draft-ietf-ospf-link-overload-13.txt   draft-ietf-ospf-link-overload-14.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 25, 2018 H. Gredler Expires: July 28, 2018 Arrcus Inc.
H. Gredler
Individual Individual
M. Nanduri M. Nanduri
ebay Corporation ebay Corporation
L. Jalil L. Jalil
Verizon Verizon
January 21, 2018 January 24, 2018
OSPF Graceful Link shutdown OSPF Graceful Link shutdown
draft-ietf-ospf-link-overload-13 draft-ietf-ospf-link-overload-14
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 routers in an OSPFv2 or OSPFv3 routing domain to be
able to advertise a link as being in a graceful-shutdown state to able to advertise a link as being in a graceful-shutdown state to
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on July 25, 2018. This Internet-Draft will expire on July 28, 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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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. Graceful-Link-Shutdown sub-TLV . . . . . . . . . . . . . . . 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 . . . . . . . . . . . . 5 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 . . . . . . . . . . . . 6 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 . . . . . . . . . . . . . . . . . . 8
5.2. Broadcast/NBMA links . . . . . . . . . . . . . . . . . . 9 5.2. Broadcast/NBMA links . . . . . . . . . . . . . . . . . . 9
5.3. Point-to-multipoint links . . . . . . . . . . . . . . . . 9 5.3. Point-to-multipoint links . . . . . . . . . . . . . . . . 9
5.4. Unnumbered interfaces . . . . . . . . . . . . . . . . . . 9 5.4. Unnumbered interfaces . . . . . . . . . . . . . . . . . . 10
5.5. Hybrid Broadcast and P2MP interfaces . . . . . . . . . . 10 5.5. Hybrid Broadcast and P2MP interfaces . . . . . . . . . . 10
6. Backward compatibility . . . . . . . . . . . . . . . . . . . 10 6. Maximum TE Metric . . . . . . . . . . . . . . . . . . . . . . 10
7. Applications . . . . . . . . . . . . . . . . . . . . . . . . 10 7. Backward compatibility . . . . . . . . . . . . . . . . . . . 10
7.1. Pseudowire Services . . . . . . . . . . . . . . . . . . . 10 8. Applications . . . . . . . . . . . . . . . . . . . . . . . . 11
7.2. Controller based Traffic Engineering Deployments . . . . 11 8.1. Pseudowire Services . . . . . . . . . . . . . . . . . . . 11
7.3. L3VPN Services and sham-links . . . . . . . . . . . . . . 12 8.2. Controller based Traffic Engineering Deployments . . . . 12
7.4. Hub and spoke deployment . . . . . . . . . . . . . . . . 13 8.3. L3VPN Services and sham-links . . . . . . . . . . . . . . 13
8. Security Considerations . . . . . . . . . . . . . . . . . . . 13 8.4. Hub and spoke deployment . . . . . . . . . . . . . . . . 13
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 9. Security Considerations . . . . . . . . . . . . . . . . . . . 13
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 13 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 14 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 14
11.1. Normative References . . . . . . . . . . . . . . . . . . 14 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 14
11.2. Informative References . . . . . . . . . . . . . . . . . 14 12.1. Normative References . . . . . . . . . . . . . . . . . . 14
12.2. Informative References . . . . . . . . . . . . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15 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 the node requires maintenance.
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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 metric in
other direction of the link and also use the link as a last-resort- other direction of the link 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 7.1. this use case is described in detail in Section 8.1.
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 other scenarios and is not restricted
to link-shutdown or link-replacement activity. to link-shutdown or 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]. Throughout this document, OSPF is
used when the text applies to both OSPFv2 and OSPFv3. OSPFv2 or 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 OSPFv3 is used when the text is specific to one version of the OSPF
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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 last resort link to prevent traffic
disruption when alternate paths are not available. 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]. The Graceful-Link-Shutdown sub- Extended Link Opaque LSA [RFC7684] for OSPFv2 and E-Router-LSA for
TLV MAY be processed by the head-end nodes or the controller as OSPFv3 [I-D.ietf-ospf-ospfv3-lsa-extend]. The Graceful-Link-Shutdown
described in the Section 7. The procedures for processing the sub-TLV MAY be processed by the head-end nodes or the controller as
described in the Section 8. 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. Graceful-Link-Shutdown sub-TLV
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].
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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 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 7. BGP Link NLRI is used to carry the link information. A Section 8. 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. 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.
