draft-ietf-ospf-link-overload-14.txt   draft-ietf-ospf-link-overload-15.txt 
Open Shortest Path First IGP S. Hegde Open Shortest Path First IGP S. Hegde
Internet-Draft Juniper Networks, Inc. Internet-Draft Juniper Networks, Inc.
Intended status: Standards Track P. Sarkar Intended status: Standards Track P. Sarkar
Expires: July 28, 2018 Arrcus Inc. Expires: August 4, 2018 Arrcus, Inc.
H. Gredler H. Gredler
Individual Individual
M. Nanduri M. Nanduri
ebay Corporation ebay Corporation
L. Jalil L. Jalil
Verizon Verizon
January 24, 2018 January 31, 2018
OSPF Graceful Link shutdown OSPF Graceful Link shutdown
draft-ietf-ospf-link-overload-14 draft-ietf-ospf-link-overload-15
Abstract Abstract
When a link is being prepared to be taken out of service, the traffic When a link is being prepared to be taken out of service, the traffic
needs to be diverted from both ends of the link. Increasing the needs to be diverted from both ends of the link. Increasing the
metric to the highest value on one side of the link is not sufficient metric to the highest value on one side of the link is not sufficient
to divert the traffic flowing in the other direction. to divert the traffic flowing in the other direction.
It is useful for routers in an OSPFv2 or OSPFv3 routing domain to be It is useful for the routers in an OSPFv2 or OSPFv3 routing domain to
able to advertise a link as being in a graceful-shutdown state to be able to advertise a link as being in a graceful-shutdown state to
indicate impending maintenance activity on the link. This indicate impending maintenance activity on the link. This
information can be used by the network devices to re-route the information can be used by the network devices to re-route the
traffic effectively. traffic effectively.
This document describes the protocol extensions to disseminate This document describes the protocol extensions to disseminate
graceful-link-shutdown information in OSPFv2 and OSPFv3. graceful-link-shutdown information in OSPFv2 and OSPFv3.
Requirements Language Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
skipping to change at page 2, line 10 skipping to change at page 2, line 10
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 July 28, 2018. This Internet-Draft will expire on August 4, 2018.
Copyright Notice Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the Copyright (c) 2018 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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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 . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Flooding Scope . . . . . . . . . . . . . . . . . . . . . . . 4 3. Flooding Scope . . . . . . . . . . . . . . . . . . . . . . . 4
4. Graceful-Link-Shutdown sub-TLV . . . . . . . . . . . . . . . 4 4. Protocol Extensions . . . . . . . . . . . . . . . . . . . . . 4
4.1. OSPFv2 graceful-link-shutdown sub-TLV . . . . . . . . . . 4 4.1. OSPFv2 graceful-link-shutdown sub-TLV . . . . . . . . . . 4
4.2. Remote IPv4 Address Sub-TLV . . . . . . . . . . . . . . . 5 4.2. Remote IPv4 Address Sub-TLV . . . . . . . . . . . . . . . 5
4.3. Local/Remote Interface ID Sub-TLV . . . . . . . . . . . . 6 4.3. Local/Remote Interface ID Sub-TLV . . . . . . . . . . . . 6
4.4. OSPFv3 Graceful-Link-Shutdown sub-TLV . . . . . . . . . . 6 4.4. OSPFv3 Graceful-Link-Shutdown sub-TLV . . . . . . . . . . 6
4.5. BGP-LS Graceful-Link-Shutdown TLV . . . . . . . . . . . . 7 4.5. BGP-LS Graceful-Link-Shutdown TLV . . . . . . . . . . . . 7
4.6. Distinguishing parallel links . . . . . . . . . . . . . . 7 4.6. Distinguishing parallel links . . . . . . . . . . . . . . 7
5. Elements of procedure . . . . . . . . . . . . . . . . . . . . 8 5. Elements of procedure . . . . . . . . . . . . . . . . . . . . 8
5.1. Point-to-point links . . . . . . . . . . . . . . . . . . 8 5.1. Point-to-point links . . . . . . . . . . . . . . . . . . 9
5.2. Broadcast/NBMA links . . . . . . . . . . . . . . . . . . 9 5.2. Broadcast/NBMA links . . . . . . . . . . . . . . . . . . 10
5.3. Point-to-multipoint links . . . . . . . . . . . . . . . . 9 5.3. Point-to-multipoint links . . . . . . . . . . . . . . . . 10
5.4. Unnumbered interfaces . . . . . . . . . . . . . . . . . . 10 5.4. Unnumbered interfaces . . . . . . . . . . . . . . . . . . 10
5.5. Hybrid Broadcast and P2MP interfaces . . . . . . . . . . 10 5.5. Hybrid Broadcast and P2MP interfaces . . . . . . . . . . 11
6. Maximum TE Metric . . . . . . . . . . . . . . . . . . . . . . 10 6. Backward compatibility . . . . . . . . . . . . . . . . . . . 11
7. Backward compatibility . . . . . . . . . . . . . . . . . . . 10 7. Applications . . . . . . . . . . . . . . . . . . . . . . . . 11
8. Applications . . . . . . . . . . . . . . . . . . . . . . . . 11 7.1. Pseudowire Services . . . . . . . . . . . . . . . . . . . 11
8.1. Pseudowire Services . . . . . . . . . . . . . . . . . . . 11 7.2. Controller based Traffic Engineering Deployments . . . . 12
8.2. Controller based Traffic Engineering Deployments . . . . 12 7.3. L3VPN Services and sham-links . . . . . . . . . . . . . . 13
8.3. L3VPN Services and sham-links . . . . . . . . . . . . . . 13 7.4. Hub and spoke deployment . . . . . . . . . . . . . . . . 14
8.4. Hub and spoke deployment . . . . . . . . . . . . . . . . 13 8. Security Considerations . . . . . . . . . . . . . . . . . . . 14
9. Security Considerations . . . . . . . . . . . . . . . . . . . 13 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 14
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 14 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 15
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 14 11.1. Normative References . . . . . . . . . . . . . . . . . . 15
12.1. Normative References . . . . . . . . . . . . . . . . . . 14 11.2. Informative References . . . . . . . . . . . . . . . . . 16
12.2. Informative References . . . . . . . . . . . . . . . . . 15 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15
1. Introduction 1. Introduction
When a node is being prepared for a planned maintenance or upgrade, When a node is being prepared for a planned maintenance or upgrade,
[RFC6987] provides mechanisms to advertise the node being in a [RFC6987] provides mechanisms to advertise the node being in a
graceful-shutdown state by setting all outgoing link costs to graceful-shutdown state by setting all outgoing link costs to
MaxLinkMetric (0xffff). These procedures are specific to the MaxLinkMetric (0xffff). These procedures are specific to the
maintenance activity on a node and cannot be used when a single link maintenance activity on a node and cannot be used when a single link
on the node requires maintenance. on a node requires maintenance.
