draft-ietf-ospf-link-overload-01.txt   draft-ietf-ospf-link-overload-02.txt 
Open Shortest Path First IGP S. Hegde Open Shortest Path First IGP S. Hegde
Internet-Draft P. Sarkar Internet-Draft Juniper Networks, Inc.
Intended status: Standards Track Juniper Networks, Inc. Intended status: Standards Track P. Sarkar
Expires: July 9, 2016 H. Gredler Expires: January 8, 2017 H. Gredler
Individual Individual
M. Nanduri M. Nanduri
Microsoft Corporation Microsoft Corporation
L. Jalil L. Jalil
Verizon Verizon
January 6, 2016 July 7, 2016
OSPF Link Overload OSPF Link Overload
draft-ietf-ospf-link-overload-01 draft-ietf-ospf-link-overload-02
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 metric on one side of the link is not
sufficient to divert the traffic flowing in the other direction. sufficient 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 being in an overload state to indicate able to advertise a link being in an overload state to indicate
skipping to change at page 2, line 7 skipping to change at page 2, line 7
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
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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 9, 2016. This Internet-Draft will expire on January 8, 2017.
Copyright Notice Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the Copyright (c) 2016 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
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to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Link overload sub-TLV . . . . . . . . . . . . . . . . . . . . 4 3. Link overload sub-TLV . . . . . . . . . . . . . . . . . . . . 4
3.1. OSPFv2 Link overload sub-TLV . . . . . . . . . . . . . . 4 3.1. OSPF Link overload sub-TLV . . . . . . . . . . . . . . . 4
3.2. OSPFv3 Link Overload sub-TLV . . . . . . . . . . . . . . 4 4. Flooding Scope . . . . . . . . . . . . . . . . . . . . . . . 4
4. Elements of procedure . . . . . . . . . . . . . . . . . . . . 5 4.1. Area scope flooding . . . . . . . . . . . . . . . . . . . 4
4.1. Point-to-point links . . . . . . . . . . . . . . . . . . 5 4.2. Link scope flooding . . . . . . . . . . . . . . . . . . . 5
4.2. Broadcast/NBMA links . . . . . . . . . . . . . . . . . . 6 5. Elements of procedure . . . . . . . . . . . . . . . . . . . . 5
4.3. Point-to-multipoint links . . . . . . . . . . . . . . . . 6 5.1. Point-to-point links . . . . . . . . . . . . . . . . . . 5
4.4. Unnumbered interfaces . . . . . . . . . . . . . . . . . . 6 5.2. Broadcast/NBMA links . . . . . . . . . . . . . . . . . . 6
5. Backward compatibility . . . . . . . . . . . . . . . . . . . 7 5.3. Point-to-multipoint links . . . . . . . . . . . . . . . . 6
6. Applications . . . . . . . . . . . . . . . . . . . . . . . . 7 5.4. Unnumbered interfaces . . . . . . . . . . . . . . . . . . 6
6.1. Pseudowire Services . . . . . . . . . . . . . . . . . . . 7 6. Backward compatibility . . . . . . . . . . . . . . . . . . . 7
6.2. Controller based Traffic Engineering Deployments . . . . 8 7. Applications . . . . . . . . . . . . . . . . . . . . . . . . 7
7. Security Considerations . . . . . . . . . . . . . . . . . . . 8 7.1. Pseudowire Services . . . . . . . . . . . . . . . . . . . 7
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 7.2. Controller based Traffic Engineering Deployments . . . . 8
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9 8. Security Considerations . . . . . . . . . . . . . . . . . . . 8
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 9 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
10.1. Normative References . . . . . . . . . . . . . . . . . . 9 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9
10.2. Informative References . . . . . . . . . . . . . . . . . 9 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
11.1. Normative References . . . . . . . . . . . . . . . . . . 9
11.2. Informative References . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
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 an [RFC6987] provides mechanisms to advertise the node being in an
overload state by setting all outgoing link costs to MAX-METRIC overload state by setting all outgoing link costs to MAX-METRIC
(0xffff). These procedures are specific to the maintenance activity (0xffff). These procedures are specific to the maintenance activity
on a node and cannot be used when a single link attached to the node on a node and cannot be used when a single link attached to the node
requires maintenance. requires maintenance.
