draft-ietf-ospf-rfc3137bis-00.txt   draft-ietf-ospf-rfc3137bis-01.txt 
Network Working Group A. Retana Network Working Group A. Retana
Internet-Draft Hewlett-Packard Co. Internet-Draft Hewlett-Packard Co.
Obsoletes: RFC3137 (if approved) L. Nguyen Obsoletes: RFC3137 (if approved) L. Nguyen
Intended status: Informational R. White Intended status: Informational A. Zinin
Expires: January 1, 2012 A. Zinin Expires: December 31, 2012 Cisco Systems, Inc.
Cisco Systems, Inc. R. White
D. McPherson D. McPherson
Verisign, Inc. Verisign, Inc.
June 30, 2011 June 29, 2012
OSPF Stub Router Advertisement OSPF Stub Router Advertisement
draft-ietf-ospf-rfc3137bis-00 draft-ietf-ospf-rfc3137bis-01
Abstract Abstract
This memo describes a backward-compatible technique that may be used This memo describes a backward-compatible technique that may be used
by OSPF (Open Shortest Path First) implementations to advertise 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. In some cases, it is level for the paths through such a router. In some cases, it is
desirable not to route transit traffic via a specific OSPF router. desirable not to route transit traffic via a specific OSPF router.
However, OSPF does not specify a standard way to accomplish this. However, OSPF does not specify a standard way to accomplish this.
skipping to change at page 1, line 40 skipping to change at page 1, line 40
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 1, 2012. This Internet-Draft will expire on December 31, 2012.
Copyright Notice Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the Copyright (c) 2012 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
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
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Requirements Language . . . . . . . . . . . . . . . . . . . . . 3 2. Requirements Language . . . . . . . . . . . . . . . . . . . . . 3
3. Proposed Solution . . . . . . . . . . . . . . . . . . . . . . . 3 3. Proposed Solution . . . . . . . . . . . . . . . . . . . . . . . 3
4. Compatibility issues . . . . . . . . . . . . . . . . . . . . . 4 4. Deployment Considerations . . . . . . . . . . . . . . . . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 4 4.1. Other Solutions . . . . . . . . . . . . . . . . . . . . . . 4
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 4 5. Maximum Link Metric . . . . . . . . . . . . . . . . . . . . . . 4
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5 6. Security Considerations . . . . . . . . . . . . . . . . . . . . 5
7.1. Normative References . . . . . . . . . . . . . . . . . . . 5 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 5
7.2. Informative References . . . . . . . . . . . . . . . . . . 5 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 5 8.1. Normative References . . . . . . . . . . . . . . . . . . . 5
8.2. Informative References . . . . . . . . . . . . . . . . . . 5
Appendix A. Changes between the -00 and -01 versions. . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 6
1. Motivation 1. Motivation
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).
skipping to change at page 4, line 11 skipping to change at page 4, line 11
router X. router X.
Note that it would be easy to address issue 1) alone by just flushing Note that it would be easy to address issue 1) alone by just flushing
router X's router-LSA from the domain. However, it does not solve router X's router-LSA from the domain. However, it does not solve
problem 2), since other routers will not be able to use links to problem 2), since other routers will not be able to use links to
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 LSInfinity (16-bit value 0xFFFF, rather than 24- other than 3) set to MaxLinkMetric.
bit value 0xFFFFFF used in summary and AS-external LSAs).
The solution above applies to both OSPFv2 [RFC2328] and OSPFv3 The solution above applies to both OSPFv2 [RFC2328] and OSPFv3
[RFC5340]. [RFC5340].
4. Compatibility issues 4. Deployment Considerations
Some inconsistency may be seen when the network is constructed of the When using MaxLinkMetric, some inconsistency may be seen if the
routers that perform intra-area Dijkstra calculation as specified in network is constructed of routers that perform intra-area Dijkstra
[RFC1247] (discarding link records in router-LSAs that have calculation as specified in [RFC1247] (discarding link records in
LSInfinity cost value) and routers that perform it as specified in router-LSAs that have a MaxLinkMetric cost value) and routers that
[RFC1583] and higher (do not treat links with LSInfinity cost as perform it as specified in [RFC1583] and higher (do not treat links
unreachable). Note that this inconsistency will not lead to routing with MaxLinkMetric cost as unreachable). Note that this
loops, because if there are some alternate paths in the network, both inconsistency will not lead to routing loops, because if there are
types of routers will agree on using them rather than the path some alternate paths in the network, both types of routers will agree
through the stub router. If the path through the stub router is the on using them rather than the path through the stub router. If the
only one, the routers of the first type will not use the stub router path through the stub router is the only one, the routers of the
for transit (which is the desired behavior), while the routers of the first type will not use the stub router for transit (which is the
second type will still use this path. desired behavior), while the routers of the second type will still
use this path.
5. Security Considerations 4.1. Other Solutions
This document describes a technique that has been implemented and
deployed in a wide variety of networks. OSPFv3 [RFC5340] introduced
additional options to provide similar, if not better, control of the
forwarding topology; the R-bit and the V6-bit provide a more granular
indication of whether a router is active and/or whether it should be
used specifically for IPv6 traffic, respectively.
It is left to network operators to decide which technique to use in
their network.
5. Maximum Link Metric
Section 3 refers to the cost of all non-stub links as MaxLinkMetric,
which is a new fixed architectural value introduced in this document.
MaxLinkMetric
The metric value indicating that the link described by an LSA
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
ones: 0xffff.
6. 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. 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 and We would also like to thank Shishio Tsuchiya, Gunter Van de Velde,
Tomohiro Yamagata for reminding us of the need to document the OSPFv3 Tomohiro Yamagata, Faraz Shamim and Acee Lindem who provided
behavior. significant input for the latest version of this document.
7. References 8. References
7.1. Normative References 8.1. Normative 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, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
7.2. Informative References 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.
Appendix A. Changes between the -00 and -01 versions.
o Defined a new architectural constant (MaxLinkMetric) to eliminate
any confusion about the interpretation of LSInfinity.
o Added a section to reference the R-bit and V6-bit in OSPFv3.
o Updated acks and contact information.
Authors' Addresses Authors' Addresses
Alvaro Retana Alvaro Retana
Hewlett-Packard Co. Hewlett-Packard Co.
2610 Wycliff Road 2610 Wycliff Road
Raleigh, NC 27607 Raleigh, NC 27607
USA USA
Email: alvaro.retana@hp.com Email: alvaro.retana@hp.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
Russ White
Cisco Systems, Inc.
7025 Kit Creek Rd.
Research Triangle Park, NC 27709
USA
Email: russwh@cisco.com
Alex Zinin Alex Zinin
Cisco Systems, Inc. Cisco Systems, Inc.
Capital Tower, 168 Robinson Rd. Capital Tower, 168 Robinson Rd.
Singapore, Singapore 068912 Singapore, Singapore 068912
Singapore Singapore
Email: azinin@cisco.com Email: azinin@cisco.com
Russ White
Verisign, Inc.
12061 Bluemont Way
Reston, VA 20190
USA
Email: riwhite@verisign.com
Danny McPherson Danny McPherson
Verisign, Inc. Verisign, Inc.
21345 Ridgetop Circle 21345 Ridgetop Circle
Dulles, VA 20166 Dulles, VA 20166
USA USA
Email: dmcpherson@verisign.com Email: dmcpherson@verisign.com
 End of changes. 18 change blocks. 
44 lines changed or deleted 79 lines changed or added

This html diff was produced by rfcdiff 1.41. The latest version is available from http://tools.ietf.org/tools/rfcdiff/