"Here To Help You": Network Protocol Interview Question and Answers

PROTOCOL INTERVIEW QUESTIONS

Q1. What is NetBIOS protocol?

NetBIOS (Network Basic Input/Output System) Protocol allows applications on separate computers to communicate over a LAN. It runs over TCP/IP giving each computer in the network a NetBIOS name and IP address. E.g. It can be used for computers running Windows 2000 (or before) to join a computer network running Windows 2000 (or later).

Q2. What is IGMP protocol?

Internet Group Management Protocol, allows internet hosts to multicast. i.e. to send messages to a group of computers. There may be a group of internet hosts interested to multicast. IGMP allows router to determine which host groups have members on a given network segment. It helps to establish group memberships. It is commonly used for streamlining videos and gaming. The protocol can be implemented both as a host side and router side. The host side is responsible to notify its membership in a group. The notification is made to a local router. This local router (router side) in turn sends out queries.

Q3. What is TCP / IP protocol?

Transmission Control Protocol / Internet Protocol: - It is a family of protocols used for communication and connection between hosts on the internet. It is the most widely used standard for transmitting data over the internet. The four layers in the protocol are (from bottom to top):- Physical layer, Data link layer, Network layer, transport layer and application layer, also called as the OSI model. In TCP/IP , IP is responsible for forwarding packets while TCP ensures the correct delivery of data from client to server. TCP detects loss of data as well.

Q4. What is HTTP (Hypertext Transfer Protocol)?

HTTP or Hyper Text Transfer Protocol is provides a set of rules to transfer files, videos, images over the world wide web. When the web browser is opened, a HTTP request call is made. A web server contains a HTTP daemon. This daemon is used to wait for HTTP requests and handle them when they arrive. The web browser from where HTTP requests are made is called as a client. These requests are sent to the server. It uses a reserved port no 80.

Q5. What is NNTP (Network News Transfer Protocol)?

NNTP or Network News Transfer Protocol is used to manage the notes posted on Unset newsgroup (a collection of posted notes on a subject posted by different users). NNTP servers are responsible for managing Usenet newsgroup collected globally. A NTTP client is a part of the web browser also called as a news reader. It uses a reserver port no 119.

Q6. What is POP3 (Post Office Protocol 3)?

POP3 or Post Office Box 3 is used fro receiving emails. It is a client server protocol which holds the email. Once the email is downloaded from the server, POP3 deletes it from the server. Ordinal numbers are used to identify specific messages.

Q7. What is SNMP (Simple Network Management Protocol)?

SNMP or Simple Network Management Protocol is typically used for managing the network. Managing the network includes managing the nodes present in the network. These nodes may be server, routers, bridges and hubs. SNMP agents are used to achieve this. Managing the network is essential because it helps to monitor network performance, detect network faults or failures, audit network usage etc. the SNMP messages like TRAP, GET or SET may be invoked by network elements or network management system.

Q8. What is Routing table?

A routing table stores the routes of the various nodes in a network. Nodes can be any electronic device connected to the network. The table is usually stored in a router or the network computer as a database or file. This information helps to fond the best possible path. The routing table has at least 3 fields: the destination network id, cost of the path, next hop or address to send the packet.

Q9. What is Routing Protocols?

Routing protocols are used to assist in achieving the basic purpose of routing. They specify the routers the method to communicate with each other. They help the routers select the best possible path between nodes. There are different types of protocols such as link-state routing protocols, path vector protocols and distance vector routing protocols. These protocols prevent routing loops to form or break if formed already. They help to decide preferred routes from a sequence of hop costs

Q10. What is Distance Vector Routing Protocols?

The main goal of Distance Vector Routing Protocols Is to find out the best path for he data packet to reach the destination. Distance here could be the hops. The three different types of Distance Vector routing protocols include:- Routing Information Protocol (RIP v1 and v2) and Interior Gateway Routing Protocol. The protocol is easy to manage however not well scalable.

The Distance Vector protocol initially prepares a Routing table which is shared with other routers. This routing table is shared between routers present in the same network. A new routing table is prepared when some new information is received from some other router. Now, the bad routing paths are removed keeping only the smallest hop paths. This new table is then communicated to other routers

Q11. What is TCP protocol?

Transmission control Protocol is used to establish communication between nodes or networks and exchange data packets. It guarantees delivery of data packets in the order they were sent. Hence it is most commonly used in all applications that require guaranteed delivery of data. It can handle both timeouts (if packets were delayed) and retransmission (if packets were lost). The stream of data is transmitted in segments. The segment header is 32 bit. it is a connectionless communication protocol at the third level (network) of the OSI model.

