draft-ietf-6man-resilient-rs-05.txt   draft-ietf-6man-resilient-rs-06.txt 
6man Working Group S. Krishnan 6man Working Group S. Krishnan
Internet-Draft Ericsson Internet-Draft Ericsson
Updates: RFC4861 (if approved) D. Anipko Updates: 4861 (if approved) D. Anipko
Intended status: Standards Track Unaffiliated Intended status: Standards Track Unaffiliated
Expires: September 10, 2015 D. Thaler Expires: October 11, 2015 D. Thaler
Microsoft Microsoft
March 9, 2015 April 9, 2015
Packet loss resiliency for Router Solicitations Packet loss resiliency for Router Solicitations
draft-ietf-6man-resilient-rs-05 draft-ietf-6man-resilient-rs-06
Abstract Abstract
When an interface on a host is initialized, the host transmits Router When an interface on a host is initialized, the host transmits Router
Solicitations in order to minimize the amount of time it needs to Solicitations in order to minimize the amount of time it needs to
wait until the next unsolicited multicast Router Advertisement is wait until the next unsolicited multicast Router Advertisement is
received. In certain scenarios, these router solicitations received. In certain scenarios, these router solicitations
transmitted by the host might be lost. This document specifies a transmitted by the host might be lost. This document specifies a
mechanism for hosts to cope with the loss of the initial Router mechanism for hosts to cope with the loss of the initial Router
Solicitations. Solicitations.
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Copyright Notice Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the Copyright (c) 2015 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Conventions used in this document . . . . . . . . . . . . 3 1.1. Conventions used in this document . . . . . . . . . . . . 2
2. Proposed algorithm . . . . . . . . . . . . . . . . . . . . . 4 2. Proposed algorithm . . . . . . . . . . . . . . . . . . . . . 4
2.1. Stopping the retransmissions . . . . . . . . . . . . . . 4 2.1. Stopping the retransmissions . . . . . . . . . . . . . . 4
3. Configuring the use of retransmissions . . . . . . . . . . . 5 3. Configuring the use of retransmissions . . . . . . . . . . . 5
4. Known Limitations . . . . . . . . . . . . . . . . . . . . . . 5 4. Known Limitations . . . . . . . . . . . . . . . . . . . . . . 5
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
6. Security Considerations . . . . . . . . . . . . . . . . . . . 5 6. Security Considerations . . . . . . . . . . . . . . . . . . . 5
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
8. Normative References . . . . . . . . . . . . . . . . . . . . 6 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
8.1. Normative References . . . . . . . . . . . . . . . . . . 6
8.2. Informative References . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction 1. Introduction
As specified in [RFC4861], when an interface on a host is As specified in [RFC4861], when an interface on a host is
initialized, in order to obtain Router Advertisements quickly, a host initialized, in order to obtain Router Advertisements quickly, a host
transmits up to MAX_RTR_SOLICITATIONS (3) Router Solicitation transmits up to MAX_RTR_SOLICITATIONS (3) Router Solicitation
messages, each separated by at least RTR_SOLICITATION_INTERVAL (4) messages, each separated by at least RTR_SOLICITATION_INTERVAL (4)
seconds. In certain scenarios, these router solicitations seconds. In certain scenarios, these router solicitations
transmitted by the host might be lost. e.g. The host is connected to transmitted by the host might be lost. e.g. The host is connected to
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upstream WAN connectivity is not active yet. In this case, the host upstream WAN connectivity is not active yet. In this case, the host
just gives up after the initial RS retransmits. just gives up after the initial RS retransmits.
Once the initial RSs are lost, the host gives up and assumes that Once the initial RSs are lost, the host gives up and assumes that
there are no routers on the link as specified in Section 6.3.7 of there are no routers on the link as specified in Section 6.3.7 of
[RFC4861]. The host will not have any form of Internet connectivity [RFC4861]. The host will not have any form of Internet connectivity
until the next unsolicited multicast Router Advertisement is until the next unsolicited multicast Router Advertisement is
received. These Router Advertisements are transmitted at most received. These Router Advertisements are transmitted at most
MaxRtrAdvInterval seconds apart (maximum value 1800 seconds). Thus MaxRtrAdvInterval seconds apart (maximum value 1800 seconds). Thus
in the worst case scenario a host would be without any connectivity in the worst case scenario a host would be without any connectivity
for 30 minutes. In general, the delay may be unacceptable in some for 30 minutes. This delay may be unacceptable in some scenarios.
scenarios.
1.1. Conventions used in this document 1.1. Conventions used in this document
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 [RFC2119]. document are to be interpreted as described in [RFC2119].
