< draft-ietf-ospf-link-overload-09.txt   draft-ietf-ospf-link-overload-16.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: February 15, 2018 H. Gredler Expires: August 8, 2018 Arrcus, Inc.
H. Gredler
Individual Individual
M. Nanduri M. Nanduri
ebay Corporation ebay Corporation
L. Jalil L. Jalil
Verizon Verizon
August 14, 2017 February 4, 2018
OSPF Link Overload OSPF Graceful Link shutdown
draft-ietf-ospf-link-overload-09 draft-ietf-ospf-link-overload-16
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 metric on one side of the link is not metric to the highest value on one side of the link is not sufficient
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 being in an overload state to indicate be able to advertise a link as being in a graceful-shutdown state to
impending maintenance activity on the link. This information can be indicate impending maintenance activity on the link. This
used by the network devices to re-route the traffic effectively. information can be used by the network devices to re-route the
traffic effectively.
This document describes the protocol extensions to disseminate link- This document describes the protocol extensions to disseminate
overload 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",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119]. document are to be interpreted as described in RFC 2119 [RFC2119].
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
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time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
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This Internet-Draft will expire on February 15, 2018. This Internet-Draft will expire on August 8, 2018.
Copyright Notice Copyright Notice
Copyright (c) 2017 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.
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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 . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Flooding Scope . . . . . . . . . . . . . . . . . . . . . . . 4 3. Flooding Scope . . . . . . . . . . . . . . . . . . . . . . . 4
4. Link-Overload sub-TLV . . . . . . . . . . . . . . . . . . . . 4 4. Protocol Extensions . . . . . . . . . . . . . . . . . . . . . 4
4.1. OSPFv2 Link-overload sub-TLV . . . . . . . . . . . . . . 4 4.1. OSPFv2 graceful-link-shutdown sub-TLV . . . . . . . . . . 4
4.2. Remote IPv4 address sub-TLV . . . . . . . . . . . . . . . 4 4.2. Remote IPv4 Address Sub-TLV . . . . . . . . . . . . . . . 4
4.3. Local/Remote Interface ID sub-TLV . . . . . . . . . . . . 5 4.3. Local/Remote Interface ID Sub-TLV . . . . . . . . . . . . 5
4.4. OSPFv3 Link-Overload sub-TLV . . . . . . . . . . . . . . 6 4.4. OSPFv3 Graceful-Link-Shutdown sub-TLV . . . . . . . . . . 6
5. Elements of procedure . . . . . . . . . . . . . . . . . . . . 6 4.5. BGP-LS Graceful-Link-Shutdown TLV . . . . . . . . . . . . 6
5.1. Point-to-point links . . . . . . . . . . . . . . . . . . 6 4.6. Distinguishing parallel links . . . . . . . . . . . . . . 7
5.2. Broadcast/NBMA links . . . . . . . . . . . . . . . . . . 7 5. Elements of procedure . . . . . . . . . . . . . . . . . . . . 8
5.3. Point-to-multipoint links . . . . . . . . . . . . . . . . 7 5.1. Point-to-point links . . . . . . . . . . . . . . . . . . 9
5.4. Unnumbered interfaces . . . . . . . . . . . . . . . . . . 8 5.2. Broadcast/NBMA links . . . . . . . . . . . . . . . . . . 9
5.5. Hybrid Broadcast and P2MP interfaces . . . . . . . . . . 8 5.3. Point-to-multipoint links . . . . . . . . . . . . . . . . 10
6. Backward compatibility . . . . . . . . . . . . . . . . . . . 8 5.4. Unnumbered interfaces . . . . . . . . . . . . . . . . . . 10
7. Applications . . . . . . . . . . . . . . . . . . . . . . . . 8 5.5. Hybrid Broadcast and P2MP interfaces . . . . . . . . . . 10
7.1. Pseudowire Services . . . . . . . . . . . . . . . . . . . 8 6. Backward compatibility . . . . . . . . . . . . . . . . . . . 10
