draft-ietf-bfd-intervals-04.txt   draft-ietf-bfd-intervals-05.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 Updates: RFC5880 (if approved) Cisco Systems
Expires: March 6, 2015 G. Mirsky Intended status: Informational G. Mirsky
Ericsson Expires: April 17, 2015 Ericsson
September 2, 2014 October 14, 2014
Common Interval Support in Bidirectional Forwarding Detection Common Interval Support in Bidirectional Forwarding Detection
draft-ietf-bfd-intervals-04 draft-ietf-bfd-intervals-05
Abstract Abstract
Bidirectional Forwarding Detection (BFD) requires that messages are Bidirectional Forwarding Detection (BFD) requires that messages are
transmitted at regular intervals and provides a way to negotiate the transmitted at regular intervals and provides a way to negotiate the
interval used by BFD peers. Some BFD implementations may be interval used by BFD peers. Some BFD implementations may be
restricted to only support several interval values. When such BFD restricted to only support several interval values. When such BFD
implementations speak to each other, there is a possibility of two implementations speak to each other, there is a possibility of two
sides not being able to find a common value for the interval to run sides not being able to find a common value for the interval to run
BFD sessions. BFD sessions.
This document defines a small set of interval values for BFD that we This document updates RFC 5880 by defining a small set of interval
call "Common Intervals", and recommends implementations to support values for BFD that we call "Common Intervals", and recommends
the defined intervals. This solves the problem of finding an implementations to support the defined intervals. This solves the
interval value that both BFD speakers can support while allowing a problem of finding an interval value that both BFD speakers can
simplified implementation as seen for hardware-based BFD. It does support while allowing a simplified implementation as seen for
not restrict an implementation from supporting more intervals in hardware-based BFD. It does not restrict an implementation from
addition to the Common Intervals. supporting more intervals in addition to the Common 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 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 March 6, 2015. This Internet-Draft will expire on April 17, 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 . . . . . . . . . . . . . . . . . . . . . . . . 2 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 . . . . . . . . . . . . . . . . . . . . . 4 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . 5 5. Security Considerations . . . . . . . . . . . . . . . . . . . 4
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
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 values are in the Common Interval set . . . 5 Appendix A. Why some values are in the Common Interval 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 . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction 1. Introduction
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agree on a interval to run any BFD sessions. agree on a interval to run any BFD sessions.
3. Well-defined, Common Intervals 3. Well-defined, Common Intervals
The problem can be reduced by defining interval values that are The problem can be reduced by defining interval values that are
supported by all implementations. Then the adjustment mechanism supported by all implementations. Then the adjustment mechanism
could find a commonly supported interval without deviating too much could find a commonly supported interval without deviating too much
from the original request. from the original request.
In technical terms the requirement is as follows: a BFD In technical terms the requirement is as follows: a BFD
implementation SHOULD support all values in the set of Common implementation should support all values in the set of Common
Interval values which are equal to or larger than the fastest, i.e. Interval values which are equal to or larger than the fastest, i.e.
lowest, interval the particular BFD implementation supports. lowest, interval the particular BFD implementation supports.
The proposed set of Common Interval values is: 3.3msec, 10msec, This document defines the set of Common Interval values to be:
20msec, 50msec, 100msec and 1sec. 3.3msec, 10msec, 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 the This document is not adding new requirements with respect to the
precision with which a timer value must be implemented. Supporting precision with which a timer value must be implemented. Supporting
an interval value means to advertise this value in the an interval value means to advertise this value in the
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6. Acknowledgements 6. Acknowledgements
We would like to thank Sylvain Masse and Anca Zamfir for bringing up We would like to thank Sylvain Masse and Anca Zamfir for bringing up
the discussion about the Poll sequence, and Jeffrey Haas helped the discussion about the Poll sequence, and Jeffrey Haas helped
finding the fine line between "exact" and "pedantic". finding the fine line between "exact" and "pedantic".
7. References 7. References
7.1. Normative References 7.1. 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 [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] [GR-253-CORE]
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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
[G.8013_Y.1731] implementations, especially hardware. It allows [G.8013_Y.1731] implementations, especially hardware. It allows
to support large scale of 9 x 100msec setups and would be a to support large scale of 9 x 100msec setups and would be a
replacement for 3 x 300msec configurations used by customers to replacement for 3 x 300msec configurations used by customers to
have a detection time slightly below 1sec for VoIP setups. have a detection time slightly below 1sec for VoIP setups.
o 1sec: as mentioned in [RFC5880]. While the interval for Down o 1sec: as mentioned in [RFC5880]. While the interval for Down
packets can be 1sec or larger this draft proposes to use exactly packets can be 1sec or larger this draft recommends to use exactly
1sec to avoid interoperability issues. 1sec to avoid interoperability issues.
The proposed value for large intervals is 10sec, allowing for a The recommended value for large intervals is 10sec, allowing for a
timeout of 42.5 minutes with a multiplier of 255. This value is kept timeout of 42.5 minutes with a multiplier of 255. This value is kept
outside the Common Interval set as it is not required for normal BFD outside the Common Interval set as it is not required for normal BFD
operations, which occur in the sub-second range. Instead the operations, which occur in the sub-second range. Instead the
expected usage is for graceful restart, if needed. expected usage is for graceful restart, if needed.
Appendix B. Timer adjustment with non-identical interval sets Appendix B. Timer adjustment with non-identical interval sets
[RFC5880] implicitly assumes that a BFD implementation can support [RFC5880] implicitly assumes that a BFD implementation can support
any timer value equal or above the advertised value. When a BFD any timer value equal or above the advertised value. When a BFD
speaker starts a poll sequence then the peer must reply with the speaker starts a poll sequence then the peer must reply with the
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