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Versions: (draft-spallagatti-bfd-vxlan) 00 01 02 03 04 05 06

BFD                                                   S. Pallagatti, Ed.
Internet-Draft                                                   Rtbrick
Intended status: Standards Track                             S. Paragiri
Expires: June 29, 2019                                  Juniper Networks
                                                             V. Govindan
                                                            M. Mudigonda
                                                                   Cisco
                                                               G. Mirsky
                                                               ZTE Corp.
                                                       December 26, 2018


                             BFD for VXLAN
                        draft-ietf-bfd-vxlan-06

Abstract

   This document describes the use of the Bidirectional Forwarding
   Detection (BFD) protocol in Virtual eXtensible Local Area Network
   (VXLAN) overlay 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 https://datatracker.ietf.org/drafts/current/.

   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 June 29, 2019.

Copyright Notice

   Copyright (c) 2018 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
   (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.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
     2.2.  Requirements Language . . . . . . . . . . . . . . . . . .   4
   3.  Use cases . . . . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  Deployment  . . . . . . . . . . . . . . . . . . . . . . . . .   5
   5.  BFD Packet Transmission over VXLAN Tunnel . . . . . . . . . .   6
     5.1.  BFD Packet Encapsulation in VXLAN . . . . . . . . . . . .   7
   6.  Reception of BFD packet from VXLAN Tunnel . . . . . . . . . .   8
     6.1.  Demultiplexing of the BFD packet  . . . . . . . . . . . .   8
   7.  Use of reserved VNI . . . . . . . . . . . . . . . . . . . . .   9
   8.  Echo BFD  . . . . . . . . . . . . . . . . . . . . . . . . . .   9
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
   10. Security Considerations . . . . . . . . . . . . . . . . . . .   9
   11. Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  10
   12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  10
   13. References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     13.1.  Normative References . . . . . . . . . . . . . . . . . .  10
     13.2.  Informational References . . . . . . . . . . . . . . . .  11
   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 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, discussed in section 3 [RFC7348], by providing Layer 2
   overlay scheme on a Layer 3 network.  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 VTEPs in hypervisors.  However, the
   concepts are equally applicable to non-virtualized hosts attached to
   VTEPs in switches.





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   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 VXLAN
   Tunnel End Point (VTEP) (hypervisor/TOR).  VTEPs (hypervisor/TOR) are
   responsible for encapsulating and decapsulating frames exchanged
   among VMs.

   Ability to monitor path continuity, i.e., perform proactive
   continuity check (CC) for these tunnels, is important.  The
   asynchronous mode of BFD, as defined in [RFC5880], can be used to
   monitor a VXLAN tunnel.  Use of [I-D.ietf-bfd-multipoint] is for
   future study.

   Also, BFD in VXLAN can be used to monitor the particular service
   nodes that are designated to handle Layer 2 broadcast properly,
   unknown unicast, and multicast traffic.  Such nodes, discussed in
   details in [RFC8293], are often referred to as "replicators", are
   usually virtual VTEPs and can be monitored by physical VTEPs to
   minimize BUM traffic directed to the unavailable replicator.

   This document describes the use of Bidirectional Forwarding Detection
   (BFD) protocol VXLAN to enable monitoring continuity of the path
   between Network Virtualization Edges (NVEs) and/or availability of a
   replicator service node using BFD.

   In this document, the terms NVE and VTEP are used interchangeably.

2.  Conventions used in this document

2.1.  Terminology

   BFD - Bidirectional Forwarding Detection

   CC - Continuity Check

   NVE - Network Virtualization Edge

   TOR - Top of Rack

   VM - Virtual Machine

   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.  Use cases

   The primary use case of BFD for VXLAN is for continuity check of a
   tunnel.  By exchanging BFD control packets between VTEPs, an operator
   exercises the VXLAN path in both the underlay and overlay thus
   ensuring the VXLAN path availability and VTEPs reachability.  BFD
   failure detection can be used for maintenance.  There are other use
   cases such as the following:

      Layer 2 VMs:

         Deployments might have VMs with only L2 capabilities and not
         have an IP address assigned or, in other cases, VMs are
         assigned IP address but are restricted to communicate only
         within their subnet.  BFD being an L3 protocol can be used as a
         tunnel CC mechanism, where BFD will start and terminate at the
         NVEs, e.g., VTEPs.

         It is possible to aggregate the CC sessions for multiple
         tenants by running a BFD session between the VTEPs over VxLAN
         tunnel.

      Fault localization:

         It is also possible that VMs are L3 aware and can host a BFD
         session.  In these cases, BFD sessions can be established among
         VMs for CC.  Also, BFD sessions can be created among VTEPs for
         tunnel CC.  Having a hierarchical OAM model helps localize
         faults though it requires additional consideration of, for
         example, coordination of BFD intervals across the OAM layers

      Service node reachability:

         The service node is responsible for sending BUM traffic.  In
         case a service node tunnel terminates at a VTEP, and that VTEP
         might not even host VM.  BFD session between TOR/hypervisor and
         service node can be used to monitor service node reachability.