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LSP re-routing policies at the ingress to route the LSPs away from LSP re-routing policies at the ingress to route the LSPs away from
the link. 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. When the devices in the by means of pseudo-wires or L2-circuits. When the devices in the
underlying network go for maintenance, it is useful to divert the underlying network go for maintenance, it is useful to divert the
traffic away from the node before the maintenance is actually traffic away from the node before the maintenance is actually
scheduled. Since the nodes in the underlying network are not visible scheduled. Since the nodes in the underlying network are not visible
to OSPF, the existing stub router mechanism described in [RFC6987] to OSPF, the existing stub router mechanism described in [RFC6987]
cannot be used. Application specific to this use case is described cannot be used. Application specific to this use case is described
in Section 6.1 in Section 7.1
This document provides mechanisms to advertise link overload state in This document provides mechanisms to advertise link overload state in
the flexible encodings provided by OSPFv2 Prefix/Link Attribute the flexible encodings provided by RI LSA( [RFC7770]) for OSPFv2 and
Advertisement( [I-D.ietf-ospf-prefix-link-attr]) and OSPFv3 Extended OSPFv3. Throughout this document, OSPF is used when the text applies
LSA ([I-D.ietf-ospf-ospfv3-lsa-extend]). Throughout this document, to both OSPFv2 and OSPFv3. OSPFv2 or OSPFv3 is used when the text is
OSPF is used when the text applies to both OSPFv2 and OSPFv3. OSPFv2 specific to one version of the OSPF protocol.
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 the traffic from 1. Advertise impending maintenance activity so that the traffic from
both directions can be diverted away from the link. both directions can be diverted away from the link.
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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 the impending so that LSP ingress routers/controllers can learn the impending
maintenance activity and apply specific policies to re-route the maintenance activity and apply specific policies to re-route the
LSP for traffic-engineering based deployments. LSP 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. Link overload sub-TLV 3. Link overload sub-TLV
3.1. OSPFv2 Link overload sub-TLV 3.1. OSPF Link overload sub-TLV
The Link Overload sub-TLV is carried as part of the Extended Link TLV The Link Overload sub-TLV is defined as below. This sub-TLV is
as defined in [I-D.ietf-ospf-prefix-link-attr] for OSPFv2. attached to the Link TLV [RFC3630] and carried in RI LSA [RFC7770]
for OSPFv2 and OSPFv3
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 IP address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Link Overload sub-TLV for OSPFv2 Figure 1: Link Overload sub-TLV for OSPFv2
Type : TBA (suggested value 4) Type : TBA (suggested value 35)
Length: 4 Length: 0
Value: Remote IPv4 address. The remote IP4 address is used to 4. Flooding Scope
identify the particular link that is in the overload state when there
are multiple parallel links between two nodes.
3.2. OSPFv3 Link Overload sub-TLV The link overload information can be flood in area scoped RI LSA or
link scoped RI LSA or both based on the need of the application.
Section 7 describes applications requiring area scope as well as link
scope Link-overload information. The Link TLV and the link-overload
sub-tlv MAY appear in any instance of the RI-LSA.
The Link Overload sub-TLV is carried in the Router-Link TLV as 4.1. Area scope flooding
defined in the [I-D.ietf-ospf-ospfv3-lsa-extend] for OSPFv3. The
Router-Link TLV contains the neighbour interface-id and can uniquely
identify the link on the remote node.
