Unsolicited BFD for Sessionless Applications
draft-ietf-bfd-unsolicited-02
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft that was ultimately published as RFC 9468.
Expired & archived
|
|
|---|---|---|---|
| Authors | Enke Chen , Naiming Shen , Robert Raszuk , Reshad Rahman | ||
| Last updated | 2021-01-29 (Latest revision 2020-07-28) | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Formats | |||
| Reviews |
TSVART Last Call review
(of
-11)
by Magnus Westerlund
Ready w/issues
GENART Last Call review
(of
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by Dan Romascanu
Ready w/nits
|
||
| Additional resources | Mailing list discussion | ||
| Stream | WG state | In WG Last Call | |
| Document shepherd | Jeffrey Haas | ||
| IESG | IESG state | Became RFC 9468 (Proposed Standard) | |
| Consensus boilerplate | Unknown | ||
| Telechat date | (None) | ||
| Responsible AD | (None) | ||
| Send notices to | Jeffrey Haas <jhaas@pfrc.org> |
draft-ietf-bfd-unsolicited-02
Network Working Group E. Chen
Internet-Draft Cisco Systems
Intended status: Standards Track N. Shen
Expires: January 29, 2021 Zededa
R. Raszuk
Bloomberg LP
R. Rahman
Cisco Systems
July 28, 2020
Unsolicited BFD for Sessionless Applications
draft-ietf-bfd-unsolicited-02
Abstract
For operational simplification of "sessionless" applications using
BFD, in this document we present procedures for "unsolicited BFD"
that allow a BFD session to be initiated by only one side, and be
established without explicit per-session configuration or
registration by the other side (subject to certain per-interface or
per-router policies).
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
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
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://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
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on January 29, 2021.
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Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Procedures for Unsolicited BFD . . . . . . . . . . . . . . . 3
3. YANG Data Model . . . . . . . . . . . . . . . . . . . . . . . 4
3.1. Unsolicited BFD Hierarchy . . . . . . . . . . . . . . . . 4
3.2. Unsolicited BFD Module . . . . . . . . . . . . . . . . . 5
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
5. Security Considerations . . . . . . . . . . . . . . . . . . . 9
5.1. BFD Protocol Security Considerations . . . . . . . . . . 9
5.2. YANG Module Security Considerations . . . . . . . . . . . 9
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
6.1. Normative References . . . . . . . . . . . . . . . . . . 10
6.2. Informative References . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12
1. Introduction
The current implementation and deployment practice for BFD ([RFC5880]
and [RFC5881]) usually requires BFD sessions be explicitly configured
or registered on both sides. This requirement is not an issue when
an application like BGP [RFC4271] has the concept of a "session" that
involves both sides for its establishment. However, this requirement
can be operationally challenging when the prerequisite "session" does
not naturally exist between two endpoints in an application.
Simultaneous configuration and coordination may be required on both
sides for BFD to take effect. For example:
o When BFD is used to keep track of the "liveness" of the nexthop of
static routes. Although only one side may need the BFD
functionality, currently both sides need to be involved in
specific configuration and coordination and in some cases static
routes are created unnecessarily just for BFD.
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o When BFD is used to keep track of the "liveness" of the third-pary
nexthop of BGP routes received from the Route Server [RFC7947] at
an Internet Exchange Point (IXP). As the third-party nexthop is
different from the peering address of the Route Server, for BFD to
work, currently two routers peering with the Route Server need to
have routes and nexthops from each other (although indirectly via
the Router Server), and the nexthop of each router must be present
at the same time. These issues are also discussed in
[I-D.ietf-idr-rs-bfd].
Clearly it is beneficial and desirable to reduce or eliminate
unnecessary configurations and coordination in these "sessionless"
applications using BFD.
In this document we present procedures for "unsolicited BFD" that
allow a BFD session to be initiated by only one side, and be
established without explicit per-session configuration or
registration by the other side (subject to certain per-interface or
per-router policies).
With "unsolicited BFD" there is potential risk for excessive resource
usage by BFD from "unexpected" remote systems. To mitigate such
risks, several mechanisms are recommended in the Security
Considerations section.
Compared to the "Seamless BFD" [RFC7880], this proposal involves only
minor procedural enhancements to the widely deployed BFD itself.
Thus we believe that this proposal is inherently simpler in the
protocol itself and deployment. As an example, it does not require
the exchange of BFD discriminators over an out-of-band channel before
the BFD session bring-up.
When BGP Add-Path [RFC7911] is deployed at an IXP using the Route
Server, multiple BGP paths (when exist) can be made available to the
clients of the Router Server as described in [RFC7947]. The
"unsolicited BFD" can be used in BGP route selection by these clients
to eliminate paths with "inaccessible nexthops".
