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Versions: 00 01 02 03 04 05 draft-ietf-bfd-stability

Routing Working Group                                          A. Mishra
Internet-Draft                                           M. Jethanandani
Intended status: Standards Track                               A. Saxena
Expires: December 12, 2015                             Ciena Corporation
                                                           S. Pallagatti
                                                        Juniper Networks
                                                                 M. Chen
                                                                  Huawei
                                                                  P. Fan
                                                            China Mobile
                                                           June 10, 2015


                             BFD Stability
                   draft-ashesh-bfd-stability-03.txt

Abstract

   This document describes extensions to the Bidirectional Forwarding
   Detection (BFD) protocol to measure BFD stability.  Specifically, it
   describes a mechanism for detection of BFD frame loss.

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 <xref
   target="RFC2119">RFC 2119</xref>.

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 http://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 December 12, 2015.






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Copyright Notice

   Copyright (c) 2015 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
   (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  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Use cases . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  BFD Null-Authentication TLV . . . . . . . . . . . . . . . . .   3
   4.  Theory of Operations  . . . . . . . . . . . . . . . . . . . .   4
     4.1.  Loss Measurement  . . . . . . . . . . . . . . . . . . . .   4
     4.2.  Delay Measurement . . . . . . . . . . . . . . . . . . . .   5
   5.  IANA Requirements . . . . . . . . . . . . . . . . . . . . . .   5
   6.  Security Consideration  . . . . . . . . . . . . . . . . . . .   6
   7.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .   6
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   6
   9.  Normative References  . . . . . . . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   The Bidirectional Forwarding Detection (BFD) protocol operates by
   transmitting and receiving control frames, generally at high
   frequency, over the datapath being monitored.  In order to prevent
   significant data loss due to a datapath failure, the tolerance for
   lost or delayed frames (the Detection Time as described in RFC 5880)
   is set to the smallest feasible value.

   This document proposes a mechanism to detect delayed or lost frames
   in a BFD session in addition to the datapath fault detection
   mechanisms of BFD.  Such a mechanism presents significant value with
   the ability to measure the stability of BFD sessions and provides
   data to the operators.

   This document does not propose BFD extension to measure data traffic
   loss or delay on a link or tunnel and the scope is limited to BFD
   frames.



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2.  Use cases

   Legacy BFD can't detect any BFD frame delay or loss if delay or loss
   does not last for dead interval.  Frequent delay or loss of BFD
   frames could potentially lead to flap.

   It may be possible that network has healthy link or tunnel but only
   BFD frames are getting dropped or delayed.  This potentially leads to
   network convergence or use of suboptimal path when fast reroute is
   enabled such as:

      Routing protocols with LFA enabled, BFD is used to monitor the
      link.

      Aggregate Ethernet with BFD to monitor each member link.

      Primary and protected tunnels with BFD to monitor tunnels.

   This proposal will help BFD session to give more information to
   operator about the health of BFD session that could be used to avoid
   BFD session flap with faulty BFD path on a healthy link or tunnel.

   In a faulty link or tunnel scenario operator can use BFD health
   information to dynamically run delay and loss measurement OAM
   protocol (CFM or LM-DM) to further isolate the issue.

3.  BFD Null-Authentication TLV

   The functionality proposed for BFD stability measurement is achieved
   by appending the Null-Authentication TLV to the BFD control frame.

   The Null-Authentication TLV (called 0-Auth in this document) extends
   the existing BFD Authentication TLV structure by adding a new Auth-
   Type of <IANA Assigned>.  This TLV carries the Sequence Number for
   frame loss measurement and optional sender timestmap.

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   Auth Type   |   Auth Len    |  Auth Key ID  |   Reserved    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                        Sequence Number                        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                      Sender timestmap                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   where:




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   Auth Type: The Authentication Type, which in this case is <IANA
   assigned> (Null Authentication).

   Auth Len: The length of the Authentication Section, in bytes.  Length
   depends on the Auth Key ID.

   Auth Key ID: The Authentication Key ID is used to control optional
   feature.  Vales are:

                   0 -- BFD loss measurement
                   1 -- BFD loss and delay measurement
               2-255 -- Reserved for future use

   when value is set to 0 then last 4 bytes of this TLV MUST not be
   present in the packet, Auth Len MUST be set to 8 bytes.  When set to
   1 Auth Len MUST be set to 12.

   Sequence Number: This indicates the sequence number for this packet
   and MUST be present in every 0-Auth TLV.  This value is incremented
   by 1 for every frame transmitted while the session state is UP.  A
   value of 0 indicates a request by sender to reset the sequence number
   correlation logic at the receiver.  The first frame transmitted by
   the sender MAY set this field to 0.

