draft-ietf-lsr-isis-rfc5306bis-07.txt   draft-ietf-lsr-isis-rfc5306bis-08.txt 
IS-IS for IP Internets L. Ginsberg IS-IS for IP Internets L. Ginsberg
Internet-Draft P. Wells Internet-Draft P. Wells
Obsoletes: 5306 (if approved) Cisco Systems, Inc. Obsoletes: 5306 (if approved) Cisco Systems, Inc.
Intended status: Standards Track September 18, 2019 Intended status: Standards Track September 19, 2019
Expires: March 21, 2020 Expires: March 22, 2020
Restart Signaling for IS-IS Restart Signaling for IS-IS
draft-ietf-lsr-isis-rfc5306bis-07 draft-ietf-lsr-isis-rfc5306bis-08
Abstract Abstract
This document describes a mechanism for a restarting router to signal This document describes a mechanism for a restarting router to signal
to its neighbors that it is restarting, allowing them to reestablish to its neighbors that it is restarting, allowing them to reestablish
their adjacencies without cycling through the down state, while still their adjacencies without cycling through the down state, while still
correctly initiating database synchronization. correctly initiating database synchronization.
This document additionally describes a mechanism for a router to This document additionally describes a mechanism for a router to
signal its neighbors that it is preparing to initiate a restart while signal its neighbors that it is preparing to initiate a restart while
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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 March 21, 2020. This Internet-Draft will expire on March 22, 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
skipping to change at page 5, line 29 skipping to change at page 5, line 29
system. It indicates the time after which the router will declare system. It indicates the time after which the router will declare
that it has failed to achieve database synchronization (by setting that it has failed to achieve database synchronization (by setting
the overload bit in its own LSP). This is initialized to 65535 the overload bit in its own LSP). This is initialized to 65535
seconds, but is set to the minimum of the remaining times of received seconds, but is set to the minimum of the remaining times of received
IIHs containing a restart TLV with the Restart Acknowledgement (RA) IIHs containing a restart TLV with the Restart Acknowledgement (RA)
set and an indication that the neighbor has an adjacency in the "UP" set and an indication that the neighbor has an adjacency in the "UP"
state to the restarting router. (See Section 3.2.1a.) state to the restarting router. (See Section 3.2.1a.)
3.2. Restart TLV 3.2. Restart TLV
A new TLV is defined to be included in IIH PDUs. The presence of A new TLV is defined to be included in IIH PDUs. The TLV includes
this TLV indicates that the sender supports the functionality defined flags that are used to convey information during a (re)start. The
in this document. The TLV includes flags that are used to convey absence of this TLV indicates that the sender supports none of the
information during a (re)start. All IIHs transmitted by a router functionality defined in this document. Therefore, if a router
that supports this capability MUST include this TLV. supports any of the functionality defined in this document it MUST
include this TLV in all transmitted IIHs.
Type 211 Type 211
Length: Number of octets in the Value field (1 to (3 + ID Length)) Length: Number of octets in the Value field (1 to (3 + ID Length))
Value Value
No. of octets No. of octets
+-----------------------+ +-----------------------+
| Flags | 1 | Flags | 1
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is expecting an RA on a LAN circuit should assume that the is expecting an RA on a LAN circuit should assume that the
acknowledgement is directed at the local system if the TLV acknowledgement is directed at the local system if the TLV
is received with RA set and Restarting Neighbor System ID is received with RA set and Restarting Neighbor System ID
is not present. It is an implementation choice whether to is not present. It is an implementation choice whether to
continue to accept (on a LAN) a TLV with RA set and continue to accept (on a LAN) a TLV with RA set and
Restarting Neighbor System ID absent. Note that the omission Restarting Neighbor System ID absent. Note that the omission
of the Restarting Neighbor System ID only introduces ambiguity of the Restarting Neighbor System ID only introduces ambiguity
in the case where there are multiple systems on a LAN in the case where there are multiple systems on a LAN
simultaneously performing restart. simultaneously performing restart.
