Open Shortest Path First IGP S. Hegde
Internet-Draft Juniper Networks, Inc.
Intended status: Standards Track P. Sarkar
Expires: July 5, 2018 H. Gredler
Individual
M. Nanduri
ebay Corporation
L. Jalil
Verizon
January 1, 2018
OSPF Link Overload
draft-ietf-ospf-link-overload-11
Abstract
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
metric to the highest metric on one side of the link is not
sufficient to divert the traffic flowing in the other direction.
It is useful for routers in an OSPFv2 or OSPFv3 routing domain to be
able to advertise a link as being in an overload state to indicate
impending maintenance activity on the link. This information can be
used by the network devices to re-route the traffic effectively.
This document describes the protocol extensions to disseminate link-
overload information in OSPFv2 and OSPFv3.
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
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time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on July 5, 2018.
Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Flooding Scope . . . . . . . . . . . . . . . . . . . . . . . 4
4. Link-Overload sub-TLV . . . . . . . . . . . . . . . . . . . . 4
4.1. OSPFv2 Link-overload sub-TLV . . . . . . . . . . . . . . 4
4.2. Remote IPv4 Address Sub-TLV . . . . . . . . . . . . . . . 4
4.3. Local/Remote Interface ID Sub-TLV . . . . . . . . . . . . 5
4.4. OSPFv3 Link-Overload sub-TLV . . . . . . . . . . . . . . 6
4.5. BGP-LS Link-overload TLV . . . . . . . . . . . . . . . . 6
4.6. Distinguishing parallel links . . . . . . . . . . . . . . 7
5. Elements of procedure . . . . . . . . . . . . . . . . . . . . 8
5.1. Point-to-point links . . . . . . . . . . . . . . . . . . 8
5.2. Broadcast/NBMA links . . . . . . . . . . . . . . . . . . 8
5.3. Point-to-multipoint links . . . . . . . . . . . . . . . . 9
5.4. Unnumbered interfaces . . . . . . . . . . . . . . . . . . 9
5.5. Hybrid Broadcast and P2MP interfaces . . . . . . . . . . 9
6. Backward compatibility . . . . . . . . . . . . . . . . . . . 10
7. Applications . . . . . . . . . . . . . . . . . . . . . . . . 10
7.1. Pseudowire Services . . . . . . . . . . . . . . . . . . . 10
7.2. Controller based Traffic Engineering Deployments . . . . 11
7.3. L3VPN Services and sham-links . . . . . . . . . . . . . . 12
7.4. Hub and spoke deployment . . . . . . . . . . . . . . . . 13
8. Security Considerations . . . . . . . . . . . . . . . . . . . 13
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 13
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 14
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11.1. Normative References . . . . . . . . . . . . . . . . . . 14
11.2. Informative References . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15
1. Introduction
When a node is being prepared for a planned maintenance or upgrade,
[RFC6987] provides mechanisms to advertise the node being in an
overload state by setting all outgoing link costs to MaxLinkMetric
(0xffff). These procedures are specific to the maintenance activity
on a node and cannot be used when a single link on the node requires
maintenance.
In traffic-engineering deployments, LSPs need to be diverted from the
link without disrupting the services. [RFC5817] describes
requirements and procedures for graceful shutdown of MPLS links. It
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
route the LSPs away from the link.
Many OSPFv2 or OSPFv3 deployments run on overlay networks provisioned
by means of pseudo-wires or L2-circuits. Prior to devices in the
underlying network going offline for maintenance, it is useful to
divert the traffic away from the node before the maintenance is
actually performed. Since the nodes in the underlying network are
not visible to OSPF, the existing stub router mechanism described in
[RFC6987] cannot be used. An application specific to this use case
is described in Section 7.1.
This document provides mechanisms to advertise link-overload state in
the flexible encodings provided by OSPFv2 Prefix/Link Attribute
Advertisement [RFC7684]. 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
The motivation of this document is to reduce manual intervention
during maintenance activities. The following objectives help to
accomplish this in a range of deployment scenarios.
