Fundamentals of Computer Networks Midterm Questions

Which term has the meaning of this statement: taking a packet arriving on one of a host's incoming links and forwards it to one of the host's outgoing links according to its destination?

Packet switches

What is the correct display filter that shows all TCP traffic running on port 80 on Wireshark?

tcp and tcp.port == 80

What Wireshark feature recovers a file for captured FTP data packets?

Follow Stream

What is the correct definition of the Internet?

The Internet is a computer network that interconnects billions of computing devices via coaxial cable, copper wire, or optical fiber.

What is the correct display filter that shows everything, but excludes FTP traffic on Wireshark?

not ftp

What are the three things that are defined in a network protocol?

Format and order of messages, and what actions are taken.

What is the correct display filter that shows all Web traffic on Wireshark?

http or https

True or False:

In packet switching networks, the computing devices are interconnected through communication links and packet switches.

True

True or False:

In packet switched networks, the resources needed along a path to provide for communication between the end systems are reserved for the duration of the communication session.

False

What is the Wireshark display filter that shows all the traffic except ARP, DNS and DHCP?

not (arp or dns or dhcp)

True or False:

A packet is stored at the router until it has fully arrived.

True

True or False:

Wireshark is a packet sniffer that can be used to capture and analyze network packets.

True

What menu item in Wireshark contains the feature that allows you to recover a file for captured FTP data packets?

Statistics ————> conversations

Wi-Fi can be called three networks; what are those networks?

1. Wireless Local Area Networks

2. Wireless LANs

3. IEEE 802.11 networks

What Wireshark display filter gets all HTTP and FTP traffic with 192.168.1.33 being either the source IP or the destination IP?

(http or ftp) and ip.addr == 192.168.1.33

What is true about the layered architecture used in computer networking?

1. Allows us to discuss and better understand a well-defined, specific part of a large and complex system

2. When a layer's implementation is changed, the remainder of the system remains unchanged.

3. Provides modularity and makes it much easier to change implementation provided at each layer.

What layer in the OSI model allows the two communicating applications to interpret the meaning of data exchanged?

Presentation Layer

What application-layer protocols are on top of UDP?

DNS, SNMP, and DHCP

True or False:

Layered architecture is only used in the TCP/IP model, not in the OSI model.

False

The data unit at the network layer is...

IP datagram

The data unit at the transport layer is...

segment

The data unit at the data link layer is...

frame

The data unit at the physical layer is...

raw bits

True or False:

The more layers the better in any protocol models.

False

True or False:

Layering provides modularity, which makes it easier to change implementation of services provided at each layer, and keep the remainder of the system unchanged if a layer's implementation is changed.

True

What was the TCP/IP protocol model designed for?

It is designed to model the data communication between two applications running in two different hosts.

What app-layer protocols ONLY use TCP services at layer 4 (transport layer)?

HTTPS, HTTP, SMTP, and FTP

True or False:

TCP does not guarantee the delivery of messages to their destinations.

False

True or False:

TCP is more efficient than UDP.

False

Which layer of the OSI model implements the functions to maintain data across multiple users?

Session

True or False:

SNMP is not a URL protocol.

True

What is the solution to browsers' problem of supporting a rapidly growing collection of file types?

When a server returns a page, it also returns some additional information about the page including its MIME type.

True or False:

A browser plug-in extends the browser for supporting new file types.

True

True or False:

Web servers can use caching and multiple threading to improve performance.

True

A client browser's state is maintained by...

cookies of a browser

What command restarts the DHCP lease process in Windows?

ipconfig /renew

Name the four steps, in order, in a successful DHCP process:

1. DHCP server discovery

2. Receive DHCP server offer

3. DHCP request from server offers

4. Server DHCP acknowledgement for request confirming parameters

True or False:

For HTTP request messages, the accepts header gives the browser a chance to tell the Web server which format it wants for a resource.

True

What are the HTTP Request Methods for HTTP 1.0?

GET, HEAD, POST

The arp -a command displays...

the current contents of the ARP cache table on your computer

To clear the ARP cache, use the following command

arp -d

Why would an ARP frame have a destination MAC address of 00:00:00:00:00:00?

To indicate the ARP frame was broadcasted to all the hosts on the network.

What technology allows an HTTP client to retrieve individual data items from a Web server to update a section of the webpage without having to reload an entire page?

AJAX

"HTTP 1.1 supports pipeline requests" means...

a client browser can send the 2nd request to a Web server before the response to the 1st request has arrived

True or False:

TCP uses the fast-start procedure to increase the throughput rapidly to improve the performance of data communication between two application end points

False

If a browser received a new file format from a Web server within an HTTP response page, it may not know how to interpret and display on it. The browser may...

refer to a table of MIME types

True or False:

By default, HTTP runs on port 80 and HTTPS runs on port 443.

True

HTML content type is identified by...