2. Procedures for Unsolicited BFD
With "unsolicited BFD", one side takes the "Active role" and the
other side takes only the "Passive role" as described in [RFC5880].
On the passive side, the "unsolicited BFD" SHOULD be configured
explicitly on an interface. 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 its BFD Control packets. The
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"Discriminator", however, MUST be chosen to allow multiple
unsolicited BFD sessions.
The active side initiates the BFD Control packets as specified in
[RFC5880]. The passive side does not initiates the BFD Control
packets.
When the passive side receives a BFD Control packet from the active
side with 0 as the "remote-discriminator", and it does not find an
existing session with the same source address as in the packet and
"unsolicited BFD" is allowed on the interface by local policy, it
SHOULD then create a matching BFD session toward the active side
(based on the source address and destination address in the BFD
Control packet) as if the session were locally registered. It would
then start sending the BFD Control packets and perform necessary
procedure for bringing up, maintaining and tearing down the BFD
session. If the BFD session fails to get established within certain
specified time, or if an established BFD session goes down, the
passive side would stop sending BFD Control packets and delete the
BFD session created until the BFD Control packets is initiated by the
active side again.
The "Passive role" may change to the "Active role" when a local
client registers for the same BFD session, and from the "Active role
" to the "Passive role " when there is no longer any locally
registered client for the BFD session.
3. YANG Data Model
This section extends the YANG data model for BFD [I-D.ietf-bfd-yang]
to cover the unsolicited BFD.
3.1. Unsolicited BFD Hierarchy
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module: ietf-bfd-unsolicited
augment /rt:routing/rt:control-plane-protocols
/rt:control-plane-protocol/bfd:bfd/bfd-ip-sh:ip-sh:
+--rw unsolicited {bfd-unsol:unsolicited-params-global}?
+--rw enable? boolean
+--rw local-multiplier? multiplier
+--rw (interval-config-type)?
+--:(tx-rx-intervals)
| +--rw desired-min-tx-interval? uint32
| +--rw required-min-rx-interval? uint32
+--:(single-interval) {single-minimum-interval}?
+--rw min-interval? uint32
augment /rt:routing/rt:control-plane-protocols
/rt:control-plane-protocol/bfd:bfd/bfd-ip-sh:ip-sh
/bfd-ip-sh:interfaces:
+--rw unsolicited {bfd-unsol:unsolicited-params-per-interface}?
+--rw enable? boolean
+--rw local-multiplier? multiplier
+--rw (interval-config-type)?
+--:(tx-rx-intervals)
| +--rw desired-min-tx-interval? uint32
| +--rw required-min-rx-interval? uint32
+--:(single-interval) {single-minimum-interval}?
+--rw min-interval? uint32
augment /rt:routing/rt:control-plane-protocols
/rt:control-plane-protocol/bfd:bfd/bfd-ip-sh:ip-sh
/bfd-ip-sh:sessions/bfd-ip-sh:session:
+--ro unsolicited
+--ro role? bfd-unsol:unsolicited-role
3.2. Unsolicited BFD Module
<CODE BEGINS> file "ietf-bfd-unsolicited@2019-06-26.yang"
module ietf-bfd-unsolicited {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-bfd-unsolicited";
prefix "bfd-unsol";
// RFC Ed.: replace occurences of XXXX/YYYY with actual RFC numbers
// and remove this note
import ietf-bfd-types {
prefix "bfd-types";
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reference "RFC XXXX: YANG Data Model for BFD";
}
import ietf-bfd {
prefix "bfd";
reference "RFC XXXX: YANG Data Model for BFD";
}
import ietf-bfd-ip-sh {
prefix "bfd-ip-sh";
reference "RFC XXXX: YANG Data Model for BFD";
}
import ietf-routing {
prefix "rt";
reference
"RFC 8349: A YANG Data Model for Routing Management
(NMDA version)";
}
organization "IETF BFD Working Group";
contact
"WG Web: <http://tools.ietf.org/wg/bfd>
WG List: <rtg-bfd@ietf.org>
Editors: Enke Chen (enkechen@cisco.com),
Naiming Shen (naiming@cisco.com),
Robert Raszuk (robert@raszuk.net),
Reshad Rahman (rrahman@cisco.com)";
description
"This module contains the YANG definition for BFD unsolicited
as per RFC YYYY.