1. Advertise impending maintenance activity so that traffic from
both directions can be diverted away from the link.
2. Allow the solution to be backward compatible so that nodes that
do not understand the new advertisement do not cause routing
loops.
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3. Advertise the maintenance activity to other nodes in the network
so that LSP ingress routers/controllers can learn of the
impending maintenance activity and apply specific policies to re-
route the LSPs for traffic-engineering based deployments.
4. Allow the link to be used as last resort link to prevent traffic
disruption when alternate paths are not available.
3. Flooding Scope
The link-overload information is flooded in area-scoped Extended Link
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 procedures for processing the Link-Overload sub-TLV are described
in Section 5.
4. Link-Overload sub-TLV
4.1. OSPFv2 Link-overload sub-TLV
The Link-Overload sub-TLV identifies the link as being in overload
state.It is advertised in extended Link TLV of the Extended Link
Opaque LSA as defined in [RFC7684].
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Link-Overload sub-TLV for OSPFv2
Type : TBA (suggested value 7)
Length: 0
4.2. Remote IPv4 Address Sub-TLV
This sub-TLV specifies the IPv4 address of remote endpoint on the
link. It is advertised in the Extended Link TLV as defined in
[RFC7684]. This sub-TLV is optional and MAY be advertised in area-
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scoped Extended Link Opaque LSA to identify the link when there are
multiple parallel links between two nodes.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote IPv4 address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Remote IPv4 Address Sub-TLV
Type : TBA (suggested value 8)
Length: 4
Value: Remote IPv4 address. The remote IP4 address is used to
identify the particular link when there are multiple parallel links
between two nodes.
4.3. Local/Remote Interface ID Sub-TLV
This sub-TLV specifies local and remote interface identifiers. It is
advertised in the Extended Link TLV as defined in [RFC7684]. This
sub-TLV is optional and MAY be advertised in area-scoped Extended
Link Opaque LSA to identify the link when there are multiple parallel
unnumbered links between two nodes. The local interface-id is
generally readily available. One of the mechanisms to obtain remote
interface-id is described in [RFC4203].
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local Interface ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote Interface ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: Local/Remote Interface ID Sub-TLV
Type : TBA (suggested value 9)
Length: 8
Value: 4 octets of Local Interface ID followed by 4 octets of Remote
interface ID.
4.4. OSPFv3 Link-Overload sub-TLV
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
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 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: Link-Overload sub-TLV for OSPFv3
Type : TBA (Suggested value 7)
Length: 0
4.5. BGP-LS Link-overload TLV
BGP-LS as defined in [RFC7752] is a mechanism to distribute network
information to external entities using BGP routing protocol. link-
overload is an imporatant link information that the external entities
can use for various usecases as defined in Section 7. BGP Link NLRI
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is used to carry the link information. a new TLV called Link-
Overload is defined to describe the link attribute corresponding to
link-overload state.
4.6. Distinguishing parallel links
++++++++++I.w I.y +++++++++
|Router A|------------------|Router B |
| |------------------| |
++++++++++I.x I.z++++++++++
Figure 5: Parallel Linkls
Consider two routers A and B connected with two parallel point-to-
point interfaces. I.w and I.x represent the Interface address on
Router A's side and I.y and I.z represent Interface addresses on
Router B's side. The extended link opaque LSA as described in
[RFC7684] describes links using link-type, Link-ID and Link-data.
For ex. Link with address I.w is described as below on Router A.
Link-type = Point-to-point
Link-ID: Router-ID B
Link-Data = I.w
A third node (controller or head-end) in the network cannot
distinguish the Interface on router B which is connected to this
particular Interface with the above information. Interface with
address I.y or I.z could be chosen due to this ambiguity. In such
cases Remote-IPv4 Address sub-TLV should be originated and added to
the extended link-TLV. The usecases as described in Section 7
require controller or head-end nodes to interpret the link-overload
information and hence the need for the RemoteIPv4 address sub-TLV.
