Computer Networking

Computer Networking:

A networking is any collection of independent computers that communicate with one another over a shared network medium. A computer network is a collection of two or more connected computers. When these computers are joined in a network, people can share files and peripherals such as modems, printers, tape backup drives, or CD-ROM drives. When networks at multiple locations are connected using services available from phone companies, people can send e-mail, share links to the global Internet, or conduct videoconferences in real time with other remote users. As companies rely on applications like electronic mail and database management for core business operations, computer networking becomes increasingly more important.

Every Network Required following Devices:

1.   At least two computers Server or Client workstation.

2.   Networking Interface Card’s (NIC) LAN Card.

3.   A connection medium, usually a wire or cable, although wireless communication between networked computers and peripherals is also possible.

4.   Network Operating system software, such as Microsoft Windows NT or 2000, Novell NetWare, UNIX and Linux.

5.   RJ-45 Connecters.

6.   Network cable tester.

7.   Crimping tools.

8.   LAN card drivers.

Types of Networks:

LANs (Local Area Networks)

A network is any collection of independent computers that communicate with one another over a shared network medium. LANs are networks usually confined to a geographic area, such as a single building or a college campus. LANs can be small, linking as few as three computers, but often link hundreds of computers used by thousands of people. The development of standard networking protocols and media has resulted in worldwide proliferation of LANs throughout business and educational organizations.

WANs (Wide Area Networks)

Wide area networking combines multiple LANs that are geographically separate. This is accomplished by connecting the different LANs using services such as dedicated leased phone lines, dial-up phone lines (both synchronous and asynchronous), satellite links, and data packet carrier services. Wide area networking can be as simple as a modem and remote access server for employees to dial into, or it can be as complex as hundreds of branch offices globally linked using special routing protocols and filters to minimize the expense of sending data sent over vast distances.

MANs (Metropolitan area Networks)

The refers to a network of computers with in a City. A metropolitan area network (MAN) is a network that interconnects users with computer resources in a geographic area or region larger than that covered by even a large LAN but smaller than the area covered by a WAN. The term is applied to the interconnection of networks in a city into a single larger network (which may then also offer efficient connection to a wide area network). It is also used to mean the interconnection of several local area networks by bridging them with backbone lines. The latter usage is also sometimes referred to as a campus network.

GANs (Global area Networks)

The Refers to any network that is composed of different interconnected computer networks (WANs) and also covers an unlimited geographical area. [Source: Adapted from ATIS]

Wi - Fi ( Wireless Networks)

Most agree that wireless networking represent the future of computer and Internet connectivity worldwide. Wi-Fi continues to be the pre-eminent technology for building general-purpose wireless networks.

Network Topologies:

       A network topology is the geometric arrangement of Computers and cable links in a LAN.

There are three topology’s to think about when you get into networks.

1. Bus Topology.

2. Ring Topology.

3. Star Topology.
Bus Topology:

        In the bus topology, each computer, server, peripheral etc. attaches directly to a common cable. This topology most often serves as the backbone for a network. In some instances, such as in classrooms or labs, a bus will connect small workgroups

Figure: Bus topology

                                             

Advantages of a Bus Topology

1.    Easy to connect a computer or peripheral to a linear bus.

2.    Requires less cable length than a star topology.

Disadvantages of a Bus Topology

1.    Entire network shuts down if there is a break in the main cable.

2.    Terminators are required at both ends of the backbone cable.

3.    Difficult to identify the problem if the entire network shuts down.

4.    Not meant to be used as a stand-alone solution in a large building.

Ring Topology:

            A ring topology connects the computers along a single path whose ends are joined to form a circle. The circle might be logical only but the physical arrangement of the cabling might be similar to star topology, with a hub or concentrator at the center. The ring topology is commonly used in token ring networks that the ring of a token ring network is concentrated inside a device called a Multistation Access Unit (MAU) and fiber

Figure: Ring topology

Advantages of a Ring Topology

1.    One computer cannot monopolize the network.

2.     It Continue to function after capacity is exceeded but the speed will be slow.

Disadvantages of a Ring Topology

1.    Failure of one computer can affect the whole network.

2.    It is difficult to troubleshoot.

3.    Adding and removing computers disrupts the network.

Star Topology:

            A star topology connects the computers by individual cables to a central unit, usually a hub. When a computer or other networking component transmits a signal to the network, the signal travels to the hub. Then, the hub forwards the signal simultaneously to all other computers connected to the hub. Star topology is the most popular way to connect computers in a workgroup network.

