draft-ietf-ospf-link-overload-03.txt   draft-ietf-ospf-link-overload-04.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: August 16, 2017 H. Gredler Expires: August 22, 2017 H. Gredler
Individual Individual
M. Nanduri M. Nanduri
Microsoft Corporation Microsoft Corporation
L. Jalil L. Jalil
Verizon Verizon
February 12, 2017 February 18, 2017
OSPF Link Overload OSPF Link Overload
draft-ietf-ospf-link-overload-03 draft-ietf-ospf-link-overload-04
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
impending maintenance activity on the link. This information can be impending maintenance activity on the link. This information can be
used by the network devices to re-route the traffic effectively. used by the network devices to re-route the traffic effectively.
This document describes the protocol extensions to disseminate link This document describes the protocol extensions to disseminate 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].
Status of This Memo Status of This Memo
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
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 August 16, 2017. This Internet-Draft will expire on August 22, 2017.
Copyright Notice Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the Copyright (c) 2017 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
(http://trustee.ietf.org/license-info) in effect on the date of (http://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
skipping to change at page 2, line 31 skipping to change at page 2, line 31
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. Flooding Scope . . . . . . . . . . . . . . . . . . . . . . . 4 3. Flooding Scope . . . . . . . . . . . . . . . . . . . . . . . 4
3.1. Area scope flooding . . . . . . . . . . . . . . . . . . . 4 3.1. Area scope flooding . . . . . . . . . . . . . . . . . . . 4
3.2. Link scope flooding . . . . . . . . . . . . . . . . . . . 4 3.2. Link scope flooding . . . . . . . . . . . . . . . . . . . 4
4. Link overload sub-TLV . . . . . . . . . . . . . . . . . . . . 4 4. Link-Overload sub-TLV . . . . . . . . . . . . . . . . . . . . 4
4.1. OSPFv2 Link overload sub-TLV . . . . . . . . . . . . . . 4 4.1. OSPFv2 Link-overload sub-TLV . . . . . . . . . . . . . . 4
4.2. OSPFv3 Link Overload sub-TLV . . . . . . . . . . . . . . 5 4.2. OSPFv3 Link-Overload sub-TLV . . . . . . . . . . . . . . 5
5. Elements of procedure . . . . . . . . . . . . . . . . . . . . 5 5. Elements of procedure . . . . . . . . . . . . . . . . . . . . 5
5.1. Point-to-point links . . . . . . . . . . . . . . . . . . 6 5.1. Point-to-point links . . . . . . . . . . . . . . . . . . 6
5.2. Broadcast/NBMA links . . . . . . . . . . . . . . . . . . 6 5.2. Broadcast/NBMA links . . . . . . . . . . . . . . . . . . 6
5.3. Point-to-multipoint links . . . . . . . . . . . . . . . . 7 5.3. Point-to-multipoint links . . . . . . . . . . . . . . . . 7
5.4. Unnumbered interfaces . . . . . . . . . . . . . . . . . . 7 5.4. Unnumbered interfaces . . . . . . . . . . . . . . . . . . 7
5.5. Hybrid Broadcast and P2MP interfaces . . . . . . . . . . 7
6. Backward compatibility . . . . . . . . . . . . . . . . . . . 7 6. Backward compatibility . . . . . . . . . . . . . . . . . . . 7
7. Applications . . . . . . . . . . . . . . . . . . . . . . . . 7 7. Applications . . . . . . . . . . . . . . . . . . . . . . . . 7
7.1. Pseudowire Services . . . . . . . . . . . . . . . . . . . 7 7.1. Pseudowire Services . . . . . . . . . . . . . . . . . . . 8
7.2. Controller based Traffic Engineering Deployments . . . . 8 7.2. Controller based Traffic Engineering Deployments . . . . 8
8. Security Considerations . . . . . . . . . . . . . . . . . . . 9 8. Security Considerations . . . . . . . . . . . . . . . . . . . 9
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 9 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
11.1. Normative References . . . . . . . . . . . . . . . . . . 10 11.1. Normative References . . . . . . . . . . . . . . . . . . 10
11.2. Informative References . . . . . . . . . . . . . . . . . 10 11.2. Informative References . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
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.
