draft-ietf-ospf-link-overload-00.txt   draft-ietf-ospf-link-overload-01.txt 
Open Shortest Path First IGP S. Hegde Open Shortest Path First IGP S. Hegde
Internet-Draft P. Sarkar Internet-Draft P. Sarkar
Intended status: Standards Track H. Gredler Intended status: Standards Track Juniper Networks, Inc.
Expires: April 21, 2016 Juniper Networks, Inc. Expires: July 9, 2016 H. Gredler
Individual
M. Nanduri M. Nanduri
Microsoft Corporation Microsoft Corporation
L. Jalil L. Jalil
Verizon Verizon
October 19, 2015 January 6, 2016
OSPF Link Overload OSPF Link Overload
draft-ietf-ospf-link-overload-00 draft-ietf-ospf-link-overload-01
Abstract Abstract
Many OSPFv2 or OSPFv3 deployments run on overlay networks provisioned When a link is being prepared to be taken out of service, the traffic
by means of pseudo-wires or L2-circuits. When the devices in the needs to be diverted from both ends of the link. Increasing the
underlying network go for maintenance, it is useful to divert the metric to the highest metric on one side of the link is not
traffic away from the node before the maintenance is actually sufficient to divert the traffic flowing in the other direction.
scheduled. Since the nodes in the underlying network are not visible
to OSPF, the existing stub router mechanism described in [RFC3137]
cannot be used.
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
impending maintenance activity in the underlying network devices. impending maintenance activity on the link. This information can be
This information can be used by the network devices to re-route the used by the network devices to re-route the traffic effectively.
traffic effectively.
This document describes the protocol extensions to disseminate link This document describes the protocol extensions to disseminate link
overload information in OSPFv2 and OSPFv3. overload 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].
skipping to change at page 2, line 10 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
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 http://datatracker.ietf.org/drafts/current/. Drafts is at http://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 April 21, 2016. This Internet-Draft will expire on July 9, 2016.
Copyright Notice Copyright Notice
Copyright (c) 2015 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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publication of this document. Please review these documents publication of this document. Please review these documents
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to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
skipping to change at page 2, line 36 skipping to change at page 2, line 33
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. OSPFv2 Link overload sub-TLV . . . . . . . . . . . . . . 4
3.2. OSPFv3 Link Overload sub-TLV . . . . . . . . . . . . . . 4 3.2. OSPFv3 Link Overload sub-TLV . . . . . . . . . . . . . . 4
4. Elements of procedure . . . . . . . . . . . . . . . . . . . . 5 4. Elements of procedure . . . . . . . . . . . . . . . . . . . . 5
4.1. Point-to-point links . . . . . . . . . . . . . . . . . . 5 4.1. Point-to-point links . . . . . . . . . . . . . . . . . . 5
4.2. Broadcast/NBMA links . . . . . . . . . . . . . . . . . . 5 4.2. Broadcast/NBMA links . . . . . . . . . . . . . . . . . . 6
4.3. Point-to-multipoint links . . . . . . . . . . . . . . . . 6 4.3. Point-to-multipoint links . . . . . . . . . . . . . . . . 6
4.4. Unnumbered interfaces . . . . . . . . . . . . . . . . . . 6 4.4. Unnumbered interfaces . . . . . . . . . . . . . . . . . . 6
5. Backward compatibility . . . . . . . . . . . . . . . . . . . 6 5. Backward compatibility . . . . . . . . . . . . . . . . . . . 7
6. Applications . . . . . . . . . . . . . . . . . . . . . . . . 6 6. Applications . . . . . . . . . . . . . . . . . . . . . . . . 7
6.1. Pseudowire Services . . . . . . . . . . . . . . . . . . . 7 6.1. Pseudowire Services . . . . . . . . . . . . . . . . . . . 7
6.2. Controller based Traffic Engineering Deployments . . . . 7 6.2. Controller based Traffic Engineering Deployments . . . . 8
7. Security Considerations . . . . . . . . . . . . . . . . . . . 8 7. Security Considerations . . . . . . . . . . . . . . . . . . . 8
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 9 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
10.1. Normative References . . . . . . . . . . . . . . . . . . 9 10.1. Normative References . . . . . . . . . . . . . . . . . . 9
10.2. Informative References . . . . . . . . . . . . . . . . . 9 10.2. Informative References . . . . . . . . . . . . . . . . . 9
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,
[RFC3137] 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.
