draft-ietf-ospf-link-overload-09.txt   draft-ietf-ospf-link-overload-10.txt 
Open Shortest Path First IGP S. Hegde Open Shortest Path First IGP S. Hegde
Internet-Draft Juniper Networks, Inc. Internet-Draft Juniper Networks, Inc.
Intended status: Standards Track P. Sarkar Intended status: Standards Track P. Sarkar
Expires: February 15, 2018 H. Gredler Expires: May 30, 2018 H. Gredler
Individual Individual
M. Nanduri M. Nanduri
ebay Corporation ebay Corporation
L. Jalil L. Jalil
Verizon Verizon
August 14, 2017 November 26, 2017
OSPF Link Overload OSPF Link Overload
draft-ietf-ospf-link-overload-09 draft-ietf-ospf-link-overload-10
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 as 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
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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 https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on February 15, 2018. This Internet-Draft will expire on May 30, 2018.
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
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
skipping to change at page 3, line 11 skipping to change at page 3, line 11
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 12
11.1. Normative References . . . . . . . . . . . . . . . . . . 12 11.1. Normative References . . . . . . . . . . . . . . . . . . 12
11.2. Informative References . . . . . . . . . . . . . . . . . 12 11.2. Informative References . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13
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 MaxLinkMetric
(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 on the node requires on a node and cannot be used when a single link on the node requires
maintenance. maintenance.
In traffic-engineering deployments, LSPs need to be diverted from the In traffic-engineering deployments, LSPs need to be diverted from the
link without disrupting the services. [RFC5817] describes link without disrupting the services. [RFC5817] describes
requirements and procedures for graceful shutdown of MPLS links. It requirements and procedures for graceful shutdown of MPLS links. It
is useful to be able to advertise the impending maintenance activity is useful to be able to advertise the impending maintenance activity
on the link and to have LSP re-routing policies at the ingress to on the link and to have LSP re-routing policies at the ingress to
route the LSPs away from the link. route the LSPs away from the link.
Many OSPFv2 or OSPFv3 deployments run on overlay networks provisioned Many OSPFv2 or OSPFv3 deployments run on overlay networks provisioned
by means of pseudo-wires or L2-circuits. Prior to devices in the by means of pseudo-wires or L2-circuits. Prior to devices in the
underlying network going offline for maintenance, it is useful to underlying network going offline for maintenance, it is useful to
divert the traffic away from the node before the maintenance is divert the traffic away from the node before the maintenance is
actually scheduled. Since the nodes in the underlying network are actually performed. Since the nodes in the underlying network are
not visible to OSPF, the existing stub router mechanism described in not visible to OSPF, the existing stub router mechanism described in
[RFC6987] cannot be used. An application specific to this use case [RFC6987] cannot be used. An application specific to this use case
is described 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]). Throughout this document, OSPF is used Advertisement [RFC7684]. Throughout this document, OSPF is used when
when the text applies to both OSPFv2 and OSPFv3. OSPFv2 or OSPFv3 is the text applies to both OSPFv2 and OSPFv3. OSPFv2 or OSPFv3 is used
used when the text is specific to one version of the OSPF protocol. when the text is specific to one version of the OSPF protocol.
2. Motivation 2. Motivation
The motivation of this document is to reduce manual intervention The motivation of this document is to reduce manual intervention
during maintenance activities. The following objectives help to during maintenance activities. The following objectives help to
accomplish this in a range of deployment scenarios. accomplish this in a range of deployment scenarios.
1. Advertise impending maintenance activity so that traffic from 1. Advertise impending maintenance activity so that traffic from
both directions can be diverted away from the link. both directions can be diverted away from the link.
skipping to change at page 4, line 12 skipping to change at page 4, line 12
3. Advertise the maintenance activity to other nodes in the network 3. Advertise the maintenance activity to other nodes in the network
so that LSP ingress routers/controllers can learn of the so that LSP ingress routers/controllers can learn of the
impending maintenance activity and apply specific policies to re- impending maintenance activity and apply specific policies to re-
route the LSPs for traffic-engineering based deployments. route the LSPs for traffic-engineering based deployments.
4. Allow the link to be used as last resort link to prevent traffic 4. Allow the link to be used as last resort link to prevent traffic
disruption when alternate paths are not available. disruption when alternate paths are not available.