7.2. Controller based Traffic Engineering Deployments . . . . 10 7. Applications . . . . . . . . . . . . . . . . . . . . . . . . 11
7.3. L3VPN Services and sham-links . . . . . . . . . . . . . . 10 7.1. Overlay Network . . . . . . . . . . . . . . . . . . . . . 11
7.4. Hub and spoke deployment . . . . . . . . . . . . . . . . 11 7.2. Controller based Deployments . . . . . . . . . . . . . . 12
8. Security Considerations . . . . . . . . . . . . . . . . . . . 11 7.3. L3VPN Services and sham-links . . . . . . . . . . . . . . 13
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 7.4. Hub and spoke deployment . . . . . . . . . . . . . . . . 13
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 12 8. Security Considerations . . . . . . . . . . . . . . . . . . . 13
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
11.1. Normative References . . . . . . . . . . . . . . . . . . 12 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 14
11.2. Informative References . . . . . . . . . . . . . . . . . 12 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 14
11.1. Normative References . . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13 11.2. Informative References . . . . . . . . . . . . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16
1. Introduction 1. Introduction
When a node is being prepared for a planned maintenance or upgrade, This document describes a mechanism for gracefully taking a link out
[RFC6987] provides mechanisms to advertise the node being in an of service while allowing it to be used if no other path is
overload state by setting all outgoing link costs to MAX-METRIC available.It also provides a mechanism to divert the traffic from
(0xffff). These procedures are specific to the maintenance activity both directions of the link.
on a node and cannot be used when a single link on the node requires
maintenance.
In traffic-engineering deployments, LSPs need to be diverted from the
link without disrupting the services. [RFC5817] describes
requirements and procedures for graceful shutdown of MPLS links. It
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
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 scheduled. 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. An application specific to this use case [RFC6987] cannot be used. In a service provider's network, there may
is described in Section 7.1. 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
directions. This document provides a mechanism to change the metric
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
this use case is described in detail in Section 7.1.
This document provides mechanisms to advertise link-overload state in This document provides mechanisms to advertise graceful-link-shutdown
the flexible encodings provided by OSPFv2 Prefix/Link Attribute state in the flexible encodings provided by OSPFv2 Prefix/Link
Advertisement([RFC7684]). Throughout this document, OSPF is used Attribute Advertisement [RFC7684] and E-Router-LSA
when the text applies to both OSPFv2 and OSPFv3. OSPFv2 or OSPFv3 is [I-D.ietf-ospf-ospfv3-lsa-extend] fr OSPFv3. Throughout this
used when the text is specific to one version of the OSPF protocol. document, OSPF is used when the text applies to both OSPFv2 and
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 of 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 link-overload information is flooded in area scoped Extended Link The graceful-link-shutdown information is flooded in area-scoped
Opaque LSA [RFC7684]. The Link-Overload sub-TLV MAY be processed by Extended Link Opaque LSA [RFC7684] for OSPFv2 and E-Router-LSA for
the head-end nodes or the controller as described in the Section 7. OSPFv3 [I-D.ietf-ospf-ospfv3-lsa-extend]. The Graceful-Link-Shutdown
The procedures for processing the Link-Overload sub-TLV are described sub-TLV MAY be processed by the head-end nodes or the controller as
in Section 5. described in the Section 7. The procedures for processing the
Graceful-Link-Shutdown sub-TLV are described in Section 5.