When a link is being prepared to be taken out of service, the traffic In traffic-engineering deployments, LSPs need to be moved away from
needs to be diverted from both ends of the link. Changing the metric the link without disrupting the services. It is useful to be able to
on one side of the link is not sufficient to divert the traffic advertise the impending maintenance activity on the link and to have
flowing in both directions. In traffic-engineering deployments, LSPs LSP re-routing policies at the ingress to route the LSPs away from
need to be moved away from the link without disrupting the services. the link.
It is useful to be able to advertise the impending maintenance
activity on the link and to have LSP rerouting policies at the
ingress to route the LSPs away from the link.
It is useful for routers in OSPFv2 or OSPFv3 routing domain to be Many OSPFv2 or OSPFv3 deployments run on overlay networks provisioned
able to advertise a link being in an overload state to indicate by means of pseudo-wires or L2-circuits. When the devices in the
impending maintenance activity on the link. This document provides underlying network go for maintenance, it is useful to divert the
mechanisms to advertise link overload state in the flexible encodings traffic away from the node before the maintenance is actually
provided by OSPFv2 Prefix/Link Attribute Advertisement( scheduled. Since the nodes in the underlying network are not visible
[I-D.ietf-ospf-prefix-link-attr]) and OSPFv3 Extended LSA to OSPF, the existing stub router mechanism described in [RFC6987]
([I-D.ietf-ospf-ospfv3-lsa-extend]). Throughout this document, OSPF cannot be used. Application specific to this use case is described
is used when the text applies to both OSPFv2 and OSPFv3. OSPFv2 or in Section 6.1
OSPFv3 is used when the text is specific to one version of the OSPF
protocol. This document provides mechanisms to advertise link overload state in
the flexible encodings provided by OSPFv2 Prefix/Link Attribute
Advertisement( [I-D.ietf-ospf-prefix-link-attr]) and OSPFv3 Extended
LSA ([I-D.ietf-ospf-ospfv3-lsa-extend]). Throughout this 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 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.
skipping to change at page 4, line 25 skipping to change at page 4, line 27
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 | | Remote IP address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Link Overload sub-TLV for OSPFv2 Figure 1: Link Overload sub-TLV for OSPFv2
Type : TBA Type : TBA (suggested value 4)
Length: 4 Length: 4
Value: Remote IPv4 address. The remote IP4 address is used to Value: Remote IPv4 address. The remote IP4 address is used to
identify the particular link that is in the overload state when there identify the particular link that is in the overload state when there
are multiple parallel links between two nodes. are multiple parallel links between two nodes.
3.2. OSPFv3 Link Overload sub-TLV 3.2. OSPFv3 Link Overload sub-TLV
The Link Overload sub-TLV is carried in the Router-Link TLV as The Link Overload sub-TLV is carried in the Router-Link TLV as
defined in the [I-D.ietf-ospf-ospfv3-lsa-extend] for OSPFv3. The defined in the [I-D.ietf-ospf-ospfv3-lsa-extend] for OSPFv3. The
Router-Link TLV contains the neighbor interface-id and can uniquely Router-Link TLV contains the neighbour interface-id and can uniquely
identify the link on the remote node. 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 2: Link Overload sub-TLV for OSPFv3 Figure 2: Link Overload sub-TLV for OSPFv3
Type : TBA Type : TBA (Suggested value 4)
Length: 0 Length: 0
4. Elements of procedure 4. 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 by
the sub-TLV is overloaded. The node that has the link to be taken the sub-TLV is overloaded. The node that has the link to be taken
out of service sets metric of the link to MAX-METRIC (0xffff) and re- out of service SHOULD originate the Link Overload sub-TLV in the
originates the Router-LSA. The TE metric is set to MAX-TE-METRIC-1 Extended Link TLV in the Extended Link Opaque LSA as defined in
(0xfffffffe) and the node also re-originates the TE Link Opaque LSAs.
