



BFD                                                   S. Pallagatti, Ed.
Internet-Draft                                                    VMware
Intended status: Informational                            G. Mirsky, Ed.
Expires: April 29, 2021                                        ZTE Corp.
                                                             S. Paragiri
                                                  Individual Contributor
                                                             V. Govindan
                                                            M. Mudigonda
                                                                   Cisco
                                                        October 26, 2020


                             BFD for VXLAN
                        draft-ietf-bfd-vxlan-16

Abstract

   This document describes the use of the Bidirectional Forwarding
   Detection (BFD) protocol in point-to-point Virtual eXtensible Local
   Area Network (VXLAN) tunnels used to form an overlay network.

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
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   This Internet-Draft will expire on April 29, 2021.

Copyright Notice

   Copyright (c) 2020 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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   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect



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   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.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions Used in this Document . . . . . . . . . . . . . .   3
     2.1.  Acronyms  . . . . . . . . . . . . . . . . . . . . . . . .   3
     2.2.  Requirements Language . . . . . . . . . . . . . . . . . .   4
   3.  Deployment  . . . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  Use of the Management VNI . . . . . . . . . . . . . . . . . .   5
   5.  BFD Packet Transmission over VXLAN Tunnel . . . . . . . . . .   6
   6.  Reception of BFD Packet from VXLAN Tunnel . . . . . . . . . .   8
   7.  Echo BFD  . . . . . . . . . . . . . . . . . . . . . . . . . .   8
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   10. Contributors  . . . . . . . . . . . . . . . . . . . . . . . .   9
   11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   9
   12. References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     12.1.  Normative References . . . . . . . . . . . . . . . . . .  10
     12.2.  Informational References . . . . . . . . . . . . . . . .  10
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  11

1.  Introduction

   "Virtual eXtensible Local Area Network" (VXLAN) [RFC7348] provides an
   encapsulation scheme that allows building an overlay network by
   decoupling the address space of the attached virtual hosts from that
   of the network.

   One use of VXLAN is in data centers interconnecting virtual machines
   (VMs) of a tenant.  VXLAN addresses requirements of the Layer 2 and
   Layer 3 data center network infrastructure in the presence of VMs in
   a multi-tenant environment by providing a Layer 2 overlay scheme on a
   Layer 3 network [RFC7348].  Another use is as an encapsulation for
   Ethernet VPN [RFC8365].

   This document is written assuming the use of VXLAN for virtualized
   hosts and refers to VMs and VXLAN Tunnel End Points (VTEPs) in
   hypervisors.  However, the concepts are equally applicable to non-
   virtualized hosts attached to VTEPs in switches.

   In the absence of a router in the overlay, a VM can communicate with
   another VM only if they are on the same VXLAN segment.  VMs are
   unaware of VXLAN tunnels as a VXLAN tunnel is terminated on a VTEP.




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   VTEPs are responsible for encapsulating and decapsulating frames
   exchanged among VMs.

   The ability to monitor path continuity, i.e., perform proactive
   continuity check (CC) for point-to-point (p2p) VXLAN tunnels, is
   important.  The asynchronous mode of BFD, as defined in [RFC5880], is
   used to monitor a p2p VXLAN tunnel.

   In the case where a Multicast Service Node (MSN) (as described in
   Section 3.3 of [RFC8293]) participates in VXLAN, the mechanisms
   described in this document apply and can, therefore, be used to test
   the continuity of the path between the source NVE and the MSN.

   This document describes the use of Bidirectional Forwarding Detection
   (BFD) protocol to enable monitoring continuity of the path between
   VXLAN VTEPs that are performing as Network Virtualization Endpoints,
   and/or between the source NVE and a replicator MSN using a Management
   VNI (Section 4).  All other uses of the specification to test toward
   other VXLAN endpoints are out of the scope.

2.  Conventions Used in this Document

2.1.  Acronyms

   BFD Bidirectional Forwarding Detection

   CC Continuity Check

   p2p Point-to-point

   MSN Multicast Service Node

   NVE Network Virtualization Endpoint

   VFI Virtual Forwarding Instance

   VM Virtual Machine

   VNI VXLAN Network Identifier (or VXLAN Segment ID)

   VTEP VXLAN Tunnel End Point

   VXLAN Virtual eXtensible Local Area Network








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2.2.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "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.

3.  Deployment

   Figure 1 illustrates the scenario with two servers, each of them
   hosting two VMs.  The servers host VTEPs that terminate two VXLAN
   tunnels with VXLAN Network Identifier (VNI) number 100 and 200
   respectively.  Separate BFD sessions can be established between the
   VTEPs (IP1 and IP2) for monitoring each of the VXLAN tunnels (VNI 100
   and 200).  Using a BFD session to monitor a set of VXLAN VNIs between
   the same pair of VTEPs might help to detect and localize problems
   caused by misconfiguration.  An implementation that supports this
   specification MUST be able to control the number of BFD sessions that
   can be created between the same pair of VTEPs.  This method is
   applicable whether the VTEP is a virtual or physical device.






























