draft-ietf-ospf-rfc3137bis-02.txt   draft-ietf-ospf-rfc3137bis-03.txt 
Network Working Group A. Retana Network Working Group A. Retana
Internet-Draft Hewlett-Packard Co. Internet-Draft L. Nguyen
Obsoletes: RFC3137 (if approved) L. Nguyen Obsoletes: 3137 (if approved) Cisco Systems, Inc.
Intended status: Informational A. Zinin Intended status: Informational A. Zinin
Expires: January 17, 2013 Cisco Systems, Inc. Expires: July 21, 2013 Cinarra Systems
R. White R. White
D. McPherson D. McPherson
Verisign, Inc. Verisign, Inc.
July 16, 2012 January 17, 2013
OSPF Stub Router Advertisement OSPF Stub Router Advertisement
draft-ietf-ospf-rfc3137bis-02 draft-ietf-ospf-rfc3137bis-03
Abstract Abstract
This document describes a backward-compatible technique that may be This document describes a backward-compatible technique that may be
used by OSPF (Open Shortest Path First) implementations to advertise used by OSPF (Open Shortest Path First) implementations to advertise
unavailability to forward transit traffic or to lower the preference unavailability to forward transit traffic or to lower the preference
level for the paths through such a router. level for the paths through such a router.
Status of this Memo Status of this Memo
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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 January 17, 2013. This Internet-Draft will expire on July 21, 2013.
Copyright Notice Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
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publication of this document. Please review these documents publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
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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. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Requirements Language . . . . . . . . . . . . . . . . . . . . . 3 2. Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.1. OSPFv3-only Solution . . . . . . . . . . . . . . . . . . . 4
3.1. OSPFv3-only Solution . . . . . . . . . . . . . . . . . . . 4 3. Maximum Link Metric . . . . . . . . . . . . . . . . . . . . . . 4
4. Maximum Link Metric . . . . . . . . . . . . . . . . . . . . . . 4 4. Deployment Considerations . . . . . . . . . . . . . . . . . . . 4
5. Deployment Considerations . . . . . . . . . . . . . . . . . . . 4 5. Security Considerations . . . . . . . . . . . . . . . . . . . . 5
6. Security Considerations . . . . . . . . . . . . . . . . . . . . 5 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 5 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 5
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5 8. Informative References . . . . . . . . . . . . . . . . . . . . 5
8.1. Normative References . . . . . . . . . . . . . . . . . . . 5 Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . . 5
8.2. Informative References . . . . . . . . . . . . . . . . . . 5 A.1. Changes between the -00 and -01 versions. . . . . . . . . . 5
Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . . 6
A.1. Changes between the -00 and -01 versions. . . . . . . . . . 6
A.2. Changes between the -01 and -02 versions. . . . . . . . . . 6 A.2. Changes between the -01 and -02 versions. . . . . . . . . . 6
A.3. Changes between the -02 and -03 versions. . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 6 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 6
1. Motivation 1. Introduction
In some situations, it may be advantageous to inform routers in a In some situations, it may be advantageous to inform routers in a
network not to use a specific router as a transit point, but still network not to use a specific router as a transit point, but still
route to it. Possible situations include the following: route to it. Possible situations include the following:
o The router is in a critical condition (for example, has very high o The router is in a critical condition (for example, has very high
CPU load or does not have enough memory to store all LSAs or build CPU load or does not have enough memory to store all LSAs or build
the routing table). the routing table).
o Graceful introduction and removal of the router to/from the o Graceful introduction and removal of the router to/from the
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routers from using it for transit routing, while still routing routers from using it for transit routing, while still routing
packets to the router's own IP addresses, i.e., the router is packets to the router's own IP addresses, i.e., the router is
announced as a stub. announced as a stub.
