draft-ietf-dna-simple-16.txt   draft-ietf-dna-simple-17.txt 
Network Working Group S. Krishnan Network Working Group S. Krishnan
Internet-Draft Ericsson Internet-Draft Ericsson
Intended status: Standards Track G. Daley Intended status: Standards Track G. Daley
Expires: February 11, 2011 NetStar Networks Expires: February 26, 2011 NetStar Networks
August 10, 2010 August 25, 2010
Simple procedures for Detecting Network Attachment in IPv6 Simple procedures for Detecting Network Attachment in IPv6
draft-ietf-dna-simple-16 draft-ietf-dna-simple-17
Abstract Abstract
Detecting Network Attachment allows hosts to assess if its existing Detecting Network Attachment allows hosts to assess if its existing
addressing or routing configuration is valid for a newly connected addressing or routing configuration is valid for a newly connected
network. This document provides simple procedures for detecting network. This document provides simple procedures for detecting
network attachment in IPv6 hosts, and procedures for routers to network attachment in IPv6 hosts, and procedures for routers to
support such services. support such services.
Status of this Memo Status of this Memo
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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 February 11, 2011. This Internet-Draft will expire on February 26, 2011.
Copyright Notice Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the Copyright (c) 2010 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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detecting network attachment (Simple DNA) that has the following detecting network attachment (Simple DNA) that has the following
characteristics. characteristics.
o Routers do not have to be modified to support this scheme. o Routers do not have to be modified to support this scheme.
o The most common use cases are optimized. o The most common use cases are optimized.
o In the worst case, detection latency is equal to that of standard o In the worst case, detection latency is equal to that of standard
neighbor discovery so that performance is never degraded. neighbor discovery so that performance is never degraded.
o False positives are not acceptable. A host MUST NOT wrongly o False positives are not acceptable. A host must not wrongly
conclude that it has reattached to a previouly visited network. conclude that it has reattached to a previouly visited network.
o False negatives are acceptable. A host MAY fail to identify a o False negatives are acceptable. A host may fail to identify a
previously visited link correctly and attempt to acquire fresh previously visited link correctly and attempt to acquire fresh
addressing and configuration information. addressing and configuration information.
2.2. Applicability 2.2. Applicability
The Simple DNA protocol provides substantial benefits over standard The Simple DNA protocol provides substantial benefits over standard
neighbor discovery procedures [RFC4861] in some scenarios and does neighbor discovery procedures [RFC4861] in some scenarios and does
not provide any benefit at all in certain other scenarios. This is not provide any benefit at all in certain other scenarios. This is
intentional as Simple DNA was designed for simplicity rather than intentional as Simple DNA was designed for simplicity rather than
completeness. In particular, the Simple DNA protocol provides completeness. In particular, the Simple DNA protocol provides
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valid. The Simple DNA protocol follows an alternate approach where valid. The Simple DNA protocol follows an alternate approach where
it relies on probing each previously known router to determine it relies on probing each previously known router to determine
whether to use information learnt from THAT router. This allows whether to use information learnt from THAT router. This allows
simple DNA to probe routers learnt from multiple earlier attachments simple DNA to probe routers learnt from multiple earlier attachments
to optimize movement between a known set of links. to optimize movement between a known set of links.
2.4. DNA Overview 2.4. DNA Overview
Detecting Network Attachment is performed by hosts after detecting a Detecting Network Attachment is performed by hosts after detecting a
link-layer "up" indication. The host uses a combination of unicast link-layer "up" indication. The host uses a combination of unicast
Neighbor Solicitations (NSs), multicast Router Solicitations (RSs) Neighbor Solicitations (NSs) and multicast Router Solicitations (RSs)
and DHCPv6 message exchanges in order to determine whether previously in order to determine whether previously encountered routers are
encountered routers are present on the link, and if they are not, present on the link, in which case an existing configuration can be
acquire the new configuration information. reused. If previously encountered routers are not present then
either IPv6 Stateless Address Autoconfiguration and/or DHCPv6 is used
for configuration.