I.y is carried in the extended-link-TLV which unambiguously
identifies the interface on the remote side. OSPFv3 Router-link-TLV
as described in [I-D.ietf-ospf-ospfv3-lsa-extend] contains Interface
ID and neighbor's Interface-ID which can uniquely identify connecting
interface on the remote side and hence OSPFv3 does not require
seperate Remote-IPv6 address to be advertised along with OSPFv2-link-
overload-sub-TLV.
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5. Elements of procedure
As defined in [RFC7684] every link on the node will have a separate
Extended Link Opaque LSA. The node that has the link to be taken out
of service SHOULD advertise the Link-Overload sub-TLV in the Extended
Link TLV of the Extended Link Opaque LSA as defined in [RFC7684] for
OSPFv2. The Link-Overload sub-TLV indicates that the link identified
by the sub-TLV is overloaded. The Link-Overload information is
advertised as a property of the link and is flooded across the area.
This information can be used by ingress routers or controllers to
take special actions. An 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
link identified as overloaded depends on the link type.
5.1. Point-to-point links
The node that has the link to be taken out of service MUST set metric
of the link to MaxLinkMetric (0xffff) and re-originate its router-
LSA. The TE metric SHOULD be set to MAX-TE-METRIC (0xfffffffe) and
the node SHOULD re-originate the corresponding TE Link Opaque LSAs.
When a Link-Overload sub-TLV is received for a point-to-point link,
the remote node MUST identify the local link which corresponds to the
overloaded link and set the metric to MaxLinkMetric (0xffff)and the
remote node MUST re-originate its router-LSA with the changed metric.
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.
The Extended link opaque LSAs and the Extended link TLV are not
scoped for multi-topology [RFC4915]. In multi-topology deployments
[RFC4915], the Link-Overload sub-TLV advertised in an Extended Link
opaque LSA corresponds to all the topologies which include the link.
The receiver node SHOULD change the metric in the reverse direction
for all the topologies which include the remote link and re-originate
the router-LSA as defined in [RFC4915].
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.
5.2. Broadcast/NBMA links
Broadcast or NBMA networks in OSPF are represented by a star topology
where the Designated Router (DR) is the central point to which all
other routers on the broadcast or NBMA network logically connect. As
a result, routers on the broadcast or NBMA network advertise only
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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,
the MaxLinkMetric on the remote link cannot be changed since all the
neighbors are on same link. Setting the link cost to MaxLinkMetric
would impact paths going via all neighbors.
The node that has the link to be taken out of service MUST set metric
of the link to MaxLinkMetric (0xffff) and re-originate the Router-
LSA. The TE metric SHOULD be set to MAX-TE-METRIC( 0xfffffffe) and
the node SHOULD re-originate the corresponding TE Link Opaque LSAs.
For a broadcast link, the two part metric as described in [RFC8042]
is used. The node originating the Link-Overload sub-TLV MUST set the
metric in the Network-to-Router Metric sub-TLV to MaxLinkMetric
(0xffff) for OSPFv2 and OSPFv3 and re-originate the corresponding
LSAs. The nodes that receive the two-part metric should follow the
procedures described in [RFC8042]. The backward compatibility
procedures described in [RFC8042] should be followed to ensure loop
free routing.
5.3. Point-to-multipoint links
Operation for the point-to-multipoint links is similar to the point-
to-point links. When a Link-Overload sub-TLV is received for a
point-to-multipoint link the remote node MUST identify the neighbour
which corresponds to the overloaded link and set the metric to
MaxLinkMetric (0xffff). The remote node MUST re-originate the
router-LSA with the changed metric for the correponding neighbor.