4. Link-Overload sub-TLV 4. Protocol Extensions
4.1. OSPFv2 Link-overload sub-TLV 4.1. OSPFv2 graceful-link-shutdown sub-TLV
The Link-Overload sub-TLV identifies the link being in overload The Graceful-Link-Shutdown sub-TLV identifies the link as being
state.It is carried in extended Link TLV in the Extended Link Opaque gracefully shutdown. It is advertised in extended Link TLV of the
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Link-Overload sub-TLV for OSPFv2 Figure 1: Graceful-Link-Shutdown sub-TLV for OSPFv2
Type : TBA (suggested value 5) 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 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 4) 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 a particular link on the 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 extended Link TLV as defined in [RFC7684].This sub-TLV advertised in the Extended Link TLV as defined in [RFC7684]. This
is optional and MAY be advertised in area scoped Extended Link Opaque sub-TLV is optional and MAY be advertised in an area-scoped Extended
LSA to identify the link when there are multiple parallel unnumbered Link Opaque LSA to identify the link when there are multiple parallel
links between two nodes. The local interface-id is generally readily unnumbered links between two nodes. The local interface-id is
available. One of the mechanisms to obtain remote interface-id is generally readily available. One of the mechanisms to obtain remote
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local Interface ID | | Local Interface ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote Interface ID | | Remote Interface ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: Local/Remote Interface ID sub-TLV Figure 3: Local/Remote Interface ID Sub-TLV
Type : TBA (suggested value 11) Type : TBA (suggested value 9)
Length: 8 Length: 8
Value: 4 octets of Local Interface ID followed by 4 octets of Remote Value: 4 octets of Local Interface ID followed by 4 octets of Remote
interface ID. interface ID.
4.4. OSPFv3 Link-Overload sub-TLV 4.4. OSPFv3 Graceful-Link-Shutdown sub-TLV
The definition of OSPFv3 Link-Overload sub-TLV is defined below. The The Graceful-Link-Shutdown sub-TLV is carried in the Router-Link TLV
area scoped advertisement of Link-Overload sub-TLV for OSPFv3 will be as defined in the [I-D.ietf-ospf-ospfv3-lsa-extend] for OSPFv3. The
described in a separate document. Router-Link TLV contains the neighbour interface-id and can uniquely
identify the link on the remote node.
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: Link-Overload sub-TLV for OSPFv3 Figure 4: Graceful-Link-Shutdown sub-TLV for OSPFv3
Type : TBA (Suggested value 4) Type : TBA (Suggested value 7)
Length: 0
4.5. BGP-LS Graceful-Link-Shutdown TLV
BGP-LS as defined in [RFC7752] is a mechanism to distribute network
information to the external entities using BGP routing protocol.
Graceful-link-shutdown is an important link information that the
external entities can use for various use cases as defined in
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
attribute corresponding to graceful-link-shutdown state. The TLV
format is as described in [RFC7752] sec 3.1. There is no value field
and length field is set to zero for this TLV.
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 Length: 0
4.6. Distinguishing parallel links
++++++++++I.w I.y +++++++++
|Router A|------------------|Router B |
| |------------------| |
++++++++++I.x I.z++++++++++
Figure 6: Parallel Linkls
Consider two routers A and B connected with two parallel point-to-
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 B's side. The extended link opaque LSA as described in
[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.
Link-type = Point-to-point
Link-ID: Router-ID of B
Link-Data = I.w
A third node (controller or head-end) in the network cannot
distinguish the Interface on router B which is connected to this
particular Interface with the above information. Interface with
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
the Extended Link TLV. The use cases as described in Section 7
require controller or head-end nodes to interpret the graceful-link-
shutdown information and hence the need for the Remote IPv4 address
sub-TLV. I.y is carried in the Extended Link TLV which unambiguously
identifies the interface on the remote side. OSPFv3 Router-link-TLV
as described in [I-D.ietf-ospf-ospfv3-lsa-extend] contains Interface
ID and neighbor's Interface-ID which can uniquely identify connecting
interface on the remote side and hence OSPFv3 does not require
seperate Remote-IPv6 address to be advertised along with the OSPFv3-
Graceful-Link-Shutdown sub-TLV.
