1Which layer of the OSI model is primarily responsible for process-to-process delivery of the entire message?
A.Session Layer
B.Data Link Layer
C.Network Layer
D.Transport Layer
Correct Answer: Transport Layer
Explanation:
While the Network layer oversees host-to-host delivery, the Transport Layer ensures process-to-process delivery using port numbers.
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2The Transport Layer creates a connection between the source and destination ports. This type of addressing is known as:
A.Physical addressing
B.Service-point (Port) addressing
C.Logical addressing
D.Domain addressing
Correct Answer: Service-point (Port) addressing
Explanation:
Port addressing (or Service-point addressing) identifies specific processes running on the host, which is the function of the Transport Layer.
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3Which of the following services is NOT typically provided by the Transport Layer?
A.Routing
B.Error Control
C.Flow Control
D.Segmentation and Reassembly
Correct Answer: Routing
Explanation:
Routing is a function of the Network Layer (determining the path for packets). The Transport Layer handles flow control, error control, and segmentation.
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4In the context of the Transport Layer, what is multiplexing?
A.Connecting multiple routers together
B.Sending data from multiple processes to the network layer via a single transport protocol
C.Splitting one signal into multiple frequencies
D.Distributing incoming packets to different processes
Correct Answer: Sending data from multiple processes to the network layer via a single transport protocol
Explanation:
Multiplexing at the Transport Layer involves gathering data from several application processes and sending them down to the Network Layer.
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5What is the size of the Sequence Number field in the TCP header?
A.16 bits
B.64 bits
C.8 bits
D.32 bits
Correct Answer: 32 bits
Explanation:
The Sequence Number field in TCP is 32 bits long, allowing for distinct sequence numbers.
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6The minimum and maximum lengths of a TCP header are, respectively:
A.20 bytes and 60 bytes
B.20 bytes and 40 bytes
C.20 bytes and 65535 bytes
D.8 bytes and 20 bytes
Correct Answer: 20 bytes and 60 bytes
Explanation:
The mandatory TCP header is 20 bytes. With the maximum size of the Options field (40 bytes), the total header size can reach 60 bytes.
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7In the TCP header, the Window Size field is used for:
A.Flow Control
B.Connection Establishment
C.Error Detection
D.Congestion Control
Correct Answer: Flow Control
Explanation:
The Window Size field (16 bits) advertises the amount of data the receiver is willing to accept, which is the core mechanism of Flow Control.
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8Which flag in the TCP header is set to 1 to initiate a connection?
A.SYN
B.FIN
C.URG
D.RST
Correct Answer: SYN
Explanation:
The SYN (Synchronize) flag is used during the three-way handshake to initiate a connection and synchronize sequence numbers.
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9If a TCP sender sends a segment with Sequence Number and payload length , what will be the Acknowledgement Number in the receiver's response (assuming successful receipt)?
A.
B.
C.
D.
Correct Answer:
Explanation:
The Acknowledgement Number indicates the next byte expected. If bytes starting at with length are received, the next expected byte is .
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10Which of the following correctly describes the TCP Three-Way Handshake?
A.SYN ACK FIN
B.REQ RES ACK
C.SYN ACK SYN-ACK
D.SYN SYN-ACK ACK
Correct Answer: SYN SYN-ACK ACK
Explanation:
The client sends a SYN, the server responds with a SYN-ACK, and the client confirms with an ACK.
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11The HLEN (Header Length) field in the TCP header is 4 bits. What is the multiplier used to calculate the total header size in bytes?
A.1 byte
B.8 bytes
C.4 bytes
D.16 bytes
Correct Answer: 4 bytes
Explanation:
The value in the HLEN field represents the number of 4-byte words. Therefore, the value is multiplied by 4 to get the total bytes.
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12What is the purpose of the Urgent Pointer field in the TCP header?
A.It requests an immediate acknowledgement.
B.It indicates the sequence number of the last byte of urgent data.
C.It resets the connection immediately.
D.It points to the beginning of the next segment.
Correct Answer: It indicates the sequence number of the last byte of urgent data.
Explanation:
The Urgent Pointer is valid only if the URG flag is set. It defines a value that must be added to the sequence number to find the end of the urgent data.
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13In TCP, the PSH (Push) flag informs the receiver to:
A.Prioritize this packet over others in the network.
