WorksheetsApplication Layer MCQs
Total questions: 99
Worksheet time: 52mins
The application layer is where network applications and their application-layer protocols reside.
True
False
Which of these is NOT a common application-layer protocol?
HTTP
IP
SMTP
DNS
In the client-server architecture, the client is typically the one that:
Is always-on
Initiates contact with the server
Has a static IP address
Is located in a data center
A characteristic of a P2P architecture is:
It relies on a powerful central server
Peers are intermittently connected and can change IP addresses
It is easier to manage than client-server
It does not exhibit self-scalability
A process is:
The physical machine
A program running on a device
The network connection
The operating system
The interface between the application process and the transport layer protocol is called a:
Port
Socket
Protocol
Router
To identify a specific process on a specific host, one needs:
The host's IP address
The port number
Both the IP address and port number
The MAC address
The well-known port number for HTTP is:
25
53
80
110
An application-layer protocol defines all of the following EXCEPT:
The types of messages exchanged
The syntax of message fields
The semantics of the information in messages
The voltage levels on the physical wire
A protocol like HTTP, defined in an RFC and usable by anyone, is a(n) ________ protocol.
Open
Proprietary
Secret
Outdated
For a real-time audio application, which transport service requirement is most critical?
100% reliable data transfer
High throughput
Timing (low delay)
Security
For a file transfer application, which transport service requirement is most critical?
Timing
High throughput
Loss tolerance
Low security
TCP provides which of the following services?
Reliable data transfer, flow control, congestion control
Unreliable data transfer, timing guarantees
Minimum bandwidth guarantee
Unordered data delivery
UDP provides which of the following services?
Reliable data transfer
Connection-oriented service
Unreliable data transfer
Congestion control
An application might choose UDP over TCP to:
Get guaranteed delivery
Avoid connection establishment delays
Have built-in congestion control
Ensure in-order delivery
TLS provides encryption at which level?
Between the application and transport layers
At the network layer
At the physical layer
Only for email
A web page is typically composed of:
A single HTML file
A base HTML file and several referenced objects
Only text
Only images
In the context of the web, the client is usually the:
Web server
Browser
DNS server
Mail server
The protocol used to transfer web pages is:
FTP
SMTP
HTTP
DNS
HTTP uses ________ as its underlying transport protocol.
UDP
TCP
ICMP
IP
HTTP is stateless, meaning:
It cannot maintain a TCP connection
The server maintains no information about past client requests
It only works within one country
It uses stateless packet switching
Non-persistent HTTP requires ________ TCP connection(s) per object.
One
Two
Multiple
Zero
The main disadvantage of non-persistent HTTP is:
It is less secure
It requires more RTTs and causes more OS overhead
It cannot transfer images
It uses UDP
Persistent HTTP:
Sends one object and closes the connection
Sends multiple objects over a single TCP connection
Is an older, obsolete standard
Is only used for email
The HTTP request message method used to retrieve information is:
POST
PUT
GET
HEAD
The HTTP request message method used to send data to a server (e.g., form data) is:
POST
PUT
GET
HEAD
The HTTP response status code 200 means:
Request succeeded
Moved permanently
Not found
Server error
The HTTP response status code 404 means:
Request succeeded
Moved permanently
Not found
Server error
Cookies are used primarily to:
Store web pages on the user's disk
Introduce security vulnerabilities
Maintain state (user-specific information) on the client side
Speed up TCP connections
A "third-party cookie" is most often used for:
User authentication on the main site
Tracking users across different sites
Storing shopping cart contents
Encrypting user data
A web cache (proxy server) serves what primary purpose?
To act as a firewall
To reduce response time and reduce traffic on an access link
To increase the load on origin servers
To generate cookies
The Conditional GET HTTP mechanism is used to:
Force a download
Check if a cached object is still valid
Upload a new file
Delete a cookie
HTTP/2 improves performance over HTTP/1.1 by:
Switching to UDP
Allowing multiple requests and responses to be interleaved in a single connection
Removing all headers
Making connections non-persistent
A problem with HTTP/2 is that packet loss in the underlying TCP connection can:
Be completely avoided
Stall all object transmissions
Only affect one object
Automatically switch the connection to UDP
The protocol used to send mail from one server to another is:
HTTP
FTP
SMTP
POP3
The three major components of the email system are:
User agents, mail servers, SMTP
Browsers, clients, servers
TCP, IP, HTTP
POP, IMAP, HTTP
SMTP is a ________ protocol, meaning the sending server pushes the message to the receiving server.