0 1 2 3 For OSPFv2, Link overload Sub-TLV is carried in the Link TLV as
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 defined in [RFC3630]. Link TLV is carried in area scoped RI LSA
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ [RFC7770]. When there are more than one parallel links between two
| Type | Length | nodes, the link carrying link-overload information, need to be
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ uniquely identified among the parallel links. Remote interface IP
address sub-tlv as defined by [RFC3630] is also carried in the Link
TLV which is used by the remote nodes to uniquely identify the
overloaded link.
Figure 2: Link Overload sub-TLV for OSPFv3 For OSPFv3, Link-overload sub-tlv is carried in Link TLV as defined
in [RFC5329] Link TLV is carried in the OSPFv3 area scoped RI-LSA
[RFC7770]
Type : TBA (Suggested value 4) 4.2. Link scope flooding
Length: 0 The link local scope RI-LSA corresponds to the link on which the LSA
arrives and there is no need to explicitly carry the link TLV. The
Link overload sub-TLV is carried in the RI-LSA for both OSPFv2 and
OSPFv3.
4. Elements of procedure 5. Elements of procedure
The Link Overload sub-TLV indicates that the link identified in by The Link Overload sub-TLV indicates that the link identified in which
the sub-TLV is overloaded. The node that has the link to be taken it is carried is overloaded. The node that has the link to be taken
out of service SHOULD originate the Link Overload sub-TLV in the out of service SHOULD originate the Link Overload sub-TLV in the Link
Extended Link TLV in the Extended Link Opaque LSA as defined in TLV in the RI LSA as defined in [RFC7770]. The link-overload
[I-D.ietf-ospf-prefix-link-attr] for OSPFv2 or in the E-Router-LSA as information is carried as a property of the link and is flooded
defined in [I-D.ietf-ospf-ospfv3-lsa-extend] for OSPFv3. The link- across the area. This information can be used by ingress routers or
overload information is carried as a property of the link and is controllers to take special actions. Application specific to this
flooded across the area. This information can be used by ingress use case is described in Section 7.2.
routers or controllers to take special actions. Application specific
to this use case is described in Section 6.2.
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 as overloaded depends on the link type. link identified as overloaded depends on the link type.
4.1. Point-to-point links 5.1. Point-to-point links
The node that has the link to be taken out of service SHOULD set The node that has the link to be taken out of service SHOULD set
metric of the link to MAX-METRIC (0xffff) and re- originate the metric of the link to MAX-METRIC (0xffff) and re- originate the
Router-LSA. The TE metric SHOULD be set to MAX-TE-METRIC-1 Router-LSA. The TE metric SHOULD be set to MAX-TE-METRIC-1
(0xfffffffe) and the node SHOULD re-originate the TE Link Opaque (0xfffffffe) and the node SHOULD re-originate the TE Link Opaque
LSAs. When a Link Overload sub-TLV is received for a point-to-point LSAs. When a Link Overload sub-TLV is received for a point-to-point
link, the remote node SHOULD identify the local link which link either by link local or area scoped RI-LSA, the remote node
corresponds to the overloaded link and set the metric to MAX-METRIC SHOULD identify the local link which corresponds to the overloaded
(0xffff). The remote node MUST re-originate the router-LSA with the link and set the metric to MAX-METRIC (0xffff). The remote node MUST
changed metric and flood into the OSPF area. The TE metric SHOULD be re-originate the router-LSA with the changed metric and flood into
set to MAX-TE-METRIC-1 (0xfffffffe) and the TE opaque LSA for the the OSPF area. The TE metric SHOULD be set to MAX-TE-METRIC-1
link MUST be re-originated with new value. (0xfffffffe) and the TE opaque LSA for the link MUST be re-originated
with new value.
In multi-topology deployments [RFC4915], the Link overload Sub-TLV In multi-topology deployments [RFC4915], the Link overload Sub-TLV
carried in an Extended Link opaque LSA corresponds to all the carried in an RI LSA corresponds to all the topologies the link
topologies the link belongs to. The receiver node SHOULD change the belongs to. The receiver node SHOULD change the metric in the
metric in the reverse direction corresponding to all the topologies reverse direction corresponding to all the topologies to which the
to which the reverse link belongs. reverse link belongs.