In traffic-engineering deployments, LSPs need to be moved away from In traffic-engineering deployments, LSPs need to be diverted from the
the link without disrupting the services. It is useful to be able to link without disrupting the services. It is useful to be able to
advertise the impending maintenance activity on the link and to have advertise the impending maintenance activity on the link and to have
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. Prior to devices in the
underlying network go for maintenance, it is useful to divert the underlying network going offline for maintenance, it is useful to
traffic away from the node before the maintenance is actually divert the traffic away from the node before the maintenance is
scheduled. Since the nodes in the underlying network are not visible actually scheduled. Since the nodes in the underlying network are
to OSPF, the existing stub router mechanism described in [RFC6987] not visible to OSPF, the existing stub router mechanism described in
cannot be used. Application specific to this use case is described [RFC6987] cannot be used. An application specific to this use case
in Section 7.1 is described 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 OSPFv2 Prefix/Link Attribute
Advertisement( [RFC7684]) and OSPFv3 Extended LSA Advertisement([RFC7684]) and RI LSA ([RFC7770]). Throughout this
([I-D.ietf-ospf-ospfv3-lsa-extend]). Throughout this document, OSPF document, OSPF is used when the text applies to both OSPFv2 and
is used when the text applies to both OSPFv2 and OSPFv3. OSPFv2 or OSPFv3. OSPFv2 or OSPFv3 is used when the text is specific to one
OSPFv3 is used when the text is specific to one version of the OSPF version of the OSPF protocol.
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 traffic from
both directions can be diverted away from the link. both directions can be diverted away from the link.
2. Allow the solution to be backward compatible so that nodes that 2. Allow the solution to be backward compatible so that nodes that
do not understand the new advertisement do not cause routing do not understand the new advertisement do not cause routing
loops. loops.
3. Advertise the maintenance activity to other nodes in the network 3. Advertise the maintenance activity to other nodes in the network
so that LSP ingress routers/controllers can learn the impending so that LSP ingress routers/controllers can learn of the
maintenance activity and apply specific policies to re-route the impending maintenance activity and apply specific policies to re-
LSP 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 link overload information can be flood in area scoped extended The link-overload information can be flooded in area scoped extended
link LSA [RFC7684] or link scoped RI LSA [RFC7770] or both based on link LSA [RFC7684] or a link scoped RI LSA [RFC7770] or both based on
the need of the application. Section 7 describes applications the needs of the application. Section 7 describes applications
requiring area scope as well as link scope Link-overload information. requiring area scope as well as link scope link-overload information.
3.1. Area scope flooding 3.1. Area scope flooding
For OSPFv2, Link overload Sub-TLV is carried in the extended Link TLV For OSPFv2, Link-Overload sub-TLV is carried in the extended Link TLV
as defined in [RFC7684] . as defined in [RFC7684].
3.2. Link scope flooding 3.2. Link scope flooding
The link local scope RI LSA MAY carry the link overload sub TLV as The link local scope RI LSA MAY carry the Link-Overload sub-TLV as
defined in Section 4.The link local scope RI-LSA corresponds to the defined in Section 4. The link local scope RI-LSA corresponds to the
link on which the LSA arrives and there is no need to explicitly link on which the LSA arrives and there is no need to explicitly
specify the remote ipv4 address.The remote ipv4 address field MAY be specify the remote IPv4 address. The remote IPv4 address field MAY
zero when the link overload sub-TLV is carried in the link local RI be zero when the Link-Overload sub-TLV is carried in the link local
LSA. The link-overload sub-tlv MAY appear in any instance of the RI LSA. The Link-Overload sub-TLV MAY appear in any instance of the
link local RI-LSA. The Link overload sub-TLV is carried in the RI- link local RI-LSA. The Link-Overload sub-TLV is carried in the RI-
LSA for both OSPFv2 and OSPFv3. LSA for both OSPFv2 and OSPFv3.
4. Link overload sub-TLV 4. Link-Overload sub-TLV
4.1. OSPFv2 Link overload sub-TLV 4.1. OSPFv2 Link-overload sub-TLV
The Link Overload sub-TLV identifies the link being in overload The Link-Overload sub-TLV identifies the link being in overload
state. It is carried in extended Link TLV as defined in [RFC7684] or state. It is carried in extended Link TLV as defined in [RFC7684] or
link local scope RI LSA as defined in [RFC7770]. link local scope RI LSA as defined in [RFC7770].
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 (suggested value 4) 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.
