Transcript IP Address Autoconfiguration for Ad Hoc Networks

IP Address Autoconfiguration for
Ad Hoc Networks
Presented by
William List
References
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
[1] “IP Address Autoconfiguration for Ad Hoc
Networks” (work in progress) draft-ietf-manetautoconf-01.txt, November 2001
[2] “IPv6 Stateless Autoconfiguration” RFC
1971, December 1998
[3] “Dynamic Configuration of IPv4 Link-Local
Addresses” (work in progress) draft-ietfzeroconf-ipv4-linklocal-07.txt, August 2002
Problem
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Methods for IP address autoconfiguration on a
fixed network assume that an address is
unique for a single link [2,3]
In an ad hoc network, a mobile node’s IP
address must be unique across several links,
or hops [1].
–
Need to be able to perform Duplicate Address
Detection (DAD) within the ad hoc cloud
Solution
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IPv4
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–
Select an address
Use two new ICMP packets to check for duplicates
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AREQ and AREP
IPv6
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–
Select an address
Use two modified NDP messages to check for
duplicates
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AREQ and AREP (Solicitation and Advertisement)
Selecting an Address (IPv4)
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Divide 169.254/16 network into ranges
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–
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Select a tentative address from the first range
Select a temporary address from the second range
Using the temporary address
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Broadcast an ICMP AREQ message
The tentative address is placed in the Requested
IPv4 Address field
Set ADDRESS_DISCOVERY timer
IPv4 Address Request and Reply
Address Request
0
1
2
3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
Type
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Reserved
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+---------------+---------------+---------------+---------------+
|
Originator’s IPv4 Address
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+-------------------------------+-------------------------------+
|
Requested IPv4 Address
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+-------------------------------+-------------------------------+
Address Response
0
1
2
3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
Type
|
Reserved
|
+---------------+---------------+---------------+---------------+
|
Requested IPv4 Address
|
+-------------------------------+-------------------------------+
Processing AREQs
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Previously processed requests are discarded
Create reverse routing entry using the
temporary address
If Own IP address = Requested address
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Send a AREP
Else
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Rebroadcast AREQ to neighbors
Processing AREPs
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If an AREP is received, the address is a
duplicate
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Pick a new address and try again
If no AREP is heard before timeout
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Try again for AREQ_RETRIES times
If no response, then the address is unique in the ad
hoc network
Drawbacks
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Must include handling code for new ICMP
message type
How long to wait for replies?
Network partitioning and joining
Selecting an Address (IPv6)
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Cannot use link-local prefixes
–
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If no other prefix is available
–
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Use MANET_PREFIX + EUI 64 identifier
Generate a temporary address for AREQAREP exchange
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Multiple hops in an ad hoc network
Use MANET_INITIAL_PREFIX
Broadcast AREQ to all-nodes mcast address
IPv6 Address Request and Reply
Address Request
0
1
2
3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
Type
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Code
|
Checksum
|
+---------------+---------------+---------------+---------------+
|M|
Reserved
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+-------------------------------+-------------------------------+
|
Requested IPv6 Address
|
+
Address Response
0
1
2
3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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Type
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Code
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Checksum
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+---------------+---------------+---------------+---------------+
|R|S|O|M|
Reserved
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+-------------------------------+-------------------------------+
|
Requested IPv6 Address
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+
Processing AREQs
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Same rules as for IPv4
Send AREP AREP_ADDRESS_RETRIES
times to increase robustness
Can be returned to the source using link-local
address if necessary
Processing AREPs
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If AREP is received, interface must be disabled
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Manual configuration necessary
No response heard
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IP address is valid
Other prefixes can be discovered using special
gateways (next week!)