Chapter 9 - Computer Networks - Term 3 (SWQ)

What is the advantage of segmenting?

Enables many different communications, from many different users, to be interleaved (multiplexed) on the same network.

A client application needs to terminate a TCP communication session with a server. Discuss the termination process steps.

In order to terminate a TCP session, the client sends to the server a segment with the FIN flag set. The server acknowledges the client by sending a segment with the ACK flag set. The server sends a FIN to the client to terminate the server to client session. The client acknowledges the termination by sending a segment with the ACK flag set.

What is the reason of generating ISN at random?

Prevents some certain types of attacks.

PSH

Push Functions

RST

Reset the connection

What would be the order of the TCP segments, when they arrive at destination device?

Segments may arrive out of order.

Explain how the TCP connection is established?

Step 1 - The initiating client requests a client-to-server communication session with the server. Step 2 - The server acknowledges the client-to-server communication session and requests a server-to-client communication session. Step 3 - The initiating client acknowledges the server-to-client communication session.

Refer to the figure above to explain the steps needed to show how the TCP connection is established.

Step 1 - The initiating client requests a client-to-server communication session with the server. Step 2 - The server acknowledges the client-to-server communication session and requests a server-to-client communication session. Step 3 - The initiating client acknowledges the server-to-client communication session.

Characteristics of UDP

- Best effort delivery - Fast - Less overhead - Less load on network

Which of the following is a part of three-way-handshake?

- Establishes that the destination device is present on the network. - Verifies that the destination device is active and accepting requests on the destination port that the client intends to use. - Informs the destination that client intends to establish a communication session on that port.

Features of TCP

- Establishing a session to ensure the application is ready to receive the data - Lost segments are resent so the data is received completely - Same-order delivery to ensure segments are reassembled into the proper order - Flow control to ensure that the receiver is able to process the data being received - Reliable Delivery (TCP and UDP have nothing to do with IP Addresses so whenever a question relates them to IP Addresses as a feature, choose IP feature answer as not a feature)

Features of UDP

- No ordered data reconstruction - Unreliable delivery - Connectionless - No Flow Control

List the three basic operations of reliability with TCP.

- Numbering and tracking data segments transmitted to a specific host from a specific application - Acknowledging received data - Retransmitting any unacknowledged data after a certain period of time

TCP's basic operations

- Numbering and tracking data segments. - Acknowledging received segments. - Re-transmit any unacknowledged data.

TCP Header

- Source Port (16 bits) and Destination Port (16 bits)-Used to identify the application.• Sequence number (32 bits)-Used for data reassembly purposes.• Acknowledgment number (32 bits)-Indicates the data that has been received.• Header length (4 bits)-Known as ʺdata offsetʺ. Indicates the length of the TCP segment header.• Reserved (6 bits)-This field is reserved for the future.• Control bits (6 bits)-Includes bit codes, or flags, which indicate the purpose and function of the TCP segment.• Window size (16 bits)-Indicates the number of bytes that can be accepted at one time.• Checksum (16 bits)-Used for error checking of the segment header and data.• Urgent (16 bits)-Indicates if data is urgent

Discuss three of the transport layer responsibilities in the TCP/IP model.

-Tracking the individual communication streams between applications on the source and destination hosts - Segmenting data at the source and reassembling the data at the destination - Identifying the proper application for each communication stream through the use of port numbers - Multiplexing the communications of multiple users or applications over a single network - Managing the reliability requirements of applications

How many bits are reserved in TCP header to set the control flags?

6 bits

Which of the following TCP services ensures that the application is ready to receive the data? A.Establishing a session B.Same order delivery C.Reliable delivery D.Flow control E.Data reassembly

A

Which of the following TCP services prevents the need for retransmission of the data when the receiving host's resources are overwhelmed A.Flow control B.Same order delivery C.Reliable delivery D.Establishing a session E.Data reassembly

A

Which of the following data types is perfectly suited to UDP? A.Live video B.SMS C.Email messages D.Documents E.Numerical data

A

Which of the following is considered a reliable, full-featured transport layer protocol, which ensures that all of the data arrives at the destination A.TCP B.UDP C.IP D.TFTP E.DNS

A

What would be the ISN of the first segment?

