . .   6
     4.1.  Applicability Statement . . . . . . . . . . . . . . . . .   6
     4.2.  Congestion Control Functionality  . . . . . . . . . . . .   7
     4.3.  UDP Checksum  . . . . . . . . . . . . . . . . . . . . . .   7
       4.3.1.  UDP Zero Checksum Handling with IPv6  . . . . . . . .   8
     4.4.  Ethernet Encapsulated Payloads  . . . . . . . . . . . . .   9
   5.  Backward Compatibility  . . . . . . . . . . . . . . . . . . .  10
     5.1.  Detection of ETR Capabilities . . . . . . . . . . . . . .  10
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
     6.1.  LISP-GPE Next Protocol Registry . . . . . . . . . . . . .  10
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
   8.  Acknowledgements and Contributors . . . . . . . . . . . . . .  11
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  11
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  11
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  12
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  13

1.  Introduction

   The LISP Data-Plane is defined in [I-D.ietf-lisp-rfc6830bis].  It
   specifies an encapsulation format that carries IPv4 or IPv6 packets
   (henceforth jointly referred to as IP) in a LISP header and outer
   UDP/IP transport.

   The LISP Data-Plane header does not specify the protocol being
   encapsulated and therefore is currently limited to encapsulating only
   IP packet payloads.  Other protocols, most notably Virtual eXtensible
   Local Area Network (VXLAN) [RFC7348] (which defines a similar header
   format to LISP), are used to encapsulate Layer-2 (L2) protocols such
   as Ethernet.

   This document defines an extension for the LISP header, as defined in
   [I-D.ietf-lisp-rfc6830bis], to indicate the inner protocol, enabling
   the encapsulation of Ethernet, IP or any other desired protocol all
   the while ensuring compatibility with existing LISP deployments.

   A flag in the LISP header, called the P-bit, is used to signal the
   presence of the 8-bit Next Protocol field.  The Next Protocol field,
   when present, uses 8 bits of the field that was allocated to the
   echo-noncing and map-versioning features in
   [I-D.ietf-lisp-rfc6830bis].  Those two features are no longer
   available when the P-bit is used.  However, appropriate LISP-GPE shim
   headers can be defined to specify capabilities that are equivalent to
   echo-noncing and/or map-versioning.

   Since all of the reserved bits of the LISP Data-Plane header have
   been allocated, LISP-GPE can also be used to extend the LISP Data-
   Plane header by defining Next Protocol "shim" headers that implements
   new data plane functions not supported in the LISP header.  For
   example, the use of the Group-Based Policy (GBP) header
   [I-D.lemon-vxlan-lisp-gpe-gbp] or of the In-situ Operations,
   Administration, and Maintenance (IOAM) header
   [I-D.brockners-ippm-ioam-vxlan-gpe] with LISP-GPE, can be considered
   an extension to add support in the Data-Plane for Group-Based Policy
   functionalities or IOAM metadata.

1.1.  Conventions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

1.2.  Definition of Terms

   This document uses terms already defined in

2.  LISP Header Without Protocol Extensions

   As described in Section 1, the LISP header has no protocol identifier
   that indicates the type of payload being carried.  Because of this,
   LISP is limited to carrying IP payloads.

   The LISP header [I-D.ietf-lisp-rfc6830bis] contains a series of flags
   (some defined, some reserved), a Nonce/Map-version field and an
   instance ID/Locator-status-bit field.  The flags provide flexibility
   to define how the various fields are encoded.  Notably, Flag bit 5 is
   the last reserved bit in the LISP header.

        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
       |N|L|E|V|I|R|K|K|            Nonce/Map-Version                  |
       |                 Instance ID/Locator-Status-Bits               |

                           Figure 1: LISP Header

3.  Generic Protocol Extension for LISP (LISP-GPE)

   This document defines two changes to the LISP header in order to
   support multi-protocol encapsulation: the introduction of the P-bit
   and the definition of a Next Protocol field.  This document specifies
   the protocol behavior when the P-bit is set to 1, no changes are
   introduced when the P-bit is set to 0.  The LISP-GPE header is shown
   in Figure 2 and described below.

