Computer Network midterm

Which one of the following is not a protocol?

a) TCP b) IP c) Ethernet d) MSN

d) MSN

Which one of the following is not a purely Client-Server model?

a) Web b) Email c) Instant messaging d) CougarView or D2L

c) Instant messaging

Which one about TP3 is correct?

a) Twisted pair with bandwidth 1Mbps b) Twisted pair with bandwidth 5Mbps c) Twisted pair with bandwidth 10Mbps d) Twisted pair with bandwidth 100Mbps

C) Twisted pair with bandwidth 10Mbps

Which one of the following is not a peer-to-peer model?

a) Skype b) BitTorrent c) Ebay d) Instant messaging

c) Ebay

All links share the backbone bandwidth 20Mbps, each link uses TDM with10slots/sec, how many users at most are allowed to use the resources concurrently?

a) 2 b) 10 c) 15 d) 20

B) 10

All links share the backbone bandwidth 20Mbps, each link uses FDM with 10Kbps,how many users at most are allowed to use this resource concurrently? a) 2 b) 200 c) 2000 d) 10

C) 2000

Suppose N users share a link with bandwidth 1 Mb/seach user:100 kb/s when "active"active 20% of timeif TDM is used, how many user at most can be accommodated?

a) 10 b) 5 c) 20 d) 15

B) 5

Suppose N users share a link with bandwidth 1 Mb/seach user:100 kb/s when "active"active 20% of timeif FDM is used, how many user at most can be accommodated?

a) 5 b) 10 c) 20 d) 15

B) 10

Suppose N users share a link with bandwidth 1 Mb/seach user:100 kb/s when "active"active 20% of time if Packet Switching is used, how many user at most can be accommodated?

a) 5 b) 10 c) 20 d) any

d) any

Packet switching allows more users to use network than Circuit switching?

a) True b) False

A) true

Data loss occurs at

a) Computer hosts b) Communication links c) Routers d) repeaters

c) routers

Packet propagation delay is not determined by

a) packet size b) media type c) propagation speed d) router buffer size

d) router buffer size

If a link bandwidth is 64kbps, and a packet with size 128kbps is transferred throughthis link, please compute its transmission delay.

a) 1s b) 2s c) 0.5s d) 0.2s

b) 2s

n packet switching, packet delay is composed of __________, ____________, ___________, _____________

queue delay, processing delay, transmission, propagation

tracert/tracerout is used to trace

a) delay in circuit switching b) delay in packet switching c) delay in client-server model d) delay in peer-to-peer model

b) delay in packet switching

Which one is a network application layer protocol?

a) TCP b) UDP c) IP d) HTTP

d) HTTP

Which one is a network layer protocol?

a) TCP b) IP c) UDP d) Ethernet

B) IP

Which one is a data link layer protocol?

a) SMTP b) IP c) PPP d) IMAP

c) PPP

Data encryption cannot occur at which layer

a) transport b) data link c) network d) application

b) data link

Select the suitable features for the server in a Client-server architecture.

Always-on host

may have dynamic IP addresses

do not communicate directly with each other

Static and permanent IP address

may have dynamic IP addresses

do not communicate directly with each other

the type of a message exchanged among computers are defined at _________

link layer

application layer

Transport layer

network layer

Application layer

Which of the following are application layer protocols?

HTTP

Skype

IP

SMTP

Skype

IP

If a flow control is needed in a process communication, which protocol is used?TCP

UDP

SMTP

ICMP

TCP

Which of the following applications requires non-elastic throughput?

e-mail

instant messaging

real-timeaudio/video

file transfer

real-timeaudio/video

TCP provides the following services

Connection oriented

Security

flow control

Congestion control

Security

An email application needs ___, ____ as the application and transport protocols respectively.

