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2 Routing Working Group A. Mishra
3 Internet-Draft M. Jethanandani
4 Intended status: Standards Track A. Saxena
5 Expires: December 12, 2015 Ciena Corporation
6 S. Pallagatti
7 Juniper Networks
8 M. Chen
9 Huawei
10 P. Fan
11 China Mobile
12 June 10, 2015
14 BFD Stability
15 draft-ashesh-bfd-stability-03.txt
17 Abstract
19 This document describes extensions to the Bidirectional Forwarding
20 Detection (BFD) protocol to measure BFD stability. Specifically, it
21 describes a mechanism for detection of BFD frame loss.
23 Requirements Language
25 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
26 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
27 document are to be interpreted as described in RFC 2119.
30 Status of This Memo
32 This Internet-Draft is submitted in full conformance with the
33 provisions of BCP 78 and BCP 79.
35 Internet-Drafts are working documents of the Internet Engineering
36 Task Force (IETF). Note that other groups may also distribute
37 working documents as Internet-Drafts. The list of current Internet-
38 Drafts is at http://datatracker.ietf.org/drafts/current/.
40 Internet-Drafts are draft documents valid for a maximum of six months
41 and may be updated, replaced, or obsoleted by other documents at any
42 time. It is inappropriate to use Internet-Drafts as reference
43 material or to cite them other than as "work in progress."
45 This Internet-Draft will expire on December 12, 2015.
47 Copyright Notice
49 Copyright (c) 2015 IETF Trust and the persons identified as the
50 document authors. All rights reserved.
52 This document is subject to BCP 78 and the IETF Trust's Legal
53 Provisions Relating to IETF Documents
54 (http://trustee.ietf.org/license-info) in effect on the date of
55 publication of this document. Please review these documents
56 carefully, as they describe your rights and restrictions with respect
57 to this document. Code Components extracted from this document must
58 include Simplified BSD License text as described in Section 4.e of
59 the Trust Legal Provisions and are provided without warranty as
60 described in the Simplified BSD License.
62 Table of Contents
64 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
65 2. Use cases . . . . . . . . . . . . . . . . . . . . . . . . . . 3
66 3. BFD Null-Authentication TLV . . . . . . . . . . . . . . . . . 3
67 4. Theory of Operations . . . . . . . . . . . . . . . . . . . . 4
68 4.1. Loss Measurement . . . . . . . . . . . . . . . . . . . . 4
69 4.2. Delay Measurement . . . . . . . . . . . . . . . . . . . . 5
70 5. IANA Requirements . . . . . . . . . . . . . . . . . . . . . . 5
71 6. Security Consideration . . . . . . . . . . . . . . . . . . . 6
72 7. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 6
73 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
74 9. Normative References . . . . . . . . . . . . . . . . . . . . 6
75 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
77 1. Introduction
79 The Bidirectional Forwarding Detection (BFD) protocol operates by
80 transmitting and receiving control frames, generally at high
81 frequency, over the datapath being monitored. In order to prevent
82 significant data loss due to a datapath failure, the tolerance for
83 lost or delayed frames (the Detection Time as described in RFC 5880)
84 is set to the smallest feasible value.
86 This document proposes a mechanism to detect delayed or lost frames
87 in a BFD session in addition to the datapath fault detection
88 mechanisms of BFD. Such a mechanism presents significant value with
89 the ability to measure the stability of BFD sessions and provides
90 data to the operators.
92 This document does not propose BFD extension to measure data traffic
93 loss or delay on a link or tunnel and the scope is limited to BFD
94 frames.
96 2. Use cases
98 Legacy BFD can't detect any BFD frame delay or loss if delay or loss
99 does not last for dead interval. Frequent delay or loss of BFD
100 frames could potentially lead to flap.
102 It may be possible that network has healthy link or tunnel but only
103 BFD frames are getting dropped or delayed. This potentially leads to
104 network convergence or use of suboptimal path when fast reroute is
105 enabled such as:
107 Routing protocols with LFA enabled, BFD is used to monitor the
108 link.
110 Aggregate Ethernet with BFD to monitor each member link.
112 Primary and protected tunnels with BFD to monitor tunnels.
114 This proposal will help BFD session to give more information to
115 operator about the health of BFD session that could be used to avoid
116 BFD session flap with faulty BFD path on a healthy link or tunnel.
118 In a faulty link or tunnel scenario operator can use BFD health
119 information to dynamically run delay and loss measurement OAM
120 protocol (CFM or LM-DM) to further isolate the issue.
122 3. BFD Null-Authentication TLV
124 The functionality proposed for BFD stability measurement is achieved
125 by appending the Null-Authentication TLV to the BFD control frame.
127 The Null-Authentication TLV (called 0-Auth in this document) extends
128 the existing BFD Authentication TLV structure by adding a new Auth-
129 Type of . This TLV carries the Sequence Number for
130 frame loss measurement and optional sender timestmap.
132 0 1 2 3
133 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
134 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
135 | Auth Type | Auth Len | Auth Key ID | Reserved |
136 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
137 | Sequence Number |
138 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
139 | Sender timestmap |
140 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
142 where:
144 Auth Type: The Authentication Type, which in this case is (Null Authentication).
147 Auth Len: The length of the Authentication Section, in bytes. Length
148 depends on the Auth Key ID.