It must be emphasized that the solution provides real benefits in It must be emphasized that the solution provides real benefits in
networks designed with at least some level of redundancy so that networks designed with at least some level of redundancy so that
traffic can be routed around the stub router. Otherwise, traffic traffic can be routed around the stub router. Otherwise, traffic
destined for the networks reachable through such a stub router may destined for the networks reachable through such a stub router may
still be routed through it. still be routed through it.
2. Requirements Language 2. Solutions
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 [RFC2119].
3. Solutions
The solution introduced in this document solves two challenges The solution introduced in this document solves two challenges
associated with the outlined problem. In the description below, associated with the outlined problem. In the description below,
router X is the router announcing itself as a stub. router X is the router announcing itself as a stub.
1) Making other routers prefer routes around router X while 1) Making other routers prefer routes around router X while
performing the Dijkstra calculation. performing the Dijkstra calculation.
2) Allowing other routers to reach IP prefixes directly connected to 2) Allowing other routers to reach IP prefixes directly connected to
router X. router X.
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router X in Dijkstra (no back link), and because router X will not router X in Dijkstra (no back link), and because router X will not
have links to its neighbors. have links to its neighbors.
To address both problems, router X announces its router-LSA to the To address both problems, router X announces its router-LSA to the
neighbors with the costs of all non-stub links (links of the types neighbors with the costs of all non-stub links (links of the types
other than 3) set to MaxLinkMetric. other than 3) set to MaxLinkMetric.
The solution above applies to both OSPFv2 [RFC2328] and OSPFv3 The solution above applies to both OSPFv2 [RFC2328] and OSPFv3
[RFC5340]. [RFC5340].
3.1. OSPFv3-only Solution 2.1. OSPFv3-only Solution
OSPFv3 [RFC5340] introduced additional options to provide similar, if OSPFv3 [RFC5340] introduced additional options to provide similar, if
not better, control of the forwarding topology; the R-bit provides a not better, control of the forwarding topology; the R-bit provides a
more granular indication of whether a router is active and should be more granular indication of whether a router is active and should be
used for transit traffic. used for transit traffic.
It is left to network operators to decide which technique to use in It is left to network operators to decide which technique to use in
their network. their network.
4. Maximum Link Metric 3. Maximum Link Metric
Section 3 refers to the cost of all non-stub links as MaxLinkMetric, Section 2 refers to the cost of all non-stub links as MaxLinkMetric,
which is a new fixed architectural value introduced in this document. which is a new fixed architectural value introduced in this document.
MaxLinkMetric MaxLinkMetric
The metric value indicating that the link described by an LSA The metric value indicating that the link described by an LSA
should not be used as transit. Used in router-LSAs (see should not be used as transit. Used in router-LSAs (see
Section 3). It is defined to be the 16-bit binary value of all Section 2). It is defined to be the 16-bit binary value of all
ones: 0xffff. ones: 0xffff.
5. Deployment Considerations 4. Deployment Considerations
When using MaxLinkMetric, some inconsistency may be seen if the When using MaxLinkMetric, some inconsistency may be seen if the
network is constructed of routers that perform intra-area Dijkstra network is constructed of routers that perform intra-area Dijkstra
calculation as specified in [RFC1247] (discarding link records in calculation as specified in [RFC1247] (discarding link records in
router-LSAs that have a MaxLinkMetric cost value) and routers that router-LSAs that have a MaxLinkMetric cost value) and routers that
perform it as specified in [RFC1583] and higher (do not treat links perform it as specified in [RFC1583] and higher (do not treat links
with MaxLinkMetric cost as unreachable). Note that this with MaxLinkMetric cost as unreachable). Note that this
inconsistency will not lead to routing loops, because if there are inconsistency will not lead to routing loops, because if there are
some alternate paths in the network, both types of routers will agree some alternate paths in the network, both types of routers will agree
on using them rather than the path through the stub router. If the on using them rather than the path through the stub router. If the
path through the stub router is the only one, the routers of the path through the stub router is the only one, the routers of the
first type will not use the stub router for transit (which is the first type will not use the stub router for transit (which is the
desired behavior), while the routers of the second type will still desired behavior), while the routers of the second type will still
use this path. use this path.