When the originator of the Link Overload sub-TLV purges the Extended When the originator of the Link Overload sub-TLV purges the RI-LSA or
Link Opaque LSA/E-Router-LSA or re-originates it without the Link re-originates it without the Link Overload sub-TLV, the remote node
Overload sub-TLV, the remote node must re-originate the appropriate must re-originate the appropriate LSAs with the metric and TE metric
LSAs with the metric and TE metric values set to their original values set to their original values.
values.
4.2. 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 connect logically. 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 MAX-METRIC on the remote link cannot be changed since all the
neighbours are on same link. Setting the link cost to MAX-METRIC neighbours are on same link. Setting the link cost to MAX-METRIC
would impact paths going via all neighbours. would impact paths going via all neighbours.
The node that has the link to be taken out of service SHOULD set The node that has the link to be taken out of service SHOULD set
metric of the link to MAX-METRIC (0xffff) and re-originate the metric of the link to MAX-METRIC (0xffff) and re-originate the
Router-LSA. The TE metric SHOULD be set to MAX-TE-METRIC- Router-LSA. The TE metric SHOULD be set to MAX-TE-METRIC-
1(0xfffffffe) and the node SHOULD re-originate the TE Link Opaque 1(0xfffffffe) and the node SHOULD re-originate the TE Link Opaque
LSAs. For a broadcast link, the two part metric as described in LSAs. For a broadcast link, the two part metric as described in
[I-D.ietf-ospf-two-part-metric] is used. The node originating the [I-D.ietf-ospf-two-part-metric] is used. The node originating the
Link Overload sub-TLV MUST set the metric in the Network-to-Router Link Overload sub-TLV MUST set the metric in the Network-to-Router
Metric sub-TLV to MAX-METRIC 0xffff for OSPFv2 and OSPFv3 and re- Metric sub-TLV to MAX-METRIC 0xffff for OSPFv2 and OSPFv3 and re-
originate the LSAs the TLV is carried-in. The nodes that receive the originate the LSAs the TLV is carried-in.
two part metric should follow the procedures described in
[I-D.ietf-ospf-two-part-metric]. The backward compatibility
procedures described in [I-D.ietf-ospf-two-part-metric] should be
followed to ensure loop free routing.
4.3. Point-to-multipoint links The nodes that receive the two part metric should follow the
procedures described in [I-D.ietf-ospf-two-part-metric]. The
backward compatibility procedures described in
[I-D.ietf-ospf-two-part-metric] should be followed to ensure loop
free routing.
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 Link Overload sub-TLV is received for a
point-to-multipoint link the remote node SHOULD identify the point-to-multipoint link the remote node SHOULD identify the link
neighbour which corresponds to the overloaded link and set the metric which corresponds to the overloaded link and set the metric to MAX-
to MAX-METRIC (0xffff). The remote node MUST re-originate the METRIC (0xffff). The remote node MUST re-originate the Router-LSA
Router-LSA with the changed metric and flood into the OSPF area. with the changed metric and flood into the OSPF area.
4.4. Unnumbered interfaces 5.4. Unnumbered interfaces
Unnumbered interface do not have a unique IP addresses and borrow Unnumbered interface do not have a unique IP addresses and borrow
address from other interfaces. [RFC2328] describes procedures to address from other interfaces. The Link TLV carries the local and
handle unnumbered interfaces. The link-data field in the Extended remote interface ids to uniquely identify the link when there are
Link TLV carries the interface-id instead of the IP address. The more than one parallel links between the nodes. Procedures to obtain
Link Overload sub-TLV carries the remote interface-id in the Remote- interface-id of the remote side is defined in [RFC4203] and are
ip-address field if the interface is unnumbered. Procedures to applicable to the Link TLV added in the RI LSA for the purpose of
obtain interface-id of the remote side is defined in [RFC4203]. carrying the Link overload sub-tlv.