Q12. TCP vs. UDP.

TCP guarantees the delivery of data. UDP on the other hand, does not guarantee delivery of data. TCP delivers messages in the order they were sent. UDP has no ordering mechanisms. In TCP data is sent as a stream while UDP sends data as individual packets. UDP is faster than TCP. TCP is a connection oriented protocol while UDP is connectionless.

Q13. What is UDP protocol?

User Data Protocol is a communication protocol. It is normally used as an alternative for TCP/IP. However there are a number of differences between them. UDP does not divide data into packets. Also, UDP does not send data packets in sequence. Hence, the application program must ensure the sequencing. UDP uses port numbers to distinguish user requests. It also has a checksum capability to verify the data.

Q14. What is TCP windowing concept?

TCP windowing concept is primarily used to avoid congestion in the traffic. It controls the amount of unacknowledged data a sender can send before it gets an acknowledgement back from the receiver that it has received it.

Q15. What is Trusted and Untrusted Networks?

Trusted networks: Such Networks allow data to be transferred transparently. The machines using a trusted network are usually administered by an Administrator to ensure that private and secured data is not leaked. Access to this network is limited. Computers using trusted networks are more secured and confidential because of strong firewalls.

Untrusted networks: Such networks are usually administered by the owners. They can allow improper access to sensitive or personal data. These machines are usually separate. Such machines could me more prone to attacks.

Q16. What are the different types of VPN?

Remote Access VPN:- Also called as Virtual Private dial-up network (VPDN) is mainly used in scenarios where remote access to a network becomes essential. Remote access VPN allows data to be accessed between a company’s private network and remote users through a third party service provider; Enterprise service provider. E.g Sales team is usually present over the globe. Using Remote access VPN, the sales updates can be made.
Site to Site VPN – Intranet based: This type of VPN can be used when multiple Remote locations are present and can be made to join to a single network. Machines present on these remote locations work as if they are working on a single network.
Site to Site VPN – Extranet based: This type of VPN can be used when several different companies need to work in a shared environment. E.g. Distributors and service companies. This network is more manageable and reliable

Q17. What are the different authentication methods used in VPNs?

The authentication method uses an authentication protocol. The methods are:

EAP authentication method: Extensible authentication protocol authenticates remote access connection. The authentication mechanism is decided between the remote VPN client and authenticator (ISA). The mechanism is typical in which authenticator requests for authentication information and the responses are given by the remote VPN client.
MS Chap Authentication method: Microsoft Challenge Handshake Authentication Protocol (MS-CHAP) starts with the authenticator (Remote access server) challenge. The challenge to the remote access client sends a session identifier and challenge string. The client in response sends the nonreversible encryption of the string, the identifier and password. Authenticator checks the credentials and grants access on a successful authentication.
Unencrypted passwords (PAP):- Uses plain text passwords. Does not involve encryption. Used for less secure clients.
Shiva Password Authentication Protocol (SPAP):- It is a password authentication protocol. It is less secure as the same user password is always sent in the same reversibly encrypted form

Q18. What is Tunneling?

Tunneling is a mechanism provided to transfer data securely between two networks. The data is split into smaller packets and passed through the tunnel. The data passing through the tunnel has 3 layers of encryption. The data is encapsulated. Tunneling can be approached by Point to Point tunneling protocol.

Q19. What are voluntary and compulsory tunnels?

Voluntary Tunneling
Users computer is an end point of the tunnel and acts as tunnel client. Here the client or user issues a request to configure and create a voluntary tunnel. They require a dial up or LAN connection. Example of dial up connection is internet at home where a call is made to the ISP and connection is obtained.

Compulsory tunneling
In compulsory tunneling, instead of the user a vpn remote access server configures and creates a tunnel. Hence, the end point is the Remote sever not the user.

Q20. Explain static and dynamic tunnels.

Tunnels that are created manually are static tunnels. Tunnels that are auto discovered are dynamic tunnels. In dynamic tunneling, tcp connections can be checked dynamically. If no connections exist that are routed through the tunnel, a check for more suitable gateway can be done. Static tunneling may at times require dedicated equipments.

Q21. Explain the importance of increasing and decreasing subnet bits.

Adding 1’s as a bit means increasing the subnets and decreasing the hosts. Removing or decreasing 1’s means decreasing subnets and increasing hosts. Hence by increasing or decreasing the subnet architecture can be decided as per needs.