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      +------------+-------------+
      |        Server 1          |
      | +----+----+  +----+----+ |
      | |VM1-1    |  |VM1-2    | |
      | |VNI 100  |  |VNI 200  | |
      | |         |  |         | |
      | +---------+  +---------+ |
      |        VTEP (IP1)        |
      +--------------------------+
                            |
                            |   +-------------+
                            |   |   Layer 3   |
                            +---|   Network   |
                                +-------------+
                                    |
                                    +-----------+
                                                |
                                         +------------+-------------+
                                         |         VTEP (IP2)       |
                                         | +----+----+  +----+----+ |
                                         | |VM2-1    |  |VM2-2    | |
                                         | |VNI 100  |  |VNI 200  | |
                                         | |         |  |         | |
                                         | +---------+  +---------+ |
                                         |      Server 2            |
                                         +--------------------------+


                     Figure 1: Reference VXLAN Domain

   At the same time, a service layer BFD session may be used between the
   tenants of VTEPs IP1 and IP2 to provide end-to-end fault management
   (this use case is outside the scope of this document).  In such a
   case, for VTEPs, the BFD Control packets of that session are
   indistinguishable from data packets.

   For BFD Control packets encapsulated in VXLAN (Figure 2), the inner
   destination IP address SHOULD be set to one of the loopback addresses
   from 127/8 range for IPv4 or to one of IPv4-mapped IPv6 loopback
   addresses from ::ffff:127.0.0.0/104 range for IPv6.

4.  Use of the Management VNI

   In most cases, a single BFD session is sufficient for the given VTEP
   to monitor the reachability of a remote VTEP, regardless of the
   number of VNIs.  BFD control messages MUST be sent using the
   Management VNI which acts as the as control and management channel
   between VTEPs.  An implementation MAY support operating BFD on



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   another (non-Management) VNI although the implications of this are
   outside the scope of this document.  The selection of the VNI number
   of the Management VNI MUST be controlled through a management plane.
   An implementation MAY use VNI number 1 as the default value for the
   Management VNI.  All VXLAN packets received on the Management VNI
   MUST be processed locally and MUST NOT be forwarded to a tenant.

5.  BFD Packet Transmission over VXLAN Tunnel

   BFD packets MUST be encapsulated and sent to a remote VTEP as
   explained in this section.  Implementations SHOULD ensure that the
   BFD packets follow the same forwarding path as VXLAN data packets
   within the sender system.

   BFD packets are encapsulated in VXLAN as described below.  The VXLAN
   packet format is defined in Section 5 of [RFC7348].  The value in the
   VNI field of the VXLAN header MUST be set to the value selected as
   the Management VNI.  The Outer IP/UDP and VXLAN headers MUST be
   encoded by the sender as defined in [RFC7348].
































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     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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    ~                      Outer Ethernet Header                    ~
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    ~                        Outer IPvX Header                      ~
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    ~                        Outer UDP Header                       ~
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    ~                           VXLAN Header                        ~
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    ~                    Inner Ethernet Header                      ~
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    ~                        Inner IPvX Header                      ~
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    ~                         Inner UDP Header                      ~
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    ~                       BFD Control Packet                     ~
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                   Outer Ethernet FCS                          |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

            Figure 2: VXLAN Encapsulation of BFD Control Packet

   The BFD packet MUST be carried inside the inner Ethernet frame of the
   VXLAN packet.  The choice of Destination MAC and Destination IP
   addresses for the inner Ethernet frame MUST ensure that the BFD
   Control packet is not forwarded to a tenant but is processed locally
   at the remote VTEP.  The inner Ethernet frame carrying the BFD
   Control packet- has the following format:

      Ethernet Header:



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         Destination MAC: A Management VNI, which does not have any
         tenants, will have no dedicated MAC address for decapsulated
         traffic.  The value (TBD1) SHOULD be used in this field.

         Source MAC: MAC address associated with the originating VTEP.

         Ethertype: is set to 0x0800 if the inner IP header is IPv4, and
         is set to 0x86DD if the inner IP header is IPv6.

      IP header:

         Destination IP: IP address MUST NOT be of one of tenant's IP
         addresses.  The IP address SHOULD be selected from the range
         127/8 for IPv4, for IPv6 - from the range ::ffff:127.0.0.0/104.
         Alternatively, the destination IP address MAY be set to VTEP's
         IP address.

         Source IP: IP address of the originating VTEP.

