draft-ietf-idr-bgp-bfd-strict-mode-00.txt   draft-ietf-idr-bgp-bfd-strict-mode-01.txt 
IDR WorkGroup M. Zheng IDR Workgroup M. Zheng
Internet-Draft Indivdual Contributor Internet-Draft Individual Contributor
Intended status: Standards Track A. Lindem Intended status: Standards Track A. Lindem
Expires: March 24, 2020 Cisco Systems Expires: May 5, 2020 Cisco Systems
J. Haas J. Haas
Juniper Networks, Inc. Juniper Networks, Inc.
September 21, 2019 A. Fu
Bloomberg L.P.
November 2, 2019
BGP BFD Strict-Mode BGP BFD Strict-Mode
draft-ietf-idr-bgp-bfd-strict-mode-00 draft-ietf-idr-bgp-bfd-strict-mode-01
Abstract Abstract
This document specifies extensions to RFC4271 BGP-4 that enable a BGP This document specifies extensions to RFC4271 BGP-4 that enable a BGP
speaker to negotiate additional Bidirectional Forwarding Detection speaker to negotiate additional Bidirectional Forwarding Detection
(BFD) extensions using a BGP capability. This BFD capability enables (BFD) extensions using a BGP capability. This BFD capability enables
a BGP speaker to prevent a BGP session from being established until a a BGP speaker to prevent a BGP session from being established until a
BFD session is established. It is referred to as BGP BFD "strict- BFD session is established. It is referred to as BGP BFD "strict-
mode". BGP BFD strict-mode will be supported when both the local mode". BGP BFD strict-mode will be supported when both the local
speaker and its remote peer are BFD strict-mode capable. speaker and its remote peer are BFD strict-mode capable.
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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This Internet-Draft will expire on March 24, 2020. This Internet-Draft will expire on May 5, 2020.
Copyright Notice Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the Copyright (c) 2019 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
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
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. Requirements Language . . . . . . . . . . . . . . . . . . . . 3 2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3
3. BFD Capability . . . . . . . . . . . . . . . . . . . . . . . 3 3. BFD Strict-Mode Capability . . . . . . . . . . . . . . . . . 3
4. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 4 4. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 3
5. Manageability Considerations . . . . . . . . . . . . . . . . 5 5. Manageability Considerations . . . . . . . . . . . . . . . . 4
6. Security Considerations . . . . . . . . . . . . . . . . . . . 5 6. Security Considerations . . . . . . . . . . . . . . . . . . . 4
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
8. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 5 8. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 4
9. Normative References . . . . . . . . . . . . . . . . . . . . 6 9. Normative References . . . . . . . . . . . . . . . . . . . . 4
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction 1. Introduction
Bidirectional Forwarding Detection BFD [RFC5882] enables routers to Bidirectional Forwarding Detection BFD [RFC5882] enables routers to
monitor data plane connectivity and to detect faults in the monitor data plane connectivity and to detect faults in the
bidirectional forwarding path between them. This capability is bidirectional forwarding path between them. This capability is
leveraged by routing protocols such as BGP [RFC4271] to rapidly react leveraged by routing protocols such as BGP [RFC4271] to rapidly react
to topology changes in the face of path failures. to topology changes in the face of path failures.
The BFD interaction with BGP is specified in Section 10.2 of The BFD interaction with BGP is specified in Section 10.2 of
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for BGP session establishment. for BGP session establishment.
2. Requirements Language 2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
3. BFD Capability 3. BFD Strict-Mode Capability
The BGP Capability [RFC5492] for BFD parameters will allow a BGP The BGP Strict-Mode Capability [RFC5492] will allow a BGP speaker's
speaker's BFD capabilities including its support for BFD strict-mode. to advertise this capability. The capability is defined as follows:
This capability is defined as follows:
Capability code: TBD Capability code: TBD
Capability length: 1 octet Capability length: 0 octets
Capability value: Consists of 1 octet BFD flags as follows:
+--------------------------------------------------+
| BFD Flags (8 bits) |
+--------------------------------------------------+
The use and meaning of the fields are as follows:
BFD Flags: This field contains bit flags relating to BFD.
