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 RFC 2119.
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
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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
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document authors. All rights reserved.
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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 . 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 (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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