Re: [lwip-devel] Question on comparations of sequence numbers

[Simon Goldschmidt]

narke <address@hidden> wrote:

> I mean, just for example, if the sequence number space is only 2 bit,
> then we have only 0, 1, 2, 3 as valid sequence numbers, right?  And,
> if current sequence number is 3, so the next one must be 0 ( 0 = 3 + 1
> mod 4), right?.
> 
> Well, now assume SND.UNA = 3 and SND.WND = 3, so the send window is 3,
> 0, 1 or [3, 1].   In this example, 0 is in the window and a = 3, b =
> 1, but a <= 0 <= b does not hold.
> 
> Okay, here the biggest possbile window size is 4.

OK, so now I understand. In that case, note that your example doesn't really 
hold: in real life, the maximum window size is 16 bit (unsigned) while our 
macros cast to 32 bit (signed!), so your a<=0<=b isn't really correct as it 
doesn't take care for the data types.

Simon