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.

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.

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.

What is the Public Key Encryption?

Public key encryption use public and private key for encryption and decryption. In this mechanism, public key is used to encrypt messages and only the corresponding private key can be used to decrypt them. To encrypt a message, a sender has to know recipient's public key.

What is Data encryption?

Data encryption ensures data safety and very important for confidential or critical data. It protect data from being read, altered or forged while transmission.

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).

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.

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.

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 reserve port no 119.

What is POP3 (Post Office Protocol 3)?

POP3 or Post Office Box 3 is used for 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.

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.

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.

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 found 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.

What are types of firewall architecture ?

1.    Screening Router Architecture

2.    Dual-Homed Host Architecture

3.    Screened Host Architecture

4.    Screened Subnet Architecture

What is the meaning of bastion host?

A bastion host is a specialized computer that is deliberately exposed on a public network. From a secured network perspective, it is the only node exposed to the outside world and is therefore very prone to attack. It is placed outside the firewall in single firewall systems or, if a system has two firewalls, it is often placed between the two firewalls or on the public side of a demilitarized zone (DMZ).

The bastion host processes and filters all incoming traffic and prevents malicious traffic from entering the network, acting much like a gateway. The most common examples of bastion hosts are mail, domain name system, Web and File Transfer Protocol (FTP) servers. Firewalls and routers can also become bastion hosts.

Can you explain the concept of demilitarized zone?

The concept of the DMZ, like many other network security concepts, was borrowed from military terminology. Geopolitically, a demilitarized zone (DMZ) is an area that runs between two territories that are hostile to one another or two opposing forces' battle lines.

The DMZ likewise provides a buffer zone that separates an internal network from the often hostile territory of the Internet. Sometimes it's called a "screened subnet" or a "perimeter network," but the purpose remains the same.

What is Application level Gateway?

An application layer gateway (ALG) is a feature on ScreenOS gateways that enables the gateway to parse application layer payloads and take decisions on them. Although there are other ScreenOS features, such as deep inspection, in which the gateway inspects traffic at the application layer, ALGs are typically employed to support applications that use the application layer payload to communicate the dynamic Transmission Control Protocol (TCP) or User Datagram Protocol (UDP) ports on which the applications open data connections. Such applications include the File Transfer Protocol (FTP) and various IP telephony protocols. The dynamic TCP, UDP, or other ports that are opened by the ScreenOS gateway to permit these data or secondary channels are referred to as pinholes, and are active strictly for the duration of activity on the data channel.

Can you explain the concept of demilitarized zone?

The concept of the DMZ, like many other network security concepts, was borrowed from military terminology. Geopolitically, a demilitarized zone (DMZ) is an area that runs between two territories that are hostile to one another or two opposing forces' battle lines. The DMZ likewise provides a buffer zone that separates an internal network from the often hostile territory of the Internet. Sometimes it's called a "screened subnet" or a "perimeter network," but the purpose remains the same.

Can you explain stateful inspection?

Stateful inspection, also known as dynamic packet filtering, is a firewall technology that monitors the state of active connections and uses this information to determine which network packets to allow through the firewall. Stateful inspection has largely replaced an older technology, static packet filtering. In static packet filtering, only the headers of packets are checked -- which means that an attacker can sometimes get information through the firewall simply by indicating "reply" in the header. Stateful inspection, on the other hand, analyzes packets down to the application layer. By recording session information such as IP addresses and port numbers, a dynamic packet filter can implement a much tighter security posture than a static packet filter can.

Can you explain circuit level gateway?

The circuit level gateway firewalls work at the session layer of the OSI model. They monitor TCP handshaking between the packets to determine if a requested session is legitimate. And the information passed through a circuit level gateway, to the internet, appears to have come from the circuit level gateway. So, there is no way for a remote computer or a host to determine the internal private ip addresses of an organization, for example. This technique is also called Network Address Translation where the private IP addresses originating from the different clients inside the network are all mapped to the public IP address available through the internet service provider and then sent to the outside world (Internet). This way, the packets are tagged with only the Public IP address (Firewall level) and the internal private IP addresses are not exposed to potential intruders.