Copyright (c) 2018 IETF Trust and the persons
identified as authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with or
without modification, is permitted pursuant to, and subject
to the license terms contained in, the Simplified BSD License
set forth in Section 4.c of the IETF Trust's Legal Provisions
Relating to IETF Documents
(http://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC XXXX; see
the RFC itself for full legal notices.";
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reference "RFC YYYY";
revision 2019-06-26 {
description "Initial revision.";
reference "RFC YYYY: A YANG data model for BFD unsolicited";
}
/*
* Feature definitions
*/
feature unsolicited-params-global {
description
"This feature indicates that the server supports global
parameters for unsolicited sessions.";
}
feature unsolicited-params-per-interface {
description
"This feature indicates that the server supports per-interface
parameters for unsolicited sessions.";
}
/*
* Type Definitions
*/
typedef unsolicited-role {
type enumeration {
enum unsolicited-active {
description "Active role";
}
enum unsolicited-passive {
description "Passive role";
}
}
description "Unsolicited role";
}
/*
* Augments
*/
augment "/rt:routing/rt:control-plane-protocols/"
+ "rt:control-plane-protocol/bfd:bfd/bfd-ip-sh:ip-sh" {
description
"Augmentation for BFD unsolicited parameters";
container unsolicited {
if-feature bfd-unsol:unsolicited-params-global;
description
"BFD unsolicited top level container";
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leaf enable {
type boolean;
default false;
description
"Enable BFD unsolicited globally for IP single-hop.";
}
uses bfd-types:base-cfg-parms;
}
}
augment "/rt:routing/rt:control-plane-protocols/"
+ "rt:control-plane-protocol/bfd:bfd/bfd-ip-sh:ip-sh/"
+ "bfd-ip-sh:interfaces" {
description
"Augmentation for BFD unsolicited on IP single-hop interface";
container unsolicited {
if-feature bfd-unsol:unsolicited-params-per-interface;
description
"BFD IP single-hop interface unsolicited top level container";
leaf enable {
type boolean;
default false;
description "Enable BFD unsolicited on this interface.";
}
uses bfd-types:base-cfg-parms;
}
}
augment "/rt:routing/rt:control-plane-protocols/"
+ "rt:control-plane-protocol/bfd:bfd/bfd-ip-sh:ip-sh/"
+ "bfd-ip-sh:sessions/bfd-ip-sh:session" {
description
"Augmentation for BFD unsolicited on IP single-hop session";
container unsolicited {
config false;
description
"BFD IP single-hop session unsolicited top level container";
leaf role {
type bfd-unsol:unsolicited-role;
description "Role.";
}
}
}
}
<CODE ENDS>
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4. IANA Considerations
This documents makes no IANA requests.
5. Security Considerations
5.1. BFD Protocol Security Considerations
The same security considerations as those described in [RFC5880] and
[RFC5881] apply to this document. With "unsolicited BFD" there is
potential risk for excessive resource usage by BFD from "unexpected"
remote systems. To mitigate such risks, the following measures are
RECOMMENDED:
o Limit the feature to specific interfaces, and to a single-hop BFD
with "TTL=255" [RFC5082]. In addition make sure the source
address of an incoming BFD packet belongs to the subnet of the
interface from which the BFD packet is received.
o Apply "access control" to allow BFD packets only from certain
subnets or hosts.
o Deploy the feature only in certain "trustworthy" environment,
e.g., at an IXP, or between a provider and its customers.
o Adjust BFD parameters as needed for the particular deployment and
scale.
o Use BFD authentication.
5.2. YANG Module Security Considerations
The YANG module specified in this document defines a schema for data
that is designed to be accessed via network management protocols such
as NETCONF [RFC6241] or RESTCONF [RFC8040]. The lowest NETCONF layer
is the secure transport layer, and the mandatory-to-implement secure
transport is Secure Shell (SSH) [RFC6242]. The lowest RESTCONF layer
is HTTPS, and the mandatory-to-implement secure transport is TLS
[RFC5246].
The NETCONF access control model [RFC6536] provides the means to
restrict access for particular NETCONF or RESTCONF users to a
preconfigured subset of all available NETCONF or RESTCONF protocol
operations and content.
There are a number of data nodes defined in this YANG module that are
writable/creatable/deletable (i.e., config true, which is the
default). These data nodes may be considered sensitive or vulnerable
in some network environments. Write operations (e.g., edit-config)
to these data nodes without proper protection can have a negative
effect on network operations. These are the subtrees and data nodes
and their sensitivity/vulnerability:
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/routing/control-plane-protocols/control-plane-protocol/bfd/ip-sh
/unsolicited:
o data node "enable" enables creation of unsolicited BFD IP single-
hop sessions globally, i.e. on all interfaces. See Section 5.1.
o data nodes local-multiplier, desired-min-tx-interval, required-
min-rx-interval and min-interval all impact the parameters of the
unsolicited BFD IP single-hop sessions.