         TTL or Hop Limit: MUST be set to 255 in accordance with
         [RFC5881].

      The fields of the UDP header and the BFD Control packet are
      encoded as specified in [RFC5881].

6.  Reception of BFD Packet from VXLAN Tunnel

   Once a packet is received, the VTEP MUST validate the packet.  If the
   packet is received on the management VNI and is identified as BFD
   control packet addressed to the VTEP, and then the packet can be
   processed further.  Processing of BFD control packets received on
   non-management VNI is outside the scope of this specification.

   The received packet's inner IP payload is then validated according to
   Sections 4 and 5 in [RFC5881].

7.  Echo BFD

   Support for echo BFD is outside the scope of this document.

8.  IANA Considerations

   IANA is requested to assign a single MAC address to the value TBD1
   from the "IANA Unicast 48-bit MAC Address" registry from the
   "Unassigned (small allocations)" block.  The Usage field will be "BFD
   for VXLAN" with a Reference field of this document.





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9.  Security Considerations

   Security issues discussed in [RFC5880], [RFC5881], and [RFC7348]
   apply to this document.

   This document recommends using an address from the Internal host
   loopback addresses 127/8 range for IPv4 or an IP4-mapped IPv6
   loopback address from ::ffff:127.0.0.0/104 range for IPv6 as the
   destination IP address in the inner IP header.  Using such an address
   prevents the forwarding of the encapsulated BFD control message by a
   transient node in case the VXLAN tunnel is broken as according to
   [RFC1812].

      A router SHOULD NOT forward, except over a loopback interface, any
      packet that has a destination address on network 127.  A router
      MAY have a switch that allows the network manager to disable these
      checks.  If such a switch is provided, it MUST default to
      performing the checks.

   The use of IPv4-mapped IPv6 addresses has the same property as using
   the IPv4 network 127/8, moreover, the IPv4-mapped IPv6 addresses
   prefix is not advertised in any routing protocol.

   If the implementation supports establishing multiple BFD sessions
   between the same pair of VTEPs, there SHOULD be a mechanism to
   control the maximum number of such sessions that can be active at the
   same time.

10.  Contributors


   Reshad Rahman
   rrahman@cisco.com
   Cisco


11.  Acknowledgments

   Authors would like to thank Jeff Haas of Juniper Networks for his
   reviews and feedback on this material.

   Authors would also like to thank Nobo Akiya, Marc Binderberger,
   Shahram Davari, Donald E.  Eastlake 3rd, Anoop Ghanwani, Dinesh Dutt,
   Joel Halpern, and Carlos Pignataro for the extensive reviews and the
   most detailed and constructive comments.






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12.  References

12.1.  Normative References

   [RFC1812]  Baker, F., Ed., "Requirements for IP Version 4 Routers",
              RFC 1812, DOI 10.17487/RFC1812, June 1995,
              <https://www.rfc-editor.org/info/rfc1812>.

   [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>.

   [RFC5880]  Katz, D. and D. Ward, "Bidirectional Forwarding Detection
              (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010,
              <https://www.rfc-editor.org/info/rfc5880>.

   [RFC5881]  Katz, D. and D. Ward, "Bidirectional Forwarding Detection
              (BFD) for IPv4 and IPv6 (Single Hop)", RFC 5881,
              DOI 10.17487/RFC5881, June 2010,
              <https://www.rfc-editor.org/info/rfc5881>.

   [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,
              <https://www.rfc-editor.org/info/rfc7348>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

12.2.  Informational References

   [RFC8293]  Ghanwani, A., Dunbar, L., McBride, M., Bannai, V., and R.
              Krishnan, "A Framework for Multicast in Network
              Virtualization over Layer 3", RFC 8293,
              DOI 10.17487/RFC8293, January 2018,
              <https://www.rfc-editor.org/info/rfc8293>.

   [RFC8365]  Sajassi, A., Ed., Drake, J., Ed., Bitar, N., Shekhar, R.,
              Uttaro, J., and W. Henderickx, "A Network Virtualization
              Overlay Solution Using Ethernet VPN (EVPN)", RFC 8365,
              DOI 10.17487/RFC8365, March 2018,
              <https://www.rfc-editor.org/info/rfc8365>.





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Authors' Addresses

   Santosh Pallagatti (editor)
   VMware

   Email: santosh.pallagatti@gmail.com


   Greg Mirsky (editor)
   ZTE Corp.

   Email: gregimirsky@gmail.com


   Sudarsan Paragiri
   Individual Contributor

   Email: sudarsan.225@gmail.com


   Vengada Prasad Govindan
   Cisco

   Email: venggovi@cisco.com


   Mallik Mudigonda
   Cisco

   Email: mmudigon@cisco.com





















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