6man Working Group S. Krishnan
Internet-Draft Ericsson
Intended status: Standards Track D. Anipko
Expires: January 10, 2013 D. Thaler
Microsoft
July 9, 2012
Packet loss resiliency for Router Solicitations
draft-krishnan-6man-resilient-rs-00
Abstract
When an interface on a host is initialized, the host transmits Router
Solicitations in order to minimize the amount of time it needs to
wait until the next unsolicited multicast Router Advertisement is
received. In certain scenarios, these router solicitations
transmitted by the host might be lost. This document specifies a
mechanism for hosts to cope with the loss of the initial Router
Solicitations.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
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This Internet-Draft will expire on January 10, 2013.
Copyright Notice
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document authors. All rights reserved.
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to this document. Code Components extracted from this document must
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Conventions used in this document . . . . . . . . . . . . . 3
2. Proposed algorithm . . . . . . . . . . . . . . . . . . . . . . 4
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4
4. Security Considerations . . . . . . . . . . . . . . . . . . . . 4
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 4
6. Normative References . . . . . . . . . . . . . . . . . . . . . 4
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 4
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1. Introduction
As specified in [RFC4861], when an interface on a host is
initialized, in order to obtain Router Advertisements quickly, a host
transmits up to MAX_RTR_SOLICITATIONS (3) Router Solicitation
messages, each separated by at least RTR_SOLICITATION_INTERVAL (4)
seconds. In certain scenarios, these router solicitations
transmitted by the host might be lost.
The generic scenario is that the interface on the host comes up
before it gets access to a router. Examples are
a. Host is connected to a bridged residential gateway (over Ethernet
or WiFi). LAN connectivity is achieved at interface
initialization, but the upstream WAN connectivity is not active
yet. In this case, the host just gives up after the initial RS
retransmits.
b. Accesses that turn off periodic RAs and operate only in a RS
triggered environment. In this case if the link between the AP
and the host comes up before the link between the AP and the
Controller/Router, the host will never be able to connect.
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
[RFC4861]. The host will not have any form of Internet connectivity
until the next unsolicited multicast Router Advertisement is
received. These Router Advertisements are transmitted at most
MaxRtrAdvInterval seconds apart (maximum value 1800 seconds). In the
worst case scenario, a host would be without any connectivity, on
average, for half this period (900 seconds). This delay may be
unacceptable in some scenarios.
1.1. Conventions used in this document
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].
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2. Proposed algorithm
To achieve resiliency to packet loss, the host needs to continue
retransmitting the Router Solicitations until it receives a Router
Advertisement, or until it is willing to accept that no router
exists. If the host continues retransmitting the RSs at
RTR_SOLICITATION_INTERVAL second intervals, it would cause excessive
network traffic. To achieve resiliency while keeping the network
traffic low, the host must use some form of exponential backoff
algorithm to retransmit the RSs.
3. IANA Considerations
This document does not require any IANA actions.
4. Security Considerations
This document does not present any additional security issues beyond
those specified in [RFC4861].
5. Acknowledgements
The author would like to thank Steve Baillargeon for his reviews and
suggestions that made this document better.
6. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
September 2007.
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Authors' Addresses
Suresh Krishnan
Ericsson
8400 Decarie Blvd.
Town of Mount Royal, QC
Canada
Phone: +1 514 345 7900 x42871
Email: suresh.krishnan@ericsson.com
Dmitry Anipko
Microsoft
One Microsoft Way
Redmond, WA
USA
Phone: +1 425 703 7070
Email: danipko@microsoft.com
Dave Thaler
Microsoft
One Microsoft Way
Redmond, WA
USA
Email: dthaler@microsoft.com
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