Final Exam IT 276 Data Communication

What follows is a fill in the blank question with 1 blanks. as an example of Transport protocol that is connectionless

UDP

YouTube is a network application. True False

True

A problem with the star topology is that one cannot add or remove hosts without shutting down the entire network. True False

false

The OSI model has 6 layers. True False

false

The TCP/IP protocol suite was designed in 1970s by 2 DARPA scientists—Vint Cerf and Bob Kahn. They are most often called the fathers of the Internet. True False

True

The bit ACK is needed both in the phase of establishing a TCP connection and in the phase of closing that connection. True False

True

To communicate with a Web server, a broswser uses a language called HTTP (Hypertext Transfer Protocol). True False

True

Match the following: A. Graphical web browser B. Operating systems C. American social media application D. Photo and video-sharing Application E. Cross-platform web browser 1. Google Chrome 2. Safari 3. Window 10 4. Facebook 5. Instagram

1. Google Chrome - E 2. Safari - A 3. Window 10-B 4. Facebook-C 5. Instagram-D

Match the following A. Standard B. Transport Layer Address C. Data Link Layer address D. Protocol E. Network Layer address select A B C D E 1. HTTP select A B C D E 2. HTML select A B C D E 3. IP address select A B C D E 4. Port Address select A B C D E 5. Mac Address

1. HTTP-D 2. HTML-A 3. IP address-E 4. Port Address-B 5. Mac Address-C

Match the traffic description in different layers of the TCP/IP Model using the following: A. Message B. Bits C. Packet D. Segment E. Frame select A B C D E 1. Transport Layer select A B C D E 2. Network Layer select A B C D E 3. Data Link Layer select A B C D E 4. Application Layer select A B C D E 5. Physical Layer

1. Transport Layer-D 2. Network Layer-C 3. Data Link Layer- E 4. Application Layer- A 5. Physical Layer- B

Match the following of OSI Model with correct answers: A. Addressing, routing, message delivery across networks B. Establishes & manages sessions between hosts C. Reliability, flow control, error control D. User interaction with software program E. Data formatting, compression, and encryption 1. Application Layer 2. Presentation Layer 3. Session Layer 4. Transport Layer 5. Network Layer

1:D, 2:E, 3:B, 4:C, 5:A

Socket has A. IP address plus port number B. Indicates specific NICK card in specific machine C. Not every networked application on every host uses the socket for the application to communicate with other applications on other hosts D. IP address + port address + MAC address

A. IP address plus port number

SMTP uses the following except: A. persistent connections B. UDP to transfer email message from client to server C. port 25 D. direct transfer: sending server to receiving server E. SMTP requires message (header & body) to be in 7-bit ASCII

B. UDP to transfer email message from client to server

SSL provides the following except : A. provides encrypted TCP connection B. data integrity C. Maximum Throughput D. end-point authentication

C. Maximum Throughput

In TCP: A. a lost segment is resent by the sender only if the receiver requested B. Each segment is resent automatically after the timer is expired C. Sender keep a copy of segment that he sent until the sender received acknowledgment from the receiver. D. Lost segment will be replaced by default segment created by the sender

C. Sender keep a copy of segment that he sent until the sender received acknowledgment from the receiver.

The minimum needed for a network or components of data communication system are the following except: A. At least two computers B. Shared media C. Standard to unify the system D. Shared protocol ("language") E. Data to transmit (message)

C. Standard to unify the system

FTP client: A. contacts FTP server at port 20 B. using UDP as the transport protocol C. client authorized over control connection channel D. client browses remote directory using 2nd UDP connection (for file) to server as data connection on port 22.

C. client authorized over control connection channel

protocol defines the following except: types of messages exchanged, e.g., request, response message syntax: what fields in messages & how fields are delineated message semantics meaning of information in fields rules for when and how processes send & respond to messages A. message syntax: what fields in messages & how fields are delineated B. message semantics meaning of information in fields C. round trip and processing delays D. rules for when and how processes send & respond to messages

C. round trip and processing delays

Layering advantages include all the following except: A. Allows specialization in design B. Allows easier troubleshooting C. Replacement of a protocol at one layer is easier D. A protocol at one layer must understand all layers above and below.