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4.  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 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).  The
   implementation SHOULD have a reasonable upper bound on the number of
   BFD sessions that can be created between the same pair of VTEPs.  No
   BFD packets intended for a Hypervisor VTEP should be forwarded to a
   VM as a VM may drop BFD packets leading to a false negative.  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  | |
      | |         |  |         | |
      | +---------+  +---------+ |
      | Hypervisor VTEP (IP1)    |
      +--------------------------+
                            |
                            |
                            |
                            |   +-------------+
                            |   |   Layer 3   |
                            |---|   Network   |
                                |             |
                                +-------------+
                                    |
                                    |
                                    +-----------+
                                                |
                                                |
                                         +------------+-------------+
                                         |    Hypervisor VTEP (IP2) |
                                         | +----+----+  +----+----+ |
                                         | |VM2-1    |  |VM2-2    | |
                                         | |VNI 100  |  |VNI 200  | |
                                         | |         |  |         | |
                                         | +---------+  +---------+ |
                                         |      Server 2            |
                                         +--------------------------+



                     Figure 1: Reference VXLAN domain

5.  BFD Packet Transmission over VXLAN Tunnel

   BFD packet MUST be encapsulated and sent to a remote VTEP as
   explained in Section 5.1.  Implementations SHOULD ensure that the BFD
   packets follow the same lookup path as VXLAN data packets within the
   sender system.








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5.1.  BFD Packet Encapsulation in VXLAN

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

     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 Message                     ~
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                            FCS                                |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

           Figure 2: VXLAN Encapsulation of BFD Control Message





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   The BFD packet MUST be carried inside the inner MAC frame of the
   VXLAN packet.  The inner MAC frame carrying the BFD payload has the
   following format:

      Ethernet Header:

         Destination MAC: This MUST be the dedicated MAC TBA (Section 9)
         or the MAC address of the destination VTEP.  The details of how
         the MAC address of the destination VTEP is obtained are outside
         the scope of this document.

         Source MAC: MAC address of the originating VTEP

      IP header:

         Source IP: IP address of the originating VTEP.

         Destination IP: IP address of the terminating VTEP.

         TTL: MUST be set to 1 to ensure that the BFD packet is not
         routed within the L3 underlay network.

      The fields of the UDP header and the BFD control packet are
      encoded as specified in [RFC5881] for p2p VXLAN tunnels.

6.  Reception of BFD packet from VXLAN Tunnel

   Once a packet is received, VTEP MUST validate the packet as described
   in Section 4.1 of [RFC7348].  If the Destination MAC of the inner MAC
   frame matches the dedicated MAC or the MAC address of the VTEP the
   packet MUST be processed further.

   The UDP destination port and the TTL of the inner IP packet MUST be
   validated to determine if the received packet can be processed by
   BFD.  BFD packet with inner MAC set to VTEP or dedicated MAC address
   MUST NOT be forwarded to VMs.

   To ensure BFD detects the proper configuration of VXLAN Network
   Identifier (VNI) in a remote VTEP, a lookup SHOULD be performed with
   the MAC-DA and VNI as key in the Virtual Forwarding Instance (VFI)
   table of the originating/terminating VTEP to exercise the VFI
   associated with the VNI.

6.1.  Demultiplexing of the BFD packet

   Demultiplexing of IP BFD packet has been defined in Section 3 of
   [RFC5881].  Since multiple BFD sessions may be running between two
   VTEPs, there needs to be a mechanism for demultiplexing received BFD



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   packets to the proper session.  The procedure for demultiplexing
   packets with Your Discriminator equal to 0 is different from
   [RFC5880].  For such packets, the BFD session MUST be identified
   using the inner headers, i.e., the source IP, the destination IP, and
   the source UDP port number present in the IP header carried by the
   payload of the VXLAN encapsulated packet.  The VNI of the packet
   SHOULD be used to derive interface-related information for
   demultiplexing the packet.  If BFD packet is received with non-zero
   Your Discriminator, then BFD session MUST be demultiplexed only with
   Your Discriminator as the key.

7.  Use of reserved 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 in common.  When the single BFD session is used to
   monitor reachability of the remote VTEP, an implementation SHOULD use
   a VNI of 0.

8.  Echo BFD

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

9.  IANA Considerations

   IANA has assigned TBA as a dedicated MAC address from the IANA 48-bit
   unicast MAC address registry to be used as the Destination MAC
   address of the inner Ethernet of VXLAN when carrying BFD control
   packets.

10.  Security Considerations

   The document requires setting the inner IP TTL to 1 which could be
   used as a DDoS attack vector.  Thus the implementation MUST have
   throttling in place to control the rate of BFD control packets sent
   to the control plane.  Throttling MAY be relaxed for BFD packets
   based on port number.

   The implementation SHOULD have a reasonable upper bound on the number
   of BFD sessions that can be created between the same pair of VTEPs.

   Other than inner IP TTL set to 1 and limit the number of BFD sessions
   between the same pair of VTEPs, this specification does not raise any
   additional security issues beyond those of the specifications
   referred to in the list of normative references.






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11.  Contributors


   Reshad Rahman
   rrahman@cisco.com
   Cisco


12.  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, and Anoop Ghanwani for the
   extensive reviews and the most detailed and helpful comments.

13.  References

13.1.  Normative References

   [I-D.ietf-bfd-multipoint]
              Katz, D., Ward, D., Networks, J., and G. Mirsky, "BFD for
              Multipoint Networks", draft-ietf-bfd-multipoint-19 (work
              in progress), December 2018.

   [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>.





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   [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>.

13.2.  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>.

Authors' Addresses

   Santosh Pallagatti (editor)
   Rtbrick

   Email: santosh.pallagatti@gmail.com


   Sudarsan Paragiri
   Juniper Networks
   1194 N. Mathilda Ave.
   Sunnyvale, California  94089-1206
   USA

   Email: sparagiri@juniper.net


   Vengada Prasad Govindan
   Cisco

   Email: venggovi@cisco.com


   Mallik Mudigonda
   Cisco

   Email: mmudigon@cisco.com






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   Greg Mirsky
   ZTE Corp.

   Email: gregimirsky@gmail.com















































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