Pull
Push
Peer-to-peer
Store-and-forward
A key difference between SMTP and HTTP is that SMTP requires message bodies to be in:
7-bit ASCII
Binary format
HTML
Encrypted format
Which mail access protocol allows users to manage folders on the server and keep messages on the server?
SMTP
HTTP
IMAP
FTP
The primary purpose of the Domain Name System (DNS) is to:
Route packets through the Internet
Translate hostnames to IP addresses
Send email messages
Provide web hosting
The DNS system is:
A single centralized database
A distributed and hierarchical database
A flat naming structure
Owned by a single company
The servers at the top of the DNS hierarchy are called:
.com servers
Root name servers
Authoritative name servers
Local name servers
The DNS server for a specific organization (e.g., umass.edu) that holds its definitive records is its:
Root server
TLD server
Authoritative server
Local server
The DNS record type "A" holds:
An alias name
An IP address
A mail server name
A name server name
The DNS record type "MX" holds:
An alias name
An IP address
A mail server name
A name server name
DNS caching is important because it:
Makes the Internet more secure
Improves response time and reduces traffic
Makes records permanent
Is required for email to work
A common threat to DNS is:
Packet sniffing
DDoS attacks on root/TLD servers
HTTP GET floods
Email spam
In a P2P file distribution system, scalability is achieved because:
There is a powerful central server
Each new peer adds service capacity
Peers have static IP addresses
The government regulates it
In BitTorrent, the "tit-for-tat" strategy encourages:
Free-riding (downloading without uploading)
Peers to upload to those who upload to them
Random selection of peers
Using a central tracker for all transfers
In BitTorrent, a peer requesting chunks will typically ask for the ________ chunks first.
Largest
Smallest
Rarest
Most common
Adaptive video streaming techniques like DASH allow the client to:
Adaptive video streaming techniques like DASH allow the client to:
Control the server's encoding rate
Dynamically request different quality chunks based on current bandwidth
Broadcast the video to other users
Edit the video content
A Content Distribution Network (CDN) manages scalability by:
Using a single, mega-server
Storing copies of content at geographically distributed sites
Slowing down all user connections
Using only P2P technology
The CDN strategy of placing many servers deep within access networks is called:
Bring home
Enter deep
Cluster core
Distribute wide
A socket is an interface between:
Two different hosts
The application process and the transport layer
The network layer and the link layer
The CPU and the RAM
For a simple request-reply application that can tolerate some loss, a developer would likely use:
TCP
UDP
HTTP
SMTP
In TCP socket programming, the server executes ________ to wait for a client's connection setup request.
connect()
bind() and listen()
accept()
sendto()
In UDP socket programming, the sender must explicitly pack the ________ into each datagram.
Destination's MAC address
Destination's IP address and port number
Source's port number only
Encryption key
The transport-layer protocol used by HTTP/3 is:
TCP
UDP
SCTP
TLS
QUIC is designed to improve performance by:
Reducing connection establishment time and avoiding TCP's HOL blocking
Using more complex packet headers
Eliminating the need for encryption
Working only on wired networks
The 'always-on' host in the client-server architecture is the:
Client
Server
Peer
Router
In the P2P architecture, a 'peer' is:
A dedicated, always-on server
An intermittently connected end system
A network router
A DNS server
The combination of an IP address and a port number is called a:
Socket address
MAC address
Protocol number
Checksum
The well-known port number for the SMTP email protocol is:
25
53
80
110
An application-layer protocol that is not defined in an RFC and is controlled by a company is a ________ protocol.