Figure: Star topology

Advantages of a Star Topology

1.    The failure of a single computer or cable doesn't bring down the entire network.

2.    The centralized networking equipment can reduce costs in the long run by making network management much easier.

3.    It allows several cable types in same network with a hub that can accommodate multiple cable types.

Disadvantages of a Star Topology

1.    Failure of the central hub causes the whole network failure.

2.    It is slightly more expensive than using bus topology.

Tree/Hybrid Topology:

Tree topologies are comprised of the multiple star topologies on a bus. Tree topologies integrate multiple star topologies together onto a bus. Only the hub devices can connect directly with the tree bus and each Hub functions as a root of a tree of the network devices. This bus/star/hybrid combination supports future expandability of the computer networks, much better than a bus or star.

Mesh Topology:

   Mesh topology work on the concept of routes. In Mesh topology, message sent to the destination can take any possible shortest, easiest route to reach its destination. In the previous topologies star and bus, messages are usually broadcasted to every computer, especially in bus topology. Similarly in the Ring topology message can travel in only one direction i.e clockwise or anticlockwise. Internet employs the Mesh topology and the message finds its route for its destination. Router works in find the routes for the messages and in reaching them to their destinations.The topology in which every devices connects to every other device is called a full Mesh topology unlike in the partial mesh in which every device is indirectly connected to the other devices.

Types of Communication:

1.    Unicast:-

                  It means that one to one communication.

2.    Multicast:-

                  It means that one to more than one communication (only few) .

3.    Broadcast :-

                  It means that one to other all communication . 

Protocol:

         Protocol is a “language” of Computer used to transmit data over a network. In order to two computers talk to each other, they must be using the same protocol (i.e. language).

Types of Protocol:

TCP/IP - Transmission Control Protocol / Internet Protocol:

         TCP/IP is the main transport protocol utilized in Computer networking technology. The Internet and most home networks support TCP/IP as the "language" of Computers use to find and connect with each other.

For example, use TCP/IP to communicate with Web servers.
In this Protocol Share Data, Programs, Software’s, Application and also share the Internet.
UDP - User Datagram Protocol:
         UDP is part of the Internet Protocol using which, programs running on different computers on a network can send short messages known as Datagrams to one another.
In this Protocol Share Data, Programs, Software’s, Application and Do not share the Internet.

IP Addressing

Here you will learn about ip address network introduction and general overview of routing, subnet mask, subnetting, data communication. IP address is an identifier for a computer or device on a TCP/IP network and Internet. Networks that use the TCP/IP protocols route traffic based on the IP address of the destination computer or network device. The format of the IP address is 32 bits 4 octets 4 bytes such as 100.100.10.1, 210.100.22.30, 1.10.1.2 these are the examples of the IP address. The format is a 32-bit numeric value written as four numbers and separated by periods.

Each number in the IP address can be between 0 and 255. In your private network, you can assign unique IP address randomly. However, when you want to connect your private network to the Public network such as Internet then you must need a registered IP address to communicate on the internet and to avoid duplicate address. The four numbers in an IP address are used in different ways to identify a particular network. The general internet registries such as APNIC, RIP, NCC and LACNIC assigns internet or IP addresses from the following 3 classes.

1. Class A- IP address from 0-126. It supports 16 million hosts and 126 networks.

2. Class B- IP address from 128-191. It supports 65,000 hosts and 16,000 networks.

3. Class C-IP address from 192-223. It supports 254 hosts and 2 million networks.

The number of unassigned IP address is running out and a new classless scheme called CIDR is replacing the classes based system of the IP address. In this system the A, B and C class is tied to adoption of IPV6. 

Every device connected to the Internet must need a unique identifier, which is called an IP address. An IP address is a numeric value separated by periods into four octets. These numbers are usually assigned to the ISPs (internet service providers) within region-based blocks. An IP address can be used to identify a region or a country. An internet user’s geographical location can be determined with the help of an IP address. The number system is generally difficult to remember so the IP address may also assign to a Host name.

The host names are usually easy to remember. In simple words, every website on the internet must bound or mapped with an IP address. At one time ISPs usually issue one IP address to each user. Within each ISP a DHCP (Dynamic host configuration protocol) server is configured, which dynamically assigns IP addresses from a given pool to each user who connects to the ISP. Dynamic IP addresses also limit the ability of a user to host websites, mail servers, ftp server, mail server and web portals.

Understanding IP Addresses Scheme

An IP address is an address that is used to uniquely identify a device or computer on an IP-based network. An IP address is an address used to uniquely identify a device on an IP network. An IP address can be divided into two parts network portion and a host portion. Each IP address is associated with a subnet mask. The 32 bit address is broken into 4 octets and 1 octet=8 bits. Each octet is converted to a decimal and is separated by periods.