5.4. Unnumbered interfaces
Unnumbered interface do not have a unique IP address and borrow their
address from other interfaces. [RFC2328] describes procedures to
handle unnumbered interfaces in the context of the router-LSA. We
apply a similar procedure to the Extended Link TLV advertising the
Link-Overload sub-TLV in order to handle unnumbered interfaces. The
link-data field in the Extended Link TLV includes the Local
interface-id instead of the IP address. The Local/Remote Interface
ID sub-TLV MUST be advertised when there are multiple parallel
unnumbered interfaces between two nodes. One of the mechanisms to
obtain the 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 MUST identify the neighbor which
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corresponds to the overloaded link and set the metric to
MaxLinkMetric (0xffff). All the remote nodes connected to originator
MUST re-originate the router-LSA with the changed metric for the
neighbor.
6. Backward compatibility
The mechanisms described in the document are fully backward
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
support the extensions described herein for the traffic to diverted
from the overloaded link. If the remote node doesn't support the
capability, it will still use the overloaded link but there are no
other adverse effects. In the case of broadcast links using two-part
metrics, the backward compatibility procedures as described in
[RFC8042] are applicable.
7. Applications
7.1. Pseudowire Services
Many service providers offer pseudo-wire services to customers using
L2 circuits. The IGP protocol that runs in the customer network
would also run over the pseudo-wire to create a seamless private
network for the customer. Service providers want to offer overload
functionality when the PE device is taken-out for maintenance. The
provider should guarantee that the PE is taken out for maintenance
only after the service is successfully diverted on an 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 across the
service provider's network. It is a tedious and error-prone process
to change the metric for all pseudo-wires in both directions. The
link-overload feature simplifies the process by increasing the metric
on the link in the reverse direction as well so that traffic in both
directions is diverted away from the PE undergoing maintenance. The
Link-Overload feature allows the link to be used as a last resort
link so that traffic is not disrupted when alternative paths are not
available.
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Private VLAN
=======================================
| |
| |
| ------PE3---------------PE4------CE3
| / \
| / \
CE1---------PE1----------PE2---------CE2
| \
| \
| ------CE4
| |
| |
| |
=================================
Private VLAN
Figure 6: Pseudowire Services
In the example shown in Figure 6, when the PE1 node is going out of
service for maintenance, service providers set the PE1 to overload
state. The PE1 going in to overload state triggers all the CEs
connected to the PE (CE1 in this case) 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 private VLAN
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
CE3, CE2, and CE4 also set the metric on the link to MaxLinkMetric
and the traffic from both directions gets diverted away from the
pseudowires.
7.2. Controller based Traffic Engineering Deployments
In controller-based deployments where the controller participates in
the IGP protocol, the controller can also receive the link-overload
information as a warning that link maintenance is imminent. Using
this information, the controller can find alternate paths for traffic
which uses the affected link. The controller can apply various
policies and re-route the LSPs away from the link undergoing
maintenance. If there are no alternate paths satisfying the traffic
engineering constraints, the controller might temporarily relax those
constraints and put the service on a different path. Increasing the
link metric alone does not specify the maintenance activity as the
metric could increase in events such as LDP-IGP synchronisation. An
explicit indication from the router using the link-overload sub-TLV
is needed to inform the Controller or head-end routers.
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_____________
| |
-------------| Controller |--------------
| |____________ | |
| |
|--------- Primary Path ------------------|
PE1---------P1----------------P2---------PE2
| |
| |
|________P3________|
Alternate Path
Figure 7: Controller based Traffic Engineering
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
only 1 Gbps capacity and there is no alternate path satisfying the
bandwidth constraint of 10Gbps. 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, the controller chooses a path that is less optimal
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
maintenance/upgrade.
7.3. L3VPN Services and sham-links
Many service providers offer L3VPN services to customers and CE-PE
links run OSPF [RFC4577]. When PE is taken out of service for
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
gets diverted. The interaction between OSPF and BGP is outside the
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
customers [RFC4577]. When PE goes out of service for maintenance,
all sham-links on the PE can be set to link-overload state and
traffic can be divered from both ends without having to touch the
configurations on the remote end of the sham-links.