4.2. OSPFv3 Link Overload sub-TLV 4.2. OSPFv3 Link-Overload sub-TLV
The Link Overload sub-TLV is carried in the Router-Link TLV as The OSPFv3 Link-Overload sub-TLV is carried in the link local scope
defined in the [I-D.ietf-ospf-ospfv3-lsa-extend] for OSPFv3. or in OSPFV3 RI LSA as defined in [RFC7770]. The area scope advertisement
the link local scope OSPFV3 RI LSA as defined in [RFC7770]. The of Link-Overload sub-TLV will be carried in the Router-Link TLV as
Router-Link TLV contains the neighbour interface-id and can uniquely defined in the [I-D.ietf-ospf-ospfv3-lsa-extend]and will be described
identify the link on the remote node. in a separate document. The Router-Link TLV contains the neighbour
interface-id and can uniquely identify the link on the remote node.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Link Overload sub-TLV for OSPFv3 Figure 2: Link-Overload sub-TLV for OSPFv3
Type : TBA (Suggested value 4) Type : TBA (Suggested value 4)
Length: 0 Length: 0
5. 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 by the
the sub-TLV is overloaded. The node that has the link to be taken sub-TLV is overloaded. The node that has the link to be taken out of
out of service SHOULD originate the Link Overload sub-TLV in the service SHOULD originate the Link-Overload sub-TLV in the Extended
Extended Link TLV in the Extended Link Opaque LSA as defined in Link TLV in the Extended Link Opaque LSA as defined in [RFC7684] for
OSPFv2. The Link-Overload information is carried as a property of
[RFC7684] for OSPFv2 or in the E-Router-LSA as defined in the link and is flooded across the area. This information can be
[I-D.ietf-ospf-ospfv3-lsa-extend] for OSPFv3. The link-overload used by ingress routers or controllers to take special actions. An
information is carried as a property of the link and is flooded application specific to this use case is described in Section 7.2.
across the area. This information can be used by ingress routers or
controllers to take special actions. Application specific to this
use case is described in Section 7.2.
The precise action taken by the remote node at the other end of the The precise action taken by the remote node at the other end of the
link identified as overloaded depends on the link type. link identified as overloaded 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 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, the remote node SHOULD identify the local link which
corresponds to the overloaded link and set the metric to MAX-METRIC corresponds to the overloaded link and set the metric to MAX-METRIC
(0xffff). The remote node MUST re-originate the router-LSA with the (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 changed metric. The TE metric SHOULD be set to MAX-TE-METRIC-1
set to MAX-TE-METRIC-1 (0xfffffffe) and the TE opaque LSA for the (0xfffffffe) and the TE opaque LSA for the link MUST be re-originated
link MUST be re-originated with new value. 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 Extended Link opaque LSA corresponds to all the
topologies the link belongs to. The receiver node SHOULD change the topologies the link belongs to. The receiver node SHOULD change the
metric in the reverse direction corresponding to all the topologies metric in the reverse direction corresponding to all the topologies
to which the reverse link belongs. to which the 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 Extended
Link Opaque LSA/E-Router-LSA or re-originates it without the Link Link Opaque LSA/E-Router-LSA or re-originates it without the Link-
Overload sub-TLV, the remote node must re-originate the appropriate Overload sub-TLV, the remote node must re-originate the appropriate
LSAs with the metric and TE metric values set to their original LSAs with the metric and TE metric values set to their original
values. values.
5.2. Broadcast/NBMA links 5.2. Broadcast/NBMA links
Broadcast or NBMA networks in OSPF are represented by a star topology Broadcast or NBMA networks in OSPF are represented by a star topology
where the Designated Router (DR) is the central point to which all where the Designated Router (DR) is the central point to which all
other routers on the broadcast or NBMA network connect logically. As other routers on the broadcast or NBMA network 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-
Router-LSA. The TE metric SHOULD be set to MAX-TE-METRIC- LSA. The TE metric SHOULD be set to MAX-TE-METRIC-1(0xfffffffe) and
1(0xfffffffe) and the node SHOULD re-originate the TE Link Opaque the node SHOULD re-originate the TE Link Opaque LSAs. For a
LSAs. For a broadcast link, the two part metric as described in broadcast link, the two part metric as described in [RFC8042] is
[RFC8042] is used. The node originating the Link Overload sub-TLV used. The node originating the Link-Overload sub-TLV MUST set the
MUST set the metric in the Network-to-Router Metric sub-TLV to MAX- metric in the Network-to-Router Metric sub-TLV to MAX-METRIC 0xffff
METRIC 0xffff for OSPFv2 and OSPFv3 and re-originate the LSAs the TLV for OSPFv2 and OSPFv3 and re-originate the LSAs the TLV is carried-
is carried-in. The nodes that receive the two part metric should in. The nodes that receive the two part metric should follow the
follow the procedures described in [RFC8042]. The backward procedures described in [RFC8042]. The backward compatibility
compatibility procedures described in [RFC8042] should be followed to procedures described in [RFC8042] should be followed to ensure loop
ensure loop free routing. free routing.
