[lwip-users] Re: [lwip] A couple quick lwIP questions

[John C. Toman]

Hi Marc,

Having done an lwIP port myself I think I can answer your two questions.

The answer to #2 is: uIP isn't going to be appropriate for you, because 
it doesn't contain a UDP implementation (it's TCP only).

In response to #1: If you're not using TCP or DHCP or a like protocol 
... you don't need any timers whatsoever. Another reason you might need 
a timer in your case is if you need to maintain the ARP cache, but this 
doesn't sound necessary because your system will be a server and won't 
make any client connections. In the server case, lwIP harvests all the 
ARP information it needs from the incoming connection packets and thus 
remains up to date.

The sole reason I could see a need for a timer for your application (as 
you've described it) is if you are implementing any kind of UDP packet 
retransmit capability for your protocol.

Hope this helps,

John

Marc Wells wrote:

>We have a need to implement a high speed network
>interface on an embedded processor and I've been
>looking into lwIP.  I'm hoping someone like Adam,
>Florian or Paul who is very familiar with the system
>can answer a couple of quick questions for me.
>
>We need to implement only UDP, TCP/IP is overkill
>for our purposes.  Our target system will likely be
>a PowerPC with 64MB of memory running a proprietary
>operating system.  The embedded system will act
>strictly as a server responding to packets sent by a
>remote client.
>
>My questions:
>
>1. Given the constraints (specifically, no TCP) is it
>   possible to run the lwIP code with no timers?  We
>   need all transactions be interrupt driven and don't
>   want to spend the overhead for timers.
>
>2. Would uIP be a reasonable candidate?  Code space
>   is not an issue for us but latency and code complexity
>   are.
>
>Thanks for taking the time to help me out with this,
>
>     Marc Wells
>     Credence Systems Corp.
>     Hillsboro, OR  USA
>     address@hidden
>
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