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INTERNET-DRAFT                                              Sami Boutros
Intended Status: Standard Track                              Ankur Dubey
                                                                  VMware

                                                           Reshad Rahman
                                                                   Cisco

Expires: May 31, 2018                                  November 27, 2017


                     Service Redundancy using BFD
                 draft-adubey-bfd-service-redundancy-01


Abstract

   In a data center, when multiple routing/service nodes are providing
   single active redundancy for a set of L2, L3 and/or L4-L7 services.
   Both non-revertive and revertive fail over modes are required for the
   services. This draft describes a method to achieve the non-revertive
   and revertive fail over modes for services using Bidirectional
   Forwarding Detection (BFD).

Status of this Memo

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

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as
   Internet-Drafts.

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   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at
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Copyright and License Notice

   Copyright (c) 2017 IETF Trust and the persons identified as the



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   document authors. All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://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
   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  . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1  Terminology . . . . . . . . . . . . . . . . . . . . . . . .  3
   2. Solution Overview . . . . . . . . . . . . . . . . . . . . . . .  4
     2.1 Node failover  . . . . . . . . . . . . . . . . . . . . . . .  4
     2.2 Per service failover for non-revertive services  . . . . . .  5
   3 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . .  6
   4 Security Considerations  . . . . . . . . . . . . . . . . . . . .  6
   5  IANA Considerations . . . . . . . . . . . . . . . . . . . . . .  6
   6  References  . . . . . . . . . . . . . . . . . . . . . . . . . .  6
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . .  6

























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1  Introduction

   This document describes how can a group of service/routing nodes in a
   data center providing single active redundancy for multiple L2/L3
   and/or L4/L7 services, can use BFD protocol to support non-revertive
   as well as revertive fail over mode.

   Typically, BFD is used between the group of service nodes to verify
   the connectivity as well as the aliveness of the service nodes. The
   assignment of which node in the group is the primary designated
   forwarder for a given service can be determined using a centralized
   or distributed control plane.

   The use of BFD will be to communicate the set of services that are
   being currently active on a given service node to the other service
   nodes. On a given node failure, for a given service the backup node
   will take over. If the service was configured to have a non-revertive
   fail over mode, then the backup node should continue to perform the
   service forwarding even after the primary node recovers and comes
   back up. In order to do that, the backup node MUST inform the primary
   node that it is currently active for the service. This is achieved
   through the extension we are proposing to the BFD protocol as will be
   described in the following sections.

   It is to be noted that for revertive fail over mode of operation, the
   primary node should be able to take over the active role from the
   backup node when the primary node goes back to an operational state.
   This can be as well communicated using the BFD session establishment
   between the primary node and the backup node.

1.1  Terminology

   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].
















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2. Solution Overview



                  +----------+
                  |Controller|
                  +----------+
                  //    |    \
                //      |      \
              //        |        \
      +-------+     +-------+     +-------+
      |Node1  |-BFD-|Node2  |-BFD-|Node3  |
      +-------+     +-------+     +-------+
           |--------------BFD--------|


   Figure 1:

   Figure 1 shows 3 routing nodes using BFD to implement the single
   active redundancy for revertive and non-revertive services. More than
   3 routing nodes can be used.

   Multiple L2/L3 and/or L4/L7 services are offered in a data center by
   a set of routing/service nodes providing single active redundancy.
   The provisioning of the services can be done using a centralized
   control plane implemented in a controller or using a distributed
   dynamic control plane.

2.1 Node failover

   An implementation MAY choose to support only node failover and not a
   per service failover. A node can be primary or backup for a given
   service. On a primary node failure, all non-revertive and revertive
   services will become active on the backup node.

   In figure 1, lets assume that Node1 is the primary node for a set A
   of non-revertive services with node2 as backup, and another set B of
   non-revertive services with Node3 as backup. As well, Node1 is
   primary for a set C of revertive services with Node2 as backup and,
   another set D of revertive services with Node3 as backup.