D. A protocol at one layer must understand all layers above and below

TCP handshaking is needed: A. only when you send HTTP message B. Only when you send TFTP message C. Only when you send SMTP D. Before TCP sending any application data to any destination

D. Before TCP sending any application data to any destination

SFTP is Just like FTP except: A. uses two channels for both control and data B. client contacts FTP server at port 21 C. using UDP transport protocol D. Data is encrypted and authenticate both the user and server

D. Data is encrypted and authenticate both the user and server

TCP Handshakes include the following except: A. One side sends a TCP segment with the SYN flag set B. Other side replies with a segment with both SYN and ACK set C. Original sender replies with a segment with ACK set D. Finally the sender side send test segment with multiple SYN to test the link

D. Finally the sender side send test segment with multiple SYN to test the link

TCP segment has the following except: A. Application data B. Source Port address C. Destination Port address D. Source and destination IP addresses

D. Source and destination IP addresses

Application protocols are defined by the following except: A. Types of messages exchanged, e.g., request, response B. message syntax, what fields in messages & how fields are delineated C. message semantics, meaning of information in fields D. address to identify the ID of the sender E. rules for when and how processes send & respond to messages

D. address to identify the ID of the sender

When a UDP segment is lost (i.e., is not received at the destination), UDP re-sends it. True False

False

When layering is used, a protocol at one layer needs to understand how all other layers function. True False

False

1 bit contains 8 bytes. True False

False

A TCP header length is fixed of 20 Bytes True False

False

A full mesh topology of 6 nodes has 19 links. True False

False

What makes browsing the Internet reliable is not the fact that HTTP is inherently reliable but the fact that HTTP (which is unreliable) uses TCP which is reliable. True False

True

What follows is a fill in the blank question with 1 blanks. as an example of Transport protocol that is connection orient is

TCP

When TCP receives a message from an application layer protocol (such as HTTP), it adds a TCP header to that message and the result is a TCP segment. True False

True

A Personal Area Network (PAN) connects multiple devices for the use of a single user. True False

True

A Web server is a computer that runs a program called an HTTP server such as Apache HTTP server. True False

True

A socket is an IP address and a port number. True False

True

A Campus Area Network (CAN) is a network that may span multiple buildings. True False

true

DNS stores the mappings between human-readable names of hosts on the Internet and their IP addresses. True False

true

An IPv4 packet has the value 5 in its field Header Length (HLEN). That means the header of this packet has ... A. 5 bytes B. 32 bytes C. 160 bytes D. 20 bytes E. 25 bytes

D. 20 bytes

n IPv4, the highest value of the field TTL is ... A. 64 B. 99 C. 128 D. 255 E. 65535

D. 255

The field Receive-Window has 16 bits. That means the largest values of the field Receive-window in (Decimal) is A. 16 B. 3 C. 16^2 -1 = 255 D. 2^16 -1 = 65535

D. 2^16 -1 = 65535

Consider a subnet with prefix 55.2.113.0/25. Which of the following is NOT a valid IP to assign to a device in this subnet: A. 55.2.113.27 B. 55.2.113.50 C. 55.2.113.64 D. 55.2.112.4

D. 55.2.112.4

Consider a subnet with prefix 55.2.113.0/28. Which of the following is NOT a valid IP to assign to a device in this subnet: A. 55.2.113.12 B. 55.2.113.13 C. 55.2.113.14 D. 55.2.113.16

D. 55.2.113.16

What is the maximum number of bytes that can be included in UDP payload? A. 1000 B. 65000 C. 65535 D. 65527 E. 99999

D. 65527

We need to send a file fo 1680 bytes from A to B using TCP. Each TCP segment is carried in an IPv4 packet. Assume the following: - No TCP and no IP options. - Max total length of IPv4 packets= 230 bytes. How many IP packets are needed (at least)? A. 6 B. 7 C. 8 D. 9

D. 9

Local DNS name server has the following except: A. does not strictly belong to hierarchy B. each ISP (residential ISP, company, university) has one, also called "default name server" C. when host makes DNS query, query is sent to its local DNS server D. does not have local cache of recent name-to-address translation pairs E. acts as proxy, forwards query into hierarchy

D. does not have local cache of recent name-to-address translation pairs

TCP services include the following except: A. reliable transport between sending and receiving process B. flow control: sender won't overwhelm receiver C. congestion control: throttle sender when network overloaded D. provide timing, minimum throughput guarantee, security E. connection-oriented: setup required between client and server processes

D. provide timing, minimum throughput guarantee, security

An IPv4 packet contains the value 9 in its field HEADER_LENGTH. The packet must have _______ of additional options in its header. A. 9 bytes B. 2^9 = 512 bytes C. 9^2 = 81 bytes D. 4 bytes E. 16 bytes

E. 16 bytes

POP3 has the following except: A. Download the email to your device from the email servers B. downloads what is in your inbox folder C. download draft, sent, delete, or others D. The email is deleted on the mail server once it is download to a device E. synchronizes emails between different devices. F. c& e