In traffic-engineering deployments, LSPs need to be diverted from the In traffic-engineering deployments, LSPs need to be diverted from the
link without disrupting the services. [RFC5817] describes link without disrupting the services. [RFC5817] describes
requirements and procedures for graceful shutdown of MPLS links. It requirements and procedures for graceful shutdown of MPLS links. It
is useful to be able to advertise the impending maintenance activity is useful to be able to advertise the impending maintenance activity
on the link and to have LSP re-routing policies at the ingress to on the link and to have LSP re-routing policies at the ingress to
route the LSPs away from the link. route the LSPs away from the link.
Many OSPFv2 or OSPFv3 deployments run on overlay networks provisioned Many OSPFv2 or OSPFv3 deployments run on overlay networks provisioned
by means of pseudo-wires or L2-circuits. Prior to devices in the by means of pseudo-wires or L2-circuits. Prior to devices in the
underlying network going offline for maintenance, it is useful to underlying network going offline for maintenance, it is useful to
divert the traffic away from the node before the maintenance is divert the traffic away from the node before the maintenance is
actually performed. Since the nodes in the underlying network are actually performed. Since the nodes in the underlying network are
not visible to OSPF, the existing stub router mechanism described in not visible to OSPF, the existing stub router mechanism described in
[RFC6987] cannot be used. In a service provider's network, there may [RFC6987] cannot be used. In a service provider's network, there may
be many CE-to-CE connections that run over a single PE. It is be many CE-to-CE connections that run over a single PE. It is
cumbersome to change the metric on every CE-to-CE connection in both cumbersome to change the metric on every CE-to-CE connection in both
directions. This document provides a mechanism to change metric in directions. This document provides a mechanism to change the metric
other direction of the link and also use the link as a last-resort- of the link on remote side and also use the link as a last-resort-
link if no alternate paths are available. An application specific to link if no alternate paths are available. An application specific to
this use case is described in detail in Section 8.1. this use case is described in detail in Section 7.1.
The procedures described in this draft may be used to divert the The procedures described in this draft may be used to divert the
traffic away from the link in other scenarios and is not restricted traffic away from the link in scenarios other than link-shutdown or
to link-shutdown or link-replacement activity. link-replacement activity.
This document provides mechanisms to advertise graceful-link-shutdown This document provides mechanisms to advertise graceful-link-shutdown
state in the flexible encodings provided by OSPFv2 Prefix/Link state in the flexible encodings provided by OSPFv2 Prefix/Link
Attribute Advertisement [RFC7684]. Throughout this document, OSPF is Attribute Advertisement [RFC7684] and E-Router-LSA
used when the text applies to both OSPFv2 and OSPFv3. OSPFv2 or [I-D.ietf-ospf-ospfv3-lsa-extend] fr OSPFv3. Throughout this
OSPFv3 is used when the text is specific to one version of the OSPF document, OSPF is used when the text applies to both OSPFv2 and
protocol. OSPFv3. OSPFv2 or OSPFv3 is used when the text is specific to one
version of the OSPF protocol.
2. Motivation 2. Motivation
The motivation of this document is to reduce manual intervention The motivation of this document is to reduce manual intervention
during maintenance activities. The following objectives help to during maintenance activities. The following objectives help to
accomplish this in a range of deployment scenarios. accomplish this in a range of deployment scenarios.
1. Advertise impending maintenance activity so that traffic from 1. Advertise impending maintenance activity so that traffic from
both directions can be diverted away from the link. both directions can be diverted away from the link.
2. Allow the solution to be backward compatible so that nodes that 2. Allow the solution to be backward compatible so that nodes that
do not understand the new advertisement do not cause routing do not understand the new advertisement, do not cause routing
loops. loops.
3. Advertise the maintenance activity to other nodes in the network 3. Advertise the maintenance activity to other nodes in the network
so that LSP ingress routers/controllers can learn about the so that LSP ingress routers/controllers can learn about the
impending maintenance activity and apply specific policies to re- impending maintenance activity and apply specific policies to re-
route the LSPs for traffic-engineering based deployments. route the LSPs for traffic-engineering based deployments.
4. Allow the link to be used as last resort link to prevent traffic 4. Allow the link to be used as a last resort link to prevent
disruption when alternate paths are not available. traffic disruption when alternate paths are not available.
3. Flooding Scope 3. Flooding Scope
The graceful-link-shutdown information is flooded in area-scoped The graceful-link-shutdown information is flooded in area-scoped
Extended Link Opaque LSA [RFC7684] for OSPFv2 and E-Router-LSA for Extended Link Opaque LSA [RFC7684] for OSPFv2 and E-Router-LSA for
OSPFv3 [I-D.ietf-ospf-ospfv3-lsa-extend]. The Graceful-Link-Shutdown OSPFv3 [I-D.ietf-ospf-ospfv3-lsa-extend]. The Graceful-Link-Shutdown
sub-TLV MAY be processed by the head-end nodes or the controller as sub-TLV MAY be processed by the head-end nodes or the controller as
described in the Section 8. The procedures for processing the described in the Section 7. The procedures for processing the
Graceful-Link-Shutdown sub-TLV are described in Section 5. Graceful-Link-Shutdown sub-TLV are described in Section 5.
4. Graceful-Link-Shutdown sub-TLV 4. Protocol Extensions
4.1. OSPFv2 graceful-link-shutdown sub-TLV 4.1. OSPFv2 graceful-link-shutdown sub-TLV
The Graceful-Link-Shutdown sub-TLV identifies the link as being The Graceful-Link-Shutdown sub-TLV identifies the link as being
gracefully shutdown. It is advertised in extended Link TLV of the gracefully shutdown. It is advertised in extended Link TLV of the
Extended Link Opaque LSA as defined in [RFC7684]. Extended Link Opaque LSA as defined in [RFC7684].
