Question

In a TCP connection, assume that maximum segment size (MSS) is 1000 bytes. The client process has 5400 bytes to send to the server process, which has no bytes to respond (unidirectional communication). The TCP server generates ACKs according to the rules we discussed in the text. Show the time line for the transactions during the slow start phase, indicating the value of cwnd at the beginning, at the end, and after each change. Assume that each segment header is only 20 bytes.

Answer 1

During the slow start phase of a TCP connection with an MSS of 1000 bytes, the client sends segments in increasing quantities and the server responds with ACK segments. The cwnd (congestion window) value starts with 1 segment and doubles after each round of transmission. The timeline illustrates this process.

Step-by-step explanation:

Time line for the transactions during the slow start phase:

1. First Round:

• The client sends the first segment with 1000 bytes of data and 20 bytes of header.
• The server responds with an ACK segment with 20 bytes of header.

2. Second Round:

• The client sends two segments each with 1000 bytes of data and 20 bytes of header.
• The server responds with two ACK segments each with 20 bytes of header.

3. Third Round:

• The client sends four segments each with 1000 bytes of data and 20 bytes of header.
• The server responds with four ACK segments each with 20 bytes of header.
  

4. Fourth Round:

• The client sends eight segments each with 1000 bytes of data and 20 bytes of header.
• The server responds with eight ACK segments each with 20 bytes of header.

cwnd at the beginning: 1 segment = 1000 bytes

cwnd at the end: 8 segments = 8000 bytes

cwnd after each change: 1 segment, 2 segments, 4 segments, 8 segments.