5. Elements of procedure 5. Elements of procedure
The Link-Overload sub-TLV indicates that the link identified by the As defined in [RFC7684] every link on the node will have a separate
sub-TLV is overloaded. The node that has the link to be taken out of Extended Link Opaque LSA. The node that has the link to be taken out
service SHOULD advertise the Link-Overload sub-TLV in the Extended of service MUST advertise the Graceful-Link-Shutdown sub-TLV in the
Link TLV in the Extended Link Opaque LSA as defined in [RFC7684] for Extended Link TLV of the Extended Link Opaque LSA as defined in
OSPFv2. The Link-Overload information is advertised as a property of [RFC7684] for OSPFv2 and Router-Link TLV of E-Router-LSA for OSPFv3.
the link and is flooded across the area. This information can be The Graceful-Link-Shutdown sub-TLV indicates that the link identified
by the sub-TLV is subjected to maintenance.
For the purposes of changing the metric OSPFv2 and OSPFv3 Router-LSAs
need to be re-orignated and for Traffic Engineering metric, TE Opaque
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 through the area. This information can be
used by ingress routers or controllers to take special actions. An used by ingress routers or controllers to take special actions. An
application specific to this use case is described in Section 7.2. application specific to this use case is described in Section 7.2.
When a link is ready to carry traffic, the Graceful-Lnk-Shutdown sub-
TLV MUST be removed from the Extended Link TLV/Router-Link TLV and
the corresponding LSAs MUST be readvertised. Similarly, metric MUST
be set to original values and corresponding LSAs MUST be
readvertised.
The procedures described in this draft may be used to divert the
traffic away from the link in scenarios other than link-shutdown or
link-replacement activity.
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 as overloaded depends on the link type. link identified for graceful-shutdown depends on the link type.
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 MAX-METRIC (0xffff) and re- originate the Router-LSA. of the link to MaxLinkMetric (0xffff) and re-originate its router-
The TE metric SHOULD be set to MAX-TE-METRIC -1 (0xfffffffe) and the LSA. The Traffic Engineering metric of the link SHOULD be set to
node SHOULD re-originate the TE Link Opaque LSAs. When a Link- (0xffffffff) and the node SHOULD re-originate the corresponding TE
Overload sub-TLV is received for a point-to-point link, the remote Link Opaque LSAs. When a Graceful-Link-Shutdown sub-TLV is received
node MUST identify the local link which corresponds to the overloaded for a point-to-point link, the remote node MUST identify the local
link and set the metric to MAX-METRIC (0xffff)and the remote node link which corresponds to the graceful-shutdown link and set its
MUST re-originate the router-LSA with the changed metric. The TE metric to MaxLinkMetric (0xffff) and the remote node MUST re-
metric SHOULD be set to MAX-TE-METRIC -1 (0xfffffffe) and the TE originate its router-LSA with the changed metric. When TE is
opaque LSA for the link SHOULD be re-originated with new value. enabled, the Traffic Engineering metric of the link SHOULD be set to
(0xffffffff) and follow procedures of [RFC5817]. 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.
Extended link opaque LSAs and the Extended link TLV are not scoped The Extended link opaque LSAs and the Extended link TLV are not
for multi-topology [RFC4915]. In multi-topology deployments scoped for multi-topology [RFC4915]. In multi-topology deployments
[RFC4915], the Link-Overload sub-TLV advertised in an Extended Link [RFC4915], the Graceful-Link-Shutdown sub-TLV advertised in an
opaque LSA corresponds to all the topologies which include the link. Extended Link opaque LSA corresponds to all the topologies which
The receiver node SHOULD change the metric in the reverse direction include the link. The receiver node SHOULD change the metric in the
for all the topologies which include the remote link and re-originate reverse direction for all the topologies which include the remote
the Router LSA as defined in [RFC4915]. link and re-originate the router-LSA as defined in [RFC4915].
When the originator of the Link-Overload sub-TLV purges the Extended When the originator of the Graceful-Link-Shutdown sub-TLV purges the
Link Opaque LSA or re-originates it without the Link-Overload sub- Extended Link Opaque LSA or re-originates it without the Graceful-
TLV, the remote node must re-originate the appropriate LSAs with the Link-Shutdown sub-TLV, the remote node must re-originate the
metric and TE metric values set to their original values. appropriate LSAs with the metric and TE metric values set to their
original values.
