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TCP/IP Interview Questions and Answers

Last Updated : July 21, 2023
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TCP/IP stands for Transmission Control Protocol/Internet Protocol, which is a set of rules that governs how data is transmitted and received over a network. It is one of the most widely used protocols that allows communication between different devices across various networks. Jobs in this field often need a thorough understanding of TCP/IP. In order to help you effectively prepare for future interviews, we have handpicked the most frequently asked TCP/IP interview questions and answers.

About TCP/IP

TCP/IP stands for Transmission Control Protocol/Internet Protocol, is a fundamental communication protocol suite used for transmitting data over networks, most notably the internet. It provides a standardized set of rules and conventions that govern the exchange of information between devices and systems.

TCP is responsible for ensuring reliable and error-free data transmission by breaking data into packets and reassembling them at the destination. Whereas, IP handles the addressing and routing of data packets across the network. Together, TCP/IP forms the backbone of the internet and is widely used in local area networks (LANs) and wide area networks (WANs) to enable seamless communication between computers, servers, and other networked devices.

Now that we have an overview of TCP/IP, let's begin with basic TCP/IP interview questions in the first phase and will focus on the TCP/IP interview questions and answers for experienced candidates afterward.

TCP/IP Interview Questions and Answers for Beginners

Q1 - What is TCP/IP?

Transmission Control Protocol/Internet Protocol is the full name for TCP/IP. IP is the foundation of the Internet, delivering packets from their origin to their final destination and serving as the address system for all devices communicating over it. TCP is necessary since IP does not handle error checking or packet ordering. TCP is in charge of gathering the packets and putting them together in the correct sequence, while IP delivers the information or packets to the correct location.

Q2 - How many layers does TCP/IP have, and what are they?

TCP/IP architecture consists of four layers, these are:

  • Application Layer: This layer defines how applications communicate with each other using protocols.
  • Transport Layer: This layer provides reliable data transmission using protocols. It offers functionality, including connection establishment, traffic management, and error management.
  • Network Layer: This layer handles the logical addressing and routing of packets.
  • Data-Link Layer: This layer defines how data is transferred over a physical medium. And also hides the details of the physical network.

Q3 - What is the difference between TCP and UDP?

TCP and UDP are two of the most widely used protocols on the internet. They both allow the transmission of data from a source to a destination, but they have different characteristics and features. Below we have summarized the basic difference in a tabular form.

FactorsTCP (Transmission Control Protocol)UDP (User Datagram Protocol)
SpeedSlower than UDPFaster than TCP
Flow ControlYesNo
Congestion ControlYesNo
Data DeliveryOrdered and CompleteUnordered and Incomplete
UsageWeb browsing, file transfer, email, etc.Streaming, gaming, voice-over IP, etc.

Q4 - What is the purpose of the TCP/IP handshake?

Connecting two networked devices is the main purpose of a TCP/IP handshake. It's like a handshake between two people; only it includes two gadgets exchanging messages with one another.

  • The initiating device sends the initial communication, called a SYN (synchronize) message. The connection's initial sequence number is included in this message.
  • The second message designated ACK (acknowledge), is sent by the receiver. This message confirms the first sequence number and includes the next sequence number in the connection's sequence.
  • The initiating device will send the FIN (finish) message as the third and last one. This message is delivered to signal the end of communication across the connection.

The TCP/IP handshake is a crucial element of the TCP/IP protocol required to establish communication between the two devices.

Q5 - What are some of the common IP addressing classes and their ranges?

Each device on a network has a numerical address that is assigned by a method known as IP addressing. It is divided into two parts, i.e., Network ID and Host ID.

IP addresses are further divided into five parts: A, B, C, D, and E. Each class has different values and ranges for the Network ID and Host ID. Below we have shown it with the help of a table for better understanding.

ClassNetwork IDHost IDRange
A8 Bits24 Bits1.0.0.0 to
B16 Bits16 Bits128.0.0.0 to
C24 Bits8 Bits192.0.0.0 to
DN/AN/A224.0.0.0 to
EN/AN/A240.0.0.0 to

Q6 - What is a Socket?

Socket allows when two different processes want to communicate on the same or different machines. It is identified by a combination of a port number and an IP address that further specify the device and the application that is communicating. The socket allows the identification of the destination application for data transmission by utilizing the IP address and port number.

Q7 - What is the difference between flow control and error control?

Both Flow control and error control techniques are used in data communication for reliable transmission of information. When we talk about flow control, it regulates the amount of data that the sender can send to the receiver in a way that does not cause any burden to the receiver. Whereas error control detects and rectifies any errors that might occur during the transmission process.

Below we have summarized the basic difference between flow control and error control in a tabular form.

FactorsFlow ControlError Control
PurposeTo prevent data loss due to buffer overflow at the receiverTo ensure data integrity by detecting and rectifying errors
MethodBy using feedback messages such as acknowledgments and window sizesBy using error detection codes such as parity bits and checksums
DirectionUsually, bidirectionalUsually, unidirectional
OverheadLow, as only a few bits are added to each frame or segmentHigh, as extra bits are added to each frame or packet

Q8 - What is IP datagram?