5.3. Point-to-multipoint links 5.3. Point-to-multipoint links
Operation for the point-to-multipoint links is similar to the point- Operation for the point-to-multipoint links is similar to the point-
to-point links. When a Link Overload sub-TLV is received for a to-point links. When a 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
neighbour which corresponds to the overloaded link and set the metric neighbour which corresponds to the overloaded link and set the metric
to MAX-METRIC (0xffff). The remote node MUST re-originate the to MAX-METRIC (0xffff). The remote node MUST re-originate the
Router-LSA with the changed metric and flood into the OSPF area. Router-LSA with the changed metric and flood into the OSPF area.
5.4. 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. [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 are defined in [RFC4203].
5.5. Hybrid Broadcast and P2MP interfaces
Hybrid Broadcast and P2MP interfaces represent a broadcast network
modeled as P2MP interfaces. [RFC6845] describes procedures to handle
these interfaces. Operation for the Hybrid interfaces is similar to
the P2MP interfaces. When a Link-Overload sub-TLV is received for a
hybrid link the remote node SHOULD identify the neighbour which
corresponds to the overloaded link and set the metric to MAX-METRIC
(0xffff). All the remote nodes connected to originator MUST re-
originate the Router-LSA with the changed metric and flood into the
OSPF area.
6. Backward compatibility 6. Backward compatibility
The mechanism described in the document is fully backward The mechanism described in the document is fully backward compatible.
compatible.It is required that the originator of the Link Overload It is required that the originator of the Link-Overload sub-TLV as
sub-TLV as well as the node at the remote end of the link identified well as the node at the remote end of the link identified as
as overloaded understand the extensions defined in this document. In 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 [RFC8042] are applicable. . described in [RFC8042] are applicable.
7. Applications 7. Applications
7.1. 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 3: Pseudowire Services
skipping to change at page 8, line 26 skipping to change at page 8, line 28
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.
7.2. Controller based Traffic Engineering Deployments When the PE1 node is going for maintenance, service provider sets the
PE1 to overload state. The PE1 going in overload state triggers all
the CEs connected to the PE to set their pseudowire links passing via
PE1 to link-overload state. The mechanisms used to communicate
between PE1 and CE1 is outside the scope of this document. CE1 sets
the link-overload state on its link and modifies the metric to
MAX_METRIC and floods the information, the remote end of the link
also sets the metric on the link to MAX-METRIC and the traffic from
both directions gets diverted away from the link.
7.2. Controller based Traffic Engineering Deployments
_____________ _____________
| | | |
-------------| Controller |-------------- -------------| Controller |--------------
| |____________ | | | |____________ | |
| | | |
|--------- Primary Path ------------------| |--------- Primary Path ------------------|
PE1---------P1----------------P2---------PE2 PE1---------P1----------------P2---------PE2
| | | |
| | | |
|________P3________| |________P3________|
skipping to change at page 9, line 15 skipping to change at page 9, line 29
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
which use the affected link. The controller can apply various which use the affected link. The controller can apply various
policies and re-route the LSPs away from the link undergoing 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. 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 to satisfy a constraint
constraint of 10 GB bandwidth on each link.The links P1->P3 and of 10 GB bandwidth on each link. The links P1->P3 and P3->P2 have
P3->P2 have only 1 GB capacity. and there is no alternate path only 1 GB capacity and there is no alternate path satisfying the
satisfying the bandwidth constraint of 10GB. When P1->P2 link is bandwidth constraint of 10GB. When P1->P2 link is being prepared for
being prepared for maintenance, the controller receives the link- maintenance, the controller receives the link-overload information,
overload information, as there is no alternate path available which as there is no alternate path available which satisfies the
satisfies the constraints, controller chooses a path that is less constraints, controller chooses a path that is less optimal and
optimal and sets up an alternate path via P1->P3->P2 temporarily. temporarily sets up an alternate path via P1->P3->P2. Once the
Once the traffic is diverted, P1->P2 link can be taken out for traffic is diverted, the P1->P2 link can be taken out of service for
maintenance/upgrade. maintenance/upgrade.