5.2. Broadcast/NBMA links 5.2. Broadcast/NBMA links
Broadcast or NBMA networks in OSPF are represented by a star topology Broadcast or NBMA networks in OSPF are represented by a star topology
where the Designated Router (DR) is the central point to which all where the Designated Router (DR) is the central point to which all
other routers on the broadcast or NBMA network connect logically. 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 MAX-METRIC on the remote link cannot be changed since all the the MaxLinkMetric on the remote link cannot be changed since all the
neighbours are on same link. Setting the link cost to MAX-METRIC neighbors are on same link. Setting the link cost to MaxLinkMetric
would impact paths going via all neighbours. 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 MAX-METRIC(0xffff) and re-originate the Router-LSA. of the link to MaxLinkMetric (0xffff) and re-originate the Router-
The TE metric SHOULD be set to MAX-TE-METRIC -1(0xfffffffe) and the LSA. The Traffic Engineering metric of the link SHOULD be set to (
node SHOULD re-originate the corresponding TE Link Opaque LSAs. For 0xffffffff) and the node SHOULD re-originate the corresponding TE
a broadcast link, the two part metric as described in [RFC8042] is Link Opaque LSAs. For a broadcast link, the two part metric as
used. The node originating the Link-Overload sub-TLV MUST set the described in [RFC8042] is used. The node originating the Graceful-
metric in the Network-to-Router Metric sub-TLV to MAX-METRIC 0xffff Link-Shutdown sub-TLV MUST set the metric in the Network-to-Router
for OSPFv2 and OSPFv3 and re-originate the corresponding LSAs. The Metric sub-TLV to MaxLinkMetric (0xffff) for OSPFv2 and OSPFv3 and
nodes that receive the two part metric should follow the procedures re-originate the corresponding LSAs. The nodes that receive the two-
described in [RFC8042]. The backward compatibility procedures part metric should follow the procedures described in [RFC8042]. The
described in [RFC8042] should be followed to ensure loop free backward compatibility procedures described in [RFC8042] should be
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 Link-Overload sub-TLV is received for a to-point links. When a Graceful-Link-Shutdown sub-TLV is received
point-to-multipoint link the remote node MUST identify the neighbour for a point-to-multipoint link the remote node MUST identify the
which corresponds to the overloaded link and set the metric to MAX- neighbour which corresponds to the graceful-shutdown link and set its
METRIC (0xffff). The remote node MUST re-originate the Router-LSA metric to MaxLinkMetric (0xffff). The remote node MUST re-originate
with the changed metric. 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 interfaces do not have a unique IP address and borrow
address from other interfaces. [RFC2328] describes procedures to their address from other interfaces. [RFC2328] describes procedures
handle unnumbered interfaces in the context of the Router LSA. We to 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
Link-Overload sub-TLV in to handle unnumbered interfaces. The link- Graceful-Link-Shutdown sub-TLV in order to handle unnumbered
data field in the Extended Link TLV includes the Local interface-id interfaces. The link-data field in the Extended Link TLV includes
instead of the IP address. The Local/Remote Interface ID sub-TLV the Local interface-id instead of the IP address. The Local/Remote
MUST be advertised when there are multiple parallel unnumbered Interface ID sub-TLV MUST be advertised when there are multiple
interfaces between two nodes. One of the mechanisms to obtain the parallel unnumbered interfaces between two nodes. One of the
interface-id of the remote side are defined in [RFC4203]. mechanisms to obtain the interface-id of the remote side is defined
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 Link-Overload sub-TLV is received for a the P2MP interfaces. When a Graceful-Link-Shutdown sub-TLV is
hybrid link the remote node MUST identify the neighbour which received for a hybrid link, the remote node MUST identify the
corresponds to the overloaded link and set the metric to MAX-METRIC neighbor which corresponds to the graceful-shutdown link and set its
(0xffff). All the remote nodes connected to originator MUST re- metric to MaxLinkMetric (0xffff). All the remote nodes connected to
originate the Router-LSA with the changed metric. originator MUST re-originate the router-LSA with the changed metric
for the neighbor.