F. c& e C. download draft, sent, delete, or others E. synchronizes emails between different devices

A TCP segment never gets lost in the network and this is why TCP is said to be reliable. True False

False

A Web server cannot communicate with more than a single client (i.e., Web browser) simultaneously. True False

False

A file F is split up in three IPv4 packets that are then sent from host A to host B. IPv4 guarantees that all three packets will go through the same number of routers on their way from A to B. True False

False

A home network is a WAN. True False

False

A host A receives an IPv4 packet from host B with TTL=15. This means that the packet went through 15 routers at most on its way from B to A. True False

False

A local area network (LAN) is a network that extends over a large geographical area. True False

False

A sender sends an IPv4 packet.IPv4 gives the sender exact information as to how much time the packet will take until it reaches the destination. True False

False

All Web applications require 100% reliability.

False

All academic institutions in the world have Web sites ending with ".edu" True False

False

An IPv4 header without additional options contains 32 bytes. True False

False

An IPv4 packet does not contain the IP address of the sender. True False

False

Because TCP is reliable, TCP segments never get lost. True False

False

Disadvantages of star topology are packet collisions and every station received all network traffic. A. True B. False

False

For a protocol to be reliable, it must be connection-oriented. True False

False

HTTP error 400 (Bad Request) means that the server did not find the page requested by the browser. True False

False

HTTP is a transport layer protocol. True False

False

Host A sends a sequence of TCP segments to host B. Then, host B receives all segments in the same order in which they are sent by host A. True False

False

IPv4 has an initial phase to establish connection between sender and receiver. True False

False

IPv4 is a connection-oriented protocol. True False

False

IPv4 is a transport layer protocol. True False

False

IPv4 uses the three-way handshake to establish connections. True False

False

In TCP/IP, a transport-layer protocol uses the services of an application-layer protocol. True False

False

In TCP/IP, the application is responsible for establishing connections. True False

False

In TCP/IP, the network layer is responsible for session control, error and flow control. True False

False

In client-server applications, the client does most of the work. True False

False

In iterative DNS name resolution, most of the burden falls on the root DNS servers. True False

False

In network extended star topology, each device is connected directly to all other devices and it is called a tree topology. A. True B. False

False

Multiplexing allows one message to contain data that belong to several applications. True False

False

PDF (Portable Document Format) is an open standard to present documents. True False

False

Routers need to examine the TCP headers to decide how to forward an IPv4 packet. True False

False

TCP is a proprietary standard. True False

False

TCP is an application layer protocol. True False

False

The Internet is a LAN True False

False

The Internet is under the control of a single organization. True False

False

The Web browser Google Chrome can only communicate with Apache HTTP servers. True False

False

The application layer protocol FTP is connectionless because it uses UDP as its transport protocol. True False

False

The bit ACK in not needed in the process of establishing a TCP connection. True False

False

The bit FIN is needed to establish TCP connections True False

False

The command RETR in FTP is used to retrieve the password needed to open a file. True False

False

The extended star topology does not suffer from the problem of single point of failure. True False

False

The network layer is layer 4 in the TCP/IP protocol suite. True False

False

The number of interfaces of a router is 4. The router cannot have a routing table of more than 2^4 (=16) entries. True False

False

There are 13 authoritative DNS servers in the world. True False

False

There are 15 DNS root servers. True False

False

This is a valid IPv4 address: 145.23.423.11 True False

False

Typically, FTP servers listen on port 80. True False

False

Typically, IPv4 packets are encapsulated in ICMP messages. True False

False

Typically, a TCP segment with destination port number 53 is sent to an FTP server. True False

False

UDP is an application layer protocol. True False

False

UDP is reliable. True False

False

UDP segments contain a field sequence_number to order segments at the destination. True False

False

Unlike TCP segments, UDP segments cannot be encapsulated in IP packets. True False

False

Unreliable protocols are useless. One cannot build an application using an unreliable protocol. True False

False

WAN (Wide Area Network) is to Connects multiple devices for the use of a single user, Bluetooth is one example. A. True B. False

False

When FTP is used to transfer a file, data (i.e., bytes of the file) is transmitted on the control channel. True False

False

When a device receives an incorrect UDP segment, it must ask the sender to resend that segment. True False

False

When a host receives a TCP segment, it examines the TCP header to determine the IP version of the received packet. True False

False

When it receives a packet, a router must first contact the neighboring routers to determine the best neighboring router to which the packet is to be sent. True False