150 Auth Key ID: The Authentication Key ID is used to control optional
151 feature. Vales are:
153 0 -- BFD loss measurement
154 1 -- BFD loss and delay measurement
155 2-255 -- Reserved for future use
157 when value is set to 0 then last 4 bytes of this TLV MUST not be
158 present in the packet, Auth Len MUST be set to 8 bytes. When set to
159 1 Auth Len MUST be set to 12.
161 Sequence Number: This indicates the sequence number for this packet
162 and MUST be present in every 0-Auth TLV. This value is incremented
163 by 1 for every frame transmitted while the session state is UP. A
164 value of 0 indicates a request by sender to reset the sequence number
165 correlation logic at the receiver. The first frame transmitted by
166 the sender MAY set this field to 0.
168 Sender timestamp: MUST be set to time when packet is about to leave
169 the sender system. Sender system MAY time stamp this as close to
170 wire when packet is about to leave system. Details of how sender
171 system timestamps is out of the scope of this document.
173 4. Theory of Operations
175 This mechanism allows operator to measure the loss and delay of BFD
176 CC frames.
178 4.1. Loss Measurement
180 This measurement counts the number of BFD control frames missed at
181 the receiver due to a transient change in the network such as
182 congestion. Frame-loss is detected by comparing the Sequence Number
183 field in the 0-Auth TLV in successive BFD CC frames. The Sequence
184 Number in each successive control frame generated on a BFD session by
185 the transmitter is incremented by one.
187 The first BFD 0-Auth TLV processed by the receiver that has a non-
188 zero sequence number is used for bootstrapping the logic. Each
189 successive frame after this is expected to have a Sequence Number
190 that is one greater than the Sequence Number in the previous frame.
192 BFD being aggressive protocol, sequence number may wrap to 0 within
193 few hundred days. Sender MUST ensure that when sequence number is
194 wrapped, it starts with value 1. Receiver MUST accept this BFD
195 packet and adjust his next anticipated sequence number.
197 4.2. Delay Measurement
199 Delay measurement can be done in two ways.
201 Using sender timestamp in 0-Auth TLV:
203 If AuthKey ID in 0-Auth TLV is set to 1 then sender timestamp
204 MUST be set. Delay measurement is the difference between the
205 sender timestamp on any two consecutive BFD CC frames that
206 carry the 0-Auth TLV with AuthKey ID set to 1 for a session.
207 This is a key metric to determine transient changes in
208 stability of BFD transmission engine or to determine the
209 systems capability of handling the existing load. A
210 significant deviation from the negotiated transmission interval
211 on the local node indicates potential instabilities in the BFD
212 transmission engine. Based on the timestamp measurements, the
213 operator MAY take action to configure the system to maintain
214 normal operation of the node.
216 Similar delay measurements on the receiver can be made using
217 timestamps in the meta data when packet is received. In
218 conjunction with sender delay measurements, these can indicate
219 delays caused by data-path. While a constant delay may not be
220 indicator of instability, large transient delays can decrease
221 the BFD session stability significantly.
223 Using centralized controller:
225 When AuthKey ID in 0-Auth TLV is set to 0 then sender timestmap
226 will not be present in the packet. Peers MAY still choose to
227 do delay measurement by sending their packet sent timestamps to
228 central control unit. Central control unit MAY gather all
229 timestamp information and can do delay calculation for a BFD
230 session. Details of how BFD component sends timestamps to
231 central unit is outside the scope of this document.
233 5. IANA Requirements
235 IANA is requested to assign new Auth-Type for the Null-Authentication
236 TLV for BFD Stability Measurement. The following number is
237 suggested.
239 Value Meaning
240 6 Null-Authentication TLV
242 6. Security Consideration
244 Other than concerns raised in [RFC5880] there are no new concerns
245 with this proposal.
247 7. Contributors
249 Manav Bhatia
250 manav@ionosnetworks.com
251 Ionos Networks
252 Bangalore, India
254 8. Acknowledgements
256 Authors would like to thank Nobo Akiya, Jeffery Haas, Peng Fan,
257 Dileep Singh, Basil Saji, Sagar Soni and Mallik Mudigonda who also
258 contributed to this document.
260 9. Normative References
262 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
263 Requirement Levels", BCP 14, RFC 2119, March 1997.
265 [RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection
266 (BFD)", RFC 5880, June 2010.
268 Authors' Addresses
270 Ashesh Mishra
271 Ciena Corporation
272 3939 North 1st Street
273 San Jose, CA 95134
274 USA
276 Email: mishra.ashesh@gmail.com
277 URI: www.ciena.com
279 Mahesh Jethanandani
280 Ciena Corporation
281 3939 North 1st Street
282 San Jose, CA 95134
283 USA
285 Email: mjethanandani@gmail.com
286 URI: www.ciena.com
287 Ankur Saxena
288 Ciena Corporation
289 3939 North 1st Street
290 San Jose, CA 95134
291 USA
293 Email: ankurpsaxena@gmail.com
295 Santosh Pallagatti
296 Juniper Networks
297 Juniper Networks, Exora Business Park
298 Bangalore, Karnataka 560103
299 India
301 Phone: +
302 Email: santoshpk@juniper.net
304 Mach Chen
305 Huawei
307 Email: mach.chen@huawei.com
309 Peng Fan
310 China Mobile
311 32 Xuanwumen West Street
312 Beijing, Beijing
313 China
315 Email: fanp08@gmail.com