3. Flooding Scope 3. Flooding Scope
The link-overload information is flooded in area scoped Extended Link The link-overload information is flooded in area-scoped Extended Link
Opaque LSA [RFC7684]. The Link-Overload sub-TLV MAY be processed by Opaque LSA [RFC7684]. The Link-Overload sub-TLV MAY be processed by
the head-end nodes or the controller as described in the Section 7. the head-end nodes or the controller as described in the Section 7.
The procedures for processing the Link-Overload sub-TLV are described The procedures for processing the Link-Overload sub-TLV are described
in Section 5. in Section 5.
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 as being in overload
state.It is carried in extended Link TLV in the Extended Link Opaque state.It is advertised in extended Link TLV of the Extended Link
LSA as defined in [RFC7684]. Opaque LSA as defined in [RFC7684].
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Link-Overload sub-TLV for OSPFv2 Figure 1: Link-Overload sub-TLV for OSPFv2
Type : TBA (suggested value 5) Type : TBA (suggested value 5)
Length: 0 Length: 0
4.2. Remote IPv4 address sub-TLV 4.2. Remote IPv4 address sub-TLV
This sub-TLV specifies the IPv4 address of remote endpoint on the This sub-TLV specifies the IPv4 address of remote endpoint on the
link. It is advertised in extended Link TLV as defined in link. It is advertised in the Extended Link TLV as defined in
[RFC7684].This sub-TLV is optional and MAY be advertised in area [RFC7684]. This sub-TLV is optional and MAY be advertised in area-
scoped Extended Link Opaque LSA to identify the link when there are scoped Extended Link Opaque LSA to identify the link when there are
multiple parallel links between two nodes. multiple parallel links between two nodes.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote IPv4 address | | Remote IPv4 address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
skipping to change at page 5, line 26 skipping to change at page 5, line 26
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 when there are multiple parallel links identify the particular link when there are multiple parallel links
between two nodes. between two nodes.
4.3. Local/Remote Interface ID sub-TLV 4.3. Local/Remote Interface ID sub-TLV
This sub-TLV specifies local and remote interface identifiers. It is This sub-TLV specifies local and remote interface identifiers. It is
advertised in extended Link TLV as defined in [RFC7684].This sub-TLV advertised in the Extended Link TLV as defined in [RFC7684]. This
is optional and MAY be advertised in area scoped Extended Link Opaque sub-TLV is optional and MAY be advertised in area-scoped Extended
LSA to identify the link when there are multiple parallel unnumbered Link Opaque LSA to identify the link when there are multiple parallel
links between two nodes. The local interface-id is generally readily unnumbered links between two nodes. The local interface-id is
available. One of the mechanisms to obtain remote interface-id is generally readily available. One of the mechanisms to obtain remote
described in [RFC4203]. interface-id is described in [RFC4203].
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local Interface ID | | Local Interface ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote Interface ID | | Remote Interface ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
skipping to change at page 6, line 9 skipping to change at page 6, line 9
Figure 3: Local/Remote Interface ID sub-TLV Figure 3: Local/Remote Interface ID sub-TLV
Type : TBA (suggested value 11) Type : TBA (suggested value 11)
Length: 8 Length: 8
Value: 4 octets of Local Interface ID followed by 4 octets of Remote Value: 4 octets of Local Interface ID followed by 4 octets of Remote
interface ID. interface ID.
4.4. OSPFv3 Link-Overload sub-TLV 4.4. OSPFv3 Link-Overload sub-TLV
The definition of OSPFv3 Link-Overload sub-TLV is defined below. The The Link Overload sub-TLV is carried in the Router-Link TLV as
area scoped advertisement of Link-Overload sub-TLV for OSPFv3 will be defined in the [I-D.ietf-ospf-ospfv3-lsa-extend] for OSPFv3. The
described in a separate document. Router-Link TLV contains the neighbour interface-id and can uniquely
identify the link on the remote node.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: Link-Overload sub-TLV for OSPFv3 Figure 4: 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 by the The Link-Overload sub-TLV indicates that the link identified by the
sub-TLV is overloaded. The node that has the link to be taken out of sub-TLV is overloaded. The node that has the link to be taken out of
service SHOULD advertise the Link-Overload sub-TLV in the Extended service SHOULD advertise the Link-Overload sub-TLV in the Extended
Link TLV in the Extended Link Opaque LSA as defined in [RFC7684] for Link TLV of the Extended Link Opaque LSA as defined in [RFC7684] for
OSPFv2. The Link-Overload information is advertised as a property of OSPFv2. The Link-Overload information is advertised as a property of
the link and is flooded across the area. This information can be the link and is flooded across the area. This information can be
used by ingress routers or controllers to take special actions. An used by ingress routers or controllers to take special actions. An
application specific to this use case is described in Section 7.2. application specific to this use case is described in Section 7.2.
