Routing Working Group A. Mishra
Internet-Draft Ciena Corporation
Intended status: Standards Track M. Jethanandani
Expires: September 4, 2016 Cisco Systems
A. Saxena
Ciena Corporation
S. Pallagatti
Juniper Networks
M. Chen
Huawei
P. Fan
China Mobile
March 3, 2016
BFD Stability
draft-ashesh-bfd-stability-04.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 as well as
local delay measurements for BFD transmitter and receiver.
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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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
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on September 4, 2016.
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Copyright Notice
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document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. BFD Null-Authentication TLV . . . . . . . . . . . . . . . . . 3
4. Theory of Operations . . . . . . . . . . . . . . . . . . . . 3
4.1. Loss Measurement . . . . . . . . . . . . . . . . . . . . 3
4.2. Delay Measurement . . . . . . . . . . . . . . . . . . . . 4
5. IANA Requirements . . . . . . . . . . . . . . . . . . . . . . 4
6. Security Consideration . . . . . . . . . . . . . . . . . . . 4
7. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 4
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
9. Normative References . . . . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
The Bidirectional Forwarding Detection (BFD) [RFC5880] 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 in the Detection Time, as
defined in BFD [RFC5880] 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 to
measure the stability of BFD sessions and provides data to the
operators for the cause of a BFD failure.
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 cannot detect any BFD frame delay or loss if delay or loss
does not last for dead interval. This draft proposes a method to
distinguish between a dropped and a delayed frame on the receiver.
For example, if the receiver receives BFD CC frame k at time t but
receives frame k+1 at time t+9.9ms for a 3.3ms BFD interval, the
frame is delayed. However, if the receiver receives frame k+3 at
time t+10ms, and never receives frame k+1 and/or k+2, then it has
experienced a drop. Delays can be because of congestion in the
network or because of delays in the BFD transmitter or receiver.
This proposal enables BFD engine to generate diagnostic information
on the health of each BFD session that could be used to preempt a
failure on a link that BFD was monitoring by allowing time for a
corrective action to be taken.
In a faulty datapath scenario, operator can use BFD health
information to trigger delay and loss measurement OAM protocol
(Connectivity Fault Management (CFM) or Loss Measurement (LM)-Delay
Measurement (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 (as defined in Optimizing
BFD Authentication [I-D.ietf-bfd-optimizing-authentication] ) to the
BFD control frame that do not have authentication enabled.
4. Theory of Operations
This mechanism allows operator to measure the loss, transmitter delay
and receiver delay of BFD CC frames.
When using MD5 or SHA authentication, BFD uses authentication TLV
that carries the Sequence Number. However, if non-meticulous
authentication is being used, or no authentication is in use, then
the non-authenticated BFD frames MUST include NULL-Auth TLV.
4.1. Loss Measurement
Loss measurement counts the number of BFD control frames missed at
the receiver during any Detection Time period. The loss is detected
by comparing the Sequence Number field in the Auth TLV (NULL or
otherwise) 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.
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The first BFD NULL-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.
When the Sequence Number wraps around it should start from 1 instead
of 0.
4.2. Delay Measurement
Delay measurement can be done locally & independently on the
transmitter & receiver. Hence it is out of the scope of this
document. Following is an example of how the delay measurement can
be achieved on both sides:
Transmitter Delay:
Delay measurements on the transmitter can be made by
calculating the time difference between software BFD engine
transmitting the frame and the time when the hardware puts the
frame on the wire.
Receiver Delay:
Delay measurement can be made using the time difference between
the time hardware received a BFD Frame and the time software
BFD Engine processed the frame.
While a constant delay may not be indicator of instability, large
transient delays can decrease the BFD session stability
significantly. BFD MAY choose to inform the operator about any of
the delays when the delay measurement crosses a particular threshold
value.
5. IANA Requirements
N/A
6. Security Consideration
Other than concerns raised in BFD [RFC5880] there are no new concerns
with this proposal.
7. Contributors
Manav Bhatia
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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
[I-D.ietf-bfd-optimizing-authentication]
Jethanandani, M., Mishra, A., Saxena, A., and M. Bhatia,
"Optimizing BFD Authentication", draft-ietf-bfd-
optimizing-authentication-01 (work in progress), February
2016.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection
(BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010,
<http://www.rfc-editor.org/info/rfc5880>.
Authors' Addresses
Ashesh Mishra
Ciena Corporation
3939 North 1st Street
San Jose, CA 95134
USA
Email: mishra.ashesh@outlook.com
URI: www.ciena.com
Mahesh Jethanandani
Cisco Systems
170 W. Tasman Drive
San Jose, CA 95134
USA
Email: mjethanandani@gmail.com
URI: www.cisco.com
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Ankur Saxena
Ciena Corporation
3939 North 1st Street
San Jose, CA 95134
USA
Email: ankurpsaxena@gmail.com
URI: www.ciena.com
Santosh Pallagatti
Juniper Networks
Juniper Networks, Exora Business Park
Bangalore, Karnataka 560103
India
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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