On the other hand, clearing the R-bit will consistently result in the On the other hand, clearing the R-bit will consistently result in the
router not being used as transit. router not being used as transit.
6. Security Considerations 5. Security Considerations
The technique described in this document does not introduce any new The technique described in this document does not introduce any new
security issues into the OSPF protocol. security issues into the OSPF protocol.
6. IANA Considerations
This document has no actions for IANA.
7. Acknowledgements 7. Acknowledgements
The authors of this document do not make any claims on the The authors of this document do not make any claims on the
originality of the ideas described. Among other people, we would originality of the ideas described. Among other people, we would
like to acknowledge Henk Smit for being part of one of the initial like to acknowledge Henk Smit for being part of one of the initial
discussions around this topic. discussions around this topic.
We would also like to thank Shishio Tsuchiya, Gunter Van de Velde, We would also like to thank Shishio Tsuchiya, Gunter Van de Velde,
Tomohiro Yamagata, Faraz Shamim and Acee Lindem who provided Tomohiro Yamagata, Faraz Shamim and Acee Lindem who provided
significant input for the latest version of this document. significant input for the latest version of this document.
8. References 8. Informative References
8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
8.2. Informative References
[RFC1247] Moy, J., "OSPF Version 2", RFC 1247, July 1991. [RFC1247] Moy, J., "OSPF Version 2", RFC 1247, July 1991.
[RFC1583] Moy, J., "OSPF Version 2", RFC 1583, March 1994. [RFC1583] Moy, J., "OSPF Version 2", RFC 1583, March 1994.
[RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998. [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998.
[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, July 2008. for IPv6", RFC 5340, July 2008.
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o Updated acks and contact information. o Updated acks and contact information.
A.2. Changes between the -01 and -02 versions. A.2. Changes between the -01 and -02 versions.
o Took out references to not having a standard solution and o Took out references to not having a standard solution and
incorporated the R-bit solution as part of the (renamed) incorporated the R-bit solution as part of the (renamed)
"Solutions" section. "Solutions" section.
o Various minor edits and reordered sections. o Various minor edits and reordered sections.
A.3. Changes between the -02 and -03 versions.
o Updated contact information.
o Renamed the 'Motivation' section to 'Introduction' becuase of an
error in idnits.
o Took out the rfc2119 references as none of the keywords are used
in the text.
o Added an 'IANA Considerations' section to indicate that there are
no actions required.
Authors' Addresses Authors' Addresses
Alvaro Retana Alvaro Retana
Hewlett-Packard Co. Cisco Systems, Inc.
2610 Wycliff Road 7025 Kit Creek Rd.
Raleigh, NC 27607 Research Triangle Park, NC 27709
USA USA
Email: alvaro.retana@hp.com Email: aretana@cisco.com
Liem Nguyen Liem Nguyen
Cisco Systems, Inc. Cisco Systems, Inc.
3750 Cisco Way 3750 Cisco Way
San Jose, CA 95134 San Jose, CA 95134
USA USA
Email: lhnguyen@cisco.com Email: lhnguyen@cisco.com
Alex Zinin Alex Zinin
Cisco Systems, Inc. Cinarra Systems
Capital Tower, 168 Robinson Rd. Menlo Park, CA
Singapore, Singapore 068912 USA
Singapore
Email: alex.zinin@gmail.com
Email: azinin@cisco.com
Russ White Russ White
Verisign, Inc. Verisign, Inc.
12061 Bluemont Way 12061 Bluemont Way
Reston, VA 20190 Reston, VA 20190
USA USA
Email: riwhite@verisign.com Email: riwhite@verisign.com
Danny McPherson Danny McPherson
Verisign, Inc. Verisign, Inc.
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