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
skipping to change at page 5, line 21 skipping to change at page 5, line 21
Figure 1: Graceful-Link-Shutdown sub-TLV for OSPFv2 Figure 1: Graceful-Link-Shutdown sub-TLV for OSPFv2
Type : TBA (suggested value 7) Type : TBA (suggested value 7)
Length: 0 Length: 0
4.2. Remote IPv4 Address Sub-TLV 4.2. Remote IPv4 Address Sub-TLV
This sub-TLV specifies the IPv4 address of remote endpoint on the This sub-TLV specifies the IPv4 address of remote endpoint on the
link. It is advertised in the Extended Link TLV as defined in link. It is advertised in the Extended Link TLV as defined in
[RFC7684]. This sub-TLV is optional and MAY be advertised in area- [RFC7684]. This sub-TLV is optional and MAY be advertised in an
scoped Extended Link Opaque LSA to identify the link when there are area-scoped Extended Link Opaque LSA to identify the link when there
multiple parallel links between two nodes. are multiple parallel links between two nodes.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote IPv4 address | | Remote IPv4 address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Remote IPv4 Address Sub-TLV Figure 2: Remote IPv4 Address Sub-TLV
Type : TBA (suggested value 8) Type : TBA (suggested value 8)
Length: 4 Length: 4
Value: Remote IPv4 address. The remote IP4 address is used to Value: Remote IPv4 address. The remote IPv4 address is used to
identify the particular link when there are multiple parallel links identify the particular link on remote side when there are multiple
between two nodes. parallel links between two nodes.
4.3. Local/Remote Interface ID Sub-TLV 4.3. Local/Remote Interface ID Sub-TLV
This sub-TLV specifies local and remote interface identifiers. It is This sub-TLV specifies local and remote interface identifiers. It is
advertised in the Extended Link TLV as defined in [RFC7684]. This advertised in the Extended Link TLV as defined in [RFC7684]. This
sub-TLV is optional and MAY be advertised in area-scoped Extended sub-TLV is optional and MAY be advertised in an area-scoped Extended
Link Opaque LSA to identify the link when there are multiple parallel Link Opaque LSA to identify the link when there are multiple parallel
unnumbered links between two nodes. The local interface-id is unnumbered links between two nodes. The local interface-id is
generally readily available. One of the mechanisms to obtain remote generally readily available. One of the mechanisms to obtain remote
interface-id is described in [RFC4203]. interface-id is described in [RFC4203].
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
skipping to change at page 7, line 20 skipping to change at page 7, line 20
Figure 4: Graceful-Link-Shutdown sub-TLV for OSPFv3 Figure 4: Graceful-Link-Shutdown sub-TLV for OSPFv3
Type : TBA (Suggested value 7) Type : TBA (Suggested value 7)
Length: 0 Length: 0
4.5. BGP-LS Graceful-Link-Shutdown TLV 4.5. BGP-LS Graceful-Link-Shutdown TLV
BGP-LS as defined in [RFC7752] is a mechanism to distribute network BGP-LS as defined in [RFC7752] is a mechanism to distribute network
information to external entities using BGP routing protocol. information to the external entities using BGP routing protocol.
Graceful-link-shutdown is an imporatant link information that the Graceful-link-shutdown is an imporatant link information that the
external entities can use for various use cases as defined in external entities can use for various use cases as defined in
Section 8. BGP Link NLRI is used to carry the link information. A Section 7. BGP Link NLRI is used to carry the link information. A
new TLV called Graceful-Link-Shutdown is defined to describe the link new TLV called Graceful-Link-Shutdown is defined to describe the link
attribute corresponding to graceful-link-shutdown state. The TLV attribute corresponding to graceful-link-shutdown state. The TLV
format is as described in [RFC7752] sec 3.1. There is no value field format is as described in [RFC7752] sec 3.1. There is no value field
and length field is set to zero for this TLV. and length field is set to zero for this TLV.
4.6. Distinguishing parallel links 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: Graceful-Link-Shutdown TLV for BGP-LS
Type : TBA (Suggested value 1121)
Length: 0
4.6. Distinguishing parallel links
++++++++++I.w I.y +++++++++ ++++++++++I.w I.y +++++++++
|Router A|------------------|Router B | |Router A|------------------|Router B |
| |------------------| | | |------------------| |
++++++++++I.x I.z++++++++++ ++++++++++I.x I.z++++++++++
Figure 5: Parallel Linkls Figure 6: Parallel Linkls
Consider two routers A and B connected with two parallel point-to- Consider two routers A and B connected with two parallel point-to-
point interfaces. I.w and I.x represent the Interface address on point interfaces. I.w and I.x represent the Interface address on
Router A's side and I.y and I.z represent Interface addresses on Router A's side and I.y and I.z represent Interface addresses on
Router B's side. The extended link opaque LSA as described in Router B's side. The extended link opaque LSA as described in
[RFC7684] describes links using link-type, Link-ID and Link-data. [RFC7684] describes links using link-type, Link-ID and Link-data.
For ex. Link with address I.w is described as below on Router A. For ex. Link with address I.w is described as below on Router A.
