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Quizzes > Computers & IT

16.8.3 Application Layer Services Quiz

Quick, free application layer protocols practice. Instant results.

Editorial: Review CompletedCreated By: Kelly MandersUpdated Aug 24, 2025
Difficulty: Moderate
2-5mins
Learning OutcomesCheat Sheet
Paper art style icons of email chat cloud documents on sky blue background for application layer protocols quiz.

This quiz helps you check your grasp of application layer services, from HTTP and DNS to SMTP and DHCP, and match each service to the right port and transport. After you finish, try a broader network protocols quiz, sharpen port knowledge with the port numbers quiz, or review basics in the ip networking fundamentals quiz.

Which port is the default for HTTP traffic?
25
443
80
21
HTTP uses port 80 by default for unencrypted web traffic. When a client sends an HTTP request without specifying a port, it connects to this port as per the IANA registry. Secure HTTP uses a different port (443).
Which port is used by HTTPS by default?
443
110
21
80
HTTPS secures HTTP traffic by default on port 443. This port is registered with IANA for encrypted web communications using TLS/SSL. Browsers automatically use this port when connecting via https://.
Which port is the default control port for FTP?
20
22
23
21
FTP uses port 21 by default for control commands. Data transfers may use port 20 when in active mode. Port assignments are defined by IANA for standard FTP operations.
Which protocol retrieves email from a server and typically deletes messages after download?
SMTP
POP3
IMAP
HTTP
POP3 (Post Office Protocol v3) downloads email to the client and by default removes it from the server. IMAP keeps messages on the server for multi-device access. POP3 is defined in RFC 1939.
Which protocol is used to send email between servers?
FTP
IMAP
POP3
SMTP
SMTP (Simple Mail Transfer Protocol) is designed for sending email across networks, especially between mail servers. It's defined in RFC 5321 and uses port 25 by default. Clients also use SMTP to submit outgoing mail.
What does DNS stand for?
Domain Name Service
Digital Name System
Distributed Name Service
Domain Name System
DNS stands for Domain Name System, which translates human-readable domain names to IP addresses. It's a hierarchical, distributed database maintained by numerous servers worldwide. DNS is essential for locating resources on the Internet.
In the OSI model, which layer does HTTP operate at?
Session
Network
Application
Transport
HTTP is an application-layer protocol in the OSI model, handling user-level communication for web services. It relies on TCP at the transport layer for reliable delivery. The application layer provides network services to end-user applications.
What does TLS stand for?
Transmission Layer Security
Transport Layer Security
Transfer Layer Security
Transport Link Security
TLS stands for Transport Layer Security and provides encryption, integrity, and authentication for network communication. It evolved from SSL and is defined in RFC 5246 and later updates. TLS secures protocols like HTTPS, IMAPS, and SMTPS.
What does SSH stand for?
Shell Secure
Secure Shell
Secure Socket Host
Secure Shell Protocol
SSH stands for Secure Shell and provides an encrypted channel for remote login and other network services. It replaces insecure protocols like Telnet by using strong cryptographic techniques. SSH operates typically over port 22.
Which protocol securely transfers files over an SSH connection?
SFTP
FTPS
FTP
TFTP
SFTP (SSH File Transfer Protocol) provides secure file transfer over an SSH session on port 22. Unlike FTPS, it uses only the SSH channel without separate data and control connections. SFTP ensures confidentiality and integrity.
Which protocol allows remote, unencrypted text-based communication?
Telnet
RDP
SSH
HTTP
Telnet provides an unencrypted, text-based remote terminal connection, typically on port 23. It has been largely replaced by SSH for secure communications. Telnet transmits data in plain text, posing security risks.
SMTP uses which port by default?
465
110
25
587
SMTP officially uses port 25 for server-to-server mail transfer as defined in RFC 5321. Port 587 is used for message submission by clients. Port 465 was once used for SMTPS but is deprecated.
What HTTP status code indicates that a resource was not found?
500
301
404
200
The 404 status code means the server can't find the requested resource. It's commonly returned when a URL is incorrect or the resource has been moved or deleted. Clients interpret this as a client-side error.
Which HTTP method applies partial modifications to a resource?
DELETE
PUT
PATCH
GET
PATCH is used to apply partial updates to a resource, allowing changes to a subset of its fields. PUT replaces the entire resource, while PATCH modifies only the specified fields. It's defined in RFC 5789.
Which DNS record type maps a hostname to an IPv4 address?
CNAME
AAAA
A
MX
An A record maps a domain name to its IPv4 address. AAAA records serve the same function for IPv6. CNAME creates an alias to another domain. A records are fundamental to DNS.
In SMTP, which command initiates the mail transaction specifying the sender?
DATA
MAIL FROM
RCPT TO
HELO
MAIL FROM marks the start of a mail transaction and identifies the sender's email address. HELO/EHLO is used earlier for greeting. RCPT TO specifies recipients, and DATA begins the message body.
Which IMAP command is used to select or open a specific mailbox?
FETCH
SELECT
OPEN
GET
SELECT opens a mailbox for access, allowing subsequent commands to act on that mailbox. It returns status information such as message count and flags. It's defined in RFC 3501 for IMAP.
In FTP, what is the name of the mode where the client initiates the data connection?
Active
Passive
Extended
Secure
In active mode FTP, the client opens a port and listens while the server initiates the data connection. Passive mode reverses this behavior. Active mode is the original FTP data transfer method.
Which POP3 command retrieves only the headers or top lines of a message without deleting it?
RETR
LIST
TOP
DELE
