NETWORKING

^{What is firewall?} 

^{A firewall is a hardware or software installed to provide security to the private networks connected to the internet........................} 

 

^{What are the types of firewalls?}

^{1.Packet Filtering Firewall: This type of Firewall detects packets and block unnecessary packets and makes network traffic release.}

^{2.Screening Router Firewalls:It's a software base firewall available in Router provides only light filtering.}

^{3.Computer-based Firewall:It's a firewall stored in server with an existing Operating System like Windows and UNIX.}

^{4.Hardware base Firewall:Its device like box allows strong security from public network. Mostly used by big networks}

^ENCRYPTION

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 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 .................

^{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.

  

^{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.

^{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.

 

 

^{What is Cross-site scripting (XSS)?}

An attack that occurs when an attacker uses a web application to send malicious code, generally in the form of a browser side script, to a different end user and occurs when a web application uses input from a user in the output it generates without validating or encoding it.

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..............

Trojan Horse:  A trojan horse program has the appearance of having a useful and desired function. While it may advertise its activity after launching, this information is not apparent to the user beforehand. Secretly the program performs other, undesired functions. A Trojan Horse neither replicates nor copies itself, but causes damage or compromises the security of the computer.

Worms:  A worm is a program that makes and facilitates the distribution of copies of itself; for example, from one disk drive to another, or by copying itself using email or another transport mechanism. The worm may do damage and compromise the security of the computer. It may arrive via exploitation of a system vulnerability or by clicking on an infected e-mail.

Bootsector Virus:  A virus which attaches itself to the first part of the hard disk that is read by the computer upon bootup. These are normally spread by floppy disks.

Macro Virus:  Macro viruses are viruses that use another application's macro programming

language to distribute themselves. They infect documents such as MS Word or MS Excel and are typically spread to other similar documents.

Memory Resident Viruses:  Memory Resident Viruses reside in a computers volitale memory (RAM).

They are initiated from a virus which runs on the computer and they stay in memory after it's initiating program closes.

Rootkit Virus:  A rootkit virus is an undetectable virus which attempts to allow someone to gain control of a computer system.

Polymorphic Viruses:  A polymorphic virus not only replicates itself by creating multiple files of itself, but it also changes it's digital signature every time it replicates. This makes it difficult for less sophisticated antivirus software to detect.

^{Explain about Voice Over Internet Protocol.}

VOIP is also known as broadband telephony.VOIP is to route the voice conversations over the internet.VOIP services convert telephonic signals into digital signals.Voice traffic is transmitted over Internet Protocol based networks. VOIP deploys a protocol known as session control protocol for controlling the set-up and tear-down of calls as well as audio codecs.

PHISHING ATTACK

Phishing Attack In phishing attack the hacker creates a fake web site that looks exactly like a popular site such as the SBI bank or paypal. The phishing part of the attack isthat the hacker then sends an e-mail message trying to trick the user into clicking a link that leads to the fake site. When the user attempts to log on with their accout information, the hacker records the username and password and then tries that information on the real site.

ROUTERS

A router is a device that forwards data packets between computer networks, creating an overlay internetwork. A router is connected to two or more data lines from different networks. When a data packet comes in one of the lines, the router reads the address information in the packet to determine its ultimate destination. Then, using information in its routing table or routing policy, it directs the packet to the next network on its journey. Routers perform the "traffic directing" functions on the Internet. A data packet is typically forwarded from one router to another through the networks that constitute the internetwork until it gets to its destination node.

Routers capture the information that come through broadband connection via a modem and deliver it to your computer. The router choose route for the packet so that you receive the information Firstly.

ADVANTAGES & DISADVANTAGES

Advantage of Router -

a) Router limits the collision domain.

b) Router can function on LAN & WAN>

c) Router can connects different media & architectures.

d) Router can dtermine best path/route for data to reach

the destination.

e) Router can filter the broadcasts.

Diadvantage of Router -

a) Router is more expensive than Hub, Bridge & Switch.

b) Router only waork with routable protocol.

c) Routing updates consume bandwidth.

d) Increase latency due to greater degree of packet

filtering.

There are basically 2 types of routers.

  

1. Static router: In this type the system administrator is defining the shortest path in the network. In static routers, system administrator is giving the shortest path by giving some commands.

Static router is not so efficient than dynamic routing. static routing have some limitations and used in the relatively

Smaller range of the network.

2. Dynamic router: In the dynamic routing the router can define the shortest path by itself between the nodes.

Dynamic routing is the clever type of routing and normally used in lot of places in the world while routing. In this type the router is programmed in such a way that router itself is taking the shortest path and system administrator does not have to do any thing. It saves time and cost.