Link-type = Point-to-point Link-type = Point-to-point
Link-ID: Router-ID B Link-ID: Router-ID of B
Link-Data = I.w Link-Data = I.w
A third node (controller or head-end) in the network cannot A third node (controller or head-end) in the network cannot
distinguish the Interface on router B which is connected to this distinguish the Interface on router B which is connected to this
particular Interface with the above information. Interface with particular Interface with the above information. Interface with
address I.y or I.z could be chosen due to this ambiguity. In such address I.y or I.z could be chosen due to this ambiguity. In such
cases Remote-IPv4 Address sub-TLV should be originated and added to cases Remote-IPv4 Address sub-TLV should be originated and added to
the extended link-TLV. The use cases as described in Section 8 the Extended Link TLV. The use cases as described in Section 7
require controller or head-end nodes to interpret the graceful-link- require controller or head-end nodes to interpret the graceful-link-
shutdown information and hence the need for the RemoteIPv4 address shutdown information and hence the need for the Remote IPv4 address
sub-TLV. I.y is carried in the extended-link-TLV which unambiguously sub-TLV. I.y is carried in the Extended Link TLV which unambiguously
identifies the interface on the remote side. OSPFv3 Router-link-TLV identifies the interface on the remote side. OSPFv3 Router-link-TLV
as described in [I-D.ietf-ospf-ospfv3-lsa-extend] contains Interface as described in [I-D.ietf-ospf-ospfv3-lsa-extend] contains Interface
ID and neighbor's Interface-ID which can uniquely identify connecting ID and neighbor's Interface-ID which can uniquely identify connecting
interface on the remote side and hence OSPFv3 does not require interface on the remote side and hence OSPFv3 does not require
seperate Remote-IPv6 address to be advertised along with OSPFv3- seperate Remote-IPv6 address to be advertised along with the OSPFv3-
Graceful-Link-Shutdown sub-TLV. Graceful-Link-Shutdown sub-TLV.
5. Elements of procedure 5. Elements of procedure
As defined in [RFC7684] every link on the node will have a separate As defined in [RFC7684] every link on the node will have a separate
Extended Link Opaque LSA. The node that has the link to be taken out Extended Link Opaque LSA. The node that has the link to be taken out
of service MUST advertise the Graceful-Link-Shutdown sub-TLV in the of service MUST advertise the Graceful-Link-Shutdown sub-TLV in the
Extended Link TLV of the Extended Link Opaque LSA as defined in Extended Link TLV of the Extended Link Opaque LSA as defined in
[RFC7684] for OSPFv2 and Router-Link TLV of E-Router-LSA for OSPFv3. [RFC7684] for OSPFv2 and Router-Link TLV of E-Router-LSA for OSPFv3.
The Graceful-Link-Shutdown sub-TLV indicates that the link identified The Graceful-Link-Shutdown sub-TLV indicates that the link identified
by the sub-TLV is subjected to maintenance. The Graceful-Link- by the sub-TLV is subjected to maintenance.
Shutdown information is advertised as a property of the link and is
flooded across the area. This information can be used by ingress For the purposes of changing the metric OSPFv2 and OSPFv3 Router-LSAs
routers or controllers to take special actions. An application need to be re-orignated and for Traffic Engineering metric, TE Opaque
specific to this use case is described in Section 8.2. LSAs [RFC3630] in OSPFv2 and Intra-area-TE-LSA [RFC5329]in OSPFv3
need to be re-originated.
The Graceful-Link-Shutdown information is advertised as a property of
the link and is flooded across the area. This information can be
used by ingress routers or controllers to take special actions. An
application specific to this use case is described in Section 7.2.
The precise action taken by the remote node at the other end of the The precise action taken by the remote node at the other end of the
link identified for graceful-shutdown depends on the link type. link identified for graceful-shutdown depends on the link type.
When a link is ready to carry traffic, the Graceful-Lnk-Shutdown sub-
TLV should be removed from the Extended Link TLV/Router-Link TLV and
the corresponding LSAs MUST be readvertised.
5.1. Point-to-point links 5.1. Point-to-point links
The node that has the link to be taken out of service MUST set metric The node that has the link to be taken out of service MUST set metric
of the link to MaxLinkMetric (0xffff) and re-originate its router- of the link to MaxLinkMetric (0xffff) and re-originate its router-
LSA. MAX-TE-METRIC (0xfffffffe). The TE metric SHOULD be set to LSA. The Traffic Engineering metric of the link SHOULD be set to
MAX-TE-METRIC (0xfffffffe) and the node SHOULD re-originate the (0xffffffff) and the node SHOULD re-originate the corresponding TE
corresponding TE Link Opaque LSAs. When a Graceful-Link-Shutdown Link Opaque LSAs. When a Graceful-Link-Shutdown sub-TLV is received
sub-TLV is received for a point-to-point link, the remote node MUST for a point-to-point link, the remote node MUST identify the local
identify the local link which corresponds to the graceful-shutdown link which corresponds to the graceful-shutdown link and set its
link and set the metric to MaxLinkMetric (0xffff) and the remote node metric to MaxLinkMetric (0xffff) and the remote node MUST re-
MUST re-originate its router-LSA with the changed metric. The TE originate its router-LSA with the changed metric. When TE is
metric SHOULD be set to MAX-TE-METRIC (0xfffffffe) and the TE opaque enabled, the Traffic Engineering metric of the link SHOULD be set to
LSA for the link SHOULD be re-originated with new value. (0xffffffff) and the TE opaque LSA for the link SHOULD be re-
originated with new value.Similarly, the remote node SHOULD set the
Traffic Engineering metric of the link to 0xffffffff and SHOULD re-
originate the TE Link Opaque LSA for the link with the new value.
The Extended link opaque LSAs and the Extended link TLV are not The Extended link opaque LSAs and the Extended link TLV are not
scoped for multi-topology [RFC4915]. In multi-topology deployments scoped for multi-topology [RFC4915]. In multi-topology deployments
[RFC4915], the Graceful-Link-Shutdown sub-TLV advertised in an [RFC4915], the Graceful-Link-Shutdown sub-TLV advertised in an
Extended Link opaque LSA corresponds to all the topologies which Extended Link opaque LSA corresponds to all the topologies which
include the link. The receiver node SHOULD change the metric in the include the link. The receiver node SHOULD change the metric in the
reverse direction for all the topologies which include the remote reverse direction for all the topologies which include the remote
link and re-originate the router-LSA as defined in [RFC4915]. link and re-originate the router-LSA as defined in [RFC4915].
When the originator of the Graceful-Link-Shutdown sub-TLV purges the When the originator of the Graceful-Link-Shutdown sub-TLV purges the
skipping to change at page 9, line 33 skipping to change at page 10, line 19
other routers on the broadcast or NBMA network logically connect. As other routers on the broadcast or NBMA network logically connect. As
a result, routers on the broadcast or NBMA network advertise only a result, routers on the broadcast or NBMA network advertise only
their adjacency to the DR. Routers that do not act as DR do not form their adjacency to the DR. Routers that do not act as DR do not form
or advertise adjacencies with each other. For the Broadcast links, or advertise adjacencies with each other. For the Broadcast links,
the MaxLinkMetric on the remote link cannot be changed since all the the MaxLinkMetric on the remote link cannot be changed since all the
neighbors are on same link. Setting the link cost to MaxLinkMetric neighbors are on same link. Setting the link cost to MaxLinkMetric
would impact paths going via all neighbors. would impact paths going via all neighbors.
