Chapter 10: Data Communication and Internet Services (Set-4)
In digital networks, which measurement best represents the actual useful data rate after overhead and errors
A Throughput value
B Bandwidth capacity
C Channel frequency
D DNS cache time
Bandwidth is the maximum possible capacity, but throughput is the real achieved rate after protocol overhead, congestion, retransmissions, and noise effects. That is why throughput is usually lower than bandwidth.
When a signal quality reduces due to loss of high-frequency components over distance, the effect is often called
A DNS recursion
B DHCP renewal
C Signal distortion
D NAT translation
Distortion changes the shape of the signal, so bits may be misread. It can happen due to attenuation and medium limitations, especially over long distances or poor-quality links.
Which technique reduces the effect of noise by representing data with discrete voltage levels rather than continuous values
A Analog broadcast
B Digital signaling
C Proxy caching
D DNS aliasing
Digital signaling uses defined voltage levels for 0 and 1, making it easier to recover data even with some noise. Error detection and retransmission further improve reliability in networks.
A communication link where one side can transmit anytime but the other must always listen is best classified as
A Half-duplex link
B Full-duplex link
C Session-based link
D Simplex link
In simplex, data flows in only one direction. The receiving side has no capability to send back on that channel, so feedback requires a separate channel or different system.
In OSI, the layer that provides logical addressing and path selection across networks is
A Network layer
B Data Link layer
C Transport layer
D Presentation layer
The Network layer manages logical addresses like IP and chooses routes through routers. It ensures packets can move between different networks to reach the correct destination system.
In OSI, which layer creates frames and supports local delivery using hardware addresses
A Network layer
B Session layer
C Data Link layer
D Application layer
The Data Link layer packages data into frames and uses MAC addresses for local communication. It also performs error detection and medium access control on the same network segment.
A TCP “three-way handshake” is mainly used to
A Resolve domain names
B Assign IP address
C Encrypt web traffic
D Establish reliable connection
TCP uses a handshake to synchronize sequence numbers and confirm both sides are ready. This creates a connection before data transfer, enabling reliable delivery with acknowledgments and retransmissions.
Which field is essential for TCP to reorder segments correctly at the receiver
A Subnet mask
B DNS record
C Sequence number
D Port 443
TCP includes sequence numbers so the receiver can arrange segments in the correct order, detect missing data, and request retransmission. This ensures accurate reconstruction of the original message.
UDP is often preferred for real-time voice because it
A Avoids retransmission delays
B Guarantees ordered delivery
C Uses certificates always
D Requires full handshake
Real-time voice values low latency more than perfect reliability. UDP avoids connection setup and retransmission delays, so audio arrives faster even if a small amount of loss occurs.
In HTTP, which header concept is mainly used to indicate the website domain a client wants when multiple sites share one server
A Cookie header
B Host header
C Cache header
D Accept header
The Host header tells the server which domain the client is requesting. This enables virtual hosting, where many websites share one IP address but serve different content by domain name.
A web server sends a 302 status code mainly to indicate
A Permanent redirect
B Resource missing
C Client forbidden
D Temporary redirect
HTTP 302 tells the client the resource is temporarily at another URL. Browsers follow the new location, but search engines may treat it differently than a permanent redirect like 301.
Which HTTP status code usually indicates the client must authenticate or log in
A 200 OK
B 404 Not Found
C 401 Unauthorized
D 500 Error
401 means authentication is required. The server may provide a challenge, and the client must send valid credentials. It is different from 403, which means access is refused even if identified.
In HTTPS, what is the primary job of a Certificate Authority
A Issue trusted certificates
B Assign IP addresses
C Deliver email messages
D Route web packets
A CA verifies identity (to some level) and signs certificates. Browsers trust known CAs, so they can verify that the server’s certificate is valid and belongs to the correct domain.
A “TLS handshake” mainly helps both sides to
A Assign MAC addresses
B Agree on encryption keys
C Create DNS records
D Start DHCP lease
During the TLS handshake, client and server negotiate encryption methods and establish session keys. This allows later data to be encrypted and protected against eavesdropping and tampering.
Which part of a URL usually specifies a web server’s resource location after the domain
A Host name
B Scheme name
C Path component
D Port number
The path comes after the domain and points to the specific resource, like a page or file. It helps the server locate the correct content inside the website structure.
In HTTP, caching directives are mainly controlled using
A Host header
B Content-Type header
C Upgrade header
D Cache-Control header
Cache-Control tells browsers and proxies how to store and reuse responses. It can set max age, public/private rules, and no-cache behavior, improving performance while keeping content correct.