In network communication, the IP datagram acts as a fundamental unit of information. It works in the network layer of the TCP/IP protocol stack. Every IP datagram consists of two main components: a header and a payload. The header includes essential metadata, including the source and destination IP addresses, the version of the IP protocol employed (IPv4 or IPv6), and additional control information.

Q9 - What is PING and what protocol is used by it?

PING stands for Packet Internet Network Gopher. In a computer network, a ping is a simple Internet software that can test and validate whether or not a given destination IP address exists and can receive requests.

Ping is also used to measure and evaluate the speed at which information is sent from one location (such as a computer) to another (such as a website). Ping may also be used to test connections, troubleshoot problems, and measure response times. Ping uses Internet Control Management Protocol (ICMP).

Q10 - What is a Private IP address?

Private IP addresses are commonly used for the purpose of establishing network connectivity within enterprises, offices, or home networks. Devices such as printers, smartphones, computers, and tablets that are connected to an internet network are assigned private IP addresses.

One of the key reasons private IP addresses were formed was to allow routers and devices to uniquely identify one other.

Class A, Class B, and Class C are classified as private IP addresses. We have already discussed these classes above.

Now, we have listed the TCP/IP interview questions for beginners. Let’s now move on to interview questions for experienced candidates.

TCP/IP Interview Questions and Answers for Experienced

Here are the top TCP/IP Interview Questions and Answers for experienced -

Q11 - What are TCP Flags and their types?

TCP flags are used to identify a specific connection status or to offer extra information inside TCP packet transmissions. As a result, they may be used for troubleshooting or to regulate how a specific connection is handled.

There are six types of TCP flags:

  • SYN (Synchronize): This flag is set when initiating a connection.
  • ACK (Acknowledge): This flag is set when acknowledging a packet.
  • FIN (Finish): This flag is set when terminating a connection.
  • RST (Reset): This flag is set when resetting a connection.
  • PSH (Push): This flag is set when pushing data.
  • URG (Urgent): This flag is set when sending urgent data.

Q12 - Which IP address class is mostly used and why?

There are five classes of IP addresses: A, B, C, D, and E. Every class has different range values and is used for different purposes. Out of five classes, the most used IP address class is class C, specifically designed for small networks such as small businesses or household networks.

Now, why the Class C addresses are mostly used? This is because it can support up to 254 hosts; hence the wastage of IPs is significantly less as compared to others. It is mainly utilized for home or office networks, allowing easy subnetting and address allocation.

Q13 - What is the purpose of ARP?

ARP stands for Address Resolution Protocol, which is used in TCP/IP networks.

ARP is used when a device knows the IP address of another device but doesn’t know the Mac address. At this point, ARP starts sending a request message (asking for the MAC address with a specified IP address) to all the devices that are connected to the network. At last, when the device that matches the IP address responds with its MAC address and further can easily communicate with it.

The main purpose of ARP is to map an IP address to a physical machine address, specifically a MAC address.

Q14 - How do you secure a TCP/IP network?

Here are some of the measures one can take to secure a TCP/IP network:

  • Use encryption protocols such as SSL/TLS or IPSec to protect data in transit.
  • Implement firewalls and intrusion detection systems (IDS) to block unauthorized access and monitor network traffic.
  • Apply patches and updates to operating systems and applications to fix vulnerabilities.
  • Configure strong passwords and authentication methods to prevent unauthorized users from logging in

Q15 - Explain how does TCP try to avoid network meltdown?

TCP tries to avoid network meltdown by adjusting its sending rate according to the feedback from the receiver and the network. TCP uses a mechanism called "congestion avoidance" and "Slow Start" algorithms that are defined in RFC 2001. These are mainly to reduce the data amount that is sent over a network. This further helps in reducing network congestion.

"Nagle algorithm", helps the client side of TCP from overwhelming the network with lots of small frames, defined in RFC 896.

Apart from the abovementioned algorithms, it also mandates "Silly Window Syndrome" An undesirable circumstance in which the transmitter and the recipient only exchange extremely little pieces of data. SWS is defined in RFC 813.

Q16 - How do you configure a TCP/IP network?

Below we have explained the basic steps one can take to configure a TCP/IP network:

  • Assign an IP address and a subnet mask to each device on the network
  • Configure a default gateway for each device to access other networks
  • Optionally, configure a DNS server for name resolution
  • Optionally, configure other network services such as DHCP, NTP, etc.

These are the top TCP/IP Interview Questions and Answers for experienced.


TCP/IP is a fundamental topic for anyone who wants to pursue a career in networking or related fields. In this blog, we have covered TCP/IP interview questions and answers for both beginners as well for experienced candidates. We hope that this post has helped you refresh your knowledge of TCP/IP concepts, principles, and applications, and prepare you for your next interview.

You can also check out - Basic Networking Interview Questions

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