6. Backward compatibility 6. 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 Link-Overload compatible. It is required that the node adverting the Graceful-
sub-TLV as well as the node at the remote end of the overloaded link Link-Shutdown sub-TLV as well as the node at the remote end of the
support the extensions described herein for the traffic to diverted graceful-shutdown link support the extensions described herein for
from the overloaded link. If the remote node doesn't support the the traffic to diverted from the graceful-shutdown link. If the
capability, it will still use the overloaded link but there are no remote node doesn't support the capability, it will still use the
other adverse effects. In the case of broadcast links using two-part graceful-shutdown link but there are no other adverse effects. In
metrics, the backward compatibility procedures as described in the case of broadcast links using two-part metrics, the backward
[RFC8042] are applicable. compatibility procedures as described in [RFC8042] are applicable.
7. Applications 7. Applications
7.1. Pseudowire Services 7.1. Overlay Network
Many service providers offer pseudo-wire services to customers using Many service providers offer L2 services to a customer connecting
L2 circuits. The IGP protocol that runs in the customer network different locations. The customer's IGP protocol creates a seamless
would also run over the pseudo-wire to create a seamless private private network (overlay network) across the locations for the
network for the customer. Service providers want to offer overload customer. Service providers want to offer graceful-shutdown
functionality when the PE device is taken-out for maintenance. The functionality when the PE device is taken-out for maintenance. There
provider should guarantee that the PE is taken out for maintenance can be large number of customers attached to a PE node and the remote
only after the service is successfully diverted on an alternate path. end-points for these L2 attachments circuits are spread across the
There can be large number of customers attached to a PE node and the
remote end-points for these pseudo-wires are spread across the
service provider's network. It is a tedious and error-prone process service provider's network. It is a tedious and error-prone process
to change the metric for all pseudo-wires in both directions. The to change the metric for all corresponding L2 circuits in both
link-overload feature simplifies the process by increasing the metric directions. The graceful-link-shutdown feature simplifies the
on the link in the reverse direction as well so that traffic in both process by increasing the metric on the CE-CE overlay link so that
directions is diverted away from the PE undergoing maintenance. The traffic in both directions is diverted away from the PE undergoing
Link-Overload feature allows the link to be used as a last resort maintenance. The Graceful-Link-Shutdown feature allows the link to
link so that traffic is not disrupted when alternative paths are not be used as a last resort link so that traffic is not disrupted when
available. alternate paths are not available.
Private VLAN ------PE3---------------PE4------CE3
======================================= / \
| | / \
| |
| ------PE3---------------PE4------CE3
| / \
| / \
CE1---------PE1----------PE2---------CE2 CE1---------PE1----------PE2---------CE2
| \ \
| \ \
| ------CE4 ------CE4
| |
| |
| |
=================================
Private VLAN
Figure 5: Pseudowire Services Figure 7: Overlay Network
In the example shown in Figure 5, 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 overload service for maintenance, a service provider sets the PE1 to stub-
state. The PE1 going in to overload state triggers all the CEs (In router state and communicates the pending maintenance action to the
this example CE1)connected to the PE to set their pseudowire links overlay customer networks. The mechanisms used to communicate
passing via PE1 to link-overload state. The mechanisms used to between PE1 and CE1 is outside the scope of this document. CE1 sets
communicate between PE1 and CE1 is outside the scope of this the graceful-link-shutdown state on its links connecting CE3, CE2 and
document. CE1 sets the link-overload state on its private VLAN CE4 and changes the metric to MaxLinkMetric and re-originates the
connecting CE3, CE2 and CE4 and changes the metric to MAX_METRIC and corresponding LSA. The remote end of the link at CE3, CE2, and CE4
re-originates the corresponding LSA. The remote end of the link at also set the metric on the link to MaxLinkMetric and the traffic from
CE3, CE2, and CE4 also set the metric on the link to MAX-METRIC and both directions gets diverted away from PE1.
the traffic from both directions gets diverted away from the
pseudowires.
