fragmented IP or UDP packets.
It may also be related to "path MTU discovery" (or lack thereof). If you set the MTU lower on one box that all these WLAN clients' traffic goes through (before the database server), and they do path MTU discovery, they should automatically lower their own MTUs to match. I'd try it on one or the other of those "Cisco things".
As far as Google not having to adjust their MTU, that's because your router probably handles the second fragment of a fragmented IP packet properly, i.e. it doesn't drop it on the floor.
(When you try to send a packet larger than a link's MTU, that link is supposed to fragment the packet. But secondary IP fragment(s) don't have the UDP or TCP header in them, so a lot of dumb -- or just improperly-configured; in this case, I wouldn't call Cisco dumb -- firewalls don't handle them properly because they don't match any allow rule.) |