TOP retrieves the header and a specified number of lines from the message body without marking it for deletion. RETR fetches the entire message. TOP is useful for previewing.
What is the default port for IMAP over SSL/TLS?
995
993
143
465
IMAPS uses port 993 to provide encrypted IMAP communication via SSL/TLS. The standard IMAP port (without encryption) is 143. Port 995 is for POP3S.
Which protocol is responsible for encrypting HTTP traffic on the web?
SHA
IPSec
SSH
TLS
TLS secures HTTP by encrypting data in transit, which is why we see HTTPS. IPSec works at the network layer, while SSH is for remote shell access. SHA is a hashing algorithm.
What is the official MIME type for JSON?
text/json
application/x-json
text/javascript
application/json
The official MIME media type for JSON as defined in RFC 8259 is application/json. While some older systems use text/json or other variants, they are not standardized.
Which port and protocol combination is used by DNS for most queries?
TCP port 53
UDP port 67
TCP port 80
UDP port 53
DNS primarily uses UDP on port 53 for query-response transactions due to its lower overhead. TCP on port 53 is used for zone transfers or response truncation.
Which protocol typically uses port 5060 for signaling?
RTSP
LDAP
SIP
NNTP
SIP (Session Initiation Protocol) uses port 5060 for unencrypted signaling in VoIP and multimedia sessions. Secure SIP (SIPS) uses port 5061.
Which HTTP header field signals the client's preference for persistent connections?
Connection: close
Keep-Alive
Proxy-Connection
Connection: keep-alive
In HTTP/1.1, Connection: keep-alive requests that the server maintain the TCP connection for multiple requests. Connection: close asks the server to close it. Keep-Alive is often used as an informal header.
During a TLS handshake, what is the primary purpose of the ServerHello message?
To request the client certificate
To send the server certificate
To choose the cipher suite
To finalize the handshake
The ServerHello message negotiates encryption parameters by selecting the cipher suite and TLS version from the client's offer. It follows ClientHello and precedes certificate exchange.
Which DNS record type is used for reverse DNS lookups?
CNAME
PTR
NS
SRV
PTR records map an IP address to a domain name, enabling reverse DNS lookups. They are stored in special reverse-mapping zones. PTRs are critical for email server verification and logging.
In SMTP, how does the client signal the end of the message data?
END
QUIT
.
DATA_END
SMTP clients terminate the DATA command with a line containing only a single period. The server responds after receiving this sentinel. This convention is defined in RFC 5321.
What is the default port for POP3 over SSL/TLS (POP3S)?
993
995
465
143
POP3S uses port 995 to provide encrypted POP3 access via TLS/SSL. Standard POP3 without encryption uses port 110. POP3S ensures confidentiality and integrity of mail retrieval.
Which class of FTP reply codes indicates a positive preliminary response?
3xx
2xx
1xx
4xx
FTP reply codes in the 1xx range are positive preliminary replies, meaning the request was accepted and the action is in progress. 2xx indicates success, 3xx for redirects, and 4xx for transient errors.
What does the TTL field in a DNS record specify?
Time to look up in reverse DNS
Time to link aggregation
Cache duration for the record
Time to live for the DNS server
TTL (Time to Live) indicates how long a DNS record can be cached by resolvers before it must be refreshed. Short TTLs increase query traffic, while long TTLs improve caching efficiency. It's defined in DNS specifications.
Which protocol is most commonly used to carry real-time media streams in VoIP?
RTSP
HTTP
SIP
RTP
RTP (Real-time Transport Protocol) carries audio and video over IP networks with timing and payload identification. SIP handles session initiation but not the media transport itself. RTP often works alongside RTCP for quality feedback.
What does HTTP status code 503 signify?
Service Unavailable
Internal Server Error
Bad Gateway
Gateway Timeout
503 Service Unavailable indicates the server is temporarily unable to handle the request, often due to maintenance or overload. Clients should retry after some time. The server may include a Retry-After header.
Which IMAP command is used to retrieve specific parts of a message by sequence number?
FETCH
COPY
SEARCH
STORE
FETCH retrieves message data such as headers or body sections by message sequence number or UID. STORE modifies flags, SEARCH finds messages, and COPY duplicates messages. FETCH is central to IMAP retrieval.
Which HTTP header specifies the preferred natural languages for response content?
Accept-Language
Accept
Accept-Encoding
Accept-Ranges
Accept-Language indicates the client's preferred languages for content negotiation. Servers can tailor responses based on this header. It's part of HTTP/1.1 standard headers.
Which DNS record type designates the mail exchange server for a domain?
A
SRV
MX
TXT
MX records specify mail exchange servers responsible for receiving email on behalf of a domain. Priority values determine order. MX is defined in RFC 1035.
During the TLS handshake, which message confirms that the handshake messages have not been tampered with?
ChangeCipherSpec
CertificateVerify
ServerKeyExchange
Finished
The Finished message includes a hash of all previous handshake messages, proving integrity and successful key exchange. Both client and server send it after ChangeCipherSpec. It's vital for verifying no tampering occurred.
In HTTP/2, which frame type initiates a new request stream with headers?
DATA
SETTINGS
PRIORITY
HEADERS
The HEADERS frame in HTTP/2 opens or continues a stream by carrying header block fragments. SETTINGS configures connection parameters, and DATA carries payload. HEADERS is essential for request initiation.
Which DNSSEC record type contains the digital signature for DNS data?
DNSKEY
DS
NSEC
RRSIG
RRSIG records hold the cryptographic signatures for DNS record sets, enabling validation of data authenticity. DNSKEY stores public keys, DS references keys in parent zones, and NSEC proves nonexistence.
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Study Outcomes

