draft-ietf-bfd-unsolicited-03.txt   draft-ietf-bfd-unsolicited-04.txt 
Network Working Group E. Chen Network Working Group E. Chen
Internet-Draft Palo Alto Networks Internet-Draft Palo Alto Networks
Intended status: Standards Track N. Shen Intended status: Standards Track N. Shen
Expires: October 24, 2021 Zededa Expires: April 18, 2022 Zededa
R. Raszuk R. Raszuk
NTT Network Innovations NTT Network Innovations
R. Rahman R. Rahman
April 22, 2021 October 15, 2021
Unsolicited BFD for Sessionless Applications Unsolicited BFD for Sessionless Applications
draft-ietf-bfd-unsolicited-03 draft-ietf-bfd-unsolicited-04
Abstract Abstract
For operational simplification of "sessionless" applications using For operational simplification of "sessionless" applications using
BFD, in this document we present procedures for "unsolicited BFD" BFD, in this document we present procedures for "unsolicited BFD"
that allow a BFD session to be initiated by only one side, and be that allow a BFD session to be initiated by only one side, and be
established without explicit per-session configuration or established without explicit per-session configuration or
registration by the other side (subject to certain per-interface or registration by the other side (subject to certain per-interface or
per-router policies). per-router policies).
skipping to change at page 1, line 47 skipping to change at page 1, line 47
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
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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 October 24, 2021. This Internet-Draft will expire on April 18, 2022.
Copyright Notice Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the Copyright (c) 2021 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
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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. Procedures for Unsolicited BFD . . . . . . . . . . . . . . . 3 2. Procedures for Unsolicited BFD . . . . . . . . . . . . . . . 3
3. YANG Data Model . . . . . . . . . . . . . . . . . . . . . . . 4 3. State Variables . . . . . . . . . . . . . . . . . . . . . . . 4
3.1. Unsolicited BFD Hierarchy . . . . . . . . . . . . . . . . 4 4. YANG Data Model . . . . . . . . . . . . . . . . . . . . . . . 5
3.2. Unsolicited BFD Module . . . . . . . . . . . . . . . . . 5 4.1. Unsolicited BFD Hierarchy . . . . . . . . . . . . . . . . 5
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 4.2. Unsolicited BFD Module . . . . . . . . . . . . . . . . . 5
5. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 9 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
6. Security Considerations . . . . . . . . . . . . . . . . . . . 9 6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 9
6.1. BFD Protocol Security Considerations . . . . . . . . . . 9 7. Security Considerations . . . . . . . . . . . . . . . . . . . 9
6.2. YANG Module Security Considerations . . . . . . . . . . . 9 7.1. BFD Protocol Security Considerations . . . . . . . . . . 9
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 10 7.2. YANG Module Security Considerations . . . . . . . . . . . 9
7.1. Normative References . . . . . . . . . . . . . . . . . . 10 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
7.2. Informative References . . . . . . . . . . . . . . . . . 12 8.1. Normative References . . . . . . . . . . . . . . . . . . 11
8.2. Informative References . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12
1. Introduction 1. Introduction
The current implementation and deployment practice for BFD ([RFC5880] The current implementation and deployment practice for BFD ([RFC5880]
and [RFC5881]) usually requires BFD sessions be explicitly configured and [RFC5881]) usually requires BFD sessions be explicitly configured
or registered on both sides. This requirement is not an issue when or registered on both sides. This requirement is not an issue when
an application like BGP [RFC4271] has the concept of a "session" that an application like BGP [RFC4271] has the concept of a "session" that
involves both sides for its establishment. However, this requirement involves both sides for its establishment. However, this requirement
can be operationally challenging when the prerequisite "session" does can be operationally challenging when the prerequisite "session" does
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Server, multiple BGP paths (when exist) can be made available to the Server, multiple BGP paths (when exist) can be made available to the
clients of the Router Server as described in [RFC7947]. The clients of the Router Server as described in [RFC7947]. The
"unsolicited BFD" can be used in BGP route selection by these clients "unsolicited BFD" can be used in BGP route selection by these clients
to eliminate paths with "inaccessible nexthops". to eliminate paths with "inaccessible nexthops".
2. Procedures for Unsolicited BFD 2. Procedures for Unsolicited BFD
With "unsolicited BFD", one side takes the "Active role" and the With "unsolicited BFD", one side takes the "Active role" and the
other side takes only the "Passive role" as described in [RFC5880]. other side takes only the "Passive role" as described in [RFC5880].