        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
       |N|L|E|V|I|P|K|K|            Reserved           | Next        Nonce/Map-Version/Next Protocol        |
       |                 Instance ID ID/Locator-Status-Bits               |

                         Figure 2: LISP-GPE Header

   P-Bit:  Flag bit 5 is defined as the Next Protocol bit.  The P-bit is
      set to 1 to indicate the presence of the 8 bit Next Protocol

      If the P-bit is clear (0) the LISP header is bit-by-bit equivalent
      to the definition in [I-D.ietf-lisp-rfc6830bis].

      When the P-bit is set to 1, bits N, E, V, and V bits 8-23 of the
      'Nonce/Map-Version/Next Protocol' field MUST be set to zero on
      transmission and ignored on receipt.  Features equivalent to those
      that were implemented with bits N,E and V in
      [I-D.ietf-lisp-rfc6830bis], such as echo-noncing and map-
      versioning, can be implemented by defining appropriate LISP-GPE
      shim headers.

      When the P-bit is set to 1, the LISP-GPE header is encoded as:

        0 x 0 0 x 1 x x
       |N|L|E|V|I|P|K|K|             0x0000            | Next Protocol |
       |                 Instance ID/Locator-Status-Bits               |

                  Figure 3: LISP-GPE with P-bit set to 1

   Next Protocol:  The  When the P-bit is set to 1, the lower 8 bits of the
      first 32-bit word are used to carry a Next Protocol.  This Next
      Protocol field contains the protocol of the encapsulated payload

      This document defines the following Next Protocol values:

      0x01 :  IPv4

      0x02 :  IPv6

      0x03 :  Ethernet

      0x04 :  Network Service Header (NSH) [RFC8300]

      0x05 to 0x7F:  Unassigned

      0x80 to 0xFF:  Unassigned (shim headers)

      The values are tracked in the IANA LISP-GPE Next Protocol Registry
      as described in Section 6.1.

   Next protocol values from Ox80 to 0xFF are assigned to protocols
   encoded as generic "shim" headers.  All shim protocols MUST use the
   header structure in Figure 3, 4, which includes a Next Protocol field.
   When a shim header is used with other protocols identified by next
   protocol values from 0x0 to 0x7F, the shim header MUST come before
   the further protocol, and the next header of the shim will indicate
   which protocol follows the shim header.

   Shim headers can be used to incrementally deploy new GPE features,
   keeping the processing of shim headers known to a given xTR
   implementation in the 'fast' path (typically an ASIC), while punting
   the processing of the remaining new GPE features to the 'slow' path.

   Shim protocols MUST have the first 32 bits defined as:

    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
   |     Type      |    Length     |   Reserved    | Next Protocol |
   |                                                               |
   ~                    Protocol Specific Fields                   ~
   |                                                               |

                           Figure 3: 4: Shim Header


   Type:  This field identifies the different messages of this protocol.

   Length:  The length, in 4-octect units, of this protocol message not
      including the first 4 octects.

   Reserved:  The use of this field is reserved to the protocol defined
      in this message.

   Next Protocol Field:  The next protocol field contains the protocol
      of the encapsulated payload.  The values are tracked in the IANA
      LISP-GPE Next Protocol Registry as described in Section 6.1.

4.  Implementation and Deployment Considerations

4.1.  Applicability Statement

   LISP-GPE conforms, as an UDP-based encapsulation protocol, to the UDP
   usage guidelines as specified in [RFC8085].  The applicability of
   these guidelines are dependent on the underlay IP network and the
   nature of the encapsulated payload.

   [RFC8085] outlines two applicability scenarios for UDP applications,
   1) general Internet and 2) controlled environment.  The controlled
   environment means a single administrative domain or adjacent set of
   cooperating domains.  A network in a controlled environment can be
   managed to operate under certain conditions whereas in general
   Internet this cannot be done.  Hence requirements for a tunnel
   protocol operating under a controlled environment can be less
   restrictive than the requirements of general internet.

   LISP-GPE scope of applicability is the same set of use cases covered
   by[I-D.ietf-lisp-rfc6830bis] for the LISP dataplane protocol.  The
   common property of these use cases is a large set of cooperating
   entities seeking to communicate over the public Internet or other
   large underlay IP infrastructures, while keeping the addressing and
   topology of the cooperating entities separate from the underlay and
   Internet topology, routing, and addressing.