B.Push the data to the application layer immediately without buffering.
C.Push the connection termination request.
D.Retransmit the previous segment.
Correct Answer: Push the data to the application layer immediately without buffering.
Explanation:
The PSH flag tells the receiver to pass the data to the application as soon as possible, rather than waiting for the buffer to fill.
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14Which TCP field includes information from the IP header (source IP, dest IP, protocol, length) to ensure the segment reached the correct destination?
A.Window Size
B.Options
C.Padding
D.Pseudo-header (used in Checksum calculation)
Correct Answer: Pseudo-header (used in Checksum calculation)
Explanation:
TCP calculates the checksum over the header, data, and a pseudo-header derived from the IP header to verify the segment is delivered to the correct IP/Protocol.
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15The standard size of a UDP header is fixed at:
A.16 bytes
B.8 bytes
C.32 bytes
D.20 bytes
Correct Answer: 8 bytes
Explanation:
The UDP header is very simple and has a fixed size of 8 bytes.
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16Which of the following fields is NOT present in a UDP header?
A.Destination Port
B.Checksum
C.Source Port
D.Sequence Number
Correct Answer: Sequence Number
Explanation:
UDP is connectionless and unreliable; it does not use Sequence Numbers or Acknowledgements.
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17Why is UDP often referred to as a connectionless protocol?
A.It only works on wireless networks.
B.It does not use IP addresses.
C.It requires a 2-way handshake instead of 3-way.
D.It does not establish a virtual circuit or handshake before transmitting data.
Correct Answer: It does not establish a virtual circuit or handshake before transmitting data.
Explanation:
UDP sends independent datagrams without establishing a connection state or performing a handshake beforehand.
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18In the UDP header, the Length field includes:
A.Only the size of the data payload.
B.The size of the pseudo-header.
C.Only the size of the header.
D.The size of the header plus the data.
Correct Answer: The size of the header plus the data.
Explanation:
The UDP Length field (16 bits) represents the total length of the user datagram, which includes the header and the data.
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19Which application would typically prefer UDP over TCP?
A.Real-time Video Streaming
B.Email (SMTP)
C.Web Browsing (HTTP)
D.File Transfer (FTP)
Correct Answer: Real-time Video Streaming
Explanation:
Real-time applications prioritize speed over absolute reliability. Dropped frames (UDP) are preferable to the latency caused by retransmissions (TCP).
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20The calculation of the Checksum in UDP is:
A.Always Mandatory
B.Optional in IPv4, Mandatory in IPv6
C.Mandatory in IPv4, Optional in IPv6
D.Always Optional
Correct Answer: Optional in IPv4, Mandatory in IPv6
Explanation:
UDP checksums are optional in IPv4 (though recommended) but were made mandatory in IPv6.
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21The Domain Name System (DNS) primarily uses which Transport Layer protocol for standard queries?
A.ICMP
B.UDP
C.TCP
D.SCTP
Correct Answer: UDP
Explanation:
Standard DNS queries (small size) typically use UDP on port 53 for speed. TCP is used for Zone Transfers or large responses.
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22Which standard port number is assigned to DNS?
A.53
B.25
C.80
D.21
Correct Answer: 53
Explanation:
DNS uses port 53.
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23In DNS, a Recursive Query puts the burden of resolution on the:
A.ISP
B.Root Server only
C.Client (Resolver)
D.Contacted Name Server
Correct Answer: Contacted Name Server
Explanation:
In a recursive query, the contacted server must return the final answer (or an error), meaning it performs the subsequent lookups on behalf of the client.
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24Which DNS record type maps a hostname to an IPv4 address?
A.MX
B.AAAA
C.CNAME
D.A
Correct Answer: A
Explanation:
The A record maps a host name to an IPv4 address. (AAAA is for IPv6, MX for mail, CNAME for aliases).
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25What is the structure of the DNS namespace?
A.Linear
B.Mesh
C.Circular
D.Inverted Tree (Hierarchical)
Correct Answer: Inverted Tree (Hierarchical)
Explanation:
DNS uses a hierarchical tree structure, starting with the Root (), followed by TLDs, Domain names, and Subdomains.
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26Which protocol is used to push email from a client to a mail server?
A.SMTP
B.HTTP
C.IMAP
D.POP3
Correct Answer: SMTP
Explanation:
SMTP (Simple Mail Transfer Protocol) is a push protocol used to send mail from client to server or between servers.