On the passive side, the "unsolicited BFD" SHOULD be explicitely On the passive side, the "unsolicited BFD" SHOULD be explicitly
configured on an interface or globally (apply to all interfaces). configured on an interface or globally (apply to all interfaces).
The BFD parameters can be either per-interface or per-router based. The BFD parameters can be either per-interface or per-router based.
It MAY also choose to use the parameters that the active side uses in It MAY also choose to use the parameters that the active side uses in
its BFD Control packets. The "My Discriminator", however, MUST be its BFD Control packets. The "My Discriminator", however, MUST be
chosen to allow multiple unsolicited BFD sessions. chosen to allow multiple unsolicited BFD sessions.
The active side starts sending the BFD Control packets as specified The active side starts sending the BFD Control packets as specified
in [RFC5880]. The passive side does not send BFD Control packets. in [RFC5880]. The passive side does not send BFD Control packets.
When the passive side receives a BFD Control packet from the active When the passive side receives a BFD Control packet from the active
side with 0 as "Your Discriminator", and it does not find an existing side with 0 as "Your Discriminator", and it does not find an existing
session with the same source address and the same "Discriminator" session with the same source address and the same "Discriminator"
pairs as in the packet and "unsolicited BFD" is allowed on the pairs as in the packet and "unsolicited BFD" is allowed on the
interface by local policy, it SHOULD then create a matching BFD interface by local policy, it MUST create a matching BFD session
session toward the active side (based on the source address and toward the active side (based on the source address and destination
destination address in the BFD Control packet) as if the session were address in the BFD Control packet) as if the session were locally
locally registered. It would then start sending the BFD Control registered. It would then start sending the BFD Control packets and
packets and perform necessary procedure for bringing up, maintaining perform necessary procedure for bringing up, maintaining and tearing
and tearing down the BFD session. If the BFD session fails to get down the BFD session. If the BFD session fails to get established
established within certain specified time, or if an established BFD within certain specified time, or if an established BFD session goes
session goes down, the passive side would stop sending BFD Control down, the passive side would stop sending BFD Control packets and MAY
packets and delete the BFD session created until the BFD Control delete the BFD session created until the BFD Control packets is
packets is initiated by the active side again. initiated by the active side again.
When on the passive side Unsolicited BFD sessions goes down an
implementation MAY keep such session state for a configurable amount
of time. Temporarily keeping such local state may permit retrieving
additional operational information of such session which went down.
The "Passive role" may change to the "Active role" when a local The "Passive role" may change to the "Active role" when a local
client registers for the same BFD session, and from the "Active role client registers for the same BFD session, and from the "Active role
" to the "Passive role " when there is no longer any locally " to the "Passive role " when there is no longer any locally
registered client for the BFD session. registered client for the BFD session.
3. YANG Data Model 3. State Variables
This document defines a new state variable called Unsolicited Role.
bfd.UnsolicitedRole
The operational mode of BFD interface when configured for unsolicited
behaviour. Options can be either PASSIVE, ACTIVE or NULL (NULL - not
initialized) for unsolicited BFD sessions. Default (not configured
for unsolicited behaviour) MUST be set to NULL if present on the
interface.
4. YANG Data Model
This section extends the YANG data model for BFD [I-D.ietf-bfd-yang] This section extends the YANG data model for BFD [I-D.ietf-bfd-yang]
to cover the unsolicited BFD. to cover the unsolicited BFD.
3.1. Unsolicited BFD Hierarchy 4.1. Unsolicited BFD Hierarchy
module: ietf-bfd-unsolicited module: ietf-bfd-unsolicited
augment /rt:routing/rt:control-plane-protocols augment /rt:routing/rt:control-plane-protocols
/rt:control-plane-protocol/bfd:bfd/bfd-ip-sh:ip-sh: /rt:control-plane-protocol/bfd:bfd/bfd-ip-sh:ip-sh:
+--rw unsolicited {bfd-unsol:unsolicited-params-global}? +--rw unsolicited {bfd-unsol:unsolicited-params-global}?
+--rw enable? boolean +--rw enable? boolean
+--rw local-multiplier? multiplier +--rw local-multiplier? multiplier
+--rw (interval-config-type)? +--rw (interval-config-type)?
+--:(tx-rx-intervals) +--:(tx-rx-intervals)
| +--rw desired-min-tx-interval? uint32 | +--rw desired-min-tx-interval? uint32
| +--rw required-min-rx-interval? uint32 | +--rw required-min-rx-interval? uint32
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| +--rw desired-min-tx-interval? uint32 | +--rw desired-min-tx-interval? uint32
| +--rw required-min-rx-interval? uint32 | +--rw required-min-rx-interval? uint32
+--:(single-interval) {single-minimum-interval}? +--:(single-interval) {single-minimum-interval}?