HTTP, TCP

SMTP, UDP

SMTP, TCP

FTP, UDP

SMTP, TCP

______ can send a HTTP request, and _____ can send a HTTP response.IE, Firefox

Firefox, Apache Web server

Safari, IE

Apache Web Server, Safari

Firefox, Apache Web server

Persistent HTTP connection means

Multiple objects can be sent over single TCP connection between client and server

Multiple objects can be sent over multiple TCP connections between client andserver

Single object can be sent over Single TCP connection between client and server

At most one object is sent over a TCP connection

Multiple objects can be sent over single TCP connection between client and server

Get /~yang/ HTTP/1.1 Host: cs.ColumbusState.edu. This is a

HTTP response

HTTP request

HTTP response and request

Neither HTTP response nor request

HTTP request

Cookie file is kept on

Server's host, and managed by user's browser

user's host, and managed by user's browser

user's host, and managed by server's browser

server's host, and managed by server'sbrowser

user's host, and managed by user's browser

Which of the following is not correct about a pure P2P architecture?

There is no always-on server.

Permanent and static IP address must be used for each computer.

any computer can talk to any other computers

It is highly scalable

Permanent and static IP address must be used for each computer.

Select the reasons to use web caching.

reduce response time for client request

reduce traffic on an institution's access link

enables "poor" content providers to effectively delivercontent

make the network more secure

make the network more secure

Which of the following is correct?

Skype is a voice-over-TCP P2P application

Skype sets up a client to client connection, so it does not need anyserver

Skype users find the address of a remote party through peer-to-peer.

Skype uses distributed servers to find the address of a remote party

Skype uses distributed servers to find the address of a remote party

A process is a program running in a host. Two processes in different hosts communicate by

exchanging messages

inter-processcommunication

shared memory

email

exchanging messages

A Server process can initiate a communication.

True

False

False

A process that waits to be contacted is called

Client process

Server process

Client-server process

none of the above

server process

A process in a computer can send a message through a ____ to communicate with the othercomputers.

shared memory

socket

email

network

socket

32 bit IP address is used to identify

a process

a host

a network

a server

a host

A process in a computer can be uniquely identified by

IP address

TCP address

Port number

IP address and Port number

IP address and Port number

TCP uses different control connections, and different data connections to transfer different files.

True

False

False

Select the major components of e-mail

user agents

user browsers

mail servers

SMTP

user browsers

Which one is used to compose, edit, and read email messages?

email server

user browser

user agents

email protocol

user agents

Outgoing and incoming messages in e-mail are stored on

client user agents server email server

email server

SMTP is used to transfer message between ___ and ___.

user agent, user agent

user agent, email server

email server, email server

email server, user agent

email server, email server

SMTP uses TCP to reliably transfer email message from server to server.

True

False

True

SMTP uses

persistent connections

non-persistent connections

HTTP persistent connections

HTTP non-persistent connections

persistent connections

Which of the following protocols cannot be used to access email?

HTTP

POP

SMTP

IMAP

SMTP

DNS system uses

Centralized database to map IP to names

distributed database to map hostnames to IP address

multiple centralized database to map IP to names

none of the above

distributed database to map hostnames to IP address

Select the DNS services

hostname to IP address translation

host aliasing

load distribution

IP address to hostname translation

IP address to hostname translation

Select the reasons for non-centralized DNS

Single point of failure

maintenance

simpleness

efficiency

simpleness

If you are located in an EDU domain to access the web server www.amazon.com, what is thecorrect resolving process?

your DNS server-->EDU DNS server-->COM DNS server-->amazon.com DNS server

your DNS server--> edu DNS server-->root DNS server-->com DNS server-->amazon.com DNSservers

your DNS server-->EDU DNS server-->COM DNS server-->root DNS server

your DNS server-->Root DNS server-->COM DNS server-->EDU DNS server

your DNS server--> edu DNS server-->root DNS server-->com DNS server-->amazon.com DNSservers

if you want to add a resource record to resolve the hostname www.ColumbusState.edu to address196.12.10.4 in your DNS server, which one is the correct format?

(www.ColumbusState.edu, 196.12.10.4, CNAME, 20)

(www.ColumbusState.edu, 196.12.10.4, NS, 20)

(www.ColumbusState.edu, 196.12.10.4, A, 20)

(www.ColumbusState.edu, 196.12.10.4, MX, 20)

(www.ColumbusState.edu, 196.12.10.4, A, 20)

Server can only use one socket to talk with multiple clients.

