Re: [lwip-users] Re-Transmission from PC is ignored due to sequence number

[address@hidden]

On 23.04.2018 17:18, Patrick Klos wrote:
> [..]
> > Thinking about the retransmission from PC side:
> > Shouldn't lwip also do a retransmission of the lost frame?
> > You know, these bytes never get acknowledged by PC.
> Yes, the LwIP side should have retransmitted the packet.  Packet 21 of
> the trace file shows an ACK of 00009b45, so even though the LwIP device
> thought it sent a response to the PC (bumping the ACK to 00009b56), LwIP
> should have noticed that and resent the data from the previous packet.

On what basis do you say that? Retransmissions are triggered mainly in 
two ways:
a) timeout (this did not happen here)
b) dup-acks: a fast retansmission is done if 2 duplicate acks are 
receiver (i.e. three times the same ACK). This is not the case here, we 
just received the 2nd ACK.

I'm still saying lwIP is correct.

Simon