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27Post Office Protocol version 3 (POP3) is primarily used for:
A.Encrypting email content
B.Sending emails between servers
C.Resolving domain names
D.Retrieving emails from a server to a client
Correct Answer: Retrieving emails from a server to a client
Explanation:
POP3 is a pull protocol used by a user agent to retrieve and download emails from a mail server.
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28What is the main advantage of IMAP over POP3?
A.IMAP does not require authentication.
B.IMAP allows managing emails directly on the server (folders, flags).
C.IMAP uses UDP for reliability.
D.IMAP is faster.
Correct Answer: IMAP allows managing emails directly on the server (folders, flags).
Explanation:
IMAP keeps email on the server, allowing synchronization across multiple devices and folder management, whereas standard POP3 downloads and deletes.
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29SMTP uses which port number by default?
A.23
B.110
C.21
D.25
Correct Answer: 25
Explanation:
The standard port for SMTP is 25.
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30Which standard extends email to support non-ASCII text, audio, and video attachments?
A.FTP
B.NVT
C.TELNET
D.MIME
Correct Answer: MIME
Explanation:
MIME (Multipurpose Internet Mail Extensions) extends the format of email to support text in character sets other than ASCII, as well as attachments.
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31FTP (File Transfer Protocol) establishes two connections between client and server. They are:
A.Upload connection and Download connection
B.Control connection and Data connection
C.TCP connection and UDP connection
D.Primary connection and Backup connection
Correct Answer: Control connection and Data connection
Explanation:
FTP uses separate connections: a Control connection (Port 21) for commands and a Data connection (Port 20) for transferring files.
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32Which port is used for the FTP Control Connection?
A.21
B.80
C.22
D.20
Correct Answer: 21
Explanation:
Port 21 is used to establish the control connection where commands are sent.
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33In FTP, the control connection is considered "out-of-band". What does this mean?
A.It has higher bandwidth.
B.It uses a different frequency.
C.It operates outside the internet.
D.It uses a separate channel/socket from the data transfer.
Correct Answer: It uses a separate channel/socket from the data transfer.
Explanation:
Out-of-band means control information is sent over a separate logical link (Port 21) than the actual data (Port 20).
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34What is SD-WAN (Software Defined Wide Area Network)?
A.A protocol strictly for fiber optics.
B.A hardware-only solution for connecting LANs.
C.A new version of the internet protocol.
D.A virtual WAN architecture that decouples network software services from underlying hardware.
Correct Answer: A virtual WAN architecture that decouples network software services from underlying hardware.
Explanation:
SD-WAN applies SDN concepts to WANs, abstracting the control plane from the data plane to manage routing via software.
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35A key benefit of SD-WAN regarding transport independence is:
A.It only works with MPLS.
B.It allows the aggregation of multiple connection types (MPLS, 4G, Broadband, LTE).
C.It requires satellite connections.
D.It removes the need for IP addresses.
Correct Answer: It allows the aggregation of multiple connection types (MPLS, 4G, Broadband, LTE).
Explanation:
SD-WAN can bond various transport links (MPLS, Internet, LTE) into a single virtual overlay, optimizing performance and cost.
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36In SD-WAN, what is ZTP?
A.Zone Transfer Protocol
B.Zero Touch Provisioning
C.Zigzag Transmission Path
D.Zero Transmission Protocol
Correct Answer: Zero Touch Provisioning
Explanation:
Zero Touch Provisioning allows devices to be configured automatically upon connection to the network without manual local setup.
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37Unlike traditional router-based WANs, SD-WAN manages the network via:
A.Manual CLI configuration on every device
B.Peer-to-peer negotiation
C.A Centralized Controller
D.The Physical Layer
Correct Answer: A Centralized Controller
Explanation:
SD-WAN uses a centralized controller to push policies and configurations to all edge devices.
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38What is the primary function of a CDN (Content Delivery Network)?
A.To distribute content to edge servers closer to users to reduce latency.
B.To replace the DNS system.
C.To generate dynamic content for websites.
D.To compress files for storage.
Correct Answer: To distribute content to edge servers closer to users to reduce latency.
Explanation:
CDNs cache content in geographically distributed servers (Edge Servers) to deliver it to users from the nearest location, reducing latency.