The node that has the link to be taken out of service MUST set metric The node that has the link to be taken out of service MUST set metric
of the link to MaxLinkMetric (0xffff) and re-originate the Router- of the link to MaxLinkMetric (0xffff) and re-originate the Router-
LSA. The TE metric SHOULD be set to MAX-TE-METRIC( 0xfffffffe) and LSA. The Traffic Engineering metric of the link SHOULD be set to (
the node SHOULD re-originate the corresponding TE Link Opaque LSAs. 0xffffffff) and the node SHOULD re-originate the corresponding TE
For a broadcast link, the two part metric as described in [RFC8042] Link Opaque LSAs. For a broadcast link, the two part metric as
is used. The node originating the Graceful-Link-Shutdown sub-TLV described in [RFC8042] is used. The node originating the Graceful-
MUST set the metric in the Network-to-Router Metric sub-TLV to Link-Shutdown sub-TLV MUST set the metric in the Network-to-Router
MaxLinkMetric (0xffff) for OSPFv2 and OSPFv3 and re-originate the Metric sub-TLV to MaxLinkMetric (0xffff) for OSPFv2 and OSPFv3 and
corresponding LSAs. The nodes that receive the two-part metric re-originate the corresponding LSAs. The nodes that receive the two-
should follow the procedures described in [RFC8042]. The backward part metric should follow the procedures described in [RFC8042]. The
compatibility procedures described in [RFC8042] should be followed to backward compatibility procedures described in [RFC8042] should be
ensure loop free routing. followed to ensure loop free routing.
5.3. Point-to-multipoint links 5.3. Point-to-multipoint links
Operation for the point-to-multipoint links is similar to the point- Operation for the point-to-multipoint links is similar to the point-
to-point links. When a Graceful-Link-Shutdown sub-TLV is received to-point links. When a Graceful-Link-Shutdown sub-TLV is received
for a point-to-multipoint link the remote node MUST identify the for a point-to-multipoint link the remote node MUST identify the
neighbour which corresponds to the graceful-shutdown link and set the neighbour which corresponds to the graceful-shutdown link and set its
metric to MaxLinkMetric (0xffff). The remote node MUST re-originate metric to MaxLinkMetric (0xffff). The remote node MUST re-originate
the router-LSA with the changed metric for the correponding neighbor. the router-LSA with the changed metric for the correponding neighbor.
5.4. Unnumbered interfaces 5.4. Unnumbered interfaces
Unnumbered interface do not have a unique IP address and borrow their Unnumbered interface do not have a unique IP address and borrow their
address from other interfaces. [RFC2328] describes procedures to address from other interfaces. [RFC2328] describes procedures to
handle unnumbered interfaces in the context of the router-LSA. We handle unnumbered interfaces in the context of the router-LSA. We
apply a similar procedure to the Extended Link TLV advertising the apply a similar procedure to the Extended Link TLV advertising the
Graceful-Link-Shutdown sub-TLV in order to handle unnumbered Graceful-Link-Shutdown sub-TLV in order to handle unnumbered
skipping to change at page 10, line 26 skipping to change at page 11, line 12
mechanisms to obtain the interface-id of the remote side are defined mechanisms to obtain the interface-id of the remote side are defined
in [RFC4203]. in [RFC4203].
5.5. Hybrid Broadcast and P2MP interfaces 5.5. Hybrid Broadcast and P2MP interfaces
Hybrid Broadcast and P2MP interfaces represent a broadcast network Hybrid Broadcast and P2MP interfaces represent a broadcast network
modeled as P2MP interfaces. [RFC6845] describes procedures to handle modeled as P2MP interfaces. [RFC6845] describes procedures to handle
these interfaces. Operation for the Hybrid interfaces is similar to these interfaces. Operation for the Hybrid interfaces is similar to
the P2MP interfaces. When a Graceful-Link-Shutdown sub-TLV is the P2MP interfaces. When a Graceful-Link-Shutdown sub-TLV is
received for a hybrid link, the remote node MUST identify the received for a hybrid link, the remote node MUST identify the
neighbor which corresponds to the graceful-shutdown link and set the neighbor which corresponds to the graceful-shutdown link and set its
metric to MaxLinkMetric (0xffff). All the remote nodes connected to metric to MaxLinkMetric (0xffff). All the remote nodes connected to
originator MUST re-originate the router-LSA with the changed metric originator MUST re-originate the router-LSA with the changed metric
for the neighbor. for the neighbor.
6. Maximum TE Metric 6. Backward compatibility
MAX-TE-METRIC is a new fixed architectural value introduced in this
document.
The metric value indicates that a link with this metric should be
used as a last-resort link to carry the traffic. It is defined to be
of value 0xfffffffe.
7. Backward compatibility
The mechanisms described in the document are fully backward The mechanisms described in the document are fully backward
compatible. It is required that the node adverting the Graceful- compatible. It is required that the node adverting the Graceful-
Link-Shutdown sub-TLV as well as the node at the remote end of the Link-Shutdown sub-TLV as well as the node at the remote end of the
graceful-shutdown link support the extensions described herein for graceful-shutdown link support the extensions described herein for
the traffic to diverted from the graceful-shutdown link. If the the traffic to diverted from the graceful-shutdown link. If the
remote node doesn't support the capability, it will still use the remote node doesn't support the capability, it will still use the
graceful-shutdown link but there are no other adverse effects. In graceful-shutdown link but there are no other adverse effects. In
the case of broadcast links using two-part metrics, the backward the case of broadcast links using two-part metrics, the backward
compatibility procedures as described in [RFC8042] are applicable. compatibility procedures as described in [RFC8042] are applicable.