8. 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].
9. IANA Considerations 9. IANA Considerations
This specification updates one OSPF registry: This specification updates one OSPF registry:
OSPF Extended Link TLVs Registry OSPF Extended Link TLVs Registry
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
OSPF RI TLV Registry
i) TBD - Link-Overload sub-TLV
BGP-LS Link NLRI Registry [RFC7752]
i)TBD - Link-Overload sub-TLV
10. Acknowledgements 10. Acknowledgements
Thanks to Chris Bowers for valuable inputs and edits to the document. Thanks to Chris Bowers for valuable inputs and edits to the document.
Thanks to Jeffrey Zhang and Acee Lindem for inputs. Thanks to Jeffrey Zhang and Acee Lindem for inputs. Thanks to
Karsten Thomann for careful review and inputs.
11. References 11. References
11.1. Normative References 11.1. Normative References
[I-D.ietf-ospf-ospfv3-lsa-extend] [RFC6845] Sheth, N., Wang, L., and J. Zhang, "OSPF Hybrid Broadcast
Lindem, A., Mirtorabi, S., Roy, A., and F. Baker, "OSPFv3 and Point-to-Multipoint Interface Type", RFC 6845,
LSA Extendibility", draft-ietf-ospf-ospfv3-lsa-extend-06 DOI 10.17487/RFC6845, January 2013,
(work in progress), February 2015. <http://www.rfc-editor.org/info/rfc6845>.
[RFC7684] Psenak, P., Gredler, H., Shakir, R., Henderickx, W., [RFC7684] Psenak, P., Gredler, H., Shakir, R., Henderickx, W.,
Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute
Advertisement", RFC 7684, DOI 10.17487/RFC7684, November Advertisement", RFC 7684, DOI 10.17487/RFC7684, November
2015, <http://www.rfc-editor.org/info/rfc7684>. 2015, <http://www.rfc-editor.org/info/rfc7684>.
[RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and
S. Ray, "North-Bound Distribution of Link-State and
Traffic Engineering (TE) Information Using BGP", RFC 7752,
DOI 10.17487/RFC7752, March 2016,
<http://www.rfc-editor.org/info/rfc7752>.
[RFC7770] Lindem, A., Ed., Shen, N., Vasseur, JP., Aggarwal, R., and [RFC7770] Lindem, A., Ed., Shen, N., Vasseur, JP., Aggarwal, R., and
S. Shaffer, "Extensions to OSPF for Advertising Optional S. Shaffer, "Extensions to OSPF for Advertising Optional
Router Capabilities", RFC 7770, DOI 10.17487/RFC7770, Router Capabilities", RFC 7770, DOI 10.17487/RFC7770,
February 2016, <http://www.rfc-editor.org/info/rfc7770>. February 2016, <http://www.rfc-editor.org/info/rfc7770>.
[RFC8042] Zhang, Z., Wang, L., and A. Lindem, "OSPF Two-Part [RFC8042] Zhang, Z., Wang, L., and A. Lindem, "OSPF Two-Part
Metric", RFC 8042, DOI 10.17487/RFC8042, December 2016, Metric", RFC 8042, DOI 10.17487/RFC8042, December 2016,
<http://www.rfc-editor.org/info/rfc8042>. <http://www.rfc-editor.org/info/rfc8042>.
11.2. Informative References 11.2. Informative References
[I-D.ietf-ospf-ospfv3-lsa-extend]
Lindem, A., Mirtorabi, S., Roy, A., and F. Baker, "OSPFv3
LSA Extendibility", draft-ietf-ospf-ospfv3-lsa-extend-06
(work in progress), February 2015.
[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>.
[RFC4203] Kompella, K., Ed. and Y. Rekhter, Ed., "OSPF Extensions in [RFC4203] Kompella, K., Ed. and Y. Rekhter, Ed., "OSPF Extensions in
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