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39In a CDN architecture, the Point of Presence (PoP) refers to:
A.A physical location where CDN servers reside.
B.The user's computer.
C.The protocol used for caching.
D.The central database.
Correct Answer: A physical location where CDN servers reside.
Explanation:
A PoP is a strategic physical location (often a data center) containing one or more edge servers that cache content.
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40Which DNS mechanism is commonly used by CDNs to direct a user to the nearest edge server?
A.Reverse DNS Lookup
B.Geo-DNS / Anycast DNS
C.Static Hosts File
D.DHCP
Correct Answer: Geo-DNS / Anycast DNS
Explanation:
CDNs use intelligent DNS resolution (Geo-DNS) to resolve the domain name to the IP address of the edge server geographically closest to the user.
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41Which of the following is a security benefit often provided by CDNs?
A.Virus scanning of local hard drives
B.End-to-end encryption of the physical cable
C.DDoS (Distributed Denial of Service) mitigation
D.Automatic password generation
Correct Answer: DDoS (Distributed Denial of Service) mitigation
Explanation:
Because CDNs have massive bandwidth and distributed infrastructure, they can absorb large traffic spikes associated with DDoS attacks.
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42In the context of CDN, what is the Origin Server?
A.The first server ever built.
B.The server where the original, definitive version of the content resides.
C.The nearest edge server.
D.The user's laptop requesting the file.
Correct Answer: The server where the original, definitive version of the content resides.
Explanation:
The Origin Server holds the master copy of the content. Edge servers pull data from the Origin Server to cache it.
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43What happens in a CDN when a requested file is not in the cache (Cache Miss)?
A.The user gets a 404 error.
B.The user is redirected to a different website.
C.The connection is dropped.
D.The edge server requests the file from the Origin Server, delivers it, and caches it.
Correct Answer: The edge server requests the file from the Origin Server, delivers it, and caches it.
Explanation:
On a cache miss, the CDN fetches the content from the origin, serves it to the user, and stores it for future requests.
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44SD-WAN capability to identify traffic based on Layer 7 (Application) information is called:
A.Port Forwarding
B.Application Awareness
C.Packet Switching
D.Circuit Switching
Correct Answer: Application Awareness
Explanation:
SD-WAN can inspect packets to identify specific applications (e.g., Zoom, Netflix) and apply specific policies (QoS) to them, known as Application Awareness.
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45Which TCP mechanism prevents a sender from overwhelming the receiver?
A.Congestion Control
B.Slow Start
C.Fast Retransmit
D.Flow Control
Correct Answer: Flow Control
Explanation:
Flow control (using the Window mechanism) matches the sending rate to the receiving process's reading rate to prevent buffer overflow at the receiver.
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46Which TCP mechanism prevents a sender from overwhelming the network?
A.Error Control
B.Congestion Control
C.Keep-alive
D.Flow Control
Correct Answer: Congestion Control
Explanation:
Congestion control (using mechanisms like Slow Start and Congestion Avoidance) handles traffic to prevent network saturation.
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47In TCP connection termination, how many segments are typically exchanged?
A.2
B.6
C.4
D.3
Correct Answer: 4
Explanation:
Termination is a 4-step process: FIN (A to B), ACK (B to A), FIN (B to A), ACK (A to B).
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48What is the primary role of the User Agent in an email system?
A.To route emails through the internet.
B.To store emails permanently.
C.To maintain the DNS records for the mail server.
D.To allow the user to compose, read, and reply to messages.
Correct Answer: To allow the user to compose, read, and reply to messages.
Explanation:
The User Agent (e.g., Outlook, Thunderbird, Webmail interface) is the software the user interacts with.
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49In FTP, 'Anonymous FTP' allows a user to login with the username:
A.root
B.admin
C.anonymous
D.guest
Correct Answer: anonymous
Explanation:
Public FTP servers often allow access using the username 'anonymous', typically requiring an email address or nothing as the password.
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50Which of the following is an example of a Recent Trend in networking that moves computation closer to the source of data generation?
A.Batch Processing
B.Mainframe Computing
C.Edge Computing
D.Client-Server Architecture
Correct Answer: Edge Computing
Explanation:
Edge Computing (often used with CDNs and IoT) processes data near the edge of the network rather than in a centralized cloud, reducing latency.