Q22. Why do we need a subnet mask?

A subnet mask allows identification of host part and network part of an IP address. Subnet mask can be used to find if an IP address is present on a subnet or not

Q23. What is RTP?

Real-Time Transfer Protocol lays a standard or a way to transfer or manage real time data over a network. It does not guarantee the delivery of data or provide any quality of service. However it helps to manage the data. Which means that RTP can be used deliver the necessary data to the application to make sure it can put the received packets in the correct order Real time data examples could be audio and video.

Q24. What is RTP Multiplexing?

RTP multiplexing allows multiple media flows within a single RTP data payload between two points. This means that it can be used to carry multiple streams of data in one RTP packet. RTP multiplexing will reduce the bandwidth used. RTP multiplexing will also increase scalability

Q25.E xplain the use of RTP and RTCP protocols.

Use of RTP and RTCP:

1. RTP can be used to transfer Real time data like voice packets.
2. RTP can be used with RTCP which makes it possible to monitor data.
3. Packet loss can be detected by RTP using Sequence number

RTCP provides Qos feedback :- Packets lost, round trip time.

Q26. Describe how the multicast protocol works.

Multicast protocol or Internet protocol delivers a singles message to multiple machines. One packet from the source is replicated and sent to the destination. Every multicast message requires a multi case group. The group defines the addresses which will receive the message. The group is defined by the class D address. Different routing protocols are used to find the multicast groups and build routes for them. Distance Vector Multicast protocol is one of them. The receiver, to whom the multicast packet is sent to, needs to ‘join’ the group. Joining the group is enabled and managed by IGMP. Multicast routers are used to transmit the messages from one network to another.

Q27. Describe how to control the scope of multicast transmissions.

Controlling the scope of multicast transmission restricts the range of group members. TTL (Time To Live) is one of the mechanisms to limit the scope. If the TTL value is small, packets would only be multicast to smaller distance destinations. More the value of TTL, more would be the scope of transmission to a larger number of machines. Administrative scoping is another mechanism. In this, transmission is restricted to a specific address space of an organization or a site

Q28. What are the basic components of routers?

Components of Router:

Internal components:

ROM:- Used to store the routers bootstrap details, operating system software.
Flash memory: - holds the operating systems images. The content is retained when the router is restarted.
RAM: - Used to store the Routing tables, configuration files, caching and buffering details. Content is lost when lost router is switched off or restarted.
NVRAM:- Stores the routers startup config files. Data is non volatile.
Network interfaces to connect router to network.

External components:

Virtual terminals: For accessing routers
Network management stations.

Q29. Overview of OSI layer.

OSI stands for Open Systems Interconnection

The OSI reference model gives an overview of the layered communications and computer network protocol design.

The layers of the OSI are:

Application Layer
Presentation Layer
Session Layer
Transport Layer
Network Layer
Data Link Layer
Physical Layer

Q30. Explain different layers in the OSI model.

Application Layer:

Closest to the end user
Interact directly with the software application.

Presentation Layer:

Translates application to network format, and vice versa
Works to transform data into the form that the application layer can accept
Formats and encrypts data to be sent across a network

Session Layer

Controls the connections between computers
Establishes, manages and terminates the connections between the local and remote application.
Provides full-duplex, half-duplex, or simplex operation
Establishes checkpointing, adjournment, termination, and restart procedures

Transport Layer:

Provides transparent transfer of data between end users
Providing reliable data transfer services to the upper layers
Controls the reliability of a given link through flow control, segmentation / desegmentation, and error control.

Network Layer

Provides the functional and procedural means of transferring variable length data sequences from a source to a destination via one or more networks
Performs networkrouting functions
Performs fragmentation and reassembly, and report delivery errors.

Data Link Layer

Provides the functional and procedural means to transfer data between network entities
Detects and corrects errors that occur in the Physical Layer.

Physical Layer:

Defines the electrical and physical specifications for device

Q31. Explain the concept and capabilities of Unicast IP Addresses

It is an IP address that uniquely identifies a host in a network.
The datagram with a unicast IP address is received and processed by only a single host.

Q32. What is Routing table?

Q33. What is Routing Protocols?

Q34. What is Distance Vector Routing Protocols?

Q35. What is Application layer?