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|S| Reserved |
+-+-+-+-+-+-+-+-+
The most significant bit is defined as state of Strict-Mode ("Strict-
Mode", or "S") bit, which can be used by a BGP speaker to signal its
support for BFD Strict-mode. When set (value 1), this bit indicates
that the BGP speaker has the BFD "Strict-mode" enabled. If both
local BGP speaker and its peer have BFD strict-mode enabled, then BGP
session establishment will be prevented until a BFD session is
established between the peering addresses. A BGP speaker with BFD
strict-mode enabled MUST advertise the BFD capability with "S" bit
set.
The remaining bits are reserved and SHOULD be set to zero by the
sender and MUST be ignored by the receiver.
4. Operation 4. Operation
A BGP speaker which supports capabilities advertisement and has BFD A BGP speaker which supports capabilities advertisement MUST include
strict-mode enabled MUST include the BGP BFD capability with the "S" the BFD strict-mode capability.
Bit set in the BGP capabilities it advertises.
A BGP speaker which supports BFD capability, examines the list of A BGP speaker which supports the BFD Strict-Mode capability, examines
capabilities present in the Capabilities BFD Parameter that the the list of capabilities present in the capabilities that the speaker
speaker receives from its peer. If both the local and remote BGP receives from its peer. If both the local and remote BGP speakers
speakers have BFD strict-mode enabled, the BGP finite state machine include the BFD strict-mode capability, the BGP finite state machine
does not transition to the Established state from OpenSent or does not transition to the Established state from OpenSent or
OpenConfirm state [RFC4271] until the BFD session is in the Up state OpenConfirm state [RFC4271] until the BFD session is in the Up state
(see below for AdminDown state). This means that a KEEPALIVE message (see below for AdminDown state). This means that a KEEPALIVE message
is not sent nor is the KeepaliveTimer set. is not sent nor is the KeepaliveTimer set.
If the BFD session does not transition to the Up state, and the If the BFD session does not transition to the Up state, and the
HoldTimer has been negotiated to a non-zero value, the BGP FSM will HoldTimer has been negotiated to a non-zero value, the BGP FSM will
close the session appropriately. If the HoldTimer has been close the session appropriately. If the HoldTimer has been
negotiated to a zero value, the session should be closed after a time negotiated to a zero value, the session should be closed after a time
of X. This time X is referred as "BGP BFD Hold time". The proposed of X. This time X is referred as "BGP BFD Hold time". The proposed
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If BFD session is in the AdminDown state, then the BGP finite state If BFD session is in the AdminDown state, then the BGP finite state
machine will proceed normally without input from BFD. This means machine will proceed normally without input from BFD. This means
that BFD session "AdminDown" state WILL NOT prevent the BGP state that BFD session "AdminDown" state WILL NOT prevent the BGP state
transition to Established state from OpenConfirm. transition to Established state from OpenConfirm.
Once the BFD session has transitioned to the Up state, the BGP FSM Once the BFD session has transitioned to the Up state, the BGP FSM
may proceed to transition to the Established state from the OpenSent may proceed to transition to the Established state from the OpenSent
or OpenConfirm state appropriately. I.e. a KEEPALIVE message is or OpenConfirm state appropriately. I.e. a KEEPALIVE message is
sent, and the KeepaliveTimer is started. sent, and the KeepaliveTimer is started.
If either BGP peer has not advertised the BFD Capability with strict- If either BGP peer has not advertised the BFD Strict-Mode Capability,
mode enabled, then a BFD session WILL NOT be required for the BGP then a BFD session WILL NOT be required for the BGP session to reach
session to reach Established state. This does not preclude usage of Established state. This does not preclude usage of BFD after BGP
BFD after BGP session establishment [RFC5882]. session establishment [RFC5882].
