Chapter 10: Data Communication and Internet Services (Set-9)
In a wired link, if measured bandwidth is high but file download is still slow, the most likely metric affected is
A Subnet mask
B DNS record
C MAC address
D Throughput rate
Bandwidth is the theoretical capacity, but throughput is the real delivered rate. Congestion, retransmissions, protocol overhead, or server limits can reduce throughput even on a high-bandwidth connection.
Which factor most directly reduces transmission quality by decreasing signal-to-noise ratio on a channel
A Increased noise
B Static gateway
C DHCP lease
D URL scheme
More noise makes it harder for the receiver to distinguish correct bits from interference. This increases errors and retransmissions, lowering effective speed and reliability, especially on wireless links.
A key difference between half-duplex and full-duplex links is that full-duplex
A Sends one way
B Uses only UDP
C Sends both ways
D Uses only DNS
Full-duplex supports simultaneous transmission and reception, improving efficiency. Half-duplex supports both directions, but only one side can transmit at a time, which can reduce performance.
In OSI, the layer responsible for establishing end-to-end connections for reliable delivery is
A Data Link layer
B Physical layer
C Presentation layer
D Transport layer
The Transport layer provides end-to-end delivery services. TCP at this layer establishes connections, sequences data, and retransmits lost segments to deliver reliable ordered communication.
In OSI, which layer is primarily responsible for defining how bits are represented on the medium
A Physical layer
B Network layer
C Session layer
D Application layer
The Physical layer defines electrical/optical/radio signaling, timing, connectors, and how 0s and 1s are carried. It ensures raw bits can travel across the physical link.
In TCP/IP, the protocol responsible for routing packets across networks is
A HTTP protocol
B IP protocol
C SMTP protocol
D FTP protocol
IP provides logical addressing and routing across networks. Routers forward packets based on destination IP, enabling communication between different networks on the internet.
Encapsulation in layered networking is necessary mainly to
A Remove all headers
B Avoid IP addressing
C Increase noise level
D Add delivery information
Each layer adds headers containing addressing and control details. This allows routing, reliable transport, and correct interpretation at the receiver, even when data passes through many devices.
A key property of UDP that makes it suitable for streaming is that it
A Adds low overhead
B Guarantees retransmits
C Requires handshake
D Ensures ordering
UDP avoids connection setup and retransmission delays. Streaming and voice prefer timely delivery, so they often accept minor loss rather than waiting for missing packets.
For guaranteed delivery and correct order in file download, the correct transport is usually
A UDP protocol
B ICMP protocol
C TCP protocol
D ARP protocol
TCP ensures reliable, ordered delivery using acknowledgments and retransmissions. This is essential for file transfers and web content where missing or out-of-order data would corrupt the result.
DNS works mainly as a
A File transfer service
B Encryption service
C IP leasing service
D Name mapping service
DNS maps human-readable domain names to IP addresses so clients can locate servers. It also supports other records like MX, CNAME, and TXT for email routing and verification.
A DNS “authoritative server” is the server that
A Assigns IP leases
B Holds official records
C Sends web pages
D Transfers files
Authoritative DNS servers contain the official zone records for a domain and provide final answers. Resolvers query them to obtain correct mappings like A/AAAA or MX records.
A recursive DNS resolver mainly
A Hosts website files
B Encrypts DNS always
C Issues certificates
D Performs full lookup
A recursive resolver queries other DNS servers on behalf of the client and returns the final result. It also caches results based on TTL, improving speed for repeated lookups.
DNS TTL is important because it decides
A Cache valid time
B Email port number
C Packet header size
D Gateway IP value
TTL tells how long a DNS response can be cached before rechecking. Low TTL allows faster updates but increases queries; high TTL reduces load but delays propagation of changes.
DHCP provides dynamic addressing by
A Signing certificates
B Encrypting traffic
C Leasing IP settings
D Hosting websites
DHCP assigns IP address and other settings for a limited lease time. Devices renew leases to keep addresses, allowing efficient reuse of IPs and reducing manual configuration work.
A DHCP scope or pool is mainly a
A List of domains
B Set of cookies
C Set of ports
D Range of IPs
A DHCP pool is a set of IP addresses available for automatic assignment. The server chooses an unused address from the pool and provides it along with required network parameters.
If a device has wrong subnet mask, it may
A Break DNS caching
B Misjudge local hosts
C Disable FTP port
D Stop TLS handshake
The subnet mask determines which IPs are local. If it is wrong, the device may send local traffic to the gateway or try ARP for remote hosts, causing failures or delays.