   Sender timestamp: MUST be set to time when packet is about to leave
   the sender system.  Sender system MAY time stamp this as close to
   wire when packet is about to leave system.  Details of how sender
   system timestamps is out of the scope of this document.

4.  Theory of Operations

   This mechanism allows operator to measure the loss and delay of BFD
   CC frames.

4.1.  Loss Measurement

   This measurement counts the number of BFD control frames missed at
   the receiver due to a transient change in the network such as
   congestion.  Frame-loss is detected by comparing the Sequence Number
   field in the 0-Auth TLV in successive BFD CC frames.  The Sequence
   Number in each successive control frame generated on a BFD session by
   the transmitter is incremented by one.

   The first BFD 0-Auth TLV processed by the receiver that has a non-
   zero sequence number is used for bootstrapping the logic.  Each
   successive frame after this is expected to have a Sequence Number
   that is one greater than the Sequence Number in the previous frame.




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   BFD being aggressive protocol, sequence number may wrap to 0 within
   few hundred days.  Sender MUST ensure that when sequence number is
   wrapped, it starts with value 1.  Receiver MUST accept this BFD
   packet and adjust his next anticipated sequence number.

4.2.  Delay Measurement

   Delay measurement can be done in two ways.

      Using sender timestamp in 0-Auth TLV:

         If AuthKey ID in 0-Auth TLV is set to 1 then sender timestamp
         MUST be set.  Delay measurement is the difference between the
         sender timestamp on any two consecutive BFD CC frames that
         carry the 0-Auth TLV with AuthKey ID set to 1 for a session.
         This is a key metric to determine transient changes in
         stability of BFD transmission engine or to determine the
         systems capability of handling the existing load.  A
         significant deviation from the negotiated transmission interval
         on the local node indicates potential instabilities in the BFD
         transmission engine.  Based on the timestamp measurements, the
         operator MAY take action to configure the system to maintain
         normal operation of the node.

         Similar delay measurements on the receiver can be made using
         timestamps in the meta data when packet is received.  In
         conjunction with sender delay measurements, these can indicate
         delays caused by data-path.  While a constant delay may not be
         indicator of instability, large transient delays can decrease
         the BFD session stability significantly.

      Using centralized controller:

         When AuthKey ID in 0-Auth TLV is set to 0 then sender timestmap
         will not be present in the packet.  Peers MAY still choose to
         do delay measurement by sending their packet sent timestamps to
         central control unit.  Central control unit MAY gather all
         timestamp information and can do delay calculation for a BFD
         session.  Details of how BFD component sends timestamps to
         central unit is outside the scope of this document.

5.  IANA Requirements

   IANA is requested to assign new Auth-Type for the Null-Authentication
   TLV for BFD Stability Measurement.  The following number is
   suggested.

   Value Meaning



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   6 Null-Authentication TLV

6.  Security Consideration

   Other than concerns raised in [RFC5880] there are no new concerns
   with this proposal.

7.  Contributors

   Manav Bhatia
   manav@ionosnetworks.com
   Ionos Networks
   Bangalore, India

8.  Acknowledgements

   Authors would like to thank Nobo Akiya, Jeffery Haas, Peng Fan,
   Dileep Singh, Basil Saji, Sagar Soni and Mallik Mudigonda who also
   contributed to this document.

9.  Normative References

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

   [RFC5880]  Katz, D. and D. Ward, "Bidirectional Forwarding Detection
              (BFD)", RFC 5880, June 2010.

Authors' Addresses

   Ashesh Mishra
   Ciena Corporation
   3939 North 1st Street
   San Jose, CA  95134
   USA

   Email: mishra.ashesh@gmail.com
   URI:   www.ciena.com


   Mahesh Jethanandani
   Ciena Corporation
   3939 North 1st Street
   San Jose, CA  95134
   USA

   Email: mjethanandani@gmail.com
   URI:   www.ciena.com



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   Ankur Saxena
   Ciena Corporation
   3939 North 1st Street
   San Jose, CA  95134
   USA

   Email: ankurpsaxena@gmail.com


   Santosh Pallagatti
   Juniper Networks
   Juniper Networks, Exora Business Park
   Bangalore, Karnataka  560103
   India

   Phone: +
   Email: santoshpk@juniper.net


   Mach Chen
   Huawei

   Email: mach.chen@huawei.com


   Peng Fan
   China Mobile
   32 Xuanwumen West Street
   Beijing, Beijing
   China

   Email: fanp08@gmail.com



















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