   LISP-GPE is meant to be deployed in network environments operated by
   a single operator or adjacent set of cooperating network operators
   that fits with the definition of controlled environments in

   For the purpose of this document, a traffic-managed controlled
   environment (TMCE), outlined in [RFC8086], is defined as an IP
   network that is traffic-engineered and/or otherwise managed (e.g.,
   via use of traffic rate limiters) to avoid congestion.  Significant
   portions of text in this Section are based on [RFC8086].

   It is the responsibility of the network operators to ensure that the
   guidelines/requirements in this section are followed as applicable to
   their LISP-GPE deployments

4.2.  Congestion Control Functionality

   LISP-GPE does not natively provide congestion control functionality
   and relies on the payload protocol traffic for congestion control.
   As such LISP-GPE MUST be used with congestion controlled traffic or
   within a network that is traffic managed to avoid congestion (TMCE).
   An operator of a traffic managed network (TMCE) may avoid congestion
   by careful provisioning of their networks, rate-limiting of user data
   traffic and traffic engineering according to path capacity.

   Encapsulated payloads may have Explicit Congestion Notification
   mechanisms that may or may not be mapped to the outer IP header ECN
   field.  Such new encapsulated payolads, when registered with LISP-
   GPE, MUST be accompanied by a set of guidelines derived from
   [I-D.ietf-tsvwg-ecn-encap-guidelines] and [RFC6040].

4.3.  UDP Checksum

   For IP payloads, section 5.3 of [I-D.ietf-lisp-rfc6830bis] specifies
   how to handle UDP Checksums encouraging implementors to consider UDP
   checksum usage guidelines in section 3.4 of [RFC8085] when it is
   desirable to protect UDP and LISP headers against corruption.

   In order to provide integrity of LISP-GPE headers, options and
   payload, for example to avoid mis-delivery of payload to different
   tenant systems in case of data corruption, outer UDP checksum SHOULD
   be used with LISP-GPE when transported over IPv4.  The UDP checksum
   provides a statistical guarantee that a payload was not corrupted in
   transit.  These integrity checks are not strong from a coding or
   cryptographic perspective and are not designed to detect physical-
   layer errors or malicious modification of the datagram (see
   Section 3.4 of [RFC8085]).  In deployments where such a risk exists,
   an operator SHOULD use additional data integrity mechanisms such as
   offered by IPSec.

   An operator MAY choose to disable UDP checksum and use zero checksum
   if LISP-GPE packet integrity is provided by other data integrity
   mechanisms such as IPsec or additional checksums or if one of the
   conditions in Section 4.3.1 a, b, c are met.

   By default, UDP checksum MUST be used when LISP-GPE is transported
   over IPv6.  A tunnel endpoint MAY be configured for use with zero UDP
   checksum if additional requirements in Section 4.3.1 are met.

4.3.1.  UDP Zero Checksum Handling with IPv6

   When LISP-GPE is used over IPv6, UDP checksum is used to protect IPv6
   headers, UDP headers and LISP-GPE headers and payload from potential
   data corruption.  As such by default LISP-GPE MUST use UDP checksum
   when transported over IPv6.  An operator MAY choose to configure to
   operate with zero UDP checksum if operating in a traffic managed
   controlled environment as stated in Section 4.1 if one of the
   following conditions are met:

   a.  It is known that the packet corruption is exceptionally unlikely
       (perhaps based on knowledge of equipment types in their underlay
       network) and the operator is willing to take a risk of undetected
       packet corruption

   b.  It is judged through observational measurements (perhaps through
       historic or current traffic flows that use non zero checksum)
       that the level of packet corruption is tolerably low and where
       the operator is willing to take the risk of undetected corruption

   c.  LISP-GPE payload is carrying applications that are tolerant of
       misdelivered or corrupted packets (perhaps through higher layer
       checksum validation and/or reliability through retransmission)

   In addition LISP-GPE tunnel implementations using Zero UDP checksum
   MUST meet the following requirements:

   1.  Use of UDP checksum over IPv6 MUST be the default configuration
       for all LISP-GPE tunnels

   2.  If LISP-GPE is used with zero UDP checksum over IPv6 then such
       xTR implementation MUST meet all the requirements specified in
       section 4 of [RFC6936] and requirements 1 as specified in section
       5 of [RFC6936]

   3.  The ETR that decapsulates the packet SHOULD check the source and
       destination IPv6 addresses are valid for the LISP-GPE tunnel that
       is configured to receive Zero UDP checksum and discard other
       packets for which such check fails