The node SHOULD originate the Link Overload sub-TLV in the Extended
Link TLV in the Extended Link Opaque LSA as defined in
[I-D.ietf-ospf-prefix-link-attr] for OSPFv2 or in the E-Router-LSA as [I-D.ietf-ospf-prefix-link-attr] for OSPFv2 or in the E-Router-LSA as
defined in [I-D.ietf-ospf-ospfv3-lsa-extend] for OSPFv3. This LSA defined in [I-D.ietf-ospf-ospfv3-lsa-extend] for OSPFv3. The link-
should be flooded in the OSPF area. A node which supports this draft overload information is carried as a property of the link and is
and is at the remote end of the link identified in the Link Overload flooded across the area. This information can be used by ingress
sub-TLV MUST set the metric of the link in the reverse direction to routers or controllers to take special actions. Application specific
MAX-METRIC. In addition, the TE metric MUST be changed to to this use case is described in Section 6.2.
0xfffffffe. The remote node MUST re-originate the Router-LSA and TE
link opaque LSA with these updated metrics, and flood them into the
area.
When the originator of the Link Overload sub-TLV purges the Extended
Link Opaque LSA or re-originates it without the Link Overload sub-
TLV, the remote node must re-originate the appropriate LSAs with the
metric and TE metric values set to their original values.
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 4.1. Point-to-point links
When a Link Overload sub-TLV is received for a point-to-point link The node that has the link to be taken out of service SHOULD set
the remote node SHOULD identify the local link which corresponds to metric of the link to MAX-METRIC (0xffff) and re- originate the
the overloaded link and set the metric to MAX-METRIC (0xffff). The Router-LSA. The TE metric SHOULD be set to MAX-TE-METRIC-1
remote node MUST re-originate the router-LSA with the changed metric (0xfffffffe) and the node SHOULD re-originate the TE Link Opaque
and flood into the OSPF area. The TE metric SHOULD be set to MAX-TE- LSAs. When a Link Overload sub-TLV is received for a point-to-point
METRIC-1 (0xfffffffe) and the TE opaque LSA for the link MUST be re- link, the remote node SHOULD identify the local link which
originated with new value. corresponds to the overloaded link and set the metric to MAX-METRIC
(0xffff). The remote node MUST re-originate the router-LSA with the
changed metric and flood into the OSPF area. The TE metric SHOULD be
set to MAX-TE-METRIC-1 (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
carried in an Extended Link opaque LSA corresponds to all the
topologies the link belongs to. The receiver node SHOULD change the
metric in the reverse direction corresponding to all the topologies
to which the reverse link belongs.
When the originator of the Link Overload sub-TLV purges the Extended
Link Opaque LSA/E-Router-LSA or re-originates it without the Link
Overload sub-TLV, the remote node must re-originate the appropriate
LSAs with the metric and TE metric values set to their original
values.
4.2. Broadcast/NBMA links 4.2. 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 outgoing link cannot be changed since all the the MAX-METRIC on the remote link cannot be changed since all the
neighbors 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 neighbors. would impact paths going via all neighbours.
For a broadcast link, the two part metric as described in 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
Router-LSA. The TE metric SHOULD be set to MAX-TE-METRIC-
1(0xfffffffe) and the node SHOULD re-originate the TE Link Opaque
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 MT 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. The nodes Metric sub-TLV to MAX-METRIC 0xffff for OSPFv2 and OSPFv3 and re-
that receive the two part metric should follow the procedures originate the LSAs the TLV is carried-in. The nodes that receive the
described in [I-D.ietf-ospf-two-part-metric]. The backward two part metric should follow the procedures described in
compatibility procedures described in [I-D.ietf-ospf-two-part-metric] [I-D.ietf-ospf-two-part-metric]. The backward compatibility
should be followed to ensure loop free routing. procedures described in [I-D.ietf-ospf-two-part-metric] should be
followed to ensure loop free routing.