The HTTP request method usually used to update server data using a request body is
A POST method
B GET method
C HEAD method
D TRACE method
POST sends data in the request body and is commonly used to submit forms or create resources. It is suitable when server-side state changes, unlike GET which primarily retrieves resources.
HTTP status 403 indicates
A Resource missing
B Temporary redirect
C Server overload
D Access forbidden
403 means the server understood the request but refuses to authorize it. This is often due to permission rules, blocked access, or restricted content even if the user is identified.
HTTP status 401 usually means
A Page not found
B Permanent redirect
C Authentication required
D Request success
401 indicates the client must authenticate to access the resource. The server may request credentials; it differs from 403 where access is denied even after identification.
HTTPS uses certificates mainly to
A Verify server identity
B Assign DHCP leases
C Route IP packets
D Open FTP ports
Certificates bind a domain to a public key and are signed by trusted authorities. This lets the browser verify the site identity and then create an encrypted TLS session.
TLS protects data mainly by providing
A Packet fragmentation
B IP leasing
C DNS caching
D Encryption and integrity
TLS encrypts traffic to keep it private and adds integrity checks to detect tampering. It reduces risks like eavesdropping and modification when using HTTPS or other secure services.
Cookies help a website maintain user state because HTTP is
A Connectionless always
B Stateless by design
C Encrypted always
D Routed by DNS
HTTP does not remember previous requests automatically. Cookies store identifiers like session IDs so the server can recognize a returning browser and keep logins, carts, and preferences.
In client-server web communication, the browser acts as
A Client requester
B Server provider
C DNS authority
D DHCP server
A browser sends requests for pages and resources. The server responds with content and status codes, serving multiple clients at once, which is the basic client-server model.
FTP differs from HTTP mainly because FTP is designed for
A Domain name mapping
B Secure tunneling only
C IP address leasing
D File transfer tasks
FTP is built specifically for uploading and downloading files between client and server. HTTP is mainly for fetching web resources, though it can transfer files as part of web content.
The main security weakness of basic FTP is that it
A Uses port 443
B Requires no login
C Sends data unencrypted
D Uses only UDP
Classic FTP may send credentials and file data in plain text. Attackers can capture it on untrusted networks, so secure alternatives like SFTP or FTPS are preferred.
SFTP is generally safer than FTP because SFTP
A Encrypts credentials and data
B Uses port 80
C Removes all headers
D Uses only ICMP
SFTP uses an encrypted channel (commonly over SSH), protecting authentication and transferred files. This prevents simple sniffing attacks that can expose usernames, passwords, and file contents.
SMTP is used primarily for
A Downloading mailbox
B Syncing folders
C Resolving domains
D Sending mail messages
SMTP transfers outgoing email from clients to servers and between mail servers. Retrieval and synchronization are handled by POP3 or IMAP, not SMTP.
POP3 is commonly used when a user wants to
A Send outgoing email
B Resolve website IP
C Download emails locally
D Encrypt web pages
POP3 retrieves emails from the mail server to the client, often storing them locally. It is simple but less suited to keeping messages synchronized across multiple devices.
IMAP is preferred over POP3 when users need
A One-time download
B Multi-device email sync
C Only outgoing mail
D Faster IP routing
IMAP keeps messages on the server and synchronizes folders and read states across devices. This is ideal when the same mailbox is accessed from phones, laptops, and webmail.
Ping is most useful for quickly testing
A DNS record type
B DHCP lease time
C HTTP method use
D Host reachability
Ping checks if a host responds and measures round-trip time using ICMP echo messages. It helps identify basic connectivity problems like unreachable hosts or high network delay.
Traceroute is used to identify
A Router hop path
B Cookie expiration time
C FTP file size
D DNS zone content
Traceroute reveals each router hop to a destination by using TTL changes and ICMP responses. It helps locate where delays or failures occur along the route.
A proxy server can help organizations mainly by
A Changing MAC addresses
B Assigning IP leases
C Controlling web access
D Increasing attenuation
Proxies can filter blocked sites, log usage, enforce policies, and cache frequently used content. They act as intermediaries between clients and the internet for control and efficiency.
A VPN is often used on public Wi-Fi to
A Encrypt user traffic
B Increase bandwidth
C Disable NAT
D Lower DNS TTL
A VPN creates an encrypted tunnel to a trusted server, protecting data from local eavesdroppers. This is especially useful on public networks where traffic may be monitored.