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 MUST set metric The node that has the link to be taken out of service MUST set metric
of the link to MAX-METRIC (0xffff) and re- originate the Router-LSA. of the link to MaxLinkMetric (0xffff) and re-originate its router-
The TE metric SHOULD be set to MAX-TE-METRIC -1 (0xfffffffe) and the LSA. The TE metric SHOULD be set to MAX-TE-METRIC (0xfffffffe) and
node SHOULD re-originate the TE Link Opaque LSAs. When a Link- the node SHOULD re-originate the corresponding TE Link Opaque LSAs.
Overload sub-TLV is received for a point-to-point link, the remote When a Link-Overload sub-TLV is received for a point-to-point link,
node MUST identify the local link which corresponds to the overloaded the remote node MUST identify the local link which corresponds to the
link and set the metric to MAX-METRIC (0xffff)and the remote node overloaded link and set the metric to MaxLinkMetric (0xffff)and the
MUST re-originate the router-LSA with the changed metric. The TE remote node MUST re-originate its router-LSA with the changed metric.
metric SHOULD be set to MAX-TE-METRIC -1 (0xfffffffe) and the TE The TE metric SHOULD be set to MAX-TE-METRIC (0xfffffffe) and the TE
opaque LSA for the link SHOULD be re-originated with new value. opaque LSA for the link SHOULD be re-originated with new value.
Extended link opaque LSAs and the Extended link TLV are not scoped The Extended link opaque LSAs and the Extended link TLV are not
for multi-topology [RFC4915]. In multi-topology deployments scoped for multi-topology [RFC4915]. In multi-topology deployments
[RFC4915], the Link-Overload sub-TLV advertised in an Extended Link [RFC4915], the Link-Overload sub-TLV advertised in an Extended Link
opaque LSA corresponds to all the topologies which include the link. opaque LSA corresponds to all the topologies which include the link.
The receiver node SHOULD change the metric in the reverse direction The receiver node SHOULD change the metric in the reverse direction
for all the topologies which include the remote link and re-originate for all the topologies which include the remote link and re-originate
the Router LSA as defined in [RFC4915]. the router-LSA as defined in [RFC4915].
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 or re-originates it without the Link-Overload sub- Link Opaque LSA or re-originates it without the Link-Overload sub-
TLV, the remote node must re-originate the appropriate LSAs with the TLV, the remote node must re-originate the appropriate LSAs with the
metric and TE metric values set to their original values. metric and TE metric values set to their original values.
5.2. Broadcast/NBMA links 5.2. Broadcast/NBMA links
Broadcast or NBMA networks in OSPF are represented by a star topology Broadcast or NBMA networks in OSPF are represented by a star topology
where the Designated Router (DR) is the central point to which all where the Designated Router (DR) is the central point to which all
other routers on the broadcast or NBMA network connect logically. As other routers on the broadcast or NBMA network logically connect. As
a result, routers on the broadcast or NBMA network advertise only a result, routers on the broadcast or NBMA network advertise only
their adjacency to the DR. Routers that do not act as DR do not form their adjacency to the DR. Routers that do not act as DR do not form
or advertise adjacencies with each other. For the Broadcast links, or advertise adjacencies with each other. For the Broadcast links,
the MAX-METRIC on the remote link cannot be changed since all the the MaxLinkMetric on the remote link cannot be changed since all the
neighbours are on same link. Setting the link cost to MAX-METRIC neighbors are on same link. Setting the link cost to MaxLinkMetric
would impact paths going via all neighbours. would impact paths going via all neighbors.
