NETWORKING:-

NETWORKING:- A Computer network is a network of computers that are geographically distributed, but connected in a manner to enable meaningful transmission and exchange of data among them.

Basic Elements of a communication System.

• Sender : - Creates and sends the message.
• Medium: - Carries a message
• Receiver: - Receive a message

Networks Topologies.

• Topology of a network refers to the way in which the network's nodes(computer or other devices that need to communicate) are linked together.
• It determines the various data paths available between any pair of nodes in the network.
• Choice of a topology for a computer network depends on a combination of factors, such as:
  
  • Desired Performance of the system
  • Reliability Of the system.
  • Size(Numbers of nodes and their geographical distribution) of the system).
  • Cost of components and services required to implement network
  • Availability of communication lines

Star Topology

Advantages Of Star topology

• Star topology has minimal line cost because only "n-1" lines are required for connecting "n" nodes.
• Transmission delays between two nodes do not increase by adding new nodes to network, because any two nodes are connected via two links only.
• If any node other than the host node fails, remaining nodes are unaffected

WIRELESS USB:-

Wireless USB is a short-range, high-bandwidth wireless radio communication protocol created by the Wireless USB Promoter Group. Wireless USB is sometimes abbreviated as "WUSB", although the USB Implementers Forum discouraged this practice and instead prefers to call the technology Certified Wireless USB to distinguish it from the competing UWB standard.
Wireless USB was based on the (now defunct) WiMedia Alliance's ultra-wideband (UWB) common radio platform, which is capable of sending 480 Mbit/s at distances up to 3 metres (9.8 ft) and 110 Mbit/s at up to 10 metres (33 ft). It was designed to operate in the 3.1 to 10.6 GHz frequency range, although local regulatory policies may restrict the legal operating range for any given country.

Uses:-

 

Wireless USB is used in game controllers, printers, scanners, digital cameras, portable media players, hard disk drives and flash drives. It is also suitable for transferring parallel video streams, using USB over ultra-wideband protocols.

Bluetooth:-

Bluetooth uses short-range radio waves over distances up to approximately 10 metres. For example, Bluetooth devices such as a keyboards, pointing devices, audio head sets, printers may connect to personal digital assistants (PDAs), cell phones, or computers wirelessly.
A Bluetooth PAN is also called a piconet (combination of the prefix "pico," meaning very small or one trillionth, and network), and is composed of up to 8 active devices in a master-slave relationship (a very large number of devices can be connected in "parked" mode). The first Bluetooth device in the piconet is the master, and all other devices are slaves that communicate with the master. A piconet typically has a range of 10 metres (33 ft), although ranges of up to 100 metres (330 ft) can be reached under ideal circumstances.

Dynamic Host Configuration Protocol (DHCP) :-

The Dynamic Host Configuration Protocol (DHCP) is a standardized networking protocol used on IP networks that dynamically configures IP addresses and other information that is needed for Internet communication. DHCP allows computers and other devices to receive an IP address automatically from a central DHCP server, reducing the need for a network administrator or a user from having to configure these settings manually.

DHCP servers maintain a database of 

 available IP addresses and other kinds 

of addresses, such as a default route, 

and one or more DNS server addresses. 

DHCP may be used to configure some of these settings and the remaining settings may be manually configured.

DHCP servers typically grant IP addresses to devices only for a limited interval. Devices are responsible for renewing their IP address lease before that interval expires, and must stop using the address once the interval has expired, if they have not been able to renew it.

Non-technical

DHCP allows computers (clients) to be assigned settings from a server in a client-server model. DHCP is very common in modern networks and is used in home networks as well as larger campus networks. In home networks, the Internet Service Provider's server may assign a globally unique external IP address to a home router (or modem) and this IP address is used in Internet communications. The home router (or modem) may also use DHCP to supply a usable IP address to devices connected to the home network, allowing these devices to communicate on The Internet. The global unique IP address assigned by the Internet Service Provider (ISP) is different from any of the IP addresses assigned to the devices connected to the home router. This is because of a design consideration of IPv4 to help conserve IPv4 addresses.

Technical

Dynamic Host Configuration Protocol automates network-parameter assignment to network devices from one or more DHCP servers. Even in small networks, DHCP is useful because it makes it easy to add new machines to the network.

When a DHCP-configured client (a computer or any other network-aware device) connects to a network, the DHCP client sends a broadcast query requesting necessary information to a DHCP server. The DHCP server manages a pool of IP addresses and information about client configuration parameters such as default gateway, domain name, the name servers, other servers such as time servers , and so forth. On receiving a valid request, the server assigns the computer an IP address, a lease (length of time the allocation is valid), and other IP configuration parameters, such as the subnet mask and the default gateway. The query is typically initiated immediately after booting, and must complete before the client can initiate IP-based communication with other hosts. Upon disconnecting, the IP address is returned to the pool for use by another computer. This way, many other computers can use the same IP address within minutes of each other.