A browser “session cookie” is usually deleted when
A Browser closes
B DNS refreshes
C IP lease ends
D Router restarts
Session cookies typically live only during the browsing session. When the browser is closed, they are removed, which can log the user out unless persistent cookies are used.
In a typical login system, the cookie most commonly stores
A User password
B MAC address
C Session identifier
D Subnet mask
Websites usually store user state on the server and keep only a session ID in the browser cookie. This avoids storing sensitive data directly in the browser and improves security.
In DNS, TTL value mainly controls
A IP subnet size
B Cache duration
C Port opening time
D Packet sequence
TTL determines how long DNS answers can be cached before a fresh lookup is required. Lower TTL updates faster but increases query load; higher TTL reduces load but updates slower.
Which DNS server role is responsible for the final answer for a domain zone it manages
A Authoritative server
B Recursive resolver
C DHCP server
D Proxy server
Authoritative DNS servers store the official DNS records for a domain zone. They provide final answers like A, AAAA, MX, or CNAME records when queried by resolvers.
A recursive resolver mainly performs
A Zone file editing
B IP address translation
C Full lookup process
D Mail delivery routing
Recursive resolvers query other DNS servers on the client’s behalf, cache results, and return the final IP. This simplifies the client’s work and improves repeated lookup speed.
DHCP uses a “pool” to represent
A Stored DNS records
B Encrypted web keys
C FTP user accounts
D Available IP addresses
A DHCP pool is a range of addresses the server can assign dynamically. It helps manage many devices without manual configuration and reduces address conflicts.
Which DHCP option is critical for reaching websites using names rather than IPs
A MAC address option
B TCP port option
C DNS server option
D HTTP method option
Without a DNS server address, a device may have IP connectivity but cannot easily translate domain names into IP addresses. DHCP commonly supplies DNS server information automatically.
A subnet mask of 255.255.255.0 typically indicates
A /24 network
B /16 network
C /8 network
D /30 network
255.255.255.0 corresponds to a /24 prefix, meaning the first 24 bits are network bits. This is a common LAN subnet, allowing 254 usable host addresses in that network.
When a device sends data outside its local subnet, it sends frames to the
A DNS server MAC
B Default gateway MAC
C DHCP server MAC
D Web server MAC
For off-subnet destinations, the device forwards traffic to the default gateway (router). The IP destination stays the remote host, but the local frame uses the gateway’s MAC address.
FTP uses separate connections mainly because it has
A DNS and DHCP
B UDP and TCP
C Control and data
D HTTP and HTTPS
FTP typically uses one control connection for commands and another data connection for file transfers. This design supports directory listings and file movement but complicates firewall handling.
In basic FTP, which item is most at risk on unsecured networks
A Login credentials
B Domain name
C Subnet mask
D MAC address
Classic FTP may transmit usernames and passwords in plain text. On untrusted networks, attackers can capture credentials. Secure alternatives include SFTP or FTPS to protect sensitive data.
FTPS is best described as
A FTP with DHCP
B FTP with DNS
C FTP without ports
D FTP with TLS
FTPS is FTP secured using TLS/SSL. It encrypts authentication and data, improving security compared to plain FTP, though it can require extra firewall configuration due to multiple connections.
In networking, port numbers mainly help the operating system to
A Change IP address
B Build DNS records
C Choose correct application
D Encrypt each packet
Ports identify which application or service should receive incoming traffic on a device. For example, web servers listen on port 80/443, while mail servers use other ports.
Which port is most commonly used by SMTP for mail transfer between servers
A Port 53
B Port 25
C Port 21
D Port 110
SMTP commonly uses port 25 for server-to-server mail transfer. Client submission often uses different ports like 587, but the classic SMTP relay port is 25.
POP3 default port is commonly
A Port 110
B Port 143
C Port 25
D Port 53
POP3 typically uses port 110 for retrieving email. Secure POP3 (POP3S) often uses port 995, but the standard default port for POP3 is 110.
IMAP default port is commonly
A Port 110
B Port 21
C Port 143
D Port 80
IMAP typically uses port 143 for mailbox synchronization. Secure IMAP (IMAPS) often uses port 993, but the standard default IMAP port is 143.
A “proxy cache” can improve browsing speed mainly by
A Increasing noise levels
B Shrinking subnet masks
C Changing MAC addresses
D Reusing stored content
Proxy caches store copies of frequently accessed resources. When another user requests the same content, the proxy can serve it locally, reducing internet bandwidth usage and improving response time.