The node that has the link to be taken out of service MUST set metric The node that has the link to be taken out of service MUST set metric
of the link to MAX-METRIC(0xffff) and re-originate the Router-LSA. of the link to MaxLinkMetric (0xffff) and re-originate the Router-
The TE metric SHOULD be set to MAX-TE-METRIC -1(0xfffffffe) and the LSA. The TE metric SHOULD be set to MAX-TE-METRIC( 0xfffffffe) and
node SHOULD re-originate the corresponding TE Link Opaque LSAs. For the node SHOULD re-originate the corresponding TE Link Opaque LSAs.
a broadcast link, the two part metric as described in [RFC8042] is For a broadcast link, the two part metric as described in [RFC8042]
used. The node originating the Link-Overload sub-TLV MUST set the is used. The node originating the Link-Overload sub-TLV MUST set the
metric in the Network-to-Router Metric sub-TLV to MAX-METRIC 0xffff metric in the Network-to-Router Metric sub-TLV to MaxLinkMetric
for OSPFv2 and OSPFv3 and re-originate the corresponding LSAs. The (0xffff) for OSPFv2 and OSPFv3 and re-originate the corresponding
nodes that receive the two part metric should follow the procedures LSAs. The nodes that receive the two-part metric should follow the
described in [RFC8042]. The backward compatibility procedures procedures described in [RFC8042]. The backward compatibility
described in [RFC8042] should be followed to ensure loop free procedures described in [RFC8042] should be followed to ensure loop
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 MUST identify the neighbour point-to-multipoint link the remote node MUST identify the neighbour
which corresponds to the overloaded link and set the metric to MAX- which corresponds to the overloaded link and set the metric to
METRIC (0xffff). The remote node MUST re-originate the Router-LSA MaxLinkMetric (0xffff). The remote node MUST re-originate the
with the changed metric. router-LSA with the changed metric for the correponding neighbor.
5.4. Unnumbered interfaces 5.4. Unnumbered interfaces
Unnumbered interface do not have a unique IP address and borrow their Unnumbered interface do not have a unique IP address and borrow their
address from other interfaces. [RFC2328] describes procedures to address from other interfaces. [RFC2328] describes procedures to
handle unnumbered interfaces in the context of the Router LSA. We handle unnumbered interfaces in the context of the router-LSA. We
apply a similar procedure to the Extended Link TLV advertising the apply a similar procedure to the Extended Link TLV advertising the
Link-Overload sub-TLV in to handle unnumbered interfaces. The link- Link-Overload sub-TLV in order to handle unnumbered interfaces. The
data field in the Extended Link TLV includes the Local interface-id link-data field in the Extended Link TLV includes the Local
instead of the IP address. The Local/Remote Interface ID sub-TLV interface-id instead of the IP address. The Local/Remote Interface
MUST be advertised when there are multiple parallel unnumbered ID sub-TLV MUST be advertised when there are multiple parallel
interfaces between two nodes. One of the mechanisms to obtain the unnumbered interfaces between two nodes. One of the mechanisms to
interface-id of the remote side are defined in [RFC4203]. obtain the interface-id of the remote side are defined in [RFC4203].
5.5. Hybrid Broadcast and P2MP interfaces 5.5. Hybrid Broadcast and P2MP interfaces
Hybrid Broadcast and P2MP interfaces represent a broadcast network Hybrid Broadcast and P2MP interfaces represent a broadcast network
modeled as P2MP interfaces. [RFC6845] describes procedures to handle modeled as P2MP interfaces. [RFC6845] describes procedures to handle
these interfaces. Operation for the Hybrid interfaces is similar to these interfaces. Operation for the Hybrid interfaces is similar to
the P2MP interfaces. When a Link-Overload sub-TLV is received for a the P2MP interfaces. When a Link-Overload sub-TLV is received for a
hybrid link the remote node MUST identify the neighbour which hybrid link, the remote node MUST identify the neighbor which
corresponds to the overloaded link and set the metric to MAX-METRIC corresponds to the overloaded link and set the metric to
(0xffff). All the remote nodes connected to originator MUST re- MaxLinkMetric (0xffff). All the remote nodes connected to originator
originate the Router-LSA with the changed metric. MUST re-originate the router-LSA with the changed metric for the
neighbor.
