< draft-ketant-lsr-ospf-bfd-strict-mode-00.txt   draft-ketant-lsr-ospf-bfd-strict-mode-01.txt >
Link State Routing K. Talaulikar Link State Routing K. Talaulikar
Internet-Draft P. Psenak Internet-Draft P. Psenak
Intended status: Standards Track Cisco Systems, Inc. Intended status: Standards Track Cisco Systems, Inc.
Expires: September 5, 2019 March 4, 2019 Expires: September 12, 2019 March 11, 2019
OSPF BFD Strict-Mode OSPF BFD Strict-Mode
draft-ketant-lsr-ospf-bfd-strict-mode-00 draft-ketant-lsr-ospf-bfd-strict-mode-01
Abstract Abstract
This document specifies the extensions to OSPF that enables a router This document specifies the extensions to OSPF that enables a router
and its neighbor to signal their intention to use Bidirectional and its neighbor to signal their intention to use Bidirectional
Forwarding Detection (BFD) for their adjacency using link-local Forwarding Detection (BFD) for their adjacency using link-local
advertisement between them. The signaling of this BFD enablement, advertisement between them. The signaling of this BFD enablement,
allows the router to block and not allow the establishment of allows the router to block and not allow the establishment of
adjacency with its neighbor router until a BFD session is adjacency with its neighbor router until a BFD session is
successfully established between them. The document describes this successfully established between them. The document describes this
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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 5, 2019. This Internet-Draft will expire on September 12, 2019.
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
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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. LLS B-bit Flag . . . . . . . . . . . . . . . . . . . . . . . 3 2. LLS B-bit Flag . . . . . . . . . . . . . . . . . . . . . . . 3
3. Procedures . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Procedures . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Operations & Management Considerations . . . . . . . . . . . 5 4. Operations & Management Considerations . . . . . . . . . . . 5
5. Backward Compatibility . . . . . . . . . . . . . . . . . . . 5 5. Backward Compatibility . . . . . . . . . . . . . . . . . . . 5
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
7. Security Considerations . . . . . . . . . . . . . . . . . . . 6 7. Security Considerations . . . . . . . . . . . . . . . . . . . 6
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
9.1. Normative References . . . . . . . . . . . . . . . . . . 6 9.1. Normative References . . . . . . . . . . . . . . . . . . 6
9.2. Informative References . . . . . . . . . . . . . . . . . 7 9.2. Informative References . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction 1. Introduction
Bidirectional Forwarding Detection (BFD) [RFC5880] enables routers to Bidirectional Forwarding Detection (BFD) [RFC5880] enables routers to
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mode across different interfaces or even different neighbors on the mode across different interfaces or even different neighbors on the
same multi-access LAN interface. same multi-access LAN interface.
Once the OSPF state machine has moved beyond the Init state, any Once the OSPF state machine has moved beyond the Init state, any
change in the B-bit advertised in subsequent Hello messages MUST NOT change in the B-bit advertised in subsequent Hello messages MUST NOT
result in any trigger in either the OSPF adjacency or the BFD session result in any trigger in either the OSPF adjacency or the BFD session
management (i.e. the B-bit is considered only when in the Init management (i.e. the B-bit is considered only when in the Init
state). The disabling of BFD (or BFD strict-mode) on a router would state). The disabling of BFD (or BFD strict-mode) on a router would
result in its not setting the B-bit in its subsequent Hello messages. result in its not setting the B-bit in its subsequent Hello messages.
The disabling of BFD would result in bringing down of any established The disabling of BFD strict-mode has no change on the BFD operations
session with its neighbor and thereby also bringing down the OSPF and would not result in bringing down of any established BFD session.
adjacency as a result of the BFD state change and not the B-bit The disabling of BFD would result in the BFD session brought down due
change. to Admin reason and hence would not bring down the OSPF adjacency.
When BFD is enabled on an interface over which we already have an
existing OSPF adjacency, it would result in the router setting the
B-bit in its subsequent Hello messages. If the adjacency is already
up (i.e. in its terminal state of Full or 2-way with non-DR routers
on a LAN) with a neighbor that also support BFD strict-mode, then an
implemantion SHOULD NOT bring this adjacency down and instead use the
BFD strict-mode of operations after the next transition into Init
state. However, if the adjacency is not up, then an implementation
MAY bring such an adjacency down so it can use the BFD strict-mode
for its bring up.
4. Operations & Management Considerations 4. Operations & Management Considerations
An implementation SHOULD report the BFD session status along with the An implementation SHOULD report the BFD session status along with the
OSPF Init adjacency state when operating in BFD strict-mode and OSPF Init adjacency state when operating in BFD strict-mode and
perform logging operations on state transitions to include the BFD perform logging operations on state transitions to include the BFD
events. This allows an operator to detect scenarios where an OSPF events. This allows an operator to detect scenarios where an OSPF
adjacency may be stuck waiting for BFD session establishment. adjacency may be stuck waiting for BFD session establishment.
5. Backward Compatibility 5. Backward Compatibility
An implementation MUST support OSPF adjacency formation and An implementation MUST support OSPF adjacency formation and
operations with a neighbor router that does not advertise the BFD operations with a neighbor router that does not advertise the BFD
strict-mode capability - both when that neighbor router does not strict-mode capability - both when that neighbor router does not
support BFD and when it does support BFD but not in the strict-mode support BFD and when it does support BFD but not in the strict-mode
of operation as described in this document. Implementations MAY of operation as described in this document. Implementations MAY
provide an option to specifically enable BFD operations only in the provide an option to specifically enable BFD operations only in the
strict-mode in which case, OSPF adjacency with a neighbor that does strict-mode in which case, OSPF adjacency with a neighbor that does
not support BFD strict-mode would not be established successfully. not support BFD strict-mode would not be established successfully.
Implementations MAY provide an option to disable BFD strict-mode
which results in the router not advertising the B-bit and BFD
operations being performed in the same way as before this
specification.
The signaling specified in this document happens at a link-local The signaling specified in this document happens at a link-local
level between routers on that link. A router which does not support level between routers on that link. A router which does not support
this specification would ignore the B-bit in the LLS block of hello this specification would ignore the B-bit in the LLS block of hello
messages from its neighbors and continue to bootstrap BFD sessions, messages from its neighbors and continue to bootstrap BFD sessions,
if enabled, without holding back the OSPF adjacency formation. Since if enabled, without holding back the OSPF adjacency formation. Since
the router which does not support this specification would not have the router which does not support this specification would not have
set the B-bit in the LLS block of its own hello messages, its set the B-bit in the LLS block of its own hello messages, its
neighbor routers that support this specification would not use BFD neighbor routers that support this specification would not use BFD
strict-mode with it. As a result, the behavior would be the same as strict-mode with it. As a result, the behavior would be the same as
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