+--rw min-interval? uint32 +--rw min-interval? uint32
augment /rt:routing/rt:control-plane-protocols augment /rt:routing/rt:control-plane-protocols
/rt:control-plane-protocol/bfd:bfd/bfd-ip-sh:ip-sh /rt:control-plane-protocol/bfd:bfd/bfd-ip-sh:ip-sh
/bfd-ip-sh:sessions/bfd-ip-sh:session: /bfd-ip-sh:sessions/bfd-ip-sh:session:
+--ro unsolicited +--ro unsolicited
+--ro role? bfd-unsol:unsolicited-role +--ro role? bfd-unsol:unsolicited-role
3.2. Unsolicited BFD Module 4.2. Unsolicited BFD Module
<CODE BEGINS> file "ietf-bfd-unsolicited@2019-06-26.yang" <CODE BEGINS> file "ietf-bfd-unsolicited@2021-10-15.yang"
module ietf-bfd-unsolicited { module ietf-bfd-unsolicited {
yang-version 1.1; yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-bfd-unsolicited"; namespace "urn:ietf:params:xml:ns:yang:ietf-bfd-unsolicited";
prefix "bfd-unsol"; prefix "bfd-unsol";
// RFC Ed.: replace occurences of XXXX/YYYY with actual RFC numbers // RFC Ed.: replace occurences of YYYY with actual RFC numbers
// and remove this note // and remove this note
import ietf-bfd-types { import ietf-bfd-types {
prefix "bfd-types"; prefix "bfd-types";
reference "RFC XXXX: YANG Data Model for BFD"; reference "RFC 9127: YANG Data Model for BFD";
} }
import ietf-bfd { import ietf-bfd {
prefix "bfd"; prefix "bfd";
reference "RFC XXXX: YANG Data Model for BFD"; reference "RFC 9127: YANG Data Model for BFD";
} }
import ietf-bfd-ip-sh { import ietf-bfd-ip-sh {
prefix "bfd-ip-sh"; prefix "bfd-ip-sh";
reference "RFC XXXX: YANG Data Model for BFD"; reference "RFC 9127: YANG Data Model for BFD";
} }
import ietf-routing { import ietf-routing {
prefix "rt"; prefix "rt";
reference reference
"RFC 8349: A YANG Data Model for Routing Management "RFC 8349: A YANG Data Model for Routing Management
(NMDA version)"; (NMDA version)";
} }
organization "IETF BFD Working Group"; organization "IETF BFD Working Group";
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Editors: Enke Chen (enchen@paloaltonetworks.com), Editors: Enke Chen (enchen@paloaltonetworks.com),
Naiming Shen (naiming@zededa.com), Naiming Shen (naiming@zededa.com),
Robert Raszuk (robert@raszuk.net), Robert Raszuk (robert@raszuk.net),
Reshad Rahman (reshad@yahoo.com)"; Reshad Rahman (reshad@yahoo.com)";
description description
"This module contains the YANG definition for BFD unsolicited "This module contains the YANG definition for BFD unsolicited
as per RFC YYYY. as per RFC YYYY.
Copyright (c) 2018 IETF Trust and the persons Copyright (c) 2021 IETF Trust and the persons
identified as authors of the code. All rights reserved. identified as authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with or Redistribution and use in source and binary forms, with or
without modification, is permitted pursuant to, and subject without modification, is permitted pursuant to, and subject
to the license terms contained in, the Simplified BSD License to the license terms contained in, the Simplified BSD License
set forth in Section 4.c of the IETF Trust's Legal Provisions set forth in Section 4.c of the IETF Trust's Legal Provisions
Relating to IETF Documents Relating to IETF Documents
(http://trustee.ietf.org/license-info). (http://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC XXXX; see This version of this YANG module is part of RFC YYYY; see
the RFC itself for full legal notices."; the RFC itself for full legal notices.";
reference "RFC YYYY"; reference "RFC YYYY";
revision 2019-06-26 { revision 2021-10-15 {
description "Initial revision."; description "Initial revision.";
reference "RFC YYYY: A YANG data model for BFD unsolicited"; reference "RFC 9127: A YANG data model for BFD unsolicited";
} }
/* /*
* Feature definitions * Feature definitions
*/ */
feature unsolicited-params-global { feature unsolicited-params-global {
description description
"This feature indicates that the server supports global "This feature indicates that the server supports global
parameters for unsolicited sessions."; parameters for unsolicited sessions.";
} }
skipping to change at page 8, line 46 skipping to change at page 9, line 4
description description
"Augmentation for BFD unsolicited on IP single-hop session"; "Augmentation for BFD unsolicited on IP single-hop session";
container unsolicited { container unsolicited {
config false; config false;
description description
"BFD IP single-hop session unsolicited top level container"; "BFD IP single-hop session unsolicited top level container";
leaf role { leaf role {
type bfd-unsol:unsolicited-role; type bfd-unsol:unsolicited-role;
description "Role."; description "Role.";
} }
} }
} }
} }
<CODE ENDS> <CODE ENDS>
4. IANA Considerations 5. IANA Considerations
This documents makes no IANA requests. This documents makes no IANA requests.
