draft-ietf-bfd-intervals-01.txt   draft-ietf-bfd-intervals-02.txt 
Internet Engineering Task Force N. Akiya Internet Engineering Task Force N. Akiya
Internet-Draft M. Binderberger Internet-Draft M. Binderberger
Intended status: Informational Cisco Systems Intended status: Informational Cisco Systems
Expires: December 13, 2014 G. Mirsky Expires: January 28, 2015 G. Mirsky
Ericsson Ericsson
June 11, 2014 July 27, 2014
Common Interval Support in BFD Common Interval Support in BFD
draft-ietf-bfd-intervals-01 draft-ietf-bfd-intervals-02
Abstract Abstract
Some BFD implementations may be restricted to only support several Some BFD implementations may be restricted to only support several
interval values. When such BFD implementations speak to each other, interval values. When such BFD implementations speak to each other,
there is a possibility of two sides not being able to find a common there is a possibility of two sides not being able to find a common
interval value to run BFD sessions. interval value to run BFD sessions.
This document defines a small set of interval values for BFD that we This document defines a small set of interval values for BFD that we
call "Common intervals", and recommends implementations to support call "Common intervals", and recommends implementations to support
skipping to change at page 1, line 34 skipping to change at page 1, line 34
simplified implementation as seen for hardware-based BFD. It does simplified implementation as seen for hardware-based BFD. It does
not restrict an implementation from supporting more intervals in not restrict an implementation from supporting more intervals in
addition to the Common intervals. addition to the Common intervals.
Requirements Language Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119]. document are to be interpreted as described in RFC 2119 [RFC2119].
Status of this Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on December 13, 2014. This Internet-Draft will expire on January 28, 2015.
Copyright Notice Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the Copyright (c) 2014 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. The problem with few supported intervals . . . . . . . . . . . 3 2. The problem with few supported intervals . . . . . . . . . . 3
3. Well-defined, common intervals . . . . . . . . . . . . . . . . 4 3. Well-defined, common intervals . . . . . . . . . . . . . . . 3
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 5 5. Security Considerations . . . . . . . . . . . . . . . . . . . 4
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 5 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
7.1. Normative References . . . . . . . . . . . . . . . . . . . 5 7.1. Normative References . . . . . . . . . . . . . . . . . . 5
7.2. Informative References . . . . . . . . . . . . . . . . . . 5 7.2. Informative References . . . . . . . . . . . . . . . . . 5
Appendix A. Why some intervals are in the common set . . . . . . . 5 Appendix A. Why some intervals are in the common set . . . . . . 5
Appendix B. Timer adjustment with non-identical interval sets . . 6 Appendix B. Timer adjustment with non-identical interval sets . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction 1. Introduction
The standard [RFC5880] describes how to calculate the transmission The standard [RFC5880] describes how to calculate the transmission
interval and the detection time. It does not make any statement interval and the detection time. It does not make any statement
though how to solve a situation where one BFD speaker cannot support though how to solve a situation where one BFD speaker cannot support
the calculated value. In practice this may not been a problem as 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 long as software-implemented timers have been used and as long as the
granularity of such timers was small compared to the interval values 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 being supported, i.e. as long as the error in the timer interval was
skipping to change at page 4, line 40 skipping to change at page 4, line 21
20msec, 50msec, 100msec and 1sec. 20msec, 50msec, 100msec and 1sec.
In addition support for 10sec interval together with multiplier In addition support for 10sec interval together with multiplier
values up to 255 is recommended to support graceful restart. values up to 255 is recommended to support graceful restart.
The adjustment is always towards larger, i.e. slower, interval values The adjustment is always towards larger, i.e. slower, interval values
when the initial interval proposed by the peer is not supported. when the initial interval proposed by the peer is not supported.
This document is not adding new requirements with respect to how This document is not adding new requirements with respect to how
exact a timer value must be implemented. Supporting an interval exact a timer value must be implemented. Supporting an interval
value means to advertise this value in the DesiredMinTxInterval value means to advertise this value in the DesiredMinTxInterval and/
and/or RequiredMinRxInterval field of the BFD packets and to provide or RequiredMinRxInterval field of the BFD packets and to provide
timers that are reasonably close. [RFC5880] defines safety margins timers that are reasonably close. [RFC5880] defines safety margins
for the timers by defining a jitter range. for the timers by defining a jitter range.
How is the "Common interval set" used exactly? In the example above, How is the "Common interval set" used exactly? In the example above,
vendor "A" has a fastest interval of 10msec and thus would be vendor "A" has a fastest interval of 10msec and thus would be
required to support all intervals in the common set that are equal or required to support all intervals in the common set that are equal or
larger than 10msec, i.e. it would support 10msec, 20msec, 50msec, larger than 10msec, i.e. it would support 10msec, 20msec, 50msec,
100msec, 1sec. Vendor "B" has a fastest interval of 20msec and thus 100msec, 1sec. Vendor "B" has a fastest interval of 20msec and thus
would need to support 20msec, 50msec, 100msec and 1sec. As long as would need to support 20msec, 50msec, 100msec and 1sec. As long as
this requirement is met for the common set of values, then both this requirement is met for the common set of values, then both
skipping to change at page 5, line 38 skipping to change at page 5, line 21
[RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection [RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection
(BFD)", RFC 5880, June 2010. (BFD)", RFC 5880, June 2010.
7.2. Informative References 7.2. Informative References
[G.8013_Y.1731] [G.8013_Y.1731]
ITU-T G.8013/Y.1731, "ITU-T OAM functions and mechanisms ITU-T G.8013/Y.1731, "ITU-T OAM functions and mechanisms
for Ethernet based network", November 2013. for Ethernet based network", November 2013.
[GR-253-CORE]
Telcordia Technologies, Inc., "Synchronous Optical Network
(SONET) Transport Systems: Common Generic Criteria",
October 2009.
Appendix A. Why some intervals are in the common set Appendix A. Why some intervals are in the common set
The list of common interval values is trying to balance various The list of common interval values is trying to balance various
objectives. The list should not contain too many values as more objectives. The list should not contain too many values as more
timers may increase the implementation costs. On the other hand less timers may increase the implementation costs. On the other hand less
values produces larger gaps and adjustment jumps. More values in the values produces larger gaps and adjustment jumps. More values in the
lower interval range is thus seen as critical to support customer lower interval range is thus seen as critical to support customer
needs for fast detection in setups with multiple vendors. needs for fast detection in setups with multiple vendors.
o 3.3msec: required by MPLS-TP o 3.3msec: required by MPLS-TP, adopting the detection time of
10msec from [GR-253-CORE].
o 10msec: general consensus is to support 10msec. o 10msec: general consensus is to support 10msec. Multiple vendors
plan to or do already implement 10msec.
o 20msec: basically avoids a larger gap in this critical interval o 20msec: basically avoids a larger gap in this critical interval
region. Still allows 50-60msec detect and restore (with region. Still allows 50-60msec detect and restore (with
multiplier of 2) and covers existing software-based multiplier of 2) and covers existing software-based
implementations. implementations.
o 50msec: widely deployed interval. Supporting this value reflects o 50msec: widely deployed interval. Supporting this value reflects
reality of many BFD implementations today. reality of many BFD implementations today.
o 100msec: similar to 10msec this value allows the reuse of o 100msec: similar to 10msec this value allows the reuse of
 End of changes. 10 change blocks. 
21 lines changed or deleted 28 lines changed or added

This html diff was produced by rfcdiff 1.41. The latest version is available from http://tools.ietf.org/tools/rfcdiff/