   4.  The ITR that encapsulates the packet MAY use different IPv6
       source addresses for each LISP-GPE tunnel that uses Zero UDP
       checksum mode in order to strengthen the decapsulator's check of
       the IPv6 source address (i.e the same IPv6 source address is not
       to be used with more than one IPv6 destination address,
       irrespective of whether that destination address is a unicast or
       multicast address).  When this is not possible, it is RECOMMENDED
       to use each source address for as few LISP-GPE tunnels that use
       zero UDP checksum as is feasible

   5.  Measures SHOULD be taken to prevent LISP-GPE traffic over IPv6
       with zero UDP checksum from escaping into the general Internet.
       Examples of such measures include employing packet filters at the
       PETR and/or keeping logical or physical separation of LISP
       network from networks carrying General Internet

   The above requirements do not change either the requirements
   specified in [RFC2460] as modified by [RFC6935] or the requirements
   specified in [RFC6936].

   The requirement to check the source IPv6 address in addition to the
   destination IPv6 address, plus the recommendation against reuse of
   source IPv6 addresses among LISP-GPE tunnels collectively provide
   some mitigation for the absence of UDP checksum coverage of the IPv6
   header.  A traffic-managed controlled environment that satisfies at
   least one of three conditions listed at the beginning of this section
   provides additional assurance.

4.4.  Ethernet Encapsulated Payloads

   When a LISP-GPE router performs Ethernet encapsulation, the inner
   802.1Q [IEEE.802.1Q_2014] 3-bit priority code point (PCP) field MAY
   be mapped from the encapsulated frame to the 3-bit Type of Service
   field in the outer IPv4 header, or in the case of IPv6 the 'Traffic
   Class' field.

   When a LISP-GPE router performs Ethernet encapsulation, the inner
   header 802.1Q [IEEE.802.1Q_2014] VLAN Identifier (VID) MAY be mapped
   to, or used to determine the LISP Instance IDentifier (IID) field.

5.  Backward Compatibility

   LISP-GPE uses the same UDP destination port (4341) allocated to LISP.

   When encapsulating IP packets to a non LISP-GPE capable router the
   P-bit MUST be set to 0.  That is, the encapsulation format defined in
   this document MUST NOT be sent to a router that has not indicated
   that it supports this specification because such a router would
   ignore the P-bit (as described in [I-D.ietf-lisp-rfc6830bis]) and so
   would misinterpret the other LISP header fields possibly causing
   significant errors.

5.1.  Detection of ETR Capabilities

   The discovery of xTR capabilities to support LISP-GPE is out of the
   scope of this document.  Given that the applicability domain of LISP-
   GPE is a traffic-managed controlled environment, ITR/ETR (xTR)
   configuration mechanisms may be used for this purpose.

6.  IANA Considerations

6.1.  LISP-GPE Next Protocol Registry

   IANA is requested to set up a registry of LISP-GPE "Next Protocol".
   These are 8-bit values.  Next Protocol values in the table below are
   defined in this document.  New values are assigned under the
   Specification Required policy [RFC8126].  The protocols that are
   being assigned values do not themselves need to be IETF standards
   track protocols.

              | Next Protocol | Description | Reference     |
              | 0x00          | Reserved    | This Document |
              | 0x01          | IPv4        | This Document |
              | 0x02          | IPv6        | This Document |
              | 0x03          | Ethernet    | This Document |
              | 0x04          | NSH         | This Document |
              | 0x05..0x7F    | Unassigned  |               |
              | 0x82..0xFF    | Unassigned  |               |

7.  Security Considerations

   LISP-GPE security considerations are similar to the LISP security
   considerations and mitigation techniques documented in [RFC7835].

   LISP-GPE, as many encapsulations that use optional extensions, is
   subject to on-path adversaries that by manipulating the P-Bit and the
   packet itself can remove part of the payload or claim to encapsulate
   any protocol payload type.  Typical integrity protection mechanisms
   (such as IPsec) SHOULD be used in combination with LISP-GPE by those
   protocol extensions that want to protect from on-path attackers.

   With LISP-GPE, issues such as data-plane spoofing, flooding, and
   traffic redirection may depend on the particular protocol payload

8.  Acknowledgements and Contributors

   A special thank you goes to Dino Farinacci for his guidance and
   detailed review.