For example 0000000000.11111111.00000000.11111111 this is a binary representation of an IP address. Each octet’s decimal value ranges between 0 and 255. The binary octets convert into decimal value. Here you can see that how a binary octet converts into decimal value. The right most bit or least significant bit of an octet will hold a value of 20.

The bit left to that bit will hold a value of 21. This process continues until the left most bit or the most significant bit holds the value of 27. If all the binary bits are one the decimal representation will be like this.

1 1 1 1 1 1 1 1

128 64 32 16 8 4 2 1 (128+64+32+16+8+4+2+1=255)

Now here is a sample conversion of the octet if not all the bits are set of 1.

0 0 1 0 0 0 0 1

0 0 32 0 0 0 0 1 (0+64+0+0+0+0+0+1=33)

In the following example you can see the IP address representation both in binary and decimal values.

64. 2. 135. 19 (decimal)64+2+135+19=220

01001010.00000010.1000111.00010011 (binary)

The octets are broken down to provide a large number of the addressing scheme that can accommodate small and very large networks. There are five different classes of the IP networks. Class A, B, C, D and E. The classes from A to C and mainly in use, D and E are experimental and reserved so they are not commonly in use. Due to the classless inter domain routing (CIDR) these addresses are not practically in use.

Network/Subnet Masks

A network mask helps you which portion of the address identifies the network portion and the host portion of an IP address. The three different classes of the IP addresses have their own default masks as shown below.

Class Subnet Mask

Class A: 255.0.0.0

Class B: 255.255.0.0

Class C: 255.255.255.0

An IP address on a class A network that has not been subnetted would have an address and subnet mask pair such as 10.111.20.1 255.0.0.0. If you want to know in more detail that how a mask help you identify the network and host part of the address simply convert the IP address and subnet mask into the binary numbers.

4.16.15.1= 00000100. 00010000.00001111.00000001

255.0.0.0 = 11111111. 00000000.00000000.00000000

If you have the address and the subnet mask in the binary forms then identifying the network portion and the host portion is very easy. Any address value that has the corresponding subnet mask binary value set to 1 show the network ID. Any address bit that has corresponding subnet mask value to 0 represents the host ID.

4.16.15.1= 00000100.00010000.00001111.00000001

255.0.0.0 = 11111111.00000000.00000000.00000000

Network id | host id

If you know your IP address of a computer, you can access the services such as online games, FTP, Web and Mail servers, and remote access utilities such as Remotely Anywhere, PCToGo, PCAnywhere, Remote control etc.

How do I change my IP address?

There are a number of methods by which you can change the IP address of your computer.

What is a Proxy Server?

A proxy server is a computer that offers network and internet access services to the client computers in a network. A client computer connects to the proxy server, requests a connection, services, files and other resources on the other servers. In some cases, the proxy may alter the client’s request and the server’s response for various reasons. By using the proxy server you can hide, conceal and make your network id anonymous by hiding your IP address. To get the anonymous status on the network or Internet, strong intermediate methods are employed like cryptography etc. Examples are remailers, P2P systems etc.

There is a large number of the software available that allows you to hide your IP address with the help of the proxy servers. The well known software for this purpose is Hide IP, Stealth surf, Netconceal, Anonymous surfing, Proxify and Ghost surf.

An IP address is a unique identification number for communication between computer networks, network devices such as computers, fax machines, printers and servers. It is like the number of an apartment or a phone number. IP addresses are of two types Static and Dynamic. Internet service providers’ use dynamic IP addresses and servers usually use static IP address.

The class A of the IP address constitutes almost 50% of all the IP addresses. This class is meant for large networks like the big multinational companies. Class B networks are medium sized like used in the colleges, Universities and other educational and training institutes. Class C IP addresses are usually used for the small companies.

The Regional Internet Registry (RIP) provides the IP addresses based on the geographical distribution. RIP also offers protection against the hackers that try to access the confidential data. All the personal information recorded by the ISP is kept in confidentiality.

OSI Model:

Open System Interconnection (OSI) is a model that is used to understand how network protocols work. This model is the best known and most widely used to describe networking environments. It provides a description of how network hardware and software work together in a layered fashion to make communications possible. It also helps with trouble shooting by providing a frame of reference that describes how components are supposed to function.

