< draft-cw-bfd-unaffiliated-echo-00.txt   draft-cw-bfd-unaffiliated-echo-01.txt >
BFD Working Group W. Cheng BFD Working Group W. Cheng
Internet-Draft R. Wang Internet-Draft R. Wang
Intended status: Informational China Mobile Intended status: Informational China Mobile
Expires: September 8, 2020 X. Min Expires: January 14, 2021 X. Min
A. Liu A. Liu
ZTE ZTE Corp.
March 7, 2020 R. Rahman
Cisco Systems
July 13, 2020
Unaffiliated BFD Echo Function Unaffiliated BFD Echo Function
draft-cw-bfd-unaffiliated-echo-00 draft-cw-bfd-unaffiliated-echo-01
Abstract Abstract
Bidirectional Forwarding Detection (BFD) is a fault detection Bidirectional Forwarding Detection (BFD) is a fault detection
protocol that can quickly determine a communication failure between protocol that can quickly determine a communication failure between
devices and notify upper-layer applications [RFC5880]. BFD has two forwarding engines. This document proposes a use of BFD echo
asynchronous detecting mode and demand detection mode to satisfy where the local system supports BFD but the neighboring system does
different scenarios, also supports echo function as an adjunct to not support BFD.
both modes to reduce the device requirement for BFD.
Unaffiliated BFD echo function described in this document reuses the
BFD echo function as described in [RFC5880] and [RFC5881], but
independent of BFD asynchronous mode or BFD demand mode, that means
it doesn't need BFD protocol capability of state machine, but only
BFD echo function to a deployed device supporting BFD detection.
When using unaffiliated BFD echo function, just the local device
works on BFD protocol and the BFD peer doesn't, which only loopback
the received BFD echo packets as usual data packets without enabling
BFD protocol.
Section 6.2.2 of [BBF-TR-146] describes one use case of the
unaffiliated BFD echo function, and at least one more use case is
known in the field BFD deployment.
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 https://datatracker.ietf.org/drafts/current/. Drafts is at https://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 September 8, 2020. This Internet-Draft will expire on January 14, 2021.
Copyright Notice Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the Copyright (c) 2020 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
(https://trustee.ietf.org/license-info) in effect on the date of (https://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
skipping to change at page 2, line 31 skipping to change at page 2, line 17
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. Unaffiliated BFD Echo Behavior . . . . . . . . . . . . . . . 3 2. Unaffiliated BFD Echo Behavior . . . . . . . . . . . . . . . 3
3. Discussion . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Discussion . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Security Considerations . . . . . . . . . . . . . . . . . . . 4 4. Security Considerations . . . . . . . . . . . . . . . . . . . 4
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 5 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
7.1. Normative References . . . . . . . . . . . . . . . . . . 5 7.1. Normative References . . . . . . . . . . . . . . . . . . 5
7.2. Informative References . . . . . . . . . . . . . . . . . 5 7.2. Informative References . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction 1. Introduction
To minimize the impact of device faults on services and improve To minimize the impact of device faults on services and improve
network availability, a network device must be able to quickly detect network availability, a network device must be able to quickly detect
faults in communication with adjacent devices. Measures can then be faults in communication with adjacent devices. Measures can then be
taken to promptly rectify the faults to ensure service continuity. taken to promptly rectify the faults to ensure service continuity.
BFD is a low-overhead, short-duration method to detect faults on the BFD [RFC5880] is a low-overhead, short-duration method to detect
path between adjacent forwarding engines. The faults can be faults on the path between adjacent forwarding engines. The faults
interface, data link, and even forwarding engine faults. It is a can be interface, data link, and even forwarding engine faults. It
single, unified mechanism to monitor any media and protocol layers in is a single, unified mechanism to monitor any media and protocol
real time. layers in real time.
BFD has asynchronous detecting mode and demand detection mode to BFD defines asynchronous mode to satisfy various deployment
satisfy different scenarios, also supports echo function to reduce scenarios, also supports echo function to reduce the device
the device requirement for BFD. When the echo function is activated, requirement for BFD. When the echo function is activated, the local
the local system sends a BFD control packet and the remote system system sends a BFD echo packet and the remote system loops back the
loops back the packet through the forwarding path. If several packet through the forwarding path. If several consecutive echo
consecutive echo packets are not received, the session is declared to packets are not received, the session is declared to be Down.
be Down.