6. Backward compatibility 6. Backward compatibility
The mechanisms described in the document are fully backward The mechanisms described in the document are fully backward
compatible. It is required that the node adverting the Link-Overload compatible. It is required that the node adverting the Link-Overload
sub-TLV as well as the node at the remote end of the overloaded link sub-TLV as well as the node at the remote end of the overloaded link
support the extensions described herein for the traffic to diverted support the extensions described herein for the traffic to diverted
from the overloaded link. If the remote node doesn't support the from the overloaded link. If the remote node doesn't support the
capability, it will still use the overloaded link but there are no capability, it will still use the overloaded link but there are no
other adverse effects. In the case of broadcast links using two-part other adverse effects. In the case of broadcast links using two-part
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| | | |
| | | |
| | | |
================================= =================================
Private VLAN Private VLAN
Figure 5: Pseudowire Services Figure 5: Pseudowire Services
In the example shown in Figure 5, when the PE1 node is going out of In the example shown in Figure 5, when the PE1 node is going out of
service for maintenance, service providers set the PE1 to overload service for maintenance, service providers set the PE1 to overload
state. The PE1 going in to overload state triggers all the CEs (In state. The PE1 going in to overload state triggers all the CEs
this example CE1)connected to the PE to set their pseudowire links connected to the PE (CE1 in this case) to set their pseudowire links
passing via PE1 to link-overload state. The mechanisms used to passing via PE1 to link-overload state. The mechanisms used to
communicate between PE1 and CE1 is outside the scope of this communicate between PE1 and CE1 is outside the scope of this
document. CE1 sets the link-overload state on its private VLAN document. CE1 sets the link-overload state on its private VLAN
connecting CE3, CE2 and CE4 and changes the metric to MAX_METRIC and connecting CE3, CE2 and CE4 and changes the metric to MAX_METRIC and
re-originates the corresponding LSA. The remote end of the link at re-originates the corresponding LSA. The remote end of the link at
CE3, CE2, and CE4 also set the metric on the link to MAX-METRIC and CE3, CE2, and CE4 also set the metric on the link to MaxLinkMetric
the traffic from both directions gets diverted away from the and the traffic from both directions gets diverted away from the
pseudowires. pseudowires.
7.2. Controller based Traffic Engineering Deployments 7.2. Controller based Traffic Engineering Deployments
In controller-based deployments where the controller participates in In controller-based deployments where the controller participates in
the IGP protocol, the controller can also receive the 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 uses the affected link. The controller can apply various which uses 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
skipping to change at page 10, line 39 skipping to change at page 10, line 39
| | | |
|________P3________| |________P3________|
Alternate Path Alternate Path
Figure 6: Controller based Traffic Engineering Figure 6: Controller based Traffic Engineering
In the above example, PE1->PE2 LSP is set-up to satisfy a constraint In the above example, PE1->PE2 LSP is set-up to satisfy a constraint
of 10 Gbps bandwidth on each link. The links P1->P3 and P3->P2 have of 10 Gbps bandwidth on each link. The links P1->P3 and P3->P2 have
only 1 Gbps capacity and there is no alternate path satisfying the only 1 Gbps capacity and there is no alternate path satisfying the
bandwidth constraint of 10GB. When P1->P2 link is being prepared for bandwidth constraint of 10Gbps. When P1->P2 link is being prepared
maintenance, the controller receives the link-overload information, for maintenance, the controller receives the link-overload
as there is no alternate path available which satisfies the information, as there is no alternate path available which satisfies
constraints, controller chooses a path that is less optimal and the constraints, the controller chooses a path that is less optimal
temporarily sets up an alternate path via P1->P3->P2. Once the and temporarily sets up an alternate path via P1->P3->P2. Once the
traffic is diverted, the P1->P2 link can be taken out of service for traffic is diverted, the P1->P2 link can be taken out of service for
maintenance/upgrade. maintenance/upgrade.