True

False

False

Which one can be used as an input, as well as an output stream?

keyboard

monitor

socket

printer

socket

In a TCP process communication, which one is correct?

A server process must first be running.

A client process must first be running.

A server and a client process must be running concurrently.

It does not matter which process runs first because they can wait for eachother.

A server process must first be running.

Consider an HTTP client that wants to retrieve a Web document at a given URL. The IP addressof the HTTP server is initially unknown. what transport and application-layer protocols besidesHTTP are needed in this scenario?Application layer protocols: DNS and HTTP, Transport layer protocols: TCP for DNS; TCP forHTTP

Application layer protocols: DNS and HTTP, Transport layer protocols: TCP

Application layer protocols: DNS and HTTP, Transport layer protocols: UDP

Application layer protocols: DNS and HTTP, Transport layer protocols: UDP for DNS; TCP forHTTP

Application layer protocols: DNS and HTTP, Transport layer protocols: UDP for DNS; TCP forHTTP

HTTP response messages never have an empty message body.

True

False

False

Two distinct Web pages can be sent over the same persistent connection.

True

False

True

With non-persistent connections between browser and origin server, it is possible for a singleTCP segment to carry two distinct HTTP request messages.

True

False

False

Which of the following application layer protocols uses UDP at transport layer?HTTP

POP3

DNS

FTP

DNS

Which statement of the following is correct?

the checksum of an UDP packet can detect transfer error.

the checksum of an UDP packet can detect and recover transfer error.

the checksum of an UDP packet can neither detect nor recover transfer error.

the checksum of an UDP packet can recover transfer error.

the checksum of an UDP packet can detect transfer error.

In a UDP packet, if its payload has two 32bits integers: E666 and D555, then its checksum should be

4443

4444

5454

616f

4443

for the FSM shown in the figure, which description is correct?

rdt_send(data) is a call from network layer

udt_send(packet) is a call from application layer

rdt_send(data) is a call from application layer

packet = make_pkt(data) is happend at application layer

rdt_send(data) is a call from application layer

Rdt 2.0 is designed for handling channel packet loss.

True

False

false

Selective Repeat protocol is

the same as TCP protocol

a pipelined protocol

an application layer protocol

a network layer protocol

a pipelined protocol

Transport protocol provides a logical communication between two hosts.

True

False

False

Network layer relies on transport layer services.

True

False

False

At transport layer, sender side will

receive datagram from network layer and deliver it to application layer.

get the message from application and deliver it directly to the network layer.

receive the message from application, encapsulate it and deliver it to the network layer.

reassemble segments into messages, pass them to application layer.

receive the message from application, encapsulate it and deliver it to the network layer.

From transport layer,

a host can be identified

a process can be identified

an IP address can be identified

Packet contents can be identified

a process can be identified

TCP protocol provides

time guarantee

bandwidth guarantee

flow control

"best effort" IP

flow control

De-multiplexing at sender side delivers received segments to a correct socket.

True

False

false

An UDP packet can be delivered to the destination and the appropriate process at the destination based on(multiple choices)

Source and Destination Port

Destination IP and Port

Source IP and Port

Source and Destination IP

Destination IP and Port

With connectionless de-multiplexing, IP datagrams with different source IP addresses, but the same sourceport number, can be directed to the same destination port.

True

False

True

What kind of multiplexing/de-multiplexing service is used in the communication shown by the abovefigure?

TCP multiplexing service

connectionless de-multiplexing service

connection-oriented multiplexing service

connection-oriented de-multiplexing service

connectionless de-multiplexing service

TCP connection can be identified by

Source IP and Port

Source and destination IP, and Port

Source and destination Port

Source and destination IP

Source and destination IP, and Port

Web server uses the same socket to process different non-persistent HTTP requests.

True

False

False

Which statement of the following is correct?

twisted pair is a reliable data transmission media.

optical fiber is a reliable data transmission media.

Network layer data transfer is not reliable.

a router is a reliable data transfer device.