When using BFD echo function, it is not clear whether the devices When using BFD echo function, it is not clear whether the devices
using echo function need to support the full BFD procotol, including using echo function need to support the full BFD procotol, including
maintaining the state machine of BFD session as described in maintaining the state machine of BFD session as described in
[RFC5880] and [RFC5881]. According to different understanding, there [RFC5880] and [RFC5881]. According to different understanding, there
are two typical scenarios as below: are two typical scenarios as below:
1. Full BFD procotol capability with affiliated echo function: 1. Full BFD procotol capability with affiliated echo function:
this scenario requires all the devices to support BFD protocol. this scenario requires both the local device and the neighboring
device to support BFD protocol.
2. Only BFD echo function without full BFD procotol capability: 2. Only BFD echo function without full BFD procotol capability:
this scenario requires only the local device to support sending this scenario requires only the local device to support sending
BFD packets. BFD packets.
The two typical scenarios are both reasonable and useful, and the The two typical scenarios are both reasonable and useful, and the
latter is referred to as unaffiliated BFD echo function in this latter is referred to as unaffiliated BFD echo function in this
document. document.
Unaffiliated BFD echo function described in this document reuses the Unaffiliated BFD echo function described in this document reuses the
BFD echo function as described in [RFC5880] and [RFC5881], but BFD echo function as described in [RFC5880] and [RFC5881], but
independent of BFD asynchronous mode or BFD demand mode, that means independent of BFD asynchronous mode, that means it doesn't need BFD
it doesn't need BFD protocol capability of state machine, but only protocol capability of state machine, but only BFD echo function to a
BFD echo function to a deployed device supporting BFD detection. deployed device supporting BFD detection. When using unaffiliated
When using unaffiliated BFD echo function, just the local device BFD echo function, just the local device works on BFD protocol and
works on BFD protocol and the BFD peer doesn't, which only loopback the BFD peer doesn't, which only loopback the received BFD echo
the received BFD echo packets as usual data packets without enabling packets as usual data packets without enabling BFD protocol.
BFD protocol.
Section 6.2.2 of [BBF-TR-146] describes one use case of the Section 6.2.2 of [BBF-TR-146] describes one use case of the
unaffiliated BFD echo function, and at least one more use case is unaffiliated BFD echo function, and at least one more use case is
known in the field BFD deployment. known in the field BFD deployment.
2. Unaffiliated BFD Echo Behavior 2. Unaffiliated BFD Echo Behavior
With the more and more application of BFD detection, there are some With the more and more application of BFD detection, there are some
scenarios the BFD echo function is deployed. And due to the scenarios the BFD echo function is deployed. And due to the
different capabilities of the devices deploying BFD echo function, different capabilities of the devices deploying BFD echo function,
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After receiving a BFD echo packet, the device that does not support After receiving a BFD echo packet, the device that does not support
BFD protocol immediately loops back the packet by normal IP BFD protocol immediately loops back the packet by normal IP
forwarding, implementing quick link failure detection. As shown in forwarding, implementing quick link failure detection. As shown in
Figure 1, device A supports BFD, whereas device B does not support Figure 1, device A supports BFD, whereas device B does not support
BFD. To rapidly detect any faults with the IP link between device A BFD. To rapidly detect any faults with the IP link between device A
and device B, a BFD echo session can be provisioned and created at and device B, a BFD echo session can be provisioned and created at
device A, and device A starts sending BFD echo packets, which should device A, and device A starts sending BFD echo packets, which should
include a BFD echo session demultiplexing field, such as BFD include a BFD echo session demultiplexing field, such as BFD
discriminator defined in [RFC5880]. After receiving the BFD echo discriminator defined in [RFC5880]. After receiving the BFD echo
packets sent from device A, device B immediately loops back them, packets sent from device A, device B immediately loops back them,
implementing rapid link fault detection. this allows device A to rapidly detect a connectivity loss to device
B.
Device A Device B Device A Device B
BFD echo session BFD echo session
BFD Enabled BFD Echo packets loopback BFD Enabled BFD Echo packets loopback
+--------+ +---------+ +--------+ +---------+
| A |---------------------------------| B | | A |---------------------------------| B |
| |Inf 1 Inf 1| | | |Inf 1 Inf 1| |
+--------+10.1.1.1/24 10.1.1.2/24+---------+ +--------+10.1.1.1/24 10.1.1.2/24+---------+
BFD is supported. BFD is not supported. BFD is supported. BFD is not supported.