False

A benefit of the star topology is that if one cable or host fails, the rest of the network continues to function properly. True False

True

A browser uses a network to connect to a Web server. True False

True

A computer network is a set of connected devices (servers, PCs, laptops, phones, routers, switches, etc.) that exchange data with each other. A. True B. False

True

A connection-oriented protocol requires a phase where two parties establish a connection before they start communicating (i.e., exchanging information). True False

True

A problem with the Ring topology is that one cannot add or remove hosts without shutting down the entire network. A. True B. False

True

A protocol is a "shared language" that two entities use to communicate over a network. True False

True

A reliable protocol is a protocol that guarantees that any information sent will be properly received. True False

True

A sender X sends three IPv4 packets to a receiver Y in this order: P1, P2, P3.It is possible that these three packets arrive at Y in this order:P3, P2, P1 True False

True

A standard is an accepted model of building or way of doing something. True False

True

A wide area network (WAN) is a network that extends over a large geographical area. True False

True

An IP packet contains a layer 4 (transport layer) segment plus an IP header. True False

True

An IPv4 packet contains the IP address of the destination. True False

True

An application layer protocol defines the rules for when and how messages must be sent, e.g., when the server receives a request of type A, it must reply with a response of type B. True False

True

Browsing the Web is a network application. True False

True

Currently, most networks are packet switched and it is called IP networking. A. True B. False

True

DNS can be thought of as the phonebook of the Internet. It translates names into IP addresses. True False

True

DNS is an application-layer protocol that uses UDP as its transport-layer protocol, i.e., DNS messages will be sent in UDP segments. True False

True

Flow control in TCP refers to the mechanism that allows a receiver to specify exactly how many more bytes it is willing to receive from a given sender. True False

True

Flow control in TCP uses the field receive_window in the TCP header. True False

True

HTTP is an example of an application layer protocol. True False

True

HTTP messages are sent in TCP segments. True False

True

Host A is sending a long file to host B. TCP sends a segment from A to B that has sequence_number = 513. The length of this segment is: 19 bytes. Assuming no errors, the field sequence_number of the following segment sent in this TCP session from host A to host B must be: 532. True False

True

In TCP, the sender sends a single segment and waits a timeout period waiting to receive an ACK segment related to that segment. When the timeout period expires without receiving the expected ACK segment, the sender retransmits the segment again. True False

True

In TCP/IP, providing a reliable communication means making sure that what a sender sends is properly received by the receiver. True False

True

In TCP/IP, the network layer is responsible for routing messages across networks. True False

True

In TCP/IP, the transport layer is responsible for terminating connections. True False

True

In TCP/IP, the transport layer provides reliability for application layer protocols such as HTTP. True False

True

In Windows, the command tracert uses ICMP. True False

True

In a P2P application, a peer may at times be requesting a service from other peers and it may at times be providing a service to other peers. True False

True

In a client-server application, an application layer protocol defines the types of messages exchanged between the clients and the server, e.g., request, response. True False

True

In a ring topology, one workstation malfunction takes out the entire network. True False

True

In client-server applications, the server is considered a single point of failure. True False

True

In peer-to-peer (P2P) applications, all machines are equal. True False

True

It is possible to determine the type of the payload of an IPv4 packet (e.g., a TCP segment, a UDP segment, etc.) from information contained in the header of that IPv4 packet. True False

True

Layered communication makes troubleshooting easier. True False

True

Local DNS servers may use a local cache to avoid repeating the name resolution process for IP addresses already retrieved. True False

True

Multiplexing allows the transport layer to serve several application layer processes at the same time. True False

True

Networks are needed to send emails. True False

True

One of the many benefits of subnetting is that it allows networks to be internally organized in a way that matches the physical layout. For example, one network may be divided up into three subnets, one in every floor of a three-floor building. True False

True

Routers are called "multi-homed" devices because they may have multiple interfaces, each connected to a different network. True False

True

Routers are devices that provide services at all three layers: network layer, link layer, and physical layer. True False

True

Routers use the destination IP address included in the packets to determine how to route those packets. True False

True

Routing consists of two tasks: (i) computing good paths between sources and destinations and (ii) using those path when packets are actually sent. True False

True

Subnetting is to (logically) split up a network into smaller networks called subnets. True False

True

TCP is a connection-oriented protocol because a TCP connection must be established between two devices before they can communicate using TCP. True False

True

The DNS name resolution process finds the IP address of given host name. True False

