Chapter 3, Problem R1RQ

a)

Explanation of Solution

Step-by-step process of designing the simplest possible transport-layer protocol:

The STP (Simple Transport Protocol) takes for the process. The protocol takes the data not exceeding 1196 bytes at the sender side.

• The protocol accepts the four byte destination port number, host address, and a destination port address as a chunk which is not exceeding 1196 bytes.
• STP adds a four-byte header to each chunk and puts the port number of the destination in this header.
• The protocol then gives the destination host address and the resulting segment to the network layer.
• After receiving the address and segment, the network layer send the segment to STP at the destination host.
• STP then examines the segment and observes its port number and then the protocol extracts the data from the segment.
• The extracted data passes to the process of identified port number.

b)

Explanation of Solution

Modification:

Consider the segment has two header fields: one is “source port field” and another one is “destination port field”.

• At the source side, STP accepts the chunk of data which is not exceeding 1192 bytes. The data has destination host address, source port number, and a destination port number.
• Then, STP creates a segment which has application data, source port number, and destination port number.
• After creating segment, STP gives the two values to the network layer. They are: segment and destination port number.
• Then the STP receives host address and provides the process the source port number and the application data.

c)

Explanation of Solution

“No”, the transport layer does not do anything in the core of the computer network.

Explanation:

The reason is that the transport layer “lives” in the end systems.