Chapter 4 : OSI - Transport Layer

Which characteristics are part of TCP? (choose two) a. Reliable b. Connectionless c. No flow control d. Resends anything not received

A & D. TCP is reliable , connection - oriented protocol.

What is the purpose of sequence numbers?

A sequence number allows the transport layer function on the destination host to reassemble segments in the order in which they were transmitted.

Why does TCP use a sequence number in the header? a. to reassemble the segments into data b. to identify the application layer protocol c. to indicate the number of the next expected byte d. to show the maximum numbers of bytes allowed during a session

A. Sequence numbers are used in the TCP headers because segments could arrive at their destination in a different order than when they were sent. The numbers allow the receiving host to reassemble them in the proper order.

What are the transport layer's responsibility?

Answers could vary and could include a) keeping track of the individual conversations making place between applications on the source and destination hosts, b) segmenting data and adding a header to identify and manage each segment, c) using the header information to reassemble the segments into application data, and d) passing the assembled data to the correct application.

Which number is used by HTTP? a. 23 b. 80 c. 53 d. 110

B. Port 80 is the standard port number used with HTTP. Port 23 is Telnet, port 20 is FTP, and port 110 is POP3.

Which port number is used with SMTP? a. 20 b. 23 c. 25 5. 143

C. Port 25 is used for SMPTP.

At the transport layer, which of the following controls is used to keep a transmitting host from overflowing the buffers of a receiving host? a. best effort b. encryption c. flow control d. congestion avoidance

C. TCP used flow control to avoid buffer overflows.

During data transfer, what is the receiving host responsible for? (Choose the best two answers) a. encapsulation b. bandwidth c. segmentation d. acknowledgment e. reassembly

D & E. The receiving host has to acknowledge recipes of the packets and then reassemble them in the right order.

Which of the following determines how much data a sending host running TCP/IP can transmit before it must receive an acknowledgment? a. segment size b. transmission rate c. bandwidth c. window size

D. In TCP, window size is used to manage flow control.

End systems use port numbers to select the proper application. What is the lowest port number that can be dynamically assigned by the host system? a. 1 b. 128 c. 256 d. 1024

D. Port numbers 0 to 1023 are well - known ports. Port numbers 1024 to 49151 are the registered ports and are used by the host for dynamic port allocation. Port numbers 49152 to 65535 are the private and dynamic ports.

What is the purpose of TCP/UDP port numbers? a. to indicate the beginning of a three-way hand shake b. to reassemble the segments into the correct order c. to identify the number of data packets that can be sent without acknowledgment d. to track the different conversations crossing the network at the same time

D. Port numbers allow you to track multiple conversations generated by the same host using the same IP address.

List three network applications that use UDP.

DNS, video streaming, Voice over IP (VoIP)

in networking terms, what is reliability?

Reliability means ensuring that each segment that the source sends arrives at the destination.

What does segmentation provide to communications?

Segmentation of the data, in accordance with transport layer protocols, provides the means to both send and receive data when running multiple applications concurrently on a computer.

What is contained in the header of each segment or datagram?

The source and destination port number.

List three network applications that use TCP.

Web browsing, e-mail, file transfer.