8. Applications 7. Applications
8.1. Pseudowire Services 7.1. Pseudowire Services
Many service providers offer pseudo-wire services to customers using Many service providers offer pseudo-wire services to customers using
L2 circuits. The IGP protocol that runs in the customer network L2 circuits. The IGP protocol that runs in the customer network
would also run over the pseudo-wire to create a seamless private would also run over the pseudo-wire to create a seamless private
network for the customer. Service providers want to offer graceful- network for the customer. Service providers want to offer graceful-
shutdown functionality when the PE device is taken-out for shutdown functionality when the PE device is taken-out for
maintenance. The provider should guarantee that the PE is taken out maintenance. The provider should guarantee that the PE is taken out
for maintenance only after the service is successfully diverted on an for maintenance, only after the service is successfully diverted on
alternate path. There can be large number of customers attached to a an alternate path. There can be large number of customers attached
PE node and the remote end-points for these pseudo-wires are spread to a PE node and the remote end-points for these pseudo-wires are
across the service provider's network. It is a tedious and error- spread across the service provider's network. It is a tedious and
prone process to change the metric for all pseudo-wires in both error-prone process to change the metric for all pseudo-wires in both
directions. The graceful-link-shutdown feature simplifies the directions. The graceful-link-shutdown feature simplifies the
process by increasing the metric on the link in the reverse direction process by increasing the metric on the link in the reverse direction
as well so that traffic in both directions is diverted away from the as well so that traffic in both directions is diverted away from the
PE undergoing maintenance. The Graceful-Link-Shutdown feature allows PE undergoing maintenance. The Graceful-Link-Shutdown feature allows
the link to be used as a last resort link so that traffic is not the link to be used as a last resort link so that traffic is not
disrupted when alternative paths are not available. disrupted when alternate paths are not available.
Private VLAN overlay network
======================================= =======================================
| | | |
| | | |
| ------PE3---------------PE4------CE3 | ------PE3---------------PE4------CE3
| / \ | / \
| / \ | / \
CE1---------PE1----------PE2---------CE2 CE1---------PE1----------PE2---------CE2
| \ | \
| \ | \
| ------CE4 | ------CE4
| | | |
| | | |
| | | |
================================= =================================
Private VLAN overlay network
Figure 6: Pseudowire Services Figure 7: Pseudowire Services
In the example shown in Figure 6, when the PE1 node is going out of In the example shown in Figure 7, when the PE1 node is going out of
service for maintenance, service providers set the PE1 to graceful- service for maintenance, service providers set the PE1 to stub-router
link-shutdown state. The PE1 going in to maintenance state triggers state. The PE1 going in to maintenance state triggers all the CEs
all the CEs connected to the PE (CE1 in this case) to set their connected to the PE (CE1 in this case) to set their pseudowire links
pseudowire links passing via PE1 to graceful-link-shutdown state. passing via PE1 to graceful-link-shutdown state. The mechanisms used
The mechanisms used to communicate between PE1 and CE1 is outside the to communicate between PE1 and CE1 is outside the scope of this
scope of this document. CE1 sets the graceful-link-shutdown state on document. CE1 sets the graceful-link-shutdown state on its links
its private VLAN connecting CE3, CE2 and CE4 and changes the metric connecting CE3, CE2 and CE4 and changes the metric to MaxLinkMetric
to MaxLinkMetric and re-originates the corresponding LSA. The remote and re-originates the corresponding LSA. The remote end of the link
end of the link at CE3, CE2, and CE4 also set the metric on the link at CE3, CE2, and CE4 also set the metric on the link to MaxLinkMetric
to MaxLinkMetric and the traffic from both directions gets diverted and the traffic from both directions gets diverted away from the
away from the pseudowires. pseudowires.
8.2. Controller based Traffic Engineering Deployments 7.2. Controller based Traffic Engineering Deployments
In controller-based deployments where the controller participates in In controller-based deployments where the controller participates in
the IGP protocol, the controller can also receive the graceful-link- the IGP protocol, the controller can also receive the graceful-link-
shutdown information as a warning that link maintenance is imminent. shutdown information as a warning that link maintenance is imminent.
Using this information, the controller can find alternate paths for Using this information, the controller can find alternate paths for
traffic which uses the affected link. The controller can apply traffic which uses the affected link. The controller can apply
various policies and re-route the LSPs away from the link undergoing various policies and re-route the LSPs away from the link undergoing
maintenance. If there are no alternate paths satisfying the traffic maintenance. If there are no alternate paths satisfying the traffic
engineering constraints, the controller might temporarily relax those engineering constraints, the controller might temporarily relax those
constraints and put the service on a different path. Increasing the constraints and put the service on a different path. Increasing the
skipping to change at page 12, line 40 skipping to change at page 13, line 18
| |____________ | | | |____________ | |
| | | |
|--------- Primary Path ------------------| |--------- Primary Path ------------------|
PE1---------P1----------------P2---------PE2 PE1---------P1----------------P2---------PE2
| | | |
| | | |
|________P3________| |________P3________|
Alternate Path Alternate Path
Figure 7: Controller based Traffic Engineering Figure 8: Controller based Traffic Engineering
In the above example, PE1->PE2 LSP is set-up to satisfy a constraint In the above example, PE1->PE2 LSP is set-up to satisfy a constraint
of 10 Gbps bandwidth on each link. The links P1->P3 and P3->P2 have of 10 Gbps bandwidth on each link. The links P1->P3 and P3->P2 have
only 1 Gbps capacity and there is no alternate path satisfying the only 1 Gbps capacity and there is no alternate path satisfying the
bandwidth constraint of 10Gbps. When P1->P2 link is being prepared bandwidth constraint of 10Gbps. When P1->P2 link is being prepared
for maintenance, the controller receives the graceful-link-shutdown for maintenance, the controller receives the graceful-link-shutdown
information, as there is no alternate path available which satisfies information, as there is no alternate path available which satisfies
the constraints, the controller chooses a path that is less optimal the constraints, the controller chooses a path that is less optimal
and temporarily sets up an alternate path via P1->P3->P2. Once the and temporarily sets up an alternate path via P1->P3->P2. Once the
traffic is diverted, the P1->P2 link can be taken out of service for traffic is diverted, the P1->P2 link can be taken out of service for
maintenance/upgrade. maintenance/upgrade.