Network layer data transfer is not reliable.

the policy of Go-Back-N to handle out-of-order packets at the receiver host is

reorder them

buffer them

discard them

acknowledge them

discard them

the reason for Go-Back-N to generate duplicate ACKs is

packet buffering at thereceiver

an expected packet received

out of order packet received

an ACK from the sender

out of order packet received

the packets within the window buffer of the sender host using SR protocol

must not be acknowledged

must be acknowledged

may be acknowledged, may not be

none of the above

may be acknowledged, may not be

If the range of sequence number is from 1 to 100, how big would the window size at sender side be at mostfor SR protocol?

100

30

50

20

50

the field "receive window" in TCP header indicates

the sender tells the receiver how big the receiver window would be.

the receiver tells the sender how big the sender window would be.

the receiver tells the sender how big the receiver window would be.

the sender tells the receiver how big the sender window would be

based on the situation as shown in the figure above,

Host A needs to resend the first packet

Host A knows that the first packet has been received

Host A needs to wait for the Ack of the first packet

After timeout, Host A will resend the first unacknowledged packet.

Host A knows that the first packet has been received

A TCP connection is initiated by the server.

True

False

false

Only client side can make a request to close a TCP connection.

True

False

true

In rdt2.0, rdt_send() is called from

transport layer

application layer

datalink layer

network layer

application layer

"TCP flow control" means that a sender won't overflow the receiver by lowering the transferring rate fromthe sender to the receiver.

True

False

False

In protocol rdt1.0, udt_send() is call from

Applicationlayer

network layer

transport layer

datalink layer

transport layer

Each state of a finite state machine (FSM) can be transited to other states or itself triggered by the events received and the actions taken.

True

False

false

Please point out which of the following is correct based the following rdt 2.0 FSM.

Once a packet is sent out, it will go to the state to send the next packet.

Once a packet is sent out, it immediately goes to the state to wait for an acknowledgementfor the previous packet sent out.

Once a packet is sent out, it immediately goes to the state to wait for an acknowledgementfor the packet just sent out.

If there is an acknowledgement received, it immediately goes back to the state to send thenext packet.

Once a packet is sent out, it immediately goes to the state to wait for an acknowledgementfor the packet just sent out.

The reason for the duplicated packets received of rdt2.0 is

packet lost

sender acknowledgement lost

receiver acknowledgement lost

acknowledgement corrupted

acknowledgement corrupted

rdt3.0 can handle

packet bit error only

packet loss only

packet bit error and loss

either packet bit error or packetloss

packet bit error and loss

Sending 8000 bits data packet to the receiver side through a link with 1 Gbps bandwidth and 10 mspropagation delay, the utilization is

0.03998

0.003998

0.0003998

0.3998

0

Which of the following is correct about Go-Back-N protocol?The value of variable "next_seq_num" must be bigger than the value of "send_base" in theSending window.

it maintains one timer for each in-flight packet.

the oldest unacked packet in its sending buffer window must be acknowledged first.

Unacked packets in its buffer window must not be consecutive.

the oldest unacked packet in its sending buffer window must be acknowledged first.

Which network is a datagram network?

ATM

X.25

Frame relay

the Internet

the internet

If you want to design a network to connect 130 hosts, how to design your network address andmask?

223.272.0.0/24

223.272.0.128/24

223.272.0.192/24

223.272.0.64/24

223.272.0.0/24

The protocol DHCP works in _________ layer.

network

transport

application

IP

application

Network layer protocol ICMP message is carried over_____.

UDP

TCP

IP

HTTP

IP

How to process a big packet in IPv6?

fragmentation when needed

ICMP message "packet too big"

ignore big packet

none of the above

ICMP message "packet too big"

How will the network operate with mixed IPv4 and IPv6 routers?

Convert IPv6 datagram to IPv4 datagram

IPv6 carried as payload in IPv4 datagram among IPv4 routers

IPv4 carried as payload in IPv6 datagram among IPv6 routers

Convert IPv4 datagram to IPv6 datagram

IPv4 carried as payload in IPv6 datagram among IPv6 routers