Open
Proprietary
Standard
Secure
For a streaming video application, the most important service requirement is likely:
100% reliability
High throughput
Low delay
Strong security
TCP does NOT provide:
Reliable data transfer
Flow control
Delay guarantees
Congestion control
A benefit of using UDP is that it:
Provides congestion control
Has no connection establishment delay
Guarantees delivery
Reorders packets correctly
The primary role of TLS is to provide:
Faster data transfer
Encryption, data integrity, and endpoint authentication
Routing of packets
Conversion of hostnames to IP addresses
The first part of a URL (e.g., http://) specifies the:
Hostname
Protocol
Path name
Port number
In the HTTP protocol, the entity that responds to requests is the:
Client
Server
DNS
Router
The fundamental transport protocol for HTTP is chosen because it provides:
Low overhead and simplicity
Reliability
Timing guarantees
Broadcast capabilities
The stateless nature of HTTP simplifies server design because:
It makes connections faster
The server does not need to track client state across requests
It improves security
It allows the use of UDP
The main problem with non-persistent HTTP's use of multiple connections is:
It is less secure
It requires more RTTs and has higher OS overhead
It cannot display images
It uses too much bandwidth
Persistent HTTP can improve performance by:
Sending all objects in a single, giant message
Sending multiple objects over a single TCP connection
Using compression on all headers
Eliminating the need for DNS
The HTTP method that requests headers only (no body) is:
GET
POST
HEAD
PUT
An HTTP response status code in the 400s generally indicates:
A server error
A client error
Success
Redirection
The component of a cookie that is used to identify the user is stored:
Only on the user's host
Only on the web server
On the user's host and passed back to the server in HTTP messages
In the DNS system
A web cache satisfies a client request without involving the origin server if:
The object is not popular
The object is in the cache and is fresh
The client is using UDP
The origin server is down
The If-Modified-Since: header is part of a:
Conditional GET request
POST request
DNS query
SMTP handshake
HTTP/2 addresses the problem of Head-of-Line (HOL) blocking in HTTP/1.1 by:
Using multiple parallel TCP connections
Interleaving the transmission of multiple objects on a single connection
Switching to UDP
Removing the need for headers
The protocol responsible for transferring email from the sender's mail server to the recipient's mail server is:
POP3
IMAP
SMTP
HTTP
The user agent is the:
Mail server
Email client software
SMTP protocol
Network router
A key difference between SMTP and HTTP is that SMTP:
Uses push instead of pull
Is stateless
Uses persistent connections
Is based on UDP
The protocol that allows a user to retrieve and manage email stored on a server is:
SMTP
HTTP
FTP
IMAP
The distributed database that translates human-readable hostnames to IP addresses is:
HTTP
DNS
SMTP
BitTorrent
The hierarchical structure of DNS helps with:
Speed of light limitations
Scalability and decentralized management
Encryption of queries
Guaranteeing delivery of packets
The DNS server that your host directly contacts is your:
Root server
TLD server
Authoritative server
Local DNS server
A DNS ________ record returns the IP address for a hostname.
A
NS
MX
CNAME
The fact that DNS has more reads than writes makes it ideal for:
Caching
Encryption
Video streaming
Connection management
A P2P network is self-scalable because:
Servers are very powerful
Each peer adds resources to the system
It uses a central database
It is mandated by Internet standards
In BitTorrent, a peer that has the entire file is called a:
Leecher
Seeder
Tracker
Client
DASH allows the ________ to decide the encoding rate of the video to request.
Server
Client
Network router
CDN operator
The main goal of a CDN is to:
Create content
Bring content closer to users
Replace ISPs
Manage email servers
In socket programming, the bind() operation associates a socket with a:
Process ID
Local port number (and IP address)
Remote hostname
Encryption key
A key difference between TCP and UDP sockets is that TCP sockets are:
Connection-oriented
Unreliable
Faster for simple queries
Not addressable
HTTP/3 uses QUIC, which is implemented over ________ to avoid OS and middlebox issues with new transport protocols.
TCP
UDP
IP
TLS
QUIC combines the connection establishment with ________ establishment to reduce RTTs.
DNS
Security (TLS)
Routing
Congestion control
The concept of having multiple logical streams within a single QUIC connection helps to avoid:
Packet loss
Head-of-Line (HOL) blocking at the transport layer
DNS lookups
Encryption overhead