/routing/control-plane-protocols/control-plane-protocol/bfd/ip-sh
/interfaces/interface/unsolicited:
o data node "enable" enables creation of unsolicited BFD IP single-
hop sessions on a specific interface. See Section 5.1.
o data nodes local-multiplier, desired-min-tx-interval, required-
min-rx-interval and min-interval all impact the parameters of the
unsolicited BFD IP single-hop sessions on the interface.
Some of the readable data nodes in this YANG module may be considered
sensitive or vulnerable in some network environments. It is thus
important to control read access (e.g., via get, get-config, or
notification) to these data nodes. These are the subtrees and data
nodes and their sensitivity/vulnerability:
/routing/control-plane-protocols/control-plane-protocol/bfd/ip-sh
/sessions/session/unsolicited: access to this information discloses
the role of the local system in the creation of the unsolicited BFD
session.
6. References
6.1. Normative References
[I-D.ietf-bfd-yang]
Rahman, R., Zheng, L., Jethanandani, M., Pallagatti, S.,
and G. Mirsky, "YANG Data Model for Bidirectional
Forwarding Detection (BFD)", draft-ietf-bfd-yang-17 (work
in progress), August 2018.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC5082] Gill, V., Heasley, J., Meyer, D., Savola, P., Ed., and C.
Pignataro, "The Generalized TTL Security Mechanism
(GTSM)", RFC 5082, DOI 10.17487/RFC5082, October 2007,
<https://www.rfc-editor.org/info/rfc5082>.
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[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246,
DOI 10.17487/RFC5246, August 2008,
<https://www.rfc-editor.org/info/rfc5246>.
[RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection
(BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010,
<https://www.rfc-editor.org/info/rfc5880>.
[RFC5881] Katz, D. and D. Ward, "Bidirectional Forwarding Detection
(BFD) for IPv4 and IPv6 (Single Hop)", RFC 5881,
DOI 10.17487/RFC5881, June 2010,
<https://www.rfc-editor.org/info/rfc5881>.
[RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
and A. Bierman, Ed., "Network Configuration Protocol
(NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
<https://www.rfc-editor.org/info/rfc6241>.
[RFC6242] Wasserman, M., "Using the NETCONF Protocol over Secure
Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011,
<https://www.rfc-editor.org/info/rfc6242>.
[RFC6536] Bierman, A. and M. Bjorklund, "Network Configuration
Protocol (NETCONF) Access Control Model", RFC 6536,
DOI 10.17487/RFC6536, March 2012,
<https://www.rfc-editor.org/info/rfc6536>.
[RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
<https://www.rfc-editor.org/info/rfc8040>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
6.2. Informative References
[I-D.ietf-idr-rs-bfd]
Bush, R., Haas, J., Scudder, J., Nipper, A., and C.
Dietzel, "Making Route Servers Aware of Data Link Failures
at IXPs", draft-ietf-idr-rs-bfd-08 (work in progress),
September 2019.
[RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
Border Gateway Protocol 4 (BGP-4)", RFC 4271,
DOI 10.17487/RFC4271, January 2006,
<https://www.rfc-editor.org/info/rfc4271>.
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[RFC7880] Pignataro, C., Ward, D., Akiya, N., Bhatia, M., and S.
Pallagatti, "Seamless Bidirectional Forwarding Detection
(S-BFD)", RFC 7880, DOI 10.17487/RFC7880, July 2016,
<https://www.rfc-editor.org/info/rfc7880>.
[RFC7911] Walton, D., Retana, A., Chen, E., and J. Scudder,
"Advertisement of Multiple Paths in BGP", RFC 7911,
DOI 10.17487/RFC7911, July 2016,
<https://www.rfc-editor.org/info/rfc7911>.
[RFC7947] Jasinska, E., Hilliard, N., Raszuk, R., and N. Bakker,
"Internet Exchange BGP Route Server", RFC 7947,
DOI 10.17487/RFC7947, September 2016,
<https://www.rfc-editor.org/info/rfc7947>.
Authors' Addresses
Enke Chen
Cisco Systems
560 McCarthy Blvd.
Milpitas, CA 95035
USA
Email: enkechen@cisco.com
Naiming Shen
Zededa
Email: naiming@zededa.com
Robert Raszuk
Bloomberg LP
731 Lexington Ave
New York City, NY 10022
USA
Email: robert@raszuk.net
Reshad Rahman
Cisco Systems
2000 Innovation Drive
Kanata, Ontario K2K 3E8
Canada
Email: rrahman@cisco.com
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