draft-ietf-6man-resilient-rs-03.txt   draft-ietf-6man-resilient-rs-04.txt 
6man Working Group S. Krishnan 6man Working Group S. Krishnan
Internet-Draft Ericsson Internet-Draft Ericsson
Updates: RFC4861 (if approved) D. Anipko Updates: RFC4861 (if approved) D. Anipko
Intended status: Standards Track D. Thaler Intended status: Standards Track Unaffiliated
Expires: October 23, 2014 Microsoft Expires: April 17, 2015 D. Thaler
April 21, 2014 Microsoft
October 14, 2014
Packet loss resiliency for Router Solicitations Packet loss resiliency for Router Solicitations
draft-ietf-6man-resilient-rs-03 draft-ietf-6man-resilient-rs-04
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
Router Advertisements are never sent and the mechanism in this Router Advertisements are never sent and the mechanism in this
document is intended to work even in such scenarios. document is intended to work even in such scenarios.
Status of this Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on October 23, 2014. This Internet-Draft will expire on April 17, 2015.
Copyright Notice Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the Copyright (c) 2014 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 . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
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 . . . . . . . . . . . . . . . . . . . . . . . . . . 6 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
8.1. Normative References . . . . . . . . . . . . . . . . . . . 6 8.1. Normative References . . . . . . . . . . . . . . . . . . 5
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
transmitted by the host might be lost. transmitted by the host might be lost. e.g. The host is connected to
a bridged residential gateway over Ethernet or WiFi. LAN
The generic scenario is that the interface on the host comes up connectivity is achieved at interface initialization, but the
before it gets access to a router. Examples include: upstream WAN connectivity is not active yet. In this case, the host
just gives up after the initial RS retransmits.
a. The 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. Access networks/links that turn off periodic RAs and only send
RAs in response to RSs. In this case, if the link between the
Access Point (AP) and the host comes up before the link between
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
RA can only be triggered by an RS (as is the case, for instance,
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
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. In general, the delay may be unacceptable in some
scenarios. scenarios.
skipping to change at page 4, line 43 skipping to change at page 4, line 46
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
SHOULD stop retransmitting the RSs when Router Discovery is SHOULD stop retransmitting the RSs when Router Discovery is
successful (i.e. an RA with a non-zero Router Lifetime that results successful (i.e. an RA with a non-zero Router Lifetime that results
in a default route is received). Hosts MAY continue retransmitting in a default route is received). If an RA is recieved from a router
the RSs even after router discovery is successful. If the host and it does not result in a default route (i.e. Router Lifetime is
continues to retransmit RSs, it is RECOMMENDED that such zero) the host MUST continue retransmitting the RSs.
retransmissions be rate-limited to one every MRT. If an RA is
recieved from a router and it does 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. 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 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.
skipping to change at page 6, line 43 skipping to change at page 6, line 36
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
Dmitry Anipko Dmitry Anipko
Microsoft Unaffiliated
One Microsoft Way
Redmond, WA Phone: +1 425 442 6356
USA Email: dmitry.anipko@gmail.com
Phone: +1 425 703 7070
Email: danipko@microsoft.com
Dave Thaler Dave Thaler
Microsoft Microsoft
One Microsoft Way One Microsoft Way
Redmond, WA Redmond, WA
USA USA
Email: dthaler@microsoft.com Email: dthaler@microsoft.com
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