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Unaffiliated BFD echo function is reasonable and useful. Firstly, Unaffiliated BFD echo function is reasonable and useful. Firstly,
unaffiliated BFD echo can use BFD protocol capability in the local unaffiliated BFD echo can use BFD protocol capability in the local
BFD-supported device, while using IP forwarding capability in the BFD-supported device, while using IP forwarding capability in the
peer non-BFD-supported device, so unaffiliated BFD echo can support peer non-BFD-supported device, so unaffiliated BFD echo can support
fast detecting and manage BFD sessions very effectively. Secondly, fast detecting and manage BFD sessions very effectively. Secondly,
it is scalable when using unaffiliated BFD echo to adapt to different it is scalable when using unaffiliated BFD echo to adapt to different
capabilities of devices. capabilities of devices.
4. Security Considerations 4. Security Considerations
TBD. Unicast Reverse Path Forwarding (uRPF), as specified in [RFC3704] and
[RFC8704], is a security feature that prevents the IP address
spoofing attacks which is commonly used in DoS, DDoS. uRPF has two
modes called strict mode and loose mode. uRPF strict mode means that
the router will perform checks for all incoming packets on a certain
interface: whether the router has a matching entry for the source IP
in the routing table and whether the router uses the same interface
to reach this source IP as where the router received this packet on.
Note that the use of BFD echo function would prevent the use of uRPF
in strict mode.
5. IANA Considerations 5. IANA Considerations
This document has no IANA action requested. This document has no IANA action requested.
6. Acknowledgements 6. Acknowledgements
TBD. TBD.
7. References 7. References
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5. IANA Considerations 5. IANA Considerations
This document has no IANA action requested. This document has no IANA action requested.
6. Acknowledgements 6. Acknowledgements
TBD. TBD.
7. References 7. References
7.1. Normative References 7.1. Normative References
[RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection [RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection
(BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010, (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010,
<https://www.rfc-editor.org/info/rfc5880>. <https://www.rfc-editor.org/info/rfc5880>.
[RFC5881] Katz, D. and D. Ward, "Bidirectional Forwarding Detection [RFC5881] Katz, D. and D. Ward, "Bidirectional Forwarding Detection
(BFD) for IPv4 and IPv6 (Single Hop)", RFC 5881, (BFD) for IPv4 and IPv6 (Single Hop)", RFC 5881,
DOI 10.17487/RFC5881, June 2010, DOI 10.17487/RFC5881, June 2010,
<https://www.rfc-editor.org/info/rfc5881>. <https://www.rfc-editor.org/info/rfc5881>.
7.2. Informative References 7.2. Informative References
[BBF-TR-146] [BBF-TR-146]
Broadband Forum, "BBF Technical Report - Subscriber Broadband Forum, "BBF Technical Report - Subscriber
Sessions Issue 1", 2013, <https://www.broadband- Sessions Issue 1", 2013, <https://www.broadband-
forum.org/technical/download/TR-146.pdf>. forum.org/technical/download/TR-146.pdf>.
[RFC3704] Baker, F. and P. Savola, "Ingress Filtering for Multihomed
Networks", BCP 84, RFC 3704, DOI 10.17487/RFC3704, March
2004, <https://www.rfc-editor.org/info/rfc3704>.
[RFC8704] Sriram, K., Montgomery, D., and J. Haas, "Enhanced
Feasible-Path Unicast Reverse Path Forwarding", BCP 84,
RFC 8704, DOI 10.17487/RFC8704, February 2020,
<https://www.rfc-editor.org/info/rfc8704>.
Authors' Addresses Authors' Addresses
Weiqiang Cheng Weiqiang Cheng
China Mobile China Mobile
Beijing Beijing
CN CN
Email: chengweiqiang@chinamobile.com Email: chengweiqiang@chinamobile.com
Ruixue Wang Ruixue Wang
skipping to change at page 5, line 44 skipping to change at page 6, line 4
CN CN
Email: chengweiqiang@chinamobile.com Email: chengweiqiang@chinamobile.com
Ruixue Wang Ruixue Wang
China Mobile China Mobile
Beijing Beijing
CN CN
Email: wangruixue@chinamobile.com Email: wangruixue@chinamobile.com
Xiao Min Xiao Min
ZTE ZTE Corp.
Nanjing Nanjing
CN CN
Email: xiao.min2@zte.com.cn Email: xiao.min2@zte.com.cn
Aihua Liu Aihua Liu
ZTE ZTE Corp.
Shenzhen Shenzhen
CN CN
Email: liu.aihua@zte.com.cn Email: liu.aihua@zte.com.cn
Reshad Rahman
Cisco Systems
Kanata
CA
Email: rrahman@cisco.com
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