4.3. Point-to-multipoint links 4.3. 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 neighbor point-to-multipoint link the remote node SHOULD identify the
which corresponds to the overloaded link and set the metric to MAX- neighbour which corresponds to the overloaded link and set the metric
METRIC (0xffff). The remote node MUST re-originate the Router-LSA to MAX-METRIC (0xffff). The remote node MUST re-originate the
with the changed metric and flood into the OSPF area. Router-LSA with the changed metric and flood into the OSPF area.
4.4. Unnumbered interfaces 4.4. 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. [RFC2328] describes procedures to
handle unnumbered interfaces. The link-data field in the Extended handle unnumbered interfaces. The link-data field in the Extended
Link TLV carries the interface-id instead of the IP address. The Link TLV carries the interface-id instead of the IP address. The
Link Overload sub-TLV carries the remote interface-id in the Remote- Link Overload sub-TLV carries the remote interface-id in the Remote-
ip-address field if the interface is unnumbered. Procedures to ip-address field if the interface is unnumbered. Procedures to
obtain interface-id of the remote side is defined in [RFC4203]. obtain interface-id of the remote side is defined in [RFC4203].
skipping to change at page 7, line 28 skipping to change at page 7, line 42
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 6.2. 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 4: 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 using the affected link. The controller can apply various policies
and re-route the LSPs away from the link undergoing maintenance. If and re-route the LSPs away from the link undergoing maintenance. If
there are no alternate paths satisfying the traffic engineering there are no alternate paths satisfying the traffic engineering
constraints, the controller might temporarily relax those constraints constraints, the controller might temporarily relax those constraints
and put the service on a different path. In the above example when and put the service on a different path.
P1->P2 link is being prepared for maintenance, the controller
receives the link-overload information and sets up an alternate path In the above example, PE1->PE2 LSP is set-up which satisfies a
via P1->P3->P2. Once the traffic is diverted, P1->P2 link can be constraint of 10 GB bandwidth on each link.The links P1->P3 and
taken out for maintenance/upgrade. P3->P2 have only 1 GB capacity. and there is no alternate path
satisfying the bandwidth constraint of 10GB. When P1->P2 link is
being prepared for maintenance, the controller receives the link-
overload information, as there is no alternate path available which
satisfies the constraints, controller chooses a path that is less
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
maintenance/upgrade.
7. Security Considerations 7. 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 8. IANA Considerations
This specification updates one OSPF registry: This specification updates one OSPF registry:
skipping to change at page 9, line 8 skipping to change at page 9, line 20
i) TBD - Link Overload sub TLV i) TBD - Link Overload sub TLV
OSPFV3 Router Link TLV Registry OSPFV3 Router Link TLV Registry
i) TBD - Link Overload sub TLV i) TBD - Link Overload sub TLV
9. Acknowledgements 9. 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 and Acee Lindem for inputs.
10. References 10. References
10.1. Normative References 10.1. 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-06 LSA Extendibility", draft-ietf-ospf-ospfv3-lsa-extend-06
(work in progress), February 2015. (work in progress), February 2015.
skipping to change at page 9, line 40 skipping to change at page 10, line 5
[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>.
[RFC3137] Retana, A., Nguyen, L., White, R., Zinin, A., and D.
McPherson, "OSPF Stub Router Advertisement", RFC 3137,
DOI 10.17487/RFC3137, June 2001,
<http://www.rfc-editor.org/info/rfc3137>.
[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>. <http://www.rfc-editor.org/info/rfc4203>.
[RFC4915] Psenak, P., Mirtorabi, S., Roy, A., Nguyen, L., and P.
Pillay-Esnault, "Multi-Topology (MT) Routing in OSPF",
RFC 4915, DOI 10.17487/RFC4915, June 2007,
<http://www.rfc-editor.org/info/rfc4915>.
[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,
<http://www.rfc-editor.org/info/rfc5340>. <http://www.rfc-editor.org/info/rfc5340>.
[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
Juniper Networks, Inc. Juniper Networks, Inc.
Embassy Business Park Embassy Business Park
Bangalore, KA 560093 Bangalore, KA 560093
India India
Email: psarkar@juniper.net Email: psarkar@juniper.net
Hannes Gredler Hannes Gredler
Juniper Networks, Inc. Individual
1194 N. Mathilda Ave.
Sunnyvale, CA 94089
US
Email: hannes@juniper.net
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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