A randomly generated number

ACK

Acknowledgement field significant

How many bytes of overhead does a TCP segment have? A.10 B.20 C.30 D.40 E.50

B

Which of the following is not true about UDP? A.It has much lower overhead than TCP because it's not connection-oriented B.Applications that use UDP are always unreliable C.It is very desirable for protocols that make simple request and reply transactions. D.It is not necessarily an inferior protocol used on the network E.It does not establish a connection before sending data

B

Which of the following is the proper way to representa socket on a web server if the web server Destination port was assigned 80? A.192.168.1.80 B.192.168.1.7:80 C.80:192.168 D.192:80 E.80

B

Explain the following statement. UDP provides the basic functions for delivering data segments between the appropriate applications, with very little overhead and data checking.

Because it is not connection-oriented and does not offer the sophisticated retransmission, sequencing, and flow control mechanisms that provide reliability.

Why does UDP provide low overhead data transport?

Because it is not connection-oriented and does not offer the sophisticated retransmission, sequencing, and flow control mechanisms that provide reliability.

Explain how TCP has the Same-Order Delivery feature

Because networks may provide multiple routes that can have different transmission rates, data can arrive in the wrong order. By numbering and sequencing the segments, TCP can ensure that these segments are reassembled into the proper order.

Which of the following is not a feature UDP required protocol properties? A.Fast B.No acknowledgment C.Resends lost data D.Delivers data as it arrives E.A and D

C

Which of the following is/are applications designed to use TCP? I.HTTP II.Email III.IP telephony A.I only B.II only C.I and II only D.I and III only E.I, II, III

C

Which of the following statements is not true about UDP overhead? I.Live video can tolerate some data loss with minimal effect, and are perfectly suited to UDP. II.UDP datagrams are sent as best effort by the transport layer protocol. III.UDP has a low overhead of 31 bytes. A.I only B.II only C.III only D.I and III only E.I, II, III

C

What does segmenting data means in computer networks?

Cutting the data into smaller chunks

For the following TCP/IP model, what is the right order of layers from top to bottom? A.Network Access >Transport>Application>Internet B.Transport>Application>Internet>Network Access C.Transport>Application>Network Access>Internet D.Application>Transport>Internet>Network Access E.Application>Internet>Transport>Network Access

D

Which of the following protocols would introduce unnecessary network traffic? i.TCP ii.UDP iii.DHCP A.i only B.ii only C.iii only D.i and iii E.ii and iii

D

Which flags are used for TCP session termination? A.RST and FIN B.SYN and ACK C.PSH and SYN D.RST and PSH E.FIN and ACK

E

SYN

Synchronize sequence numbers

What are the transport layer protocols?

TCP, UDP

Which information is used at the destination, that enables the transport layer to reconstruct the pieces of data into a complete data stream that is useful to the application layer? A.User's Information B.Network Information C.Router Information D.Footer Information E.Header Information

E

Which of the following flags is/are used for TCP session termination? I.RST II.PSH III.FIN IV.ASK A.I only B.II only C.III only D.I and II only E.III and IV only

E

Which of the following is true about UDP? I.It has much lower overhead than TCP because it's not connection-oriented II.It does not establish a connection before sending data III.It is not necessarily an inferior protocol used on the network A.I only B.II only C.III only D.I and II only E.I, II and III

E

What is the purpose of using a source port number in a TCP communication?

The source port number in a segment header is used to keep track of multiple conversations between devices. It is also used to keep an open entry for the response from the server.

How is each segment of data identified on a channel?

The transport layer adds a header containing binary data organized into several fields. It is the values in these fields that enable various transport layer protocols to perform different functions in managing data communication.

What does TCP stand for?

Transmission Control Protocol

URG

Urgent pointer field significant

What does UDP stand for?

User Datagram Protocol

B

Using the figure below, which port is used by the server to respond to client 2 as a destination port? A.Port: 49152 B.Port: 51152 C.Port: 80 D.Port: 25 E.Both Ports 80 and 25

B

What is the first layer from top to bottom called in the TCP/IP model as shown in the figure below? A.Network Access B.Transport C.Internet D.Application E.Physical

Multiplexing

What is the process indicated by letter X in the figure below?

B

Which of the following enables many different communications, from many different users, to be interleaved(multiplexed) on the same network as shown in the figure below? A.Encoding B.Multiplexing C.Decoding D.Encryption E.Decryption

Which of the following features is/areoffered for data transmission by UDP? i.Segmentation ii.Reassembly iii.Flow control iv.Reliable delivery

i and ii

What does it mean when we say UDP is known as a best-effort delivery protocol.

In the context of networking, best-effort delivery is referred to as unreliable because there is no acknowledgment that the data is received at the destination. With UDP, there are no transport layer processes that inform the sender of a successful delivery.

How do an ISN gets incremented to set the next segment number?

Incremented by the number bytes that have been transmitted.

FIN

No more data from sender