5. Backward compatibility 6. Backward compatibility
The mechanism described in the document is fully backward The mechanism described in the document is fully backward
compatible.It is required that the originator of the Link Overload compatible.It is required that the originator of the Link Overload
sub-TLV as well as the node at the remote end of the link identified sub-TLV as well as the node at the remote end of the link identified
as overloaded understand the extensions defined in this document. In as overloaded understand the extensions defined in this document. In
the case of broadcast links, the backward compatibility procedures as the case of broadcast links, the backward compatibility procedures as
described in [I-D.ietf-ospf-two-part-metric] are applicable. . described in [I-D.ietf-ospf-two-part-metric] are applicable. .
6. Applications 7. Applications
6.1. Pseudowire Services 7.1. Pseudowire Services
---------PE3----------------PE4---------- ---------PE3----------------PE4----------
| | | |
| | | |
CE1---------PE1----------------PE2---------CE2 CE1---------PE1----------------PE2---------CE2
| | | |
| | | |
----------------------------------------- -----------------------------------------
Private VLAN Private VLAN
Figure 3: Pseudowire Services Figure 2: 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 seamless private would also run over the pseudo-wire to create seamless private
network for the customer. Service providers want to offer overload network for the customer. Service providers want to offer overload
kind of functionality when the PE device is taken-out for kind of 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
across the service provider's network. It is a tedious and error- across the service provider's network. It is a tedious and error-
prone process to change the metric for all pseudo-wires in both prone process to change the metric for all pseudo-wires in both
directions.The link overload feature simplifies the process by directions.The link overload feature simplifies the process by
increasing the metric on the link in the reverse direction as well so increasing the metric on the link in the reverse direction as well so
that traffic in both directions is diverted away from the PE that traffic in both directions is diverted away from the PE
undergoing maintenance. The link-overload feature allows the link to undergoing maintenance. The link-overload feature allows the link to
be used as a last resort link so that traffic is not disrupted when be used as a last resort link so that traffic is not disrupted when
alternative paths are not available. alternative paths are not available.
6.2. Controller based Traffic Engineering Deployments 7.2. Controller based Traffic Engineering Deployments
_____________ _____________
| | | |
-------------| Controller |-------------- -------------| Controller |--------------
| |____________ | | | |____________ | |
| | | |
|--------- Primary Path ------------------| |--------- Primary Path ------------------|
PE1---------P1----------------P2---------PE2 PE1---------P1----------------P2---------PE2
| | | |
| | | |
|________P3________| |________P3________|
Alternate Path Alternate Path
Figure 4: Controller based Traffic Engineering Figure 3: Controller based Traffic Engineering
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 link-overload
information as a warning that link maintenance is imminent. Using information as a warning that link maintenance is imminent. Using
this information, the controller can find alternate paths for traffic this information, the controller can find alternate paths for traffic
using the affected link. The controller can apply various policies which use the affected link. The controller can apply various
and re-route the LSPs away from the link undergoing maintenance. If policies and re-route the LSPs away from the link undergoing
there are no alternate paths satisfying the traffic engineering maintenance. If there are no alternate paths satisfying the traffic
constraints, the controller might temporarily relax those constraints engineering constraints, the controller might temporarily relax those
and put the service on a different path. constraints and put the service on a different path.
In the above example, PE1->PE2 LSP is set-up which satisfies a In the above example, PE1->PE2 LSP is set-up which satisfies a
constraint of 10 GB bandwidth on each link.The links P1->P3 and constraint of 10 GB bandwidth on each link.The links P1->P3 and
P3->P2 have only 1 GB capacity. and there is no alternate path P3->P2 have only 1 GB capacity. and there is no alternate path
satisfying the bandwidth constraint of 10GB. When P1->P2 link is satisfying the bandwidth constraint of 10GB. When P1->P2 link is
being prepared for maintenance, the controller receives the link- being prepared for maintenance, the controller receives the link-
overload information, as there is no alternate path available which overload information, as there is no alternate path available which
satisfies the constraints, controller chooses a path that is less satisfies the constraints, controller chooses a path that is less
optimal and sets up an alternate path via P1->P3->P2 temporarily. optimal and sets up an alternate path via P1->P3->P2 temporarily.