   If Node1 fails, Node2 and Node3 will set a new diag code in the BFD
   control packet. This diag code will inform Node1 that both Node2 and
   Node3 didn't fail, and Node1 MUST NOT activate the non-revertive set
   of services A and B respectively, when it comes back up. The BFD
   control packet with the new diag code will be sent after the BFD
   session came up for at least twice the detection multiplier count.




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   Therefore, Node1 upon receiving the BFD control packet with the new
   diag code, MUST not attempt to activate the non-revertive services,
   but remain in standby state for the non-revertive services until the
   Node2 or Node3 that took over fails.

   Revertive services are assumed to revert back to the primary node
   Node1, after the node recovers. Once the BFD session comes up between
   the primary and backup nodes, the backup node should stop forwarding
   for any revertive services. A node MUST start forwarding all
   revertive services for which it is configured as a primary once the
   BFD session comes up with the corresponding backup nodes. A node MUST
   stop forwarding for revertive services for which it is a backup once
   the BFD session comes up with the corresponding primary.

2.2 Per service failover for non-revertive services

   An implementation MAY choose to support per service failover for non-
   revertive services. For example, in figure1, some non-revertive
   services could be active on Node1 while some non-revertive services
   could be active on Node2 or Node3 for better load balancing of
   services traffic. In this mode, every L2/L3 and/or L4/L7 non-
   revertive service will be identified by a unique ID known across the
   routing/service nodes providing the services.

   A bitmap will be used to represent the non-revertive services, where
   each non-revertive service is represented by one bit in the bitmap.
   All the service nodes MUST have the same mapping of the bit position
   to the non-revertive service unique ID. The bitmap position and the
   unique service ID could be maintained by a network controller.

   A node that is assigned as backup for a given non-revertive service
   node will take over as active in either of the following cases: 1)
   The node assigned as primary for this service failed. 2) This
   specific service failed on the primary node for this service.

   In case 1, the BFD session will go down since it is a node failure.
   In case 2, BFD session between the nodes will remain up. In either
   scenarios, the node assigned as secondary will become active for the
   non-revertive service. In case 1, the secondary node will set the new
   diag code in the BFD control packets once the BFD session is
   established. The new diag code will be set in the BFD control packets
   for at least twice the detection multiplier count. In case 2, this
   diag code will be set in the next BFD control packets sent after the
   node takes over as Active for a given non-revertive service. If there
   is at least one non-revertive service for which this node is not
   active AND at least 1 non-revertive service for which it is active,
   the node will also send the bitmap in the BFD control packets
   payload. The bits identifying the active non-revertive services will



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   be set in this bitmap. The new diag code and the optional bitmap
   payload will be sent in the BFD control packets for at least twice
   the detection multiplier count.

   Therefore, if a node receives a BFD control packet with the new diag
   code set but no payload in the BFD control packet, this means that it
   MUST NOT activate all non-revertive services for which this node is
   primary. Whereas, if a payload is present in the BFD control packet
   that has the new diag code set, the receiving node MUST NOT activate
   the non-revertive services indicated by the set bits in the bitmap.

   Per service failover is not applicable to revertive services. They
   will behave the same way as described in section 2.1


3 Acknowledgements


4 Security Considerations

   This document does not introduce any additional security constraints.

5  IANA Considerations

   IANA is requested to assign a new diag code from the "BFD Diagnostic
   Codes"


       Value    BFD Diagnostic Code Name
       -----    ------------------------------------------------
       0xNN     Out-lived and optional BitMap BFD control packet
                payload for non-revertive services.



6  References

   [RFC5880] D. Katz, D. Ward "Bidirectional Forwarding Detection
   (BFD)".



Authors' Addresses


   Sami Boutros
   VMware
   Email: sboutros@vmware.com



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   Ankur Dubey
   VMware
   Email: adubey@vmware.com

   Reshad Rahman
   Cisco
   Email: rrahman@cisco.com












































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