8.3. L3VPN Services and sham-links 7.3. L3VPN Services and sham-links
Many service providers offer L3VPN services to customers and CE-PE Many service providers offer L3VPN services to customers and CE-PE
links run OSPF [RFC4577]. When PE is taken out of service for links run OSPF [RFC4577]. When PE is taken out of service for
maintenance, all the links on the PE can be set to graceful-link- maintenance, all the links on the PE can be set to graceful-link-
shutdown state which will gurantee that the traffic to/from dual- shutdown state which will gurantee that the traffic to/from dual-
homed CEs gets diverted. The interaction between OSPF and BGP is homed CEs gets diverted. The interaction between OSPF and BGP is
outside the scope of this document. [RFC6987] based mechanism with outside the scope of this document. [RFC6987] based mechanism with
summaries and externals advertised with high metrics could also be summaries and externals advertised with high metrics could also be
used to achieve the same functionality when implementations support used to achieve the same functionality when implementations support
high metrics advertisement for summaries and externals. high metrics advertisement for summaries and externals.
Another useful usecase is when ISPs provide sham-link services to Another useful usecase is when ISPs provide sham-link services to
customers [RFC4577]. When PE goes out of service for maintenance, customers [RFC4577]. When PE goes out of service for maintenance,
all sham-links on the PE can be set to graceful-link-shutdown state all sham-links on the PE can be set to graceful-link-shutdown state
and traffic can be divered from both ends without having to touch the and traffic can be divered from both ends without having to touch the
configurations on the remote end of the sham-links. configurations on the remote end of the sham-links.
8.4. Hub and spoke deployment 7.4. Hub and spoke deployment
OSPF is largely deployed in Hub and Spoke deployments with a large OSPF is largely deployed in Hub and Spoke deployments with a large
number of spokes connecting to the Hub. It is a general practice to number of spokes connecting to the Hub. It is a general practice to
deploy multiple Hubs with all spokes connecting to these Hubs to deploy multiple Hubs with all spokes connecting to these Hubs to
achieve redundancy. The [RFC6987] mechanism can be used to divert achieve redundancy. The [RFC6987] mechanism can be used to divert
the spoke-to-spoke traffic from the overloaded hub router. The the spoke-to-spoke traffic from the overloaded hub router. The
traffic that flows from spokes via the hub into an external network traffic that flows from spokes via the hub into an external network
may not be diverted in certain scenarios.When a Hub node goes down may not be diverted in certain scenarios.When a Hub node goes down
for maintenance, all links on the Hub can be set to graceful-link- for maintenance, all links on the Hub can be set to graceful-link-
shutdown state and traffic gets divered from the spoke sites as well shutdown state and traffic gets divered from the spoke sites as well
without having to make configuration changes on the spokes. without having to make configuration changes on the spokes.
9. Security Considerations 8. Security Considerations
This document does not introduce any further security issues other This document utilizes the OSPF packets and LSAs described in
than those discussed in [RFC2328] and [RFC5340]. [RFC2328] , [RFC5340] , [RFC3630] and [RFC5329]. The authentication
procedures described in [RFC2328] for OSPFv2 and [RFC4552] for OSPFv3
are applicable to this document as well. This document does not
introduce any further security issues other than those discussed in
[RFC2328] and [RFC5340].
10. IANA Considerations 9. IANA Considerations
This specification updates one OSPF registry: This specification updates one OSPF registry:
OSPFv2 Extended Link TLV Sub-TLVs OSPFv2 Extended Link TLV Sub-TLVs
i) Graceful-Link-Shutdown Sub-TLV - Suggested value 7 i) Graceful-Link-Shutdown Sub-TLV - Suggested value 7
ii) Remote IPv4 Address Sub-TLV - Suggested value 8 ii) Remote IPv4 Address Sub-TLV - Suggested value 8
iii) Local/Remote Interface ID Sub-TLV - Suggested Value 9 iii) Local/Remote Interface ID Sub-TLV - Suggested Value 9
OSPFv3 Extended-LSA sub-TLV Registry OSPFv3 Extended-LSA sub-TLV Registry
i) Graceful-Link-Shutdown sub-TLV - suggested value 7 i) Graceful-Link-Shutdown sub-TLV - suggested value 7
BGP-LS Link NLRI Registry [RFC7752] BGP-LS Node Descriptor, Link Descriptor, Prefix Descriptor, and
Attribute TLVs [RFC7752]
i)Graceful-Link-Shutdown TLV - Suggested 1101 i)Graceful-Link-Shutdown TLV - Suggested 1121
11. Acknowledgements 10. Acknowledgements
Thanks to Chris Bowers for valuable inputs and edits to the document. Thanks to Chris Bowers for valuable inputs and edits to the document.
Thanks to Jeffrey Zhang, Acee Lindem and Ketan Talaulikar for inputs. Thanks to Jeffrey Zhang, Acee Lindem and Ketan Talaulikar for inputs.
Thanks to Karsten Thomann for careful review and inputs on the Thanks to Karsten Thomann for careful review and inputs on the
applications where graceful-link-shutdown is useful. applications where graceful-link-shutdown is useful.
12. References Thanks to Alia atlas, Deborah Brungard, Alvaro Retana and Tim Chown
for valuable inputs.
12.1. Normative References 11. References
11.1. Normative References
[I-D.ietf-ospf-ospfv3-lsa-extend] [I-D.ietf-ospf-ospfv3-lsa-extend]
Lindem, A., Mirtorabi, S., Roy, A., and F. Baker, "OSPFv3 Lindem, A., Roy, A., Goethals, D., Vallem, V., and F.
LSA Extendibility", draft-ietf-ospf-ospfv3-lsa-extend-10 Baker, "OSPFv3 LSA Extendibility", draft-ietf-ospf-ospfv3-
(work in progress), May 2016. lsa-extend-23 (work in progress), January 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,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328,
DOI 10.17487/RFC2328, April 1998,
<https://www.rfc-editor.org/info/rfc2328>.
[RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
(TE) Extensions to OSPF Version 2", RFC 3630,
DOI 10.17487/RFC3630, September 2003,
<https://www.rfc-editor.org/info/rfc3630>.