There are seven layers to get familiar with and these are

1.    Physical layer

2.    Data link layer

3.    Network layer

4.    Transport layer

5.    Session layer

6.    Presentation layer

7.    Application layer.

Layer	Name	Functions / Roles
7	Application Layer	It provides interfaces to use networks for software (server/client application) which uses networks (data communications). It defines the processes that the users directly Used.
6	Presentation Layer	It is used for converts the data into user-friendly formats. And Represent the Data.
5	Session Layer	Based on the specification of each application which uses networks, it establishes sessions on communications. It defines connections, terminations and so on between computers. Handle all the problems.
4	Transport Layer	It provides basic data transfer services, It provides mechanisms for the establishment, maintenance, and termination of virtual circuits, transport fault detection and recovery. Verify all data in VPN services.
3	Network Layer	It decides appropriate communication paths between two Computers which communicate on networks, based on IP Addresses. Also sending & receiving data with the help of ISP.
2	Data Link Layer	It defines communication methods between computers connected to networks directly. The specification of Computers to be communicated Based on MAC　Addresses (physical addresses). Sending & Also Receiving Data.
1	Physical Layer	It is decide physical signals and connection methods in networks. It defines function modules which define the maximum transfer rate, cable materials and connector shapes. (Cables and connector are called network media.)

RAID Concept:

RAID - Redundant Array of Independent Disks:

               It is an array of multiple independent hard disk drives that provide high performance and fault tolerance. An appropriate RAID level is selected when the volume sets are defined or created. This decision is based on disk capacity, data availability (fault tolerance or redundancy), and disk performance.
The following is the RAID level, which support in the RAID subsystem.

Raid 0:

              It is also known as striping. Writes stripping of data across multiple disk drives instead of just one disk drive. RAID 0 does not provide any data redundancy, but does offer the best high-speed data throughput. RAID 0 breaks up data into smaller blocks and then writes a block to each drive in the array. Disk striping enhances performance because multiple drives are accessed simultaneously.

Advantages

1.    Highest performance configuration for writes

2.    Lowest cost per unit of data stored

3.    All disk capacity is used to store data (none needed for fault tolerance)

Disadvantages

1.    All data on the logical drive is lost if a physical disk fails

2.    Cannot use an online spare

3.    Can only preserve data by backing it up to external disk drives

Raid 1

           RAID 1 also known as “disk mirroring”. Data written to one disk drive is simultaneously written to another disk drive. During writes, there will be a minor performance penalty when compared to writing to a single disk. If one drive fails, all data (and software applications) are preserved on the other drive. RAID 1 offers extremely high data reliability, but at the cost of doubling the required data storage capacity.

Advantages

1.    No data loss or interruption of service, if a disk fails

2.    Fast read performance - data is available from either disk

Disadvantages

1.    Cost is high - 50% of disk space is allocated for data protection

2.    Only 50% of total disk drive capacity is usable for data storage

Raid 0+1:

           RAID 0+1 is a combination of RAID 0 and RAID 1, combing stripping with disk mirroring. RAID Level 0+1 combines the fast performance of Level 0 with the data redundancy of Leve1. In this configuration, data is distributed across several disk drives, similar to Level 0, which are then duplicated to another set of drive for data protection. RAID 0+1 provides the highest read/write performance of any RAID levels, but at the cost of doubling the required data storage capacity.

Advantages

1.    Highest read and write performance of any fault-tolerant configuration

2.    No loss of data as long as none of failed disks are mirrored to another failed disk (up to half of the physical disks in the array can fail)

Disadvantages

1.    Expensive (many disks needed for fault tolerance)

2.    Only 50% of total disk drive capacity usable for data storage

Raid 5

           RAID 5 is sometimes called striping with parity at block level. In RAID 5, the parity information is written to all of the drives in the subsystems rather than concentrated on a dedicated parity disk. If one drive in the system fails, the parity information can be used to reconstruct the data from that drive. All drives in the array system can be used to seek operation at the same time, greatly increasing the performance of the RAID system.

Advantages

1.    High read performance

2.    No loss of data if one physical disk fails

3.    More disk drive capacity usable than with RAID 1+0—parity information only requires the storage space equivalent to one physical disk on the array

Disadvantages

1.    Relatively low write performance

2.    Loss of data if a second disk fails before data from the first failed disk is rebuilt

WORKGROUP:

             A workgroup is a logical collection of computers that share resources. Normally, workgroups are composed of the computers within a single department or a small company. Each computer can share resources with all other computers. In essence, all computers are of equal status. Within a company, different departments may be workgroups and each may have a unique name to identify the workgroup. Because each computer is independent, each computer is responsible for authenticating users.

DOMAIN:

               Like a workgroup, a domain is a logical collection of computers that share resources. One of the key differences is that there is a single server that is responsible for managing security and other user-related information for the domain. This server allows login validation, by which a user logs into the domain and not into a single computer.