7.2. Controller based Traffic Engineering Deployments 7.2. Controller based 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 link-overload the IGP protocol, the controller can also receive the graceful-link-
information as a warning that link maintenance is imminent. Using shutdown information as a warning that link maintenance is imminent.
this information, the controller can find alternate paths for traffic Using this information, the controller can find alternate paths for
which uses the affected link. The controller can apply various traffic which uses the affected link. The controller can apply
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
engineering constraints, the controller might temporarily relax those constraints, the controller might temporarily relax those constraints
constraints and put the service on a different path. Increasing the and put the service on a different path. Increasing the link metric
link metric alone does not specify the maintenance activity as the alone does not specify the maintenance activity as the metric could
metric could increase in events such as LDP-IGP synchronisation. An increase in events such as LDP-IGP synchronisation. An explicit
explicit indication from the router using the link-overload sub-TLV indication from the router using the graceful-link-shutdown sub-TLV
is needed to inform the Controller or head-end routers. is needed to inform the Controller or head-end routers.
_____________ _____________
| | | |
-------------| Controller |-------------- -------------| Controller |--------------
| |____________ | | | |____________ | |
| | | |
|--------- Primary Path ------------------| |--------- Primary Path ------------------|
PE1---------P1----------------P2---------PE2 PE1---------P1----------------P2---------PE2
| | | |
| | | |
|________P3________| |________P3________|
Alternate Path Alternate Path
Figure 6: 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 10GB. When P1->P2 link is being prepared for bandwidth constraint of 10Gbps. When P1->P2 link is being prepared
maintenance, the controller receives the link-overload information, for maintenance, the controller receives the graceful-link-shutdown
as there is no alternate path available which satisfies the information, as there is no alternate path available which satisfies
constraints, controller chooses a path that is less optimal and the constraints, the controller chooses a path that is less optimal
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.
7.3. 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 goes 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 link-overlaod maintenance, all the links on the PE can be set to graceful-link-
state which will gurantee that the traffic to/from dual-homed CEs shutdown state which will gurantee that the traffic to/from dual-
gets diverted. The interaction between OSPF and BGP is outside the homed CEs gets diverted. The interaction between OSPF and BGP is
scope of this document. outside the scope of this document. [RFC6987] based mechanism with
summaries and externals advertised with high metrics could also be
used to achieve the same functionality when implementations support
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, all customers [RFC4577]. When PE goes out of service for maintenance,
sham-links on the PE can be set to link-overload state and traffic all sham-links on the PE can be set to graceful-link-shutdown state
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.
7.4. Hub and spoke deployment 7.4. Hub and spoke deployment
OSPF is largely deployed in Hub and Spoke deployments with a number OSPF is largely deployed in Hub and Spoke deployments with a large
of spokes connecting to the Hub. It is a general practice to deploy number of spokes connecting to the Hub. It is a general practice to
multiple Hubs with all spokes connecting to these Hubs to achieve deploy multiple Hubs with all spokes connecting to these Hubs to
redundancy. When a Hub node goes down for maintenance, all links on achieve redundancy. The [RFC6987] mechanism can be used to divert
the Hub can be set to link-overload state and traffic gets divered the spoke-to-spoke traffic from the overloaded hub router. The
from the spoke sites as well without having to make configuration traffic that flows from spokes via the hub into an external network
changes on the spokes. 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-
shutdown state and traffic gets divered from the spoke sites as well
without having to make configuration changes on the spokes.
8. 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].