  1. Understand Core Application Layer Protocols -

    Gain clarity on the functions of HTTP, DNS, SMTP, and other key protocols that enable web browsing, email, and domain name resolution.

  2. Identify Peer-to-Peer Network Traits -

    Select the correct traits in response to "what are two characteristics of peer-to-peer networks? Choose two" questions and understand how peer nodes share resources without central servers.

  3. Distinguish TCP-Based Services -

    Answer "which three application layer protocols use TCP? Choose three" prompts by matching protocols like HTTP, FTP, and SMTP to their reliable transport requirements.

  4. Apply OSI Layer 7 Concepts -

    Navigate the 16.8.3 application layer services quiz to strengthen your knowledge of OSI layer 7 functionalities and network service interactions.

  5. Analyze Real-World Protocol Usage -

    Map common network services - such as web hosting, file transfer, and email delivery - to their corresponding application layer protocols in practical scenarios.

  6. Evaluate Your Proficiency -

    Use the common application layer protocols quizizz to assess your strengths and identify areas for improvement in understanding application layer services.

Cheat Sheet

  1. HTTP/HTTPS Basics -

    According to Kurose & Ross (7th ed.) and IETF RFC 2616, HTTP is a stateless, text-based request/response protocol using methods like GET, POST, PUT, and DELETE. A handy mnemonic such as "Please Give Pizza Directly" can help you recall GET, POST, PUT, DELETE. Remember that HTTPS wraps HTTP in TLS (RFC 5246) on port 443 to secure traffic.

  2. Domain Name System (DNS) Resolution -

    DNS, defined in RFCs 1034 and 1035, translates human-readable domains to IP addresses using recursive and iterative queries; you can visualize recursion like calling a senior colleague until resolution. Caching at each DNS server speeds up lookups, reducing latency and query loads (per ICANN best practices). Practice by tracing "dig" command outputs to see root, TLD, and authoritative steps.

  3. SMTP, POP3, and IMAP Protocols -

    SMTP (RFC 5321) on TCP port 25 handles email sending and relay, while POP3 (RFC 1939) and IMAP (RFC 3501) on ports 110/995 and 143/993 pull messages from mailboxes. IMAP supports multiple folder syncs and server-side searching, unlike the simpler download-and-delete model of POP3; remember "I Manage All Posts" for IMAP's capabilities. Testing with Telnet can help you see SMTP handshakes and IMAP mail retrieval in action.

  4. Peer-to-Peer Network Characteristics -

    Peer-to-peer (P2P) networks are decentralized and scalable, lacking a central server, which enhances resilience and distributes load among peers (per IEEE Communications surveys). Two key characteristics include resource sharing among nodes and equal peer roles, improving fault tolerance. Try contrasting BitTorrent's swarm model to client-server designs to internalize how P2P heightens availability.

  5. TCP-Based Application Layer Protocols -

    Understanding which application layer protocols use TCP is vital for common application layer protocols quizizz review; HTTP, FTP (RFC 959), and SMTP reliably transmit data over TCP's connection-oriented service. Use the mnemonic "Hot Fast Sushi" (HTTP, FTP, SMTP) to instantly recall these three core TCP-based protocols. Remember that TCP's flow control and congestion management ensure ordered, error-checked delivery for these services.

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