7.3. L3VPN Services and sham-links 7.3. L3VPN Services and sham-links
Many service providers offer L3VPN services to customers and CE-PE Many service providers offer L3VPN services to customers and CE-PE
links run OSPF [RFC4577]. When PE goes out of service for links run OSPF [RFC4577]. When PE is taken out of service for
maintenance, all the links on the PE can be set to link-overlaod maintenance, all the links on the PE can be set to link-overload
state which will gurantee that the traffic to/from dual-homed CEs state which will gurantee that the traffic to/from dual-homed CEs
gets diverted. The interaction between OSPF and BGP is outside the gets diverted. The interaction between OSPF and BGP is outside the
scope of this document. scope of this document. [RFC6987] based mechanism with summaries and
externals advertised with high metrics could also be used to achieve
the same functionality when implementations support high metrics
advertisement for summaries and externals.
Another useful usecase is when ISPs provide sham-link services to Another useful usecase is when ISPs provide sham-link services to
customers [RFC4577].When PE goes out of service for maintenance, all customers [RFC4577]. When PE goes out of service for maintenance,
sham-links on the PE can be set to link-overload state and traffic all sham-links on the PE can be set to link-overload state and
can be divered from both ends without having to touch the traffic can be divered from both ends without having to touch the
configurations on the remote end of the sham-links. configurations on the remote end of the sham-links.
7.4. Hub and spoke deployment 7.4. Hub and spoke deployment
OSPF is largely deployed in Hub and Spoke deployments with a number OSPF is largely deployed in Hub and Spoke deployments with a large
of spokes connecting to the Hub. It is a general practice to deploy number of spokes connecting to the Hub. It is a general practice to
multiple Hubs with all spokes connecting to these Hubs to achieve deploy multiple Hubs with all spokes connecting to these Hubs to
redundancy. When a Hub node goes down for maintenance, all links on achieve redundancy. The [RFC6987] mechanism can be used to divert
the Hub can be set to link-overload state and traffic gets divered the spoke-to-spoke traffic from the overloaded hub router. The
from the spoke sites as well without having to make configuration traffic that flows from spokes via the hub into an external network
changes on the spokes. may not be diverted in certain scenarios.When a Hub node goes down
for maintenance, all links on the Hub can be set to link-overload
state and traffic gets divered from the spoke sites as well without
having to make configuration changes on the spokes.
8. Security Considerations 8. Security Considerations
This document does not introduce any further security issues other This document 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:
skipping to change at page 12, line 16 skipping to change at page 12, line 17
Thanks to Chris Bowers for valuable inputs and edits to the document. Thanks to Chris Bowers for valuable inputs and edits to the document.
Thanks to Jeffrey Zhang, Acee Lindem and Ketan Talaulikar for inputs. Thanks to Jeffrey Zhang, Acee Lindem and Ketan Talaulikar for inputs.
Thanks to Karsten Thomann for careful review and inputs on the Thanks to Karsten Thomann for careful review and inputs on the
applications where link-overload is useful. applications where link-overload is useful.
11. References 11. References
11.1. Normative References 11.1. Normative 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-10
(work in progress), May 2016.
[RFC6845] Sheth, N., Wang, L., and J. Zhang, "OSPF Hybrid Broadcast [RFC6845] Sheth, N., Wang, L., and J. Zhang, "OSPF Hybrid Broadcast
and Point-to-Multipoint Interface Type", RFC 6845, and Point-to-Multipoint Interface Type", RFC 6845,
DOI 10.17487/RFC6845, January 2013, DOI 10.17487/RFC6845, January 2013,
<http://www.rfc-editor.org/info/rfc6845>. <https://www.rfc-editor.org/info/rfc6845>.
[RFC7684] Psenak, P., Gredler, H., Shakir, R., Henderickx, W., [RFC7684] Psenak, P., Gredler, H., Shakir, R., Henderickx, W.,
Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute
Advertisement", RFC 7684, DOI 10.17487/RFC7684, November Advertisement", RFC 7684, DOI 10.17487/RFC7684, November
2015, <http://www.rfc-editor.org/info/rfc7684>. 2015, <https://www.rfc-editor.org/info/rfc7684>.
[RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and [RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and
S. Ray, "North-Bound Distribution of Link-State and S. Ray, "North-Bound Distribution of Link-State and
Traffic Engineering (TE) Information Using BGP", RFC 7752, Traffic Engineering (TE) Information Using BGP", RFC 7752,
DOI 10.17487/RFC7752, March 2016, DOI 10.17487/RFC7752, March 2016,
<http://www.rfc-editor.org/info/rfc7752>. <https://www.rfc-editor.org/info/rfc7752>.