The function of a router is to manage the paths along which information is forwarded within a network. They are necessary to facilitate communication between computers and the Internet.

Routing algorithm:

For a packet to travel from source to destination it has to pass through multiple paths or sometimes a single path. So when a packet finds multiple paths to reach the destination, it has no judging methods available to find a right path. A router with the help of certain algorithms calculates the best path for the packet to reach the destination. These algorithms are called routing algorithms. This is the way in which a router finds the correct entry in its routing table. There are several algorithms available to find this best path but here I am going to discuss only the two basic types of algorithms. 

Two basic routing algorithms are,

1. Distance-vector algorithm.

2. Link state routing algorithm. 

Distance vector algorithm:

As from the name suggests it uses distance and direction to find the best path to reach the destination. The distance here is thenumber of hops a packet crosses to reach the destination. Each hop refers to a router across the path. The word vector refers to thedirection of the packet to reach the destination. It has lesser convergence time and knowledge about the whole network when compared to link state routing algorithm. Working of this distance vector algorithm can be explained in three steps. The steps are as follows,

Step 1: In this algorithm, the information about every router connected directly and routing updates will be gathered by every single router. This information about the whole network will be sent periodically to all the neighboring routers connected to it. In this way every router updates the information in its routing table. 

Step 2: All the information collected by a single router about the whole network will be sent only to its neighbors and not to all other routers in the routing table. If there is any change in the hop count or disabled paths it will updated only to its neighbors which in turn after a period passes to its neighbors.

Step 3: The above explained sharing of information will take place in a period of 30 seconds. If there is a change in the network like if a network fails or additionally a router is added to the network, the changed information will be updated only after that time period. 

Examples: 
RIP and IGRP uses distance vector routing algorithm to perform routing.

Link state routing algorithm:

This is the most popular routing algorithm used in the real time networks. It uses three tables for the calculation of the routing table entries. It is also called as 'Shortest path first algorithm'. It has several advantages over distance vector algorithm. Some of them includes, its faster convergence time, ability to handle very large networks, reliable path prediction. It uses link state advertisements to find the information about the router. Here in steps working of link state algorithm can be analyzed. The steps are,

Step 1: As from its name 'Shortest path first algorithm' it uses several calculations to find the shortest path to reach the destination. This algorithm uses link state packets or advertisements to collect the information about the neighboring routers. Only links that are connected directly are considered as neighbors. In contrast to distance vector it sends info only about neighbors. 

Step 2: In this algorithm instead of sending the routing table info only to the neighbors it sends to all the routers in the network. In this algorithm totally three tables are maintained. One is for collecting info about neighbors, one has info about the entire topology, final one is the actual routing table. 

Step 3: In this algorithm there is no periodic updates involved. A router in the network will send updates to all the routers and only if there is a change in the network. That is why it is called as event triggered updates. This event triggered updates will help the router to find its path immediately without any errors. 

Example: 
OSPF routing protocol is the perfect example which uses link state algorithm alone. 

Key factors, 

1. Hop count. 
2. Metrics.
3. Administrative Distance(AD)
4. Routing loops
5. Bandwidth and delay and so on. 


Hybrid routing algorithm: 

Some of the vendors make use of both the routing algorithms to create better performance and reliable delivery. So this hybrid protocol uses both Distance vector and Link state algorithm to making routing decisions. EIGRP which is a Cisco proprietary protocol is a perfect example for hybrid routing algorithms. EIGRP has faster convergence and good knowledge about the whole inter-network than Distance vector routing algorithm.

Difference Between Static and Dynamic Routing::

1)   Static routing manually sets up the optimal paths between the source and the destination computers. On the other hand, the dynamic routing uses dynamic protocols to update the routing table and to find the optimal path between the source and the destination computers.

2)   The routers that use the static routing algorithm do not have any controlling mechanism if any faults in the routing paths. These routers do not sense the faulty computers encountered while finding the path between two computers or routers in a network.

3)   The dynamic routing algorithms are used in the dynamic routers and these routers can sense a faulty router in the network. Also, the dynamic router eliminates the faulty router and finds out another possible optimal path from the source to the destination. If any router is down or faulty due to certain reasons, this fault is circulated in the entire network. Due to this quality of the dynamic routers, they are also called adaptive routers.

4)   The static routing is suitable for very small networks and they cannot be used in large networks. As against this, dynamic routing is used for larger networks.

5)   The static routing is the simplest way of routing the data packets from a source to a destination in a network. The dynamic routing uses complex algorithms for routing the data packets.

6)   Static routing also does not handle failures in external networks.ynamic routing protocols the ability to adapt to logical network topology changes, equipment failures or network outages 'on the fly'.

7)   Static routing is the simplest form of routing, but it is a manual process.