Because the DHCP protocol must work correctly even before DHCP clients have been configured, the DHCP server and DHCP client usually must be connected to the same network link. In larger networks, this is not practical. On such networks, each network link contains one or more DHCP relay agents. These DHCP relay agents receive messages from DHCP clients and forward them to DHCP servers. DHCP servers send responses back to the relay agent, and the relay agent then sends these responses to the DHCP client on the local network link.

Depending on implementation, the DHCP server may have three methods of allocating IP-addresses:

·         dynamic allocation: A network administrator assigns a range of IP addresses to DHCP, and each client computer on the LAN is configured to request an IP address from the DHCP server during network initialization. The request-and-grant process uses a lease concept with a controllable time period, allowing the DHCP server to reclaim (and then reallocate) IP addresses that are not renewed.

·         automatic allocation: The DHCP server permanently assigns a free IP address to a requesting client from the range defined by the administrator. This is like dynamic allocation, but the DHCP server keeps a table of past IP address assignments, so that it can preferentially assign to a client the same IP address that the client previously had.

·         static allocation: The DHCP server allocates an IP address based on a table with MAC address/IP address pairs, which are manually filled in (perhaps by a network administrator). Only clients with a MAC address listed in this table will be allocated an IP address. This feature, which is not supported by all DHCP servers, is variously called Static DHCP Assignment by DD-WRT, fixed-address by the dhcpd documentation, Address Reservation by Netgear, DHCP reservation or Static DHCP by Cisco and Linksys, and IP reservation or MAC/IP binding by various other router manufacturers.

Computer Network Model:- A computer networks communication can be based on centralized, distributed or collaborative computing. Centralized computing involves many workstations or terminals, connected to one central mainframe or other powerful computer. Distributed computing interconnects one or more personal computers and allows various services like Data sharing, hardware sharing resources sharing or network sharing. The collaborative computing is the combination of centralized and distributed computing.

What Is Switching ?.

Switching:- Every time in computer network you access the internet or another  computer network outside your immediate location, your messages are sent through a maze of transmission media and connection devices. The mechanism for moving information between different computer network and network segment is called switching in computer network.

 

How DHCP Works

DHCP provides an automated way to distribute and update IP addresses and other configuration information on a network. A DHCP server provides this information to a DHCP client through the exchange of a series of messages, known as the DHCP conversation or the DHCP transaction. If the DHCP server and DHCP clients are located on different subnets, a DHCP relay agent is used to facilitate the conversation.

What is DHCP?

Dynamic Host Configuration Protocol (DHCP) is a client/server protocol that automatically provides an Internet Protocol (IP) host with its IP address and other related configuration information such as the subnet mask and default gateway. RFCs 2131 and 2132 define DHCP as an Internet Engineering Task Force (IETF) standard based on Bootstrap Protocol (BOOTP), a protocol with which DHCP shares many implementation details. DHCP allows hosts to obtain necessary TCP/IP configuration information from a DHCP server.
The Microsoft Windows Server 2003 operating system includes a DHCP Server service, which is an optional networking component. All Windows-based clients include the DHCP client as part of TCP/IP, including Windows Server 2003, Microsoft Windows XP, Windows 2000, Windows NT 4.0, Windows Millennium Edition (Windows Me), and Windows 98.

IP

1. Short for Internet Protocol address, an IP address is an address of a computer or other network device on a network using TCP/IP. For example, the number "166.70.10.23" is an example of such an address. These addresses are similar to an addresses used on a house and is what allows data to reach the appropriate destination on a network and the Internet.

There are five classes of available IP ranges: Class A, Class B, Class C, Class D and Class E, while only A, B, and C are commonly used. Each class allows for a range of valid IP addresses. Below is a listing of these addresses.

Class	Address Range	Supports
Class A	1.0.0.1 to 126.255.255.254	Supports 16 million hosts on each of 127 networks.
Class B	128.1.0.1 to 191.255.255.254	Supports 65,000 hosts on each of 16,000 networks.
Class C	192.0.1.1 to 223.255.254.254	Supports 254 hosts on each of 2 million networks.
Class D	224.0.0.0 to 239.255.255.255	Reserved for multicast  groups.
Class E	240.0.0.0 to 254.255.255.254	Reserved for future use, or Research and Development Purposes.

Ranges 127.x.x.x are reserved for the loopback or localhost  for example, 127.0.0.1 is the common loopback address. Range 255.255.255.255 broadcasts to all hosts on the local network.

IP address breakdown

Every IP address is broke down into four sets of octes that break down into Binary to represent the actual IP address. The below table is an example of the IP 255.255.255.255. If you are new to binary, we highly recommend reading our binary and hexadecimal conversions section to get a better understanding of what we're doing in the below charts.

IP:	255	255	255	255
Binary value:	11111111	11111111	11111111	11111111
Octet value:	8	8	8	8

If we were to break down the IP "166.70.10.23", you would get the below value. In the below table, the first row is the IP address, the second row is the binary values, and the third row shows how the binary value equals the section of the IP address.

166	70	10	23
10100110	01000110	00001010	00010111
128+32+4+2=166	64+4+2=70	8+2=10	16+4+2+1=23