Author Topic: Support for AUTOIP  (Read 3380 times)

Offline mhoneywill

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Support for AUTOIP
« on: March 25, 2010, 11:13:31 AM »
Hi Mark,

How difficult would it be for uTasker to support AUTOIP IP address allocation, when in DHCP mode. So if a DHCP server cannot be found the board will fall back to a Fixed IP address, if defined, or if the fixed IP address is defined as an AUTOIP address in the range 169.254.x.x would be chosen.

LWIP has an AUTOIP module which might give some implementation idea's

Also the standard is defined here

The process looks fairly simple and seems to consist of using the ARP protocol to test and broadcast addresses. Combined with NETBIOS names this would make uTasker able to setup its own IP address very easily.



Offline mark

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Re: Support for AUTOIP
« Reply #1 on: March 26, 2010, 02:27:00 PM »
Hi Martin

If I am not mistaken, this is equivalent to (or a part of) Zero Configuration Networking based on the use of "Dynamic Configuration of IPv4 Link-Local Addresses". It is also related to IPV6's "Stateless Address Autoconfiguration".

In the case of IPV4, after reading the first half of the RFC, it seems fairly simple to allocate random link-local addresses and test and defend them according to the specification - DHCP does some similar testing for address collisions. To do it properly there are a number of things in the specification that need to be considered more, such as handling collision detection, giving up addresses, timeouts after various events are detected, and such.

The other question is how to best transition between the use of a routable address and the link-local address. The two shouldn't generally be used at the same time but during transition phases it does look as though it is possible.

Therefore I would estimate that assigning and using a link-local address would not be complicated. A larger amount of work would be required to handle all of the requirement according to the RFC in all circumstances, with some experience gathering in real application cases, whereby transition between the two modes, and especially phases where both could be in operation at the same time, could be a little trickier.



Offline aaronlawrence

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Re: Support for AUTOIP
« Reply #2 on: April 30, 2010, 12:50:17 AM »
Just to note, we will want this feature also - within about 1 year time frame.