9. IANA Considerations 9. IANA Considerations
This specification updates one OSPF registry: This specification updates one OSPF registry:
OSPF Extended Link TLVs Registry OSPFv2 Extended Link TLV Sub-TLVs
i) Link-Overload sub-TLV - Suggested value 5
ii) Remote IPv4 address sub-TLV - Suggested value 4 i) Graceful-Link-Shutdown Sub-TLV - Suggested value 7
ii) Remote IPv4 Address Sub-TLV - Suggested value 8
iii) Local/Remote Interface ID sub-TLV - Suggested Value 11 iii) Local/Remote Interface ID Sub-TLV - Suggested Value 9
OSPFV3 Router Link TLV Registry OSPFv3 Extended-LSA sub-TLV Registry
i) Link-Overload sub-TLV - suggested value 4 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)Link-Overload TLV - Suggested 1101 i)Graceful-Link-Shutdown TLV - Suggested 1121
10. 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 link-overload is useful. applications where graceful-link-shutdown is useful.
Thanks to Alia Atlas, Deborah Brungard, Alvaro Retana, Andrew G.
Malis and Tim Chown for valuable inputs.
11. References 11. References
11.1. Normative References 11.1. Normative References
[I-D.ietf-ospf-ospfv3-lsa-extend]
Lindem, A., Roy, A., Goethals, D., Vallem, V., and F.
Baker, "OSPFv3 LSA Extendibility", draft-ietf-ospf-ospfv3-
lsa-extend-23 (work in progress), January 2018.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[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>.
[RFC5817] Ali, Z., Vasseur, JP., Zamfir, A., and J. Newton,
"Graceful Shutdown in MPLS and Generalized MPLS Traffic
Engineering Networks", RFC 5817, DOI 10.17487/RFC5817,
April 2010, <https://www.rfc-editor.org/info/rfc5817>.
[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,
<http://www.rfc-editor.org/info/rfc6845>. <https://www.rfc-editor.org/info/rfc6845>.
[RFC6987] Retana, A., Nguyen, L., Zinin, A., White, R., and D.
McPherson, "OSPF Stub Router Advertisement", RFC 6987,
DOI 10.17487/RFC6987, September 2013,
<https://www.rfc-editor.org/info/rfc6987>.
[RFC7684] Psenak, P., Gredler, H., Shakir, R., Henderickx, W., [RFC7684] Psenak, P., Gredler, H., Shakir, R., Henderickx, W.,
Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute
Advertisement", RFC 7684, DOI 10.17487/RFC7684, November Advertisement", RFC 7684, DOI 10.17487/RFC7684, November
2015, <http://www.rfc-editor.org/info/rfc7684>. 2015, <https://www.rfc-editor.org/info/rfc7684>.
[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,
<http://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,
<http://www.rfc-editor.org/info/rfc8042>. <https://www.rfc-editor.org/info/rfc8042>.
11.2. Informative References 11.2. Informative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328,
DOI 10.17487/RFC2328, April 1998,
<http://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,
<http://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, <http://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,
<http://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,
<http://www.rfc-editor.org/info/rfc5340>.
[RFC5817] Ali, Z., Vasseur, JP., Zamfir, A., and J. Newton,
"Graceful Shutdown in MPLS and Generalized MPLS Traffic
Engineering Networks", RFC 5817, DOI 10.17487/RFC5817,
April 2010, <http://www.rfc-editor.org/info/rfc5817>.
[RFC6987] Retana, A., Nguyen, L., Zinin, A., White, R., and D.
McPherson, "OSPF Stub Router Advertisement", RFC 6987,
DOI 10.17487/RFC6987, September 2013,
<http://www.rfc-editor.org/info/rfc6987>.
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
Individual 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
2025 Hamilton Avenue 2025 Hamilton Avenue
San Jose, CA 98052 San Jose, CA 98052
US US
Email: mnanduri@ebay.com Email: mnanduri@ebay.com
Luay Jalil Luay Jalil
Verizon Verizon
Email: luay.jalil@verizon.com Email: luay.jalil@verizon.com
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