[RFC8042] Zhang, Z., Wang, L., and A. Lindem, "OSPF Two-Part [RFC8042] Zhang, Z., Wang, L., and A. Lindem, "OSPF Two-Part
Metric", RFC 8042, DOI 10.17487/RFC8042, December 2016, Metric", RFC 8042, DOI 10.17487/RFC8042, December 2016,
<http://www.rfc-editor.org/info/rfc8042>. <https://www.rfc-editor.org/info/rfc8042>.
11.2. Informative References 11.2. Informative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [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>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328,
DOI 10.17487/RFC2328, April 1998, DOI 10.17487/RFC2328, April 1998,
<http://www.rfc-editor.org/info/rfc2328>. <https://www.rfc-editor.org/info/rfc2328>.
[RFC4203] Kompella, K., Ed. and Y. Rekhter, Ed., "OSPF Extensions in [RFC4203] Kompella, K., Ed. and Y. Rekhter, Ed., "OSPF Extensions in
Support of Generalized Multi-Protocol Label Switching Support of Generalized Multi-Protocol Label Switching
(GMPLS)", RFC 4203, DOI 10.17487/RFC4203, October 2005, (GMPLS)", RFC 4203, DOI 10.17487/RFC4203, October 2005,
<http://www.rfc-editor.org/info/rfc4203>. <https://www.rfc-editor.org/info/rfc4203>.
[RFC4577] Rosen, E., Psenak, P., and P. Pillay-Esnault, "OSPF as the [RFC4577] Rosen, E., Psenak, P., and P. Pillay-Esnault, "OSPF as the
Provider/Customer Edge Protocol for BGP/MPLS IP Virtual Provider/Customer Edge Protocol for BGP/MPLS IP Virtual
Private Networks (VPNs)", RFC 4577, DOI 10.17487/RFC4577, Private Networks (VPNs)", RFC 4577, DOI 10.17487/RFC4577,
June 2006, <http://www.rfc-editor.org/info/rfc4577>. June 2006, <https://www.rfc-editor.org/info/rfc4577>.
[RFC4915] Psenak, P., Mirtorabi, S., Roy, A., Nguyen, L., and P. [RFC4915] Psenak, P., Mirtorabi, S., Roy, A., Nguyen, L., and P.
Pillay-Esnault, "Multi-Topology (MT) Routing in OSPF", Pillay-Esnault, "Multi-Topology (MT) Routing in OSPF",
RFC 4915, DOI 10.17487/RFC4915, June 2007, RFC 4915, DOI 10.17487/RFC4915, June 2007,
<http://www.rfc-editor.org/info/rfc4915>. <https://www.rfc-editor.org/info/rfc4915>.
[RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF [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>. <https://www.rfc-editor.org/info/rfc5340>.
[RFC5817] Ali, Z., Vasseur, JP., Zamfir, A., and J. Newton, [RFC5817] Ali, Z., Vasseur, JP., Zamfir, A., and J. Newton,
"Graceful Shutdown in MPLS and Generalized MPLS Traffic "Graceful Shutdown in MPLS and Generalized MPLS Traffic
Engineering Networks", RFC 5817, DOI 10.17487/RFC5817, Engineering Networks", RFC 5817, DOI 10.17487/RFC5817,
April 2010, <http://www.rfc-editor.org/info/rfc5817>. April 2010, <https://www.rfc-editor.org/info/rfc5817>.
[RFC6987] Retana, A., Nguyen, L., Zinin, A., White, R., and D. [RFC6987] Retana, A., Nguyen, L., Zinin, A., White, R., and D.
McPherson, "OSPF Stub Router Advertisement", RFC 6987, McPherson, "OSPF Stub Router Advertisement", RFC 6987,
DOI 10.17487/RFC6987, September 2013, DOI 10.17487/RFC6987, September 2013,
<http://www.rfc-editor.org/info/rfc6987>. <https://www.rfc-editor.org/info/rfc6987>.
Authors' Addresses Authors' Addresses
Shraddha Hegde Shraddha Hegde
Juniper Networks, Inc. Juniper Networks, Inc.
Embassy Business Park Embassy Business Park
Bangalore, KA 560093 Bangalore, KA 560093
India India
Email: shraddha@juniper.net Email: shraddha@juniper.net
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