The TCP data transfer

The HTTP connection itself lasts much longer than everything we've seen so far, but everything past the three-way TCP handshake is boring. Figure 16-26 illustrates the exchange, which consists of a series of packets in the following pattern:

1. An 802.11 Data frame containing a maximum-sized TCP segment from the web server, carrying data from TCP port 80 on the server to the random high-numbered port chosen by the client. The frame's source address is the default router, but its transmitter address is the access point.

2. An 802.11 acknowledgment from the client to the access point to acknowledge receipt of the frame in step 1.

3. An 802.11 Data frame carrying a TCP acknowledgment from the client to the server acknowledges the receipt of the data in the frame in step 1. However, the acknowledgment in this step is a TCP segment, which is higher-layer data to the MAC layer. The source MAC address of this frame is the client, and the destination MAC address is the default router. However, the default router is on a wired Ethernet, and an access point is required for bridging, so the receiver address is the MAC address of the wireless interface in the access point.

4. The access point sends an 802.11 acknowledgment for the frame in step 3 to the client.

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