True

The IPv4 address of a host on the Internet has 32 bits. True False

True

The Internet is a network of networks. True False

True

The Internet is the largest WAN in existence. True False

True

The bit FIN in the TCP header is needed during the phase of closing a connection. True False

True

The bit SYN in the TCP header is needed in the process of establishing connections. True False

True

The field HLEN in the header of an IPv4 packet gives the total number of words in the header of that packet. For example, if HLEN=6, then the total length of the header is 6 words = 6 x 4 = 24 bytes. True False

True

The field Total_Length in the IPv4 header of a packet gives the total number of bytes in the packet (header and data) True False

True

The network layer is responsible for computing good paths between hosts in the Internet. True False

True

The network layer is responsible for routing packets from sources to destinations. True False

True

The smallest number of bytes in a TCP header is 20 bytes. True False

True

These two subnets are the same:Subnet: 117.3.4.0 with Mask: 255.255.255.192Subnet: 117.3.4.0/26 True False

True

This IP address: 118.21.14.3/19 can be written in binary as follows:‭01110110‬ ‭00010101‬ ‭00001110 00000011 / 19 The host_id part of this IP address is: ‬01110 00000011 True False

True

When a TCP segment is encapsulated in an IP packet, the field Protocol in the IP header of the packet must have the value 6. True False

True

When it receives a packet, a router uses its routing table to determine on which of its output ports to forward the received packet. True False

True

When the timeout period expires, the sender must retransmit segments that are not acknowledged. True False

True

When the transport layer receives a message from the application layer, it adds to that message a header called the transport layer header. True False

True

We need to send a file fo 1680 bytes from A to B using TCP. Each TCP segment is carried in an IPv4 packet. Assume the following: - No TCP and no IP options. - Max total length of IPv4 packets= 230 bytes. If all packets except the last one have the maximal size of 230 bytes, how many bytes of IP payload (application and transport layer data) does packet 1 have? A. 210 B. 180 C. 190 D. 240

A. 210

Companion transport layer protocol TCP to UDP, UDP is A. Much faster B. No sequence numbers C. no ACK D. no reassembly in correct order E. all the above F. a, b, & c

A. Much faster B. No sequence numbers C. no ACK D. no reassembly in correct order E. all the above

How does TCP know how to reassemble? A. Use the sequence number B. Simply reassembles once all numbers in sequence are received correctly C. Passes resulting data stream to application layer D. all the above E. a&b

A. Use the sequence number B. Simply reassembles once all numbers in sequence are received correctly C. Passes resulting data stream to application layer D. all the above

the transport layer at host A wants to send the following sequence of bits to host B 101101011101 If host A uses even parity for error detection, what should be the sequence of bits actually sent by host A be? A. 1011010111011 B. 1011010111010 C. 1011010111000 D. 1011010111001

B. 1011010111010

We need to send a file fo 1680 bytes from A to B using TCP. Each TCP segment is carried in an IPv4 packet. Assume the following: - No TCP and no IP options. - Max total length of IPv4 packets= 230 bytes. If all packets except the last one have the maximal size of 230 bytes, how many bytes of TCP payload (application layer data) does packet 1 have? A. 200 B. 190 C. 180 D. 170

B. 190

In UDP header, the length of the field of Total Length in (Bytes) is A. 1 B. 2 C. 4 D. 8 E. 6

B. 2

given an IP 122.14.16.2/22 you are asked to create 10 new subnets, how many usable host IP address you can have for each new subnet? A. 64 B. 62 C. 30 D. 126 E. 128

B. 62

The field Receive-Window has 16 bits. That means the largest values of the field Receive-window in (binary) is A. 1111 B. 1010 1010 1010 1010 C. 1111 1111 1111 1111 D. 1111 1111

C. 1111 1111 1111 1111

The highest value of the field TOTAL_LENGTH in an IPv4 packet is .. A. 2048 B. 2^16 = 65536 C. 2^16 - 1 = 65535 D. 4096 E. 2^16 + 1 = 65537

C. 2^16 - 1 = 65535

A host A sends an IPv4 packet of a total length of 366 bytes (header and data, no additional options) How many bytes of (data and transport layer header) does this packet contain? A. 366 B. 512 C. 346 D. 386

C. 346

An IPv4 packet has 7 in its HLEN field and 645 in its TOTAL_LENGTH field. The packet has ________ bytes of payload (transport and application layer data) A. 638 B. 673 C. 617 D. 625

C. 617

Which of the following is NOT true. A. An IPv4 address has 4 bytes. B. An IPv4 address has 32 bits. C. An IPv4 address has 16 bits.

C. An IPv4 address has 16 bits.