> I am using lwIP 1.3.0 and it works great, but I've always wondered where > there's an approx. three second delay after the ARP response before lwIP > sends the SYN. In other words: > > 1. I initiate a TCP connection > 2. lwIP sends an ARP request almost immediately > 3. The host responds (relatively) immediately > 4. lwIP waits about three seconds before sending the SYN > > When the MAC is in the ARP cache, this doesn't happen, but still, what is > it doing during that time? Incidentally, I've noticed uIP does the same.
I guess the three seconds delay is a TCP timeout, i.e. TCP re-sends the SYN after three seconds. This is because the initial packet gets dumped because the target MAC is unknown. In contrast to uIP, lwIP has a feature called ARP queueing: if a target MAC is unknown, packets are not thrown away but held back until the ARP response arrives. This must not beturned off via the corresponding define (ARP_QUEUEING, MEMP_NUM_ARP_QUEUE defines how many packets may be queued) in your lwipopts.h! Simon -- GRATIS für alle GMX-Mitglieder: Die maxdome Movie-FLAT! Jetzt freischalten unter http://portal.gmx.net/de/go/maxdome01 _______________________________________________ lwip-users mailing list [email protected] http://lists.nongnu.org/mailman/listinfo/lwip-users