4.6. Distinguishing parallel links 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 5: Parallel Linkls
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Link-ID: Router-ID B Link-ID: Router-ID 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 7 the extended link-TLV. The use cases as described in Section 8
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 RemoteIPv4 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 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 SHOULD 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. The Graceful-Link-Shutdown sub-TLV indicates [RFC7684] for OSPFv2 and Router-Link TLV of E-Router-LSA for OSPFv3.
that the link identified by the sub-TLV is subjected to maintenance. The Graceful-Link-Shutdown sub-TLV indicates that the link identified
The Graceful-Link-Shutdown information is advertised as a property of by the sub-TLV is subjected to maintenance. The Graceful-Link-
the link and is flooded across the area. This information can be Shutdown information is advertised as a property of the link and is
used by ingress routers or controllers to take special actions. An flooded across the area. This information can be used by ingress
application specific to this use case is described in Section 7.2. routers or controllers to take special actions. An application
specific to this use case is described in Section 8.2.
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.
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 is a constant defined by this draft and set to LSA. MAX-TE-METRIC (0xfffffffe). The TE metric SHOULD be set to
0xfffffffe. The TE metric SHOULD be set to MAX-TE-METRIC MAX-TE-METRIC (0xfffffffe) and the node SHOULD re-originate the
(0xfffffffe) 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 the 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. The TE metric metric SHOULD be set to MAX-TE-METRIC (0xfffffffe) and the TE opaque
SHOULD be set to MAX-TE-METRIC (0xfffffffe) and the TE opaque LSA for LSA for the link SHOULD be re-originated with new value.
the link SHOULD be re-originated with 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
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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 the
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. Backward compatibility 6. Maximum TE Metric
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.
7. Applications 8. Applications
7.1. Pseudowire Services 8.1. 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 an
alternate path. There can be large number of customers attached to a alternate path. There can be large number of customers attached to a
PE node and the remote end-points for these pseudo-wires are spread PE node and the remote end-points for these pseudo-wires are spread
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Figure 6: Pseudowire Services Figure 6: Pseudowire Services
In the example shown in Figure 6, when the PE1 node is going out of In the example shown in Figure 6, 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 graceful-
link-shutdown state. The PE1 going in to maintenance state triggers link-shutdown state. The PE1 going in to maintenance state triggers
all the CEs connected to the PE (CE1 in this case) to set their all the CEs connected to the PE (CE1 in this case) to set their
pseudowire links passing via PE1 to graceful-link-shutdown state. pseudowire links passing via PE1 to graceful-link-shutdown state.
The mechanisms used to communicate between PE1 and CE1 is outside the The mechanisms used to communicate between PE1 and CE1 is outside the
scope of this document. CE1 sets the graceful-link-shutdown state on scope of this document. CE1 sets the graceful-link-shutdown state on
its private VLAN connecting CE3, CE2 and CE4 and changes the metric its private VLAN connecting CE3, CE2 and CE4 and changes the metric
to MAX_METRIC and re-originates the corresponding LSA. The remote to MaxLinkMetric and re-originates the corresponding LSA. The remote
end of the link at CE3, CE2, and CE4 also set the metric on the link end of the link at CE3, CE2, and CE4 also set the metric on the link
to MaxLinkMetric and the traffic from both directions gets diverted to MaxLinkMetric and the traffic from both directions gets diverted
away from the pseudowires. away from the pseudowires.
7.2. Controller based Traffic Engineering Deployments 8.2. 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 31 skipping to change at page 13, line 7
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.
7.3. L3VPN Services and sham-links 8.3. 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.
7.4. Hub and spoke deployment 8.4. 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.
8. Security Considerations 9. Security Considerations
This document does not introduce any further security issues other This document does not introduce any further security issues other
than those discussed in [RFC2328] and [RFC5340]. than those discussed in [RFC2328] and [RFC5340].
9. IANA Considerations 10. 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 Link NLRI Registry [RFC7752]
i)Graceful-Link-Shutdown TLV - Suggested 1101 i)Graceful-Link-Shutdown TLV - Suggested 1101
skipping to change at page 13, line 43 skipping to change at page 14, line 14
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 Link NLRI Registry [RFC7752]
i)Graceful-Link-Shutdown TLV - Suggested 1101 i)Graceful-Link-Shutdown TLV - Suggested 1101
10. Acknowledgements 11. 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.
11. References 12. References
11.1. Normative References 12.1. 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., Mirtorabi, S., Roy, A., and F. Baker, "OSPFv3
LSA Extendibility", draft-ietf-ospf-ospfv3-lsa-extend-10 LSA Extendibility", draft-ietf-ospf-ospfv3-lsa-extend-10
(work in progress), May 2016. (work in progress), May 2016.
[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>.
[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.
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, <https://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,
<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>.
11.2. Informative References 12.2. 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,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328,
DOI 10.17487/RFC2328, April 1998, DOI 10.17487/RFC2328, April 1998,
<https://www.rfc-editor.org/info/rfc2328>. <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>.
skipping to change at page 15, line 24 skipping to change at page 15, line 45
[RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF [RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF
for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008, for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008,
<https://www.rfc-editor.org/info/rfc5340>. <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>.
[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>.
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
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