5. Acknowledgments 6. Acknowledgments
Authors would like to thank Acee Lindem, Greg Mirsky and Raj Chetan Authors would like to thank Acee Lindem, Greg Mirsky and Raj Chetan
for their review and valuable input. for their review and valuable input.
6. Security Considerations 7. Security Considerations
6.1. BFD Protocol Security Considerations 7.1. BFD Protocol Security Considerations
The same security considerations as those described in [RFC5880] and The same security considerations and protection measures as those
[RFC5881] apply to this document. With "unsolicited BFD" there is described in [RFC5880] and [RFC5881] normatively apply to this
potential risk for excessive resource usage by BFD from "unexpected" document. With "unsolicited BFD" there is potential risk for
remote systems. To mitigate such risks, the following measures are excessive resource usage by BFD from "unexpected" remote systems. To
RECOMMENDED: mitigate such risks, the following measures are mandatory:
o Limit the feature to specific interfaces, and to a single-hop BFD o Limit the feature to specific interfaces, and to a single-hop BFD
with "TTL=255" [RFC5082]. For numbered interfaces source address with "TTL=255" [RFC5082]. For numbered interfaces source address
of an incoming BFD packet should belongs to the subnet of the of an incoming BFD packet should belongs to the subnet of the
interface from which the BFD packet is received. For unnumbered interface from which the BFD packet is received. For unnumbered
interfaces the above check should be alinged with routing protocol interfaces the above check should be aligned with routing protocol
addresses running on such pair of interfaces. addresses running on such pair of interfaces.
o Apply "access control" to allow BFD packets only from certain o Apply "access control" to allow BFD packets only from certain
subnets or hosts. subnets or hosts.
o Deploy the feature only in certain "trustworthy" environment, o Deploy the feature only in certain "trustworthy" environment,
e.g., at an IXP, or between a provider and its customers. e.g., at an IXP, or between a provider and its customers.
o Adjust BFD parameters as needed for the particular deployment and o Adjust BFD parameters as needed for the particular deployment and
scale. scale.
o Use BFD authentication. o Use BFD authentication.
6.2. YANG Module Security Considerations 7.2. YANG Module Security Considerations
The YANG module specified in this document defines a schema for data The YANG module specified in this document defines a schema for data
that is designed to be accessed via network management protocols such that is designed to be accessed via network management protocols such
as NETCONF [RFC6241] or RESTCONF [RFC8040]. The lowest NETCONF layer as NETCONF [RFC6241] or RESTCONF [RFC8040]. The lowest NETCONF layer
is the secure transport layer, and the mandatory-to-implement secure is the secure transport layer, and the mandatory-to-implement secure
transport is Secure Shell (SSH) [RFC6242]. The lowest RESTCONF layer transport is Secure Shell (SSH) [RFC6242]. The lowest RESTCONF layer
is HTTPS, and the mandatory-to-implement secure transport is TLS is HTTPS, and the mandatory-to-implement secure transport is TLS
[RFC5246]. [RFC5246].
The NETCONF access control model [RFC6536] provides the means to The NETCONF access control model [RFC6536] provides the means to
skipping to change at page 10, line 17 skipping to change at page 10, line 22
default). These data nodes may be considered sensitive or vulnerable default). These data nodes may be considered sensitive or vulnerable
in some network environments. Write operations (e.g., edit-config) in some network environments. Write operations (e.g., edit-config)
to these data nodes without proper protection can have a negative to these data nodes without proper protection can have a negative
effect on network operations. These are the subtrees and data nodes effect on network operations. These are the subtrees and data nodes
and their sensitivity/vulnerability: and their sensitivity/vulnerability:
/routing/control-plane-protocols/control-plane-protocol/bfd/ip-sh /routing/control-plane-protocols/control-plane-protocol/bfd/ip-sh
/unsolicited: /unsolicited:
o data node "enable" enables creation of unsolicited BFD IP single- o data node "enable" enables creation of unsolicited BFD IP single-
hop sessions globally, i.e. on all interfaces. See Section 6.1. hop sessions globally, i.e. on all interfaces. See Section 7.1.
o data nodes local-multiplier, desired-min-tx-interval, required- o data nodes local-multiplier, desired-min-tx-interval, required-
min-rx-interval and min-interval all impact the parameters of the min-rx-interval and min-interval all impact the parameters of the
unsolicited BFD IP single-hop sessions. unsolicited BFD IP single-hop sessions.