[RFC5329] Ishiguro, K., Manral, V., Davey, A., and A. Lindem, Ed.,
"Traffic Engineering Extensions to OSPF Version 3",
RFC 5329, DOI 10.17487/RFC5329, September 2008,
<https://www.rfc-editor.org/info/rfc5329>.
[RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF
for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008,
<https://www.rfc-editor.org/info/rfc5340>.
[RFC6845] Sheth, N., Wang, L., and J. Zhang, "OSPF Hybrid Broadcast [RFC6845] Sheth, N., Wang, L., and J. Zhang, "OSPF Hybrid Broadcast
and Point-to-Multipoint Interface Type", RFC 6845, and Point-to-Multipoint Interface Type", RFC 6845,
DOI 10.17487/RFC6845, January 2013, DOI 10.17487/RFC6845, January 2013,
<https://www.rfc-editor.org/info/rfc6845>. <https://www.rfc-editor.org/info/rfc6845>.
[RFC6987] Retana, A., Nguyen, L., Zinin, A., White, R., and D. [RFC6987] Retana, A., Nguyen, L., Zinin, A., White, R., and D.
McPherson, "OSPF Stub Router Advertisement", RFC 6987, McPherson, "OSPF Stub Router Advertisement", RFC 6987,
DOI 10.17487/RFC6987, September 2013, DOI 10.17487/RFC6987, September 2013,
<https://www.rfc-editor.org/info/rfc6987>. <https://www.rfc-editor.org/info/rfc6987>.
skipping to change at page 15, line 15 skipping to change at page 16, line 20
[RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and [RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and
S. Ray, "North-Bound Distribution of Link-State and S. Ray, "North-Bound Distribution of Link-State and
Traffic Engineering (TE) Information Using BGP", RFC 7752, Traffic Engineering (TE) Information Using BGP", RFC 7752,
DOI 10.17487/RFC7752, March 2016, DOI 10.17487/RFC7752, March 2016,
<https://www.rfc-editor.org/info/rfc7752>. <https://www.rfc-editor.org/info/rfc7752>.
[RFC8042] Zhang, Z., Wang, L., and A. Lindem, "OSPF Two-Part [RFC8042] Zhang, Z., Wang, L., and A. Lindem, "OSPF Two-Part
Metric", RFC 8042, DOI 10.17487/RFC8042, December 2016, Metric", RFC 8042, DOI 10.17487/RFC8042, December 2016,
<https://www.rfc-editor.org/info/rfc8042>. <https://www.rfc-editor.org/info/rfc8042>.
12.2. Informative References 11.2. Informative References
[RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328,
DOI 10.17487/RFC2328, April 1998,
<https://www.rfc-editor.org/info/rfc2328>.
[RFC4203] Kompella, K., Ed. and Y. Rekhter, Ed., "OSPF Extensions in [RFC4203] Kompella, K., Ed. and Y. Rekhter, Ed., "OSPF Extensions in
Support of Generalized Multi-Protocol Label Switching Support of Generalized Multi-Protocol Label Switching
(GMPLS)", RFC 4203, DOI 10.17487/RFC4203, October 2005, (GMPLS)", RFC 4203, DOI 10.17487/RFC4203, October 2005,
<https://www.rfc-editor.org/info/rfc4203>. <https://www.rfc-editor.org/info/rfc4203>.
[RFC4552] Gupta, M. and N. Melam, "Authentication/Confidentiality
for OSPFv3", RFC 4552, DOI 10.17487/RFC4552, June 2006,
<https://www.rfc-editor.org/info/rfc4552>.
[RFC4577] Rosen, E., Psenak, P., and P. Pillay-Esnault, "OSPF as the [RFC4577] Rosen, E., Psenak, P., and P. Pillay-Esnault, "OSPF as the
Provider/Customer Edge Protocol for BGP/MPLS IP Virtual Provider/Customer Edge Protocol for BGP/MPLS IP Virtual
Private Networks (VPNs)", RFC 4577, DOI 10.17487/RFC4577, Private Networks (VPNs)", RFC 4577, DOI 10.17487/RFC4577,
June 2006, <https://www.rfc-editor.org/info/rfc4577>. June 2006, <https://www.rfc-editor.org/info/rfc4577>.
[RFC4915] Psenak, P., Mirtorabi, S., Roy, A., Nguyen, L., and P. [RFC4915] Psenak, P., Mirtorabi, S., Roy, A., Nguyen, L., and P.
Pillay-Esnault, "Multi-Topology (MT) Routing in OSPF", Pillay-Esnault, "Multi-Topology (MT) Routing in OSPF",
RFC 4915, DOI 10.17487/RFC4915, June 2007, RFC 4915, DOI 10.17487/RFC4915, June 2007,
<https://www.rfc-editor.org/info/rfc4915>. <https://www.rfc-editor.org/info/rfc4915>.
[RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF
for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008,
<https://www.rfc-editor.org/info/rfc5340>.
[RFC5817] Ali, Z., Vasseur, JP., Zamfir, A., and J. Newton, [RFC5817] Ali, Z., Vasseur, JP., Zamfir, A., and J. Newton,
"Graceful Shutdown in MPLS and Generalized MPLS Traffic "Graceful Shutdown in MPLS and Generalized MPLS Traffic
Engineering Networks", RFC 5817, DOI 10.17487/RFC5817, Engineering Networks", RFC 5817, DOI 10.17487/RFC5817,
April 2010, <https://www.rfc-editor.org/info/rfc5817>. April 2010, <https://www.rfc-editor.org/info/rfc5817>.
Authors' Addresses Authors' Addresses
Shraddha Hegde Shraddha Hegde
Juniper Networks, Inc. Juniper Networks, Inc.
Embassy Business Park Embassy Business Park
Bangalore, KA 560093 Bangalore, KA 560093
India India
Email: shraddha@juniper.net Email: shraddha@juniper.net
Pushpasis Sarkar Pushpasis Sarkar
Arrcus Inc. Arrcus, Inc.
Email: pushpasis.ietf@gmail.com Email: pushpasis.ietf@gmail.com
Hannes Gredler Hannes Gredler
Individual Individual
Email: hannes@gredler.at Email: hannes@gredler.at
Mohan Nanduri Mohan Nanduri
ebay Corporation ebay Corporation
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