NAT is helpful in home networks because it
A Removes all routing
B Encrypts web pages
C Blocks all traffic
D Shares one public IP
NAT translates private internal addresses to a public address, allowing multiple devices to use one public IPv4. It conserves public IP addresses and supports typical home internet setups.
A MAC address is mainly used for delivery within
A Internet-wide routing
B Local network segment
C DNS root servers
D Email transfer chain
MAC addresses identify interfaces on a LAN and are used in frames for local delivery. Across networks, IP addressing is used for routing, while MAC addresses change per hop.
Data packets allow networks to
A Remove all noise
B Stop attenuation fully
C Avoid protocols
D Share links efficiently
Packet switching divides data into packets that can be routed dynamically, letting many users share network links. Packets can take different paths and are reassembled at the destination.
A well-known port is typically reserved for
A Common standard services
B Random user programs
C Only VPN tunnels
D Only DNS caching
Well-known ports (0–1023) are used by standard services like HTTP and SMTP. This standardization helps clients know where to connect for common network services.
DNS primarily uses which port number
A Port 21
B Port 25
C Port 110
D Port 53
DNS uses port 53, often over UDP for most queries and TCP for larger responses or zone transfers. Port 53 is the standard across DNS implementations.
When a browser shows a padlock icon, it most often means
A DNS is off
B HTTPS is active
C DHCP stopped
D FTP is secure
The padlock generally indicates a valid HTTPS connection with TLS encryption and certificate verification. It helps reduce interception and tampering risks when browsing, especially on login or payment pages.
A common use of caching on the internet is to
A Speed repeated access
B Increase packet loss
C Increase noise
D Change IP routes
Caching stores previously fetched data, like DNS answers or web content. Reusing cached results reduces repeated network requests, saves bandwidth, and improves response time for users.
A dynamic IP address is usually assigned by
A DNS resolver
B Web browser
C DHCP server
D SMTP server
DHCP servers assign IP addresses dynamically from a pool and provide other settings like gateway and DNS. This allows devices to join networks quickly without manual IP configuration.
Static IP addresses are commonly used for
A Random guest devices
B Noise reduction only
C DHCP relay agents
D Servers needing consistency
Servers often require stable IPs so DNS records and clients can reliably reach them. Dynamic addresses can change, causing service interruptions unless extra mechanisms update records quickly.
Web hosting services mainly provide
A Space for websites
B DHCP IP pools
C DNS root control
D MAC filtering lists
Hosting stores website content on internet-connected servers and provides resources like bandwidth and uptime. This allows users worldwide to access the website reliably through web protocols.
VoIP quality is most affected by which network problem
A High TTL
B High jitter
C Long domain
D Static subnet
VoIP needs steady packet timing. Jitter causes uneven arrival times, producing choppy audio. Even with good bandwidth, high jitter or packet loss can severely reduce call quality.
In a URL, the “scheme” part like https mainly indicates
A Domain ownership
B IP lease duration
C MAC address format
D Protocol to use
The scheme tells the browser which protocol to use to access the resource. “https” means HTTP over TLS, while “http” means unencrypted HTTP.
HTTP is called application-layer because it
A Routes packets directly
B Assigns IP addresses
C Serves user web data
D Encodes radio signals
HTTP operates at the application level, enabling browsers and servers to exchange web content. Lower layers handle transport (TCP), routing (IP), and physical transmission.
In TCP, acknowledgments are important because they
A Confirm received data
B Assign DNS servers
C Set subnet mask
D Open VPN tunnel
ACKs tell the sender which data arrived successfully. If ACKs are missing, TCP can retransmit. This mechanism supports reliable delivery and prevents silent data loss.
A common reason NAT can complicate some apps is that it
A Increases bandwidth
B Removes encryption
C Stops DNS caching
D Changes ports and IP
NAT rewrites IP addresses and often port numbers. Applications that embed address details in payloads or require inbound connections may fail unless NAT traversal methods or helpers are used.
The main role of the Transport layer is to provide
A Signal transmission
B End-to-end delivery
C Domain resolution
D Hardware addressing
The Transport layer manages communication between applications, using segmentation and port numbers. With TCP it can add reliability and ordering; with UDP it provides lightweight delivery.
The main role of DNS and DHCP together in a LAN is
A Addressing and naming
B Encryption and routing
C Modulation and noise
D FTP and VoIP
DHCP provides IP configuration automatically, while DNS translates names to IP addresses. Together they let devices join the network easily and access services using human-friendly names.