The functionality associated with each of the defined flags (as The RR and SA flags may both be set in the TLV under the conditions
described in the following sections) is mutually exclusive with any described in Section 3.3.2. All other flag combinations are invalid
of the other flags. Therefore, it is expected that at most one flag and MUST NOT be transmitted. Received TLVs which have invalid flag
will be set in a TLV. When transmitting a TLV multiple flags MUST combinations set MUST be ignored.
NOT be set. Received TLVs which have multiple flags set MUST be
ignored.
3.2.1. Use of RR and RA Bits 3.2.1. Use of RR and RA Bits
The RR bit is used by a (re)starting router to signal to its The RR bit is used by a (re)starting router to signal to its
neighbors that a (re)start is in progress, that an existing adjacency neighbors that a (re)start is in progress, that an existing adjacency
SHOULD be maintained even under circumstances when the normal SHOULD be maintained even under circumstances when the normal
operation of the adjacency state machine would require the adjacency operation of the adjacency state machine would require the adjacency
to be reinitialized, to request a set of CSNPs, and to request to be reinitialized, to request a set of CSNPs, and to request
setting of the SRMflags. setting of the SRMflags.
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RX PR | Set Planned Restart | RX PR | Set Planned Restart |
| state. | | state. |
| Update hold time | Update hold time
| Send PA | | Send PA |
-------------+----------------------+------------------------- -------------+----------------------+-------------------------
RX PR clr | Clear Planned | RX PR clr | Clear Planned |
and RR clr | Restart State | and RR clr | Restart State |
| Restore holdtime to | | Restore holdtime to |
| local value | | local value |
-------------+----------------------+------------------------- -------------+----------------------+-------------------------
RX PA | Proceed with planned |
| restart |
-------------+----------------------+-------------------------
RX RR | Maintain ADJ State | RX RR | Maintain ADJ State |
| Send RA | | Send RA |
| Set SRM,send CSNP | | Set SRM,send CSNP |
| (Note 1) | | (Note 1) |
| Update Hold Time, | | Update Hold Time, |
| set Restart Mode | | set Restart Mode |
| (Note 2) | | (Note 2) |
-------------+----------------------+------------------------- -------------+----------------------+-------------------------
RX RR clr | Clr Restart mode | RX RR clr | Clr Restart mode |
-------------+----------------------+------------------------- -------------+----------------------+-------------------------
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Event | Restarting | ADJ Seen | ADJ Seen | SPF Wait Event | Restarting | ADJ Seen | ADJ Seen | SPF Wait
| | RA | CSNP | | | RA | CSNP |
=================================================================== ===================================================================
Restart | Send PR | | | Restart | Send PR | | |
planned | | | | planned | | | |
------------+--------------------+-----------+-----------+------------ ------------+--------------------+-----------+-----------+------------
Planned | Send PR clr | | | Planned | Send PR clr | | |
restart | | | | restart | | | |
canceled | | | | canceled | | | |
------------+--------------------+-----------+-----------+------------ ------------+--------------------+-----------+-----------+------------
RX PA | Proceed with | | |
| planned restart | | |
------------+--------------------+-----------+-----------+------------
Router | Send IIH/RR | | | Router | Send IIH/RR | | |
restarts | ADJ Init | | | restarts | ADJ Init | | |
| Start T1,T2,T3 | | | | Start T1,T2,T3 | | |
------------+--------------------+-----------+-----------+------------ ------------+--------------------+-----------+-----------+------------
RX RR | Send RA | | | RX RR | Send RA | | |
------------+--------------------+-----------+-----------+------------ ------------+--------------------+-----------+-----------+------------
RX RA | Adjust T3 | | Cancel T1 | RX RA | Adjust T3 | | Cancel T1 |
| Goto ADJ Seen RA | | Adjust T3 | | Goto ADJ Seen RA | | Adjust T3 |
----------- +--------------------+-----------+-----------+------------ ----------- +--------------------+-----------+-----------+------------
RX CSNP set| Goto ADJ Seen CSNP | Cancel T1 | | RX CSNP set| Goto ADJ Seen CSNP | Cancel T1 | |
 End of changes. 7 change blocks. 
18 lines changed or deleted 17 lines changed or added

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