Question

List the four broad classes of services that a transport layer protocol can provide. For each of the service classes, indicate if either udp or tcp (or both) provides such a service.

Answer 1

Answer:

1. Reliability:

In TCP: TCP is a connection-oriented protocol.

• When a data file or message is sent from source to destination, there is a guarantee that a packet will be delivered until the connection does not fail.

• The data transfer between client and server in the form of reliable byte stream. Therefore, TCP is reliable.

Answer 2

Following are four broad classes of services that are applicable to both TCP and UDP protocols:

Explanation:

1. Reliability:

• In TCP:  

• When a message or data file is sent from source to destination, there is an assurance that a packet will be delivered lest the connection doesn’t fail.

• The data transmission between user and server is in the form of a reliable byte stream. Hence, TCP is reliable.

• In UDP:  

• When the message or data file is transmitted from source to destination there is no likelihood for assured delivery to destination.

• The data transfer is not feasible in the configuration of the byte stream in the case of UDP. Hence, UDP is unreliable.

2. Ordering of data:

• In TCP:  

• TCP protocol dispenses the packets in a defined order. The source transfers the second packet only after the first packet is collected at the destination. Therefore, TCP follows the ordered transmission of packets.

• In UDP:  

• UDP protocol doesn’t transmit the packets in order. The delivery of packets from the source to destination follows no definite order. Therefore, UDP follows unordered transmission.

3. Constant Throughput:

• In TCP:  

• The productivity for TCP protocol is much more than productivity for UDP protocol because TCP is reliable.

• There is surety for continuous output in TCP protocol.  

• In UDP:  

• The Productivity for UDP protocol is less than productivity for TCP protocol because UDP is unreliable.

• There is surety for continuous throughput in UDP protocol as well.

4. Timing:

• In TCP:  

• A definite number of holdups occur in receiving a response from the receiver to the user because it is connection-oriented. That means no jitter takes place in TCP.

• If packets are sent by the client but not received any response, then the client waits for timeout termination and retransmits the same packet to the receiver. Thus, the TCP protocol assures the timing services.

• In UDP:  

• UDP is a connection-less protocol and does not send any response upon receiving the packets.

• Consequently, there is no time delay in receiving responses. But the user does not know whether the packet was dropped or deferred. Thus, UDP protocol assures the timing property but it does not give the surety that the packet is delayed or not.