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7.4. Hub and spoke deployment
OSPF is largely deployed in Hub and Spoke deployments with a large
number of spokes connecting to the Hub. It is a general practice to
deploy multiple Hubs with all spokes connecting to these Hubs to
achieve redundancy. The [RFC6987] mechanism can be used to divert
the spoke-to-spoke traffic from the overloaded hub router. The
traffic that flows from spokes via the hub into an external network
may not be diverted in certain scenarios.When a Hub node goes down
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
This document does not introduce any further security issues other
than those discussed in [RFC2328] and [RFC5340].
9. IANA Considerations
This specification updates one OSPF registry:
OSPFv2 Extended Link TLV Sub-TLVs
i) Link-Overload Sub-TLV - Suggested value 7
ii) Remote IPv4 Address Sub-TLV - Suggested value 8
iii) Local/Remote Interface ID Sub-TLV - Suggested Value 9
OSPFv3 Extended-LSA sub-TLV Registry
i) Link-Overload sub-TLV - suggested value 7
BGP-LS Link NLRI Registry [RFC7752]
i)Link-Overload TLV - Suggested 1101
10. Acknowledgements
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 Karsten Thomann for careful review and inputs on the
applications where link-overload is useful.
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11. 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
and Point-to-Multipoint Interface Type", RFC 6845,
DOI 10.17487/RFC6845, January 2013,
<https://www.rfc-editor.org/info/rfc6845>.
[RFC7684] Psenak, P., Gredler, H., Shakir, R., Henderickx, W.,
Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute
Advertisement", RFC 7684, DOI 10.17487/RFC7684, November
2015, <https://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,
<https://www.rfc-editor.org/info/rfc7752>.
[RFC8042] Zhang, Z., Wang, L., and A. Lindem, "OSPF Two-Part
Metric", RFC 8042, DOI 10.17487/RFC8042, December 2016,
<https://www.rfc-editor.org/info/rfc8042>.
11.2. Informative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328,
DOI 10.17487/RFC2328, April 1998,
<https://www.rfc-editor.org/info/rfc2328>.
[RFC4203] Kompella, K., Ed. and Y. Rekhter, Ed., "OSPF Extensions in
Support of Generalized Multi-Protocol Label Switching
(GMPLS)", RFC 4203, DOI 10.17487/RFC4203, October 2005,
<https://www.rfc-editor.org/info/rfc4203>.
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Internet-Draft OSPF link overload January 2018
[RFC4577] Rosen, E., Psenak, P., and P. Pillay-Esnault, "OSPF as the
Provider/Customer Edge Protocol for BGP/MPLS IP Virtual
Private Networks (VPNs)", RFC 4577, DOI 10.17487/RFC4577,
June 2006, <https://www.rfc-editor.org/info/rfc4577>.
[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,
<https://www.rfc-editor.org/info/rfc4915>.
[RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF
for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008,
<https://www.rfc-editor.org/info/rfc5340>.
[RFC5817] Ali, Z., Vasseur, JP., Zamfir, A., and J. Newton,
"Graceful Shutdown in MPLS and Generalized MPLS Traffic
Engineering Networks", RFC 5817, DOI 10.17487/RFC5817,
April 2010, <https://www.rfc-editor.org/info/rfc5817>.
[RFC6987] Retana, A., Nguyen, L., Zinin, A., White, R., and D.
McPherson, "OSPF Stub Router Advertisement", RFC 6987,
DOI 10.17487/RFC6987, September 2013,
<https://www.rfc-editor.org/info/rfc6987>.
Authors' Addresses
Shraddha Hegde
Juniper Networks, Inc.
Embassy Business Park
Bangalore, KA 560093
India
Email: shraddha@juniper.net
Pushpasis Sarkar
Individual
Email: pushpasis.ietf@gmail.com
Hannes Gredler
Individual
Email: hannes@gredler.at
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Mohan Nanduri
ebay Corporation
2025 Hamilton Avenue
San Jose, CA 98052
US
Email: mnanduri@ebay.com
Luay Jalil
Verizon
Email: luay.jalil@verizon.com
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