MIME

True or False:

The methods that are used to improve the performance of Web applications include using a different browser.

False

True or False:

Native audio and video support is a new HTML 5 feature that is NOT available in HTML 4.

True

What command is used to look up DNS information in both Windows and Linux?

nslookup

What command clears the DNS cache on a Windows machine?

ipconfig /flushdns

What is another name for a CNAME record?

alias

What does an A record hold in a DNS database table?

IPv4 address

True or False:

Microsoft PowerPoint application is an example of a network application.

False

True or False:

One of the reasons that DNS is needed is because server's IP addresses are permanent and never change.

False

True or False:

A DNS zone is a portion of the DNS namespace that is managed by a specific organization or administrator.

True

True or False:

A domain resource record on a DNS database has the number 86400 in its second column. This domain resource record is considered highly stable.

True

True or False:

Many business computers have three distinct and world wide unique identifiers. These include the Ethernet address.

False

True or False:

DNS namespace is hierarchical from the root down with the root being named COM.

False

True or False:

A DNS server uses well-known UDP port 53 for all its UDP activities.

True

To request a new IP address from a DHCP server, run the following command...

ipconfig /renew

How many columns in the DNS database table?

5

True or False:

DNS uses both TCP and UDP services at the trans-layer.

True

What transport service primitive is ONLY called at the server side?

LISTEN

What transport service primitive is ONLY called at the client side?

CONNECT

True or False:

For an application with a server and several remote clients calling transport service primitives, a client first executes a CONNECT primitive, and then the server executes a LISTEN primitive

False

True or False:

If a socket is created with the type SOCK_STREAM, then it is a UDP socket which is connectionless

False

True or False:

After a socket is created, it should be bound to a local address (HOST, PORT) before it can listen to incoming connection requests.

True

True or False:

After the listen() method is called by the server program, it is ready to accept connection requests.

True

The backlog argument provided for the listen() method specifies...

the maximum number of queued connections

True or False:

The return value of the socket method accept() is a pair (conn, address), where conn is a new socket object that can be used to send and receive data on the connection.

True

f = open(file,'wb')

The option b means...

the file will be opened in binary mode

True or False:

The buffer size used in the socket recv() method at the server side program should be equal to the length of the data provided to the socket send() method at the client side program.

True

True or False:

The port numbers used in the socket server program and the client program MUST be the same.

True

True or False:

In Python, to write to an existing file, you must add a parameter to the open() function:

"a" - Append - will append to the end of the file

"w" - Write - will overwrite any existing content

True

True or False:

With client-server socket programming, the server program uses two sockets: one socket is used to listen for incoming connection requests, and the other one is used for data transfer with a client program.

True

How does an application at layer 5 use the services at layer 4 in the TCP/IP model?

Through a transport address which is a port number.

True or False:

client_s.connect( (host, port) );

In the above Python statement, host should hold the IP address of the client host.

False

When an application wishes to set up a connection to another application running on a remote host, how does it specify which application to connect to?

it needs to specify the port number that is associated with the application running on the remote host

True or False:

Transport Service Access Point is used to mean a specific port number at the transport layer.

True

What are the default ports for the following app-layer protocols:

1. HTTP

2. HTTPS

3. Telnet

4. SSH

1. 80

2. 443

3. 23

4. 22

In a 3-way handshake to establish TCP connection, what is the type of the TCP segment sent from the client in Step 1?

SYN

What is the interface of data communication between Transport layer (layer 4) and the App layer (layer 5)?

TSAP (port numbers)

Which app-layer protocols uses the standard port 443 by default?

HTTPS

True or False:

Both ends of a TCP connection can always release the connection if the server can receive at least one DR (Disconnect Request) sent from the client, with the help of retransmission and timers.

True

____________ allows the sender to send multiple frames before needing the acknowledgments.

Sliding window

What is the minimum size of a TCP segment?

20 bytes

What is the size of an IP pseudo-header for IPv4?

12 bytes

What is the minimum size of a UDP segment?

8 bytes

True or False:

The app-layer protocol POP-3 runs on top of TCP

True

Which flag bit in TCP header must be set if the TCP segment carries some data?

PSH

A TCP segment with the flags SYN = 1 and ACK = 1 can...

ONLY be sent from a server host to a client host.

What two flags in the TCP header are used for congestion control?

ECE (from server to client; asking to slow down transmission) and CWR (from client to server; confirming transmission has been slowed)

A TCP segment with the flags SYN = 1 and ACK = 0 is considered what?

This is a connection request segment sent from a client host

What TCP header field is used for TCP flow control?

Window size

What flag bit is used for releasing a connection?

FIN bit

What flag bit in the TCP header is used for providing information about where to find urgent data?

URG

Which part of the TCP header is used to identify a TCP segment's place in the sequence of data stream, and keep track of how much data the sender has transmitted?

TCP sequence number

True or False:

Message boundaries are preserved in a TCP connection.

False