Topology: Client ----- Intermediate Device ----- Server Client: win7 Intermediate Device: unknown Server: CentOS 5.8 The problem occurs when the client and server are trying to establish a SSL connection. It happens to one specific port, 2000. I haven't been able to replicate the problem with other port numbers. I captured packets on both client and server. After the TCP handshake, from the client's perspective, it's not receiving ACKs for its previously sent packets so it kept re-sending them. On the server side, however, it did receive those packets and sent ACK packets. The weird thing is, after the server sent those ACKs, it received a [RST, ACK] packet, from the intermediate device, for every packet it sent. What could be the cause?