2. Proposed algorithm 2. Proposed algorithm
To achieve resiliency to packet loss, the host needs to continue To achieve resiliency to packet loss, the host needs to continue
retransmitting the Router Solicitations until it receives a Router retransmitting the Router Solicitations until it receives a Router
Advertisement, or until it is willing to accept that no router Advertisement, or until it is willing to accept that no router
exists. If the host continues retransmitting the RSs at exists. If the host continues retransmitting the RSs at
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On non-multicast links, the hosts following this specification MUST On non-multicast links, the hosts following this specification MUST
continue retransmitting the RSs even after an RA that results in a continue retransmitting the RSs even after an RA that results in a
default route is received. This is required because, in such links, default route is received. This is required because, in such links,
sending an RA can only be triggered by an RS. Please note that such sending an RA can only be triggered by an RS. Please note that such
links have special mechanisms for sending RSes as well. e.g. The links have special mechanisms for sending RSes as well. e.g. The
mechanism specified in Section 8.3.4. of ISATAP [RFC5214] unicasts mechanism specified in Section 8.3.4. of ISATAP [RFC5214] unicasts
the RSes to specific routers. the RSes to specific routers.
3. Configuring the use of retransmissions 3. Configuring the use of retransmissions
Implementations of this specification MAY provide a configuration Implementations of this specification are encouraged to provide a
option to enable or disable the use of such potentially infinite configuration option to enable or disable potentially infinite RS
retransmissions. If the implementation provides such a configuration retransmissions. If a configuration option is provided, it MUST
option, it MUST be able to enable/disable retransmissions on a per- enable RS retransmissions by default. Providing an option to enable/
interface basis. disable retransmissions on a per-interface basis allows network
operators to configure RS behavior most applicable to each connected
link.
4. Known Limitations 4. Known Limitations
When an IPv6-capable host attaches to a network that does not have When an IPv6-capable host attaches to a network that does not have
IPv6 enabled, it transmits 3 (MAX_RTR_SOLICITATIONS) Router IPv6 enabled, it transmits 3 (MAX_RTR_SOLICITATIONS) Router
Solicitations as specified in [RFC4861]. If it receives no Router Solicitations as specified in [RFC4861]. If it receives no Router
Advertisements, it assumes that there are no routers present on the Advertisements, it assumes that there are no routers present on the
link and it ceases to send further RSs. With the mechanism specified link and it ceases to send further RSs. With the mechanism specified
in this document, the host will continue to retransmit RSs in this document, the host will continue to retransmit RSs
indefinitely at the rate of approximately 1 RS per hour. It is indefinitely at the rate of approximately 1 RS per hour. It is
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routers and a link where an IPv6 router is temporarily unreachable routers and a link where an IPv6 router is temporarily unreachable
but could become reachable in the future. but could become reachable in the future.
5. IANA Considerations 5. IANA Considerations
This document does not require any IANA actions. This document does not require any IANA actions.
6. Security Considerations 6. Security Considerations
This document does not present any additional security issues beyond This document does not present any additional security issues beyond
those discussed in [RFC4861]. those discussed in [RFC4861] and those RFCs that update [RFC4861].
7. Acknowledgements 7. Acknowledgements
The authors would like to thank Steve Baillargeon, Erik Kline, Andrew The authors would like to thank Steve Baillargeon, Erik Kline, Andrew
Yourtchenko, Ole Troan, Erik Nordmark, Lorenzo Colitti, Thomas Yourtchenko, Ole Troan, Erik Nordmark, Lorenzo Colitti, Thomas
Narten, Ran Atkinson, Allison Mankin, Les Ginsberg and Brian Narten, Ran Atkinson, Allison Mankin, Les Ginsberg, Brian Carpenter,
Carpenter for their reviews and suggestions that made this document Barry Leiba, Brian Haberman, Spencer Dawkins, Alia Atlas, Stephen
better. Farrell and Mehmet Ersue for their reviews and suggestions that made
this document better.
8. Normative References 8. 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.
[RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., [RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C.,
and M. Carney, "Dynamic Host Configuration Protocol for and M. Carney, "Dynamic Host Configuration Protocol for
IPv6 (DHCPv6)", RFC 3315, July 2003. IPv6 (DHCPv6)", RFC 3315, July 2003.
[RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
September 2007. September 2007.
[RFC7083] Droms, R., "Modification to Default Values of SOL_MAX_RT
and INF_MAX_RT", RFC 7083, November 2013.
8.2. Informative References
[RFC5214] Templin, F., Gleeson, T., and D. Thaler, "Intra-Site [RFC5214] Templin, F., Gleeson, T., and D. Thaler, "Intra-Site
Automatic Tunnel Addressing Protocol (ISATAP)", RFC 5214, Automatic Tunnel Addressing Protocol (ISATAP)", RFC 5214,
March 2008. March 2008.
[RFC7083] Droms, R., "Modification to Default Values of SOL_MAX_RT
and INF_MAX_RT", RFC 7083, November 2013.
Authors' Addresses Authors' Addresses
Suresh Krishnan Suresh Krishnan
Ericsson Ericsson
8400 Decarie Blvd. 8400 Decarie Blvd.
Town of Mount Royal, QC Town of Mount Royal, QC
Canada Canada
Phone: +1 514 345 7900 x42871 Phone: +1 514 345 7900 x42871
Email: suresh.krishnan@ericsson.com Email: suresh.krishnan@ericsson.com
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