Hosts implementing simple DNA may also send DHCPv6 packets, as Hosts implementing simple DNA may also send DHCPv6 packets, as
described in Section 5.5.4. Since simple DNA does not modify the described in Section 5.5.4. Since simple DNA does not modify the
DHCPv6 protocol or state machine, the operation of DHCPv6 is DHCPv6 protocol or state machine, the operation of DHCPv6 is
unchanged. unchanged.
Routers that follow the standard neighbor discovery procedure Routers that follow the standard neighbor discovery procedure
described in [RFC4861] will delay the router advertisement by a described in [RFC4861] will delay the router advertisement by a
random period between 0 and MAX_RA_DELAY_TIME (defined to be 500ms) random period between 0 and MAX_RA_DELAY_TIME (defined to be 500ms)
as described in Section 6.2.6 of [RFC4861]. In addition, consecutive as described in Section 6.2.6 of [RFC4861]. In addition, consecutive
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associate the address with the routers on link. The host MUST create associate the address with the routers on link. The host MUST create
one SDAT entry for each of the on-link routers associated with the one SDAT entry for each of the on-link routers associated with the
DHCPv6 assigned address. DHCPv6 assigned address.
5.3. Steps involved in detecting link change 5.3. Steps involved in detecting link change
The steps involved in basic detection of network attachment are: The steps involved in basic detection of network attachment are:
o Link-Layer Indication o Link-Layer Indication
o Sending of neighbor discovery and/or DHCPv6 probes o Sending of neighbor discovery probes
o Response gathering and assessment o Response gathering and assessment
These steps are described below. These steps are described below.
5.4. Link-Layer Indication 5.4. Link-Layer Indication
In order to start Detection of network attachment procedures, a host In order to start Detection of network attachment procedures, a host
typically requires a link-layer indication that the medium has become typically requires a link-layer indication that the medium has become
available [RFC4957]. available [RFC4957].
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Where unicast Neighbor Solicitations and Router Solicitations are Where unicast Neighbor Solicitations and Router Solicitations are
sent in parallel, one strategy is to forsake retransmission of sent in parallel, one strategy is to forsake retransmission of
Neighbor Solicitations and to allow retransmission only of Router Neighbor Solicitations and to allow retransmission only of Router
Solicitations or DHCPv6. In order to reduce competition between Solicitations or DHCPv6. In order to reduce competition between
unicast Neighbor Solicitations and Router Solicitations and DHCPv6 unicast Neighbor Solicitations and Router Solicitations and DHCPv6
retransmissions, a DNAv6 implementation that retransmits may utilize retransmissions, a DNAv6 implementation that retransmits may utilize
the retransmission strategy described in the DHCPv6 specification the retransmission strategy described in the DHCPv6 specification
[RFC3315], scheduling DNAv6 retransmissions between Router [RFC3315], scheduling DNAv6 retransmissions between Router
Solicitations or DHCPv6 retransmissions. Solicitations or DHCPv6 retransmissions.
If a response is received to any unicast Neighbor Solicitation or If a response is received to any unicast Neighbor Solicitation,
Router Solicitation message, pending retransmissions MUST be pending retransmissions of the same MUST be canceled. A Simple DNA
canceled. A Simple DNA implementation SHOULD NOT retransmit a implementation SHOULD NOT retransmit a Neighbor Solicitation more
Neighbor Solicitation more than twice. To provide damping in the than twice. To provide damping in the case of spurious Link Up
case of spurious Link Up indications, the host SHOULD NOT perform the indications, the host SHOULD NOT perform the Simple DNA procedure
Simple DNA procedure more than once a second. more than once a second.
6. Pseudocode for Simple DNA 6. Pseudocode for Simple DNA
/* Link up indication received on INTERFACE */ /* Link up indication received on INTERFACE */
/* Start Simple DNA process */ /* Start Simple DNA process */
/* Mark All Addresses as inoperable */ /* Mark All Addresses as inoperable */
Configured_Address_List=Get_Address_List(INTERFACE); Configured_Address_List=Get_Address_List(INTERFACE);
foreach Configured_Address in Configured_Address_List foreach Configured_Address in Configured_Address_List
{ {
 End of changes. 8 change blocks. 
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