   This Working Group (WG) document originated as draft-lewis-lisp-gpe;
   the following are its coauthors and contributors along with their
   respective affiliations at the time of WG adoption.  The editor of
   this document would like to thank and recognize them and their
   contributions.  These coauthors and contributors provided invaluable
   concepts and content for this document's creation.

   o  Darrel Lewis, Cisco Systems, Inc.

   o  Fabio Maino, Cisco Systems, Inc.

   o  Paul Quinn, Cisco Systems, Inc.

   o  Michael Smith, Cisco Systems, Inc.

   o  Navindra Yadav, Cisco Systems, Inc.

   o  Larry Kreeger

   o  John Lemon, Broadcom

   o  Puneet Agarwal, Innovium

9.  References

9.1.  Normative References

              Farinacci, D., Fuller, V., Meyer, D., Lewis, D., and A.
              Cabellos-Aparicio, "The Locator/ID Separation Protocol
              (LISP)", draft-ietf-lisp-rfc6830bis-28 (work in progress),
              November 2019.

              IEEE, "IEEE Standard for Local and metropolitan area
              networks--Bridges and Bridged Networks", IEEE 802.1Q-2014,
              DOI 10.1109/ieeestd.2014.6991462, December 2014,

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,

   [RFC6040]  Briscoe, B., "Tunnelling of Explicit Congestion
              Notification", RFC 6040, DOI 10.17487/RFC6040, November
              2010, <>.

9.2.  Informative References

              Brockners, F., Bhandari, S., Govindan, V., Pignataro, C.,
              Gredler, H., Leddy, J., Youell, S., Mizrahi, T., Kfir, A.,
              Gafni, B., Lapukhov, P., and M. Spiegel, "VXLAN-GPE
              Encapsulation for In-situ OAM Data", draft-brockners-ippm-
              ioam-vxlan-gpe-03 (work in progress), November 2019.

              Briscoe, B., Kaippallimalil, J., and P. Thaler,
              "Guidelines for Adding Congestion Notification to
              Protocols that Encapsulate IP", draft-ietf-tsvwg-ecn-
              encap-guidelines-13 (work in progress), May 2019.

              Lemon, J., Maino, F., Smith, M., and A. Isaac, "Group
              Policy Encoding with VXLAN-GPE and LISP-GPE", draft-lemon-
              vxlan-lisp-gpe-gbp-02 (work in progress), April 2019.

   [RFC2460]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460,
              December 1998, <>.

   [RFC6935]  Eubanks, M., Chimento, P., and M. Westerlund, "IPv6 and
              UDP Checksums for Tunneled Packets", RFC 6935,
              DOI 10.17487/RFC6935, April 2013,

   [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,

   [RFC7348]  Mahalingam, M., Dutt, D., Duda, K., Agarwal, P., Kreeger,
              L., Sridhar, T., Bursell, M., and C. Wright, "Virtual
              eXtensible Local Area Network (VXLAN): A Framework for
              Overlaying Virtualized Layer 2 Networks over Layer 3
              Networks", RFC 7348, DOI 10.17487/RFC7348, August 2014,

   [RFC7835]  Saucez, D., Iannone, L., and O. Bonaventure, "Locator/ID
              Separation Protocol (LISP) Threat Analysis", RFC 7835,
              DOI 10.17487/RFC7835, April 2016,

   [RFC8085]  Eggert, L., Fairhurst, G., and G. Shepherd, "UDP Usage
              Guidelines", BCP 145, RFC 8085, DOI 10.17487/RFC8085,
              March 2017, <>.

   [RFC8086]  Yong, L., Ed., Crabbe, E., Xu, X., and T. Herbert, "GRE-
              in-UDP Encapsulation", RFC 8086, DOI 10.17487/RFC8086,
              March 2017, <>.

   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <>.

   [RFC8300]  Quinn, P., Ed., Elzur, U., Ed., and C. Pignataro, Ed.,
              "Network Service Header (NSH)", RFC 8300,
              DOI 10.17487/RFC8300, January 2018,

Authors' Addresses

   Fabio Maino (editor)
   Cisco Systems
   San Jose, CA  95134

   Jennifer Lemon
   270 Innovation Drive
   San Jose, CA  95134


   Puneet Agarwal


   Darrel Lewis
   Cisco Systems
   San Jose, CA  95134


   Michael Smith
   Cisco Systems
   San Jose, CA  95134