You have a web browser with two windows open each viewing a different web page. These two web pages are hosted on the same web server. Give one set of possible values for the source and destination port numbers and IP addresses for each of the two socket connections (one connection for each web page). For example: connection 1: src-129.127.6.24, dest-129.127.8.52, src-3456, dest-7892 (note this is *not* a correct answer, it’s just to show the format to write your answer in)
Try an answer before revealing the guidance below.
Key Concepts
- TCP four-tuple
- Ephemeral source port
- Well-known port 80
- Connection demultiplexing
Answer Approach
- Decide which values are the same for both connections (client IP, server IP).
- Pick the server’s well-known destination port.
- Make the connections distinguishable through the client’s source port.
Full Answer
Answer status: Draft answer (unofficial). Revision notes, not an official marking scheme.
Example: connection 1: src-129.127.6.24, dest-203.0.113.10, src-50001, dest-80; connection 2: src-129.127.6.24, dest-203.0.113.10, src-50002, dest-80. Both connections share the client and server IP addresses and the server’s port 80; the browser uses a different ephemeral source port for each, so the four-tuples differ and the server can demultiplex them to separate sockets.
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