draft-ietf-6man-resilient-rs-01.txt   draft-ietf-6man-resilient-rs-02.txt 
6man Working Group S. Krishnan 6man Working Group S. Krishnan
Internet-Draft Ericsson Internet-Draft Ericsson
Intended status: Standards Track D. Anipko Updates: RFC4861 (if approved) D. Anipko
Expires: November 7, 2013 D. Thaler Intended status: Standards Track D. Thaler
Microsoft Expires: April 24, 2014 Microsoft
May 6, 2013 October 21, 2013
Packet loss resiliency for Router Solicitations Packet loss resiliency for Router Solicitations
draft-ietf-6man-resilient-rs-01 draft-ietf-6man-resilient-rs-02
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. Furthermore, on some links, unsolicited multicast Solicitations. Furthermore, on some links, unsolicited multicast
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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 November 7, 2013. This Internet-Draft will expire on April 24, 2014.
Copyright Notice Copyright Notice
Copyright (c) 2013 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
(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
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1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Conventions used in this document . . . . . . . . . . . . . 3 1.1. Conventions used in this document . . . . . . . . . . . . . 3
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. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6
8.1. Normative References . . . . . . . . . . . . . . . . . . . 5 8.1. Normative References . . . . . . . . . . . . . . . . . . . 6
8.2. Informative 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
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The generic scenario is that the interface on the host comes up The generic scenario is that the interface on the host comes up
before it gets access to a router. Examples include: before it gets access to a router. Examples include:
a. The host is connected to a bridged residential gateway over a. The host is connected to a bridged residential gateway over
Ethernet or WiFi. LAN connectivity is achieved at interface Ethernet or WiFi. LAN connectivity is achieved at interface
initialization, but the upstream WAN connectivity is not active initialization, but the upstream WAN connectivity is not active
yet. In this case, the host just gives up after the initial RS yet. In this case, the host just gives up after the initial RS
retransmits. retransmits.
b. Access networks/links that turn off periodic RAs and only send b. Access networks/links that turn off periodic RAs and only send
RAs in response to RSs. In this case, if the link between the AP RAs in response to RSs. In this case, if the link between the
and the host comes up before the link between the AP and the Access Point (AP) and the host comes up before the link between
Controller/Router, the host will never be able to connect. the AP and the Controller/Router, the host will never be able to
connect. This technique of turning off periodic RAs is commonly
used in several wireless LAN and datacenter networks to reduce
the amount of multicast traffic.
c. Links that are not multicast capable. In this case, sending an c. Links that are not multicast capable. In this case, sending an
RA can only be triggered by an RS (as is the case, for instance, RA can only be triggered by an RS (as is the case, for instance,
on ISATAP [RFC5214] links). on ISATAP [RFC5214] links).
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
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by [RFC4861] and the maximum retransmission time MRT was chosen to be by [RFC4861] and the maximum retransmission time MRT was chosen to be
in line with the new value of SOL_MAX_RT as specified by [SOLMAXRT]. in line with the new value of SOL_MAX_RT as specified by [SOLMAXRT].
This is to ensure that the short term behavior of the RSs is similar This is to ensure that the short term behavior of the RSs is similar
to what is experienced in current networks, and longer term to what is experienced in current networks, and longer term
persistent retransmission behavior trends towards being similar to persistent retransmission behavior trends towards being similar to
that of DHCPv6 [RFC3315] [SOLMAXRT]. that of DHCPv6 [RFC3315] [SOLMAXRT].
2.1. Stopping the retransmissions 2.1. Stopping the retransmissions
On multicast-capable links, the hosts following this specification On multicast-capable links, the hosts following this specification
MUST stop retransmitting the RSs when an RA that results in a default MUST stop retransmitting the RSs when Router Discovery is successful
route is received. If an RA is recieved from a router and it does (i.e. an RA with a non-zero Router Lifetime that results in a default
not result in a default route the host MUST continue retransmitting route is received). If an RA is recieved from a router and it does
the RSs. not result in a default route (i.e. Router Lifetime is zero) the
host MUST continue retransmitting the RSs.
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. 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
mechanism specified in Section 8.3.4. of ISATAP [RFC5214] unicasts
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 MAY provide a configuration
option to enable or disable the use of such potentially infinite option to enable or disable the use of such potentially infinite
retransmissions. If the implementation provides such a configuration retransmissions. If the implementation provides such a configuration
option, it MUST be able to enable/disable retransmissions on a per- option, it MUST be able to enable/disable retransmissions on a per-
interface basis. interface basis.
4. Known Limitations 4. Known Limitations
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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].
7. Acknowledgements 7. Acknowledgements
The author would like to thank Steve Baillargeon, and Erik Kline for The author would like to thank Steve Baillargeon, Erik Kline, Andrew
their reviews and suggestions that made this document better. Yourtchenko, and Ole Troan for their reviews and suggestions that
made this document better.
8. References 8. References
8.1. 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.
[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,
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