Once the traffic is diverted, P1->P2 link can be taken out for Once the traffic is diverted, P1->P2 link can be taken out for
maintenance/upgrade. maintenance/upgrade.
7. Security Considerations 8. 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].
8. IANA Considerations 9. IANA Considerations
This specification updates one OSPF registry: This specification updates one OSPF registry:
OSPF Extended Link TLVs Registry OSPF Link TLVs Registry
i) TBD - Link Overload sub TLV i) TBD - Link Overload sub TLV
OSPFV3 Router Link TLV Registry OSPFV3 Link TLV Registry
i) TBD - Link Overload sub TLV i) TBD - Link Overload sub TLV
9. Acknowledgements OSPF Router Information (RI)TLVs Registry
Thanks to Chris Bowers for valuable inputs and edits to the document. i) TBD - Link TLV
Thanks to Jeffrey Zhang and Acee Lindem for inputs.
10. References 10. Acknowledgements
10.1. Normative References Thanks to Chris Bowers for valuable inputs and edits to the document.
Thanks to Jeffrey Zhang and Acee Lindem for inputs.
[I-D.ietf-ospf-ospfv3-lsa-extend] 11. References
Lindem, A., Mirtorabi, S., Roy, A., and F. Baker, "OSPFv3
LSA Extendibility", draft-ietf-ospf-ospfv3-lsa-extend-06
(work in progress), February 2015.
[I-D.ietf-ospf-prefix-link-attr] 11.1. Normative References
Psenak, P., Gredler, H., Shakir, R., Henderickx, W.,
Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute
Advertisement", draft-ietf-ospf-prefix-link-attr-03 (work
in progress), February 2015.
[I-D.ietf-ospf-two-part-metric] [I-D.ietf-ospf-two-part-metric]
Wang, L., Lindem, A., DuBois, D., Julka, V., and T. Wang, L., Lindem, A., DuBois, D., Julka, V., and T.
McMillan, "OSPF Two-part Metric", draft-ietf-ospf-two- McMillan, "OSPF Two-part Metric", draft-ietf-ospf-two-
part-metric-01 (work in progress), July 2015. part-metric-01 (work in progress), July 2015.
10.2. Informative References [RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
(TE) Extensions to OSPF Version 2", RFC 3630,
DOI 10.17487/RFC3630, September 2003,
<http://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,
<http://www.rfc-editor.org/info/rfc5329>.
[RFC7770] Lindem, A., Ed., Shen, N., Vasseur, JP., Aggarwal, R., and
S. Shaffer, "Extensions to OSPF for Advertising Optional
Router Capabilities", RFC 7770, DOI 10.17487/RFC7770,
February 2016, <http://www.rfc-editor.org/info/rfc7770>.
11.2. Informative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>. <http://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,
<http://www.rfc-editor.org/info/rfc2328>. <http://www.rfc-editor.org/info/rfc2328>.
skipping to change at page 10, line 35 skipping to change at page 10, line 46
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
Juniper Networks, Inc. Individual
Embassy Business Park
Bangalore, KA 560093
India
Email: psarkar@juniper.net
Email: pushpasis.ietf@gmail.com
Hannes Gredler Hannes Gredler
Individual Individual
Email: hannes@gredler.at Email: hannes@gredler.at
Mohan Nanduri Mohan Nanduri
Microsoft Corporation Microsoft Corporation
One Microsoft Way One Microsoft Way
Redmond, WA 98052 Redmond, WA 98052
US US
Email: mnanduri@microsoft.com Email: mnanduri@microsoft.com
Luay Jalil Luay Jalil
Verizon Verizon
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