5. Manageability Considerations 5. Manageability Considerations
Auto-configuration is possible for the enabling BGP BFD restrict- Auto-configuration is possible for the enabling BGP BFD Strict-Mode.
mode. However, the configuration automation is out of the scope of However, the configuration automation is out of the scope of this
this document. document.
A BGP NOTIFICATION message subcode indicating BFD Hold timer A BGP NOTIFICATION message Subcode indicating BFD Hold timer
expiration may be required for network management. (To be discussed expiration may be required for network management. (To be discussed
in the next revision of this document.) in the next revision of this document.)
6. Security Considerations 6. Security Considerations
The mechanism defined in this document interacts with the BGP finite The mechanism defined in this document interacts with the BGP finite
state machine when so configured. The security considerations of BFD state machine when so configured. The security considerations of BFD
thus become considerations for BGP-4 [RFC4271] so used. The use of thus, become considerations for BGP-4 [RFC4271] so used. Given that
the BFD Authentication mechanism defined in [RFC5880] is thus a BFD session is required for a BGP session, a Denial-of-Service
RECOMMENDED when used to protect BGP-4 [RFC4271]. (DoS) attack on BGP can now be mounted by preventing a BFD session
between the BGP peers from being established or interrupting an
existing BFD session. The use of the BFD Authentication mechanism
defined in [RFC5880] is thus RECOMMENDED when used to protect BGP-4
[RFC4271].
7. IANA Considerations 7. IANA Considerations
This document defines a new BGP capability - BFD Capability. The This document defines a new BGP capability - BFD Capability. The
Capability Code for BFD Capability is TBD. Capability Code for BFD Capability is TBD.
IANA is requested to establish a "BGP BFD Capability Flags" registry
within the "Border Gateway Protocol (BGP) Parameters" grouping. The
Registration Procedure should be Standards Action, the initial values
as follows:
+--------------+---------------+------------+---------------+
| Bit Position | Name | Short Name | Reference |
+--------------+---------------+------------+---------------+
| 0 | Strict-Mode | S | this document |
| 1-7 | Unassigned | | this document |
+--------------+---------------+------------+---------------+
8. Acknowledgement 8. Acknowledgement
The authors would like to acknowledge the review and inputs from The authors would like to acknowledge the review and inputs from
Shyam Sethuram, Mohammed Mirza, Bruno Decraene, and Carlos Pignataro. Shyam Sethuram, Mohammed Mirza, Bruno Decraene, Carlos Pignataro, and
Enke Chen.
9. Normative References 9. Normative References
[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,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[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,
skipping to change at page 6, line 37 skipping to change at page 5, line 35
DOI 10.17487/RFC5882, June 2010, DOI 10.17487/RFC5882, June 2010,
<https://www.rfc-editor.org/info/rfc5882>. <https://www.rfc-editor.org/info/rfc5882>.
[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>.
Authors' Addresses Authors' Addresses
Mercia Zheng Mercia Zheng
Indivdual Contributor Individual Contributor
Email: merciaz.ietf@gmail.com Email: merciaz.ietf@gmail.com
Acee Lindem Acee Lindem
Cisco Systems Cisco Systems
301 Midenhall Way 301 Midenhall Way
GARY, NC 27513 GARY, NC 27513
UNITED STATES UNITED STATES
Email: acee@cisco.com Email: acee@cisco.com
Jeffrey Haas Jeffrey Haas
Juniper Networks, Inc. Juniper Networks, Inc.
1133 Innovation Way 1133 Innovation Way
SUNNYVALE, CALIFORNIA 94089 SUNNYVALE, CALIFORNIA 94089
UNITED STATES UNITED STATES
Email: jhaas@juniper.net Email: jhaas@juniper.net
Albert Fu
Bloomberg L.P.
Email: afu14@bloomberg.net
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