Slide title In CAPITALS 50 pt Slide subtitle 32 pt Simple DNA draft-krishnan-dna-simple-03 Suresh Krishnan Greg Daley

Slide titleIn CAPITALS

50 pt

Slide subtitle 32 pt

Simple DNAdraft-krishnan-dna-simple-03

Suresh Krishnan

Greg Daley

Top right corner for field-mark, customer or partner logotypes. See Best practice for example.

Slide title 40 pt


Text 24 pt

Bullets level 2-520 pt

© Ericsson AB 2008 Simple DNA 2008-03-122

Background

Hosts require procedures to simply and reliably identify if they have moved to a different IP network to the one which they have been recently connected.

In order to detect change, router and neighbor discovery messages are used to collect reachability and configuration information.

This information is used to detect whether the existing router and address prefixes are likely to be present.


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Characteristics of Simple DNA

Routers do not have to be modified to support this scheme.

Handle only the simplest and most likely use cases. Work at least as quickly as standard neighbor

discovery (RFC4861). False positives are not acceptable. A host should not

conclude that there is no link change when there is one False negatives are acceptable. A host can conclude

that there is a link change when there is none


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Applicability

Works well when hosts move between a known set of links

Does not provide much improvement when a host moves to a completely new link

– Link detection is just as good as standard neighbor discovery (never slower)

– Fast unicast RAs can make a difference here, but are not mandated


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Steps in Simple DNA

A. Link-Layer Indication

B. Probing

C. Response gathering and assessment

D. Optimistic DAD

E. Verify other configuration (not in draft yet)


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Link layer indication

The host receives a link-layer indication that the medium has become available

This indication starts up the Simple DNA process Host marks all current addresses as Optimistic Host also marks all the default router neighbor cache

entries as STALE


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Simple DNA table (SDAT)

The host maintains a table called the simple DNA table The table contains at least the following information

IPv6 Address

Valid

Lifetime

Prefix Link local address of Router

Link layer (MAC) address of router

DUID for DHCPv6 assigned address


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Probing

The host sends an RS to the All-routers multicast address

– The source address is a link local address– The address is in Optimistic state– The MAC address is inside a tentative option– Only 1 RS irrespective of the number of addresses the host

possesses

The host sends one or more unicast NSs to routers in the SDAT

The RS and the NSs are sent in parallel– This is required to have a worst case scenario to be no

worse than standard ND


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Response gathering and assesment NA is received from a previously known router

– Host verifies if both the link local ipv6 address AND the MAC address match

– If they match, the host uses all the addresses related to the router in the SDAT (unless an RA is received)

RA is received from a previously known router (probed using NS)

– Verify if the prefixes present in SDAT are present in the RA– If they are, continue to use them– If they are not, remove them from the SDAT

RA is received from a previously unknown router– Follow standard ND/SLAAC procedure for the prefixes

present in the RA. – No modifications to the SDAT


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Optimistic DAD

After the addresses are confirmed as usable either by an NA or an RA

– Verify whether the addresses are still unique Use Optimistic DAD

– Rejoin solicited node multicast addresses


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Pending work

Add an applicability section Always use a link local address as the source of NS/RS Confirm DHCP assigned addresses

– DUID exists in Simple DNA table– Should we specify the procedure in this document or a

different one?

Describe default router (re)selection procedure Clarify some unclear text Invent a new word than means valid

Documents

Slide title In CAPITALS 50 pt Slide subtitle 32 pt Simple DNA draft-krishnan-dna-simple-03 Suresh Krishnan Greg Daley