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Standardized interval support in BFD
draft-akiya-bfd-intervals-04

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Last updated: 2013-11-13
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Internet Engineering Task Force                                 N. Akiya
Internet-Draft                                           M. Binderberger
Intended status: Informational                             Cisco Systems
Expires: May 17, 2014                                  November 13, 2013

                  Standardized interval support in BFD
                      draft-akiya-bfd-intervals-04

Abstract

   This document defines a set of interval values that we call "Standard
   intervals".  Values of this set must be supported for transmitting
   BFD control packets and for calculating the detection time in the
   receive direction when the value is equal or larger than the fastest,
   i.e. lowest, interval a particular BFD implementation supports.

   This solves the problem of finding an interval value that both BFD
   speakers can support while allowing a simplified implementation as
   seen for hardware-based BFD.  It does not restrict an implementation
   from supporting more intervals in addition to the Standard intervals.

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 RFC 2119 [RFC2119].

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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   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 May 17, 2014.

Copyright Notice

   Copyright (c) 2013 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
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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  The problem with few supported intervals  . . . . . . . . . . . 3
   3.  Well-defined, standardized intervals  . . . . . . . . . . . . . 4
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
   5.  Security Considerations . . . . . . . . . . . . . . . . . . . . 5
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 5
   7.  Normative References  . . . . . . . . . . . . . . . . . . . . . 5
   Appendix A.  Why some intervals are in the standard set . . . . . . 5
   Appendix B.  Timer adjustment with non-identical interval sets  . . 6
   Appendix C.  Open/upcoming topics . . . . . . . . . . . . . . . . . 7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 8

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1.  Introduction

   The standard [RFC5880] describes how to calculate the transmission
   interval and the detection time.  It does not make any statement
   though how so solve a situation where one BFD speaker cannot support
   the calculated value.  In practice this may not been a problem as
   long as software-implemented timers have been used and as long as the
   granularity of such timers was small compared to the interval values
   being supported, i.e. as long as the error in the timer interval was
   small compared to 25 percent jitter.

   In the meantime requests exist for very fast interval values, down to
   3.3msec for MPLS-TP.  At the same time the requested scale for the
   number of BFD sessions in increasing.  Both requirements have driven
   vendors to use Network Processors (NP), FPGAs or other hardware-based

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