A VPN can help remote employees access internal resources because it
A Changes DNS root
B Extends private network
C Removes TCP ports
D Disables routing
VPNs create a secure tunnel into a private network, allowing remote users to access internal servers as if they were inside the office network, while protecting traffic over public internet.
NAT changes addresses mainly at the
A Physical layer
B Session layer
C Network layer
D Presentation layer
NAT modifies IP headers, translating private addresses to public addresses and sometimes port numbers. This is a Network layer function because it works with IP addressing and routing.
A router uses MAC addresses mainly for
A Local next hop
B Global routing
C DNS resolution
D Email transfer
Routers route using IP addresses, but to deliver a packet on the local link, they encapsulate it in a frame addressed to the next hop’s MAC address using ARP to learn it.
For VoIP quality, which issue is most harmful because it causes uneven arrival times
A DNS caching
B Static IP
C Port 80 use
D Jitter variation
Jitter is variation in packet delay. VoIP needs steady timing; jitter causes choppy audio. Buffers can reduce jitter effects, but high jitter still reduces call quality significantly.
In VoIP, which delay type is most noticeable to users during conversation
A High TTL
B High subnetting
C High latency
D High caching
Latency is the time taken for voice packets to travel. High latency creates noticeable pauses and overlapping speech, making conversation uncomfortable even if the audio quality is otherwise good.
Traceroute finds path hops mainly by using
A FTP login attempts
B TTL expiration behavior
C DNS record loops
D DHCP lease renewals
Traceroute sends packets with increasing TTL values. Each router decreases TTL; when it reaches zero, the router returns an ICMP message, allowing traceroute to list each hop along the path.
When “ping” fails but DNS still resolves, a common reason can be
A Wrong domain spelling
B DHCP not running
C ICMP blocked firewall
D FTP server down
Many systems block ICMP echo replies for security, so ping may fail even if the host is reachable through TCP/UDP services. DNS resolution only shows name-to-IP mapping exists.
A web browser showing “Not Secure” for a site usually indicates
A No valid HTTPS
B No DNS server
C No subnet mask
D No DHCP lease
Browsers warn when a site is not using HTTPS or has certificate problems. This means traffic may be unencrypted or identity cannot be verified, increasing risk during logins or data entry.
Which security benefit is most directly provided by HTTPS over HTTP
A Faster IP routing
B Encryption and integrity
C Automatic DHCP setup
D Guaranteed file download
HTTPS encrypts data to keep it private and uses integrity checks to prevent tampering. It also supports identity verification via certificates, reducing the risk of man-in-the-middle attacks.
A DNS “zone” is best described as
A User login token
B TCP connection step
C DHCP address pool
D Managed domain portion
A DNS zone is the portion of the namespace managed by a DNS server. It contains records for a domain and may include subdomains depending on how the zone is delegated.
In email systems, IMAP is preferred over POP3 mainly when users need
A One-time downloads
B Faster ping replies
C Multi-device synchronization
D Static NAT mapping
IMAP keeps mail on the server and syncs status across devices, so read/unread states and folders stay consistent. POP3 usually downloads locally and is less suited for multiple devices.
The main technical purpose of “encapsulation” is to
A Add layer information
B Remove packet headers
C Reduce DNS caching
D Increase signal noise
Encapsulation adds headers (and sometimes trailers) at each layer, providing addressing, routing, reliability, and control information. This layered packaging allows networks and applications to work together reliably.
A network “protocol” is most accurately defined as
A Type of cable
B Brand of router
C Speed measurement
D Rules for communication
Protocols define formats, timing, error handling, and procedures so devices can exchange data correctly. Without agreed rules, different systems would not interpret messages reliably.
In a client-server web model, the browser is the
A Server host
B DNS authority
C Client application
D DHCP provider
A browser requests resources like pages and images, so it acts as the client. The web server responds with content and status codes, providing services to many clients.
A “dynamic IP” can cause trouble for hosting a server mainly because
A DNS cannot work
B Address may change
C TCP cannot connect
D Ports stop existing
If a server’s public IP changes, users and DNS records may point to the old address. This breaks access until DNS is updated, which is why static IPs are preferred for hosting.
In DNS, a “CNAME” record is useful when you want
A One name as alias
B Email server priority
C Reverse IP lookup
D Subnet calculation
CNAME points one hostname to another canonical hostname. It helps manage multiple names for the same service without repeating address records, simplifying DNS maintenance.
Which item is most directly associated with identifying a running network service on a host
A Domain suffix
B TTL value
C Port number
D Noise level
A port number, combined with an IP address and protocol, identifies a specific service endpoint. For example, port 443 typically indicates HTTPS service on a web server.