slide title in capitals 50 pt slide subtitle 32 pt simple dna draft-krishnan-dna-simple-03 suresh...
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Slide titleIn CAPITALS
50 pt
Slide subtitle 32 pt
Simple DNAdraft-krishnan-dna-simple-03
Suresh Krishnan
Greg Daley
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© 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