/routing/control-plane-protocols/control-plane-protocol/bfd/ip-sh /routing/control-plane-protocols/control-plane-protocol/bfd/ip-sh
/interfaces/interface/unsolicited: /interfaces/interface/unsolicited:
o data node "enable" enables creation of unsolicited BFD IP single- o data node "enable" enables creation of unsolicited BFD IP single-
hop sessions on a specific interface. See Section 6.1. hop sessions on a specific interface. See Section 7.1.
o data nodes local-multiplier, desired-min-tx-interval, required- o data nodes local-multiplier, desired-min-tx-interval, required-
min-rx-interval and min-interval all impact the parameters of the min-rx-interval and min-interval all impact the parameters of the
unsolicited BFD IP single-hop sessions on the interface. unsolicited BFD IP single-hop sessions on the interface.
Some of the readable data nodes in this YANG module may be considered Some of the readable data nodes in this YANG module may be considered
sensitive or vulnerable in some network environments. It is thus sensitive or vulnerable in some network environments. It is thus
important to control read access (e.g., via get, get-config, or important to control read access (e.g., via get, get-config, or
notification) to these data nodes. These are the subtrees and data notification) to these data nodes. These are the subtrees and data
nodes and their sensitivity/vulnerability: nodes and their sensitivity/vulnerability:
/routing/control-plane-protocols/control-plane-protocol/bfd/ip-sh /routing/control-plane-protocols/control-plane-protocol/bfd/ip-sh
/sessions/session/unsolicited: access to this information discloses /sessions/session/unsolicited: access to this information discloses
the role of the local system in the creation of the unsolicited BFD the role of the local system in the creation of the unsolicited BFD
session. session.
7. References 8. References
8.1. Normative References
7.1. Normative References
[I-D.ietf-bfd-yang] [I-D.ietf-bfd-yang]
Rahman, R., Zheng, L., Jethanandani, M., Pallagatti, S., Rahman, R., Zheng, L., Jethanandani, M., Pallagatti, S.,
and G. Mirsky, "YANG Data Model for Bidirectional and G. Mirsky, "YANG Data Model for Bidirectional
Forwarding Detection (BFD)", draft-ietf-bfd-yang-17 (work Forwarding Detection (BFD)", draft-ietf-bfd-yang-17 (work
in progress), August 2018. in progress), August 2018.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
skipping to change at page 12, line 5 skipping to change at page 12, line 13
<https://www.rfc-editor.org/info/rfc6536>. <https://www.rfc-editor.org/info/rfc6536>.
[RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF [RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017, Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
<https://www.rfc-editor.org/info/rfc8040>. <https://www.rfc-editor.org/info/rfc8040>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
7.2. Informative References 8.2. Informative References
[I-D.ietf-idr-rs-bfd] [I-D.ietf-idr-rs-bfd]
Bush, R., Haas, J., Scudder, J., Nipper, A., and C. Bush, R., Haas, J., Scudder, J. G., Nipper, A., and C.
Dietzel, "Making Route Servers Aware of Data Link Failures Dietzel, "Making Route Servers Aware of Data Link Failures
at IXPs", draft-ietf-idr-rs-bfd-09 (work in progress), at IXPs", draft-ietf-idr-rs-bfd-09 (work in progress),
September 2020. September 2020.
[RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A [RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
Border Gateway Protocol 4 (BGP-4)", RFC 4271, Border Gateway Protocol 4 (BGP-4)", RFC 4271,
DOI 10.17487/RFC4271, January 2006, DOI 10.17487/RFC4271, January 2006,
<https://www.rfc-editor.org/info/rfc4271>. <https://www.rfc-editor.org/info/rfc4271>.
[RFC7880] Pignataro, C., Ward, D., Akiya, N., Bhatia, M., and S. [RFC7880] Pignataro, C., Ward, D., Akiya, N., Bhatia, M., and S.
 End of changes. 33 change blocks. 
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