The application layer is located at the top of the TCP/IP protocol layers. This one contains the network applications which make it possible to communicate using the lower layers. The software in this layer therefore communicates using one of the two protocols of the layer below (the transport layer), i.e. TCP or UDP. In computer networking, an application layer firewall is a firewall operating at the application layer of a protocol stack.[1] Generally it is a host using various forms of proxy servers to proxy traffic instead of routing it. As it works on the application layer, it may inspect the contents of the traffic, blocking what the firewall administrator views as inappropriate content, such as certain websites, viruses, and attempts to exploit known logical flaws in client software, and so forth. An application layer firewall does not route traffic on the network layer. All traffic stops at the firewall which may initiate its own connections if the traffic satisfies the rules.

Q36. Define DNS

The DNS translates Internet domain and host names to IP addresses. DNS automatically converts the names we type in our Web browser address bar to the IP addresses of Web servers hosting those sites. DNS implements a distributed database to store this name and address information for all public hosts on the Internet.

Q37. Define Telnet

Telnet is the main Internet protocol for creating a connection to a remote server.

Q38. Define SMTP.

SMTP - Short for Simple Mail Transfer Protocol, a protocol for sending e-mail messages between servers.

Q39. MAC vs. IP Addressing

Whereas MAC addressing works at the data link layer, IP addressing functions at the network layer (layer 3). It's a slight oversimplification, but one can think of IP addressing as supporting the software implementation and MAC addresses as supporting the hardware implementation of the network stack. The MAC address generally remains fixed and follows the network device, but the IP address changes as the network device moves from one network to another.

Q40.Define Spanning-Tree Protocol (STP)

Spanning-Tree Protocol (STP) as defined in the IEEE 802.1D is a link management protocol that provides path redundancy while preventing undesirable loops in the network. For an Ethernet network to function properly, only one active path can exist between two stations. Loops occur in networks for a variety of reasons. The most common reason you find loops in networks is the result of a deliberate attempt to provide redundancy - in case one link or switch fails, another link or switch can take over

Q41. What is VPN?

A VPN is a service that offers secure, reliable connectivity over a shared public network infrastructure such as the Internet. VPNs maintain the same security and management policies as a private network. They are the most cost effective method of establishing a virtual point-to-point connection between remote users and an enterprise customer's network.

Q42. Define broadcast domain.

It is a logical area in a computer network where any computer connected to the network can directly transmit to any other computer in the domain without having to go through a routing device.

Q43. Bridge vs switch

A bridge connects two different LAN networks. A switch is something like you can connect many computers to a switch and then one computer can connect to another through the switch. Switch is a unicast one to one connection.

Q44. Define gateway

A gateway is a network point that provides entrance into another network. On the Internet, a node or stopping point can be either a gateway node or a host (end-point) node. Both the computers of Internet users and the computers that serve pages to users are host nodes. The computers that control traffic within your company's network or at your local Internet service provider (ISP) are gateway nodes.

Q45. What is firewall?

A firewall is a hardware or software installed to provide security to the private networks connected to the internet. They can be implemented in both hardware and software, or a combination of both. All data entering or leaving the Intranet passes through the firewall which allows only the data meeting the administrators’ rules to pass through it.

Q46. What are the types of firewalls?

Packet Filtering Firewall:
This type of Firewall detects packets and block unnecessary packets and makes network traffic release.

Screening Router Firewalls:
It's a software base firewall available in Router provides only light filtering.

Computer-based Firewall:
It's a firewall stored in server with an existing Operating System like Windows and UNIX.

Hardware base Firewall:
Its device like box allows strong security from public network. Mostly used by big networks.

Proxy Server:
Proxy server allows all clients to access Internet with different access limits. Proxy server has its own firewall which filters the all packet from web server.

Q47. Define Digital Signatures.

Digital signature is an attachment to an electronic message used for security purpose. It is used to verify the authenticity of the sender.

Q48. What is Ethernet technology?

Ethernet technology is a high speed broadcast bus technology. In this type, all the station shares a single ether channel and receives every single transmitted signal.

Q49. Explain the use of network interface card, NIC.

NIC is used to connect computer to an Ethernet network.

Q50. Explain token ring technology.

In this technology, all the devices are arranged in a circle. A token moves around the circular network. A device waits for the token before it sends its frame. Once it receives token, it initiates transmission of its frame.

Q51. What is CSMA and CD concept?

In CSDA (carrier sense multiple access), presence of any digital signal in a network is checked before transmission. Data transmission occurs only when no signal is sensed. CD, Collision detection is responsible for monitoring carrier in order to avoid signal jam.