Network Problems

How is Computer Network in terms of usage

As my previous discussion, I present “Computer Network” in detailed. Now here we discussed about the most probable usage of Computer Network. Computer network can be depended on networks as LAN, MAN and WAN. Between the Boundaries of these network we can do work respectively. We have some rules to make networks and communicate with each other. These rules are divided into two terms:

Server to Client communication
Client to Client communication

Now we discussed these two of communication terms in detail, you can easily understand “How is Computer Network in terms of usage?”

Server to Client Communication:

Sever to Client Communication in computer network include Servers computer and Clients computer. There are number of servers that can create communication likewise: DHCP Server, DNS Server (Active Directory), Print Server, ISA Server, Proxy Server, Fax Server, File Server, mail Server, Application Server, Web Server, Home Sever, etc. All these servers can communicate with Client computer with respect to their tasks. Some of the servers task can be defined as follow:

What is computer network?

In this session, we discuss about computer network which is using millions of people in practical life. To understand computer network first we need to clear our mind about network “what is network?” In technical term, communication of two or more nodes in a path is known as network and combination of multiple of network is called sub-network.

Now we easily define computer network, number of computers connected in a plate-form is known as computer network. Computer network can easy our lives in communication field with the passage of time. Now a days computer networking can have multiple types of communication in which includes LAN, MAN and WAN. Without these terms computer networking cannot have any able to do work.

LAN is known as local area network. LAN is defined as computers connected in any geographical area like school, college, forums, offices or closely communicated computers.

MAN is known as Metropolitan Area Network. MAN in which multiple LAN are interconnected and is greater than local area network but smaller than wide area network.

WAN is stands by wide area network. Numbers of computers are widely connected over a large geographical area known as WAN. Communication of WAN can make an easy way to communicate one person to other person in a small time on two large geographical areas.

OSI Seven Layer Model

The open system interconnection model (osi model) is a conceptional model that characterized and standardized the communication function of telecommunication or computing system without regard of their underlying internal structure and technology. its goal is the interoperability of diverse communitcation systems with standard protocols. The model partitons a communication system into abstraction layers. The original version of the model defined seven layers.

A layer serves the layer above it and is served by the layer below it. For example, a layer that provides error-free communications across a network provides the path needed by application above it , while it calls the next lower layer to send and receive packets that comprise the content of that path. Two instances at the same layer are visualized as connected by a horizental connection in that layer.

OSI Seven Layer Model Layers Includes:

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

These layers are divided into two categories:

Media Layer
Hosted Layer

Network Addressing

IP addresses are broken into 4 octets (IPv4) separated by dots called dotted decimal notation. An octet is a byte consisting of 8 bits. The IPv4 addresses are in the following form:

192.168.10.1

There are two parts of an IP address:

Network ID
Host ID

The various classes of networks specify additional or fewer octets to designate the network ID versus the host ID.

Class	1st Octet	2nd Octet	3rd Octet	4th Octet
	Net ID	Host ID
A
	Net ID		Host ID
B
	Net ID			Host ID
C

When a network(according to webopedia and wikipedia) is set up, a netmask is also specified. The netmask determines the class of the network as shown below, except for CIDR. When the netmask is setup, it specifies some number of most significant bits with a 1's value and the rest have values of 0. The most significant part of the netmask with bits set to 1's specifies the network address, and the lower part of the address will specify the host address. When setting addresses (in CISCO) on a network, remember there can be no host address of 0 (no host address bits set), and there can be no host address with all bits set.

Class A-E networks

The addressing scheme for class A through E networks is shown below. Note: We use the 'x' character here to denote don't care situations which includes all possible numbers at the location. It is many times used to denote networks.

Network Type	Address Range	Normal Netmask	Comments
Class A	001.x.x.x to 126.x.x.x	255.0.0.0	For very large networks
Class B	128.1.x.x to 191.254.x.x	255.255.0.0	For medium size networks
Class C	192.0.1.x to 223.255.254.x	255.255.255.0	For small networks
Class D	224.x.x.x to 239.255.255.255		Used to support multicasting
Class E	240.x.x.x to 247.255.255.255

RFCs 1518 and 1519 define a system called Classless Inter-Domain Routing (CIDR) which is used to allocate IP addresses more efficiently. This may be used with subnet masks to establish networks rather than the class system shown above. A class C subnet may be 8 bits but using CIDR, it may be 12 bits.

There are some network addresses reserved for private use by the Internet Assigned Numbers Authority (IANA) which can be hidden behind a computer which uses IP masquerading to connect the private network to the internet. There are three sets of addresses reserved. These address are shown below:

10.x.x.x
172.16.x.x - 172.31.x.x
192.168.x.x

Other reserved or commonly used addresses:

127.0.0.1 - The loopback interface address. All 127.x.x.x addresses are used by the loopback interface which copies data from the transmit buffer to the receive buffer of the NIC when used.
0.0.0.0 - This is reserved for hosts that don't know their address and use BOOTP or DHCP protocols to determine their addresses.
255 - The value of 255 is never used as an address for any part of the IP address. It is reserved for broadcast addressing. Please remember, this is exclusive of CIDR. When using CIDR, all bits of the address can never be all ones.

To further illustrate, a few examples of valid and invalid addresses are listed below:

Valid addresses:

10.1.0.1 through 10.1.0.254
10.0.0.1 through 10.0.0.254
10.0.1.1 through 10.0.1.254

Invalid addresses:

10.1.0.0 - Host IP can't be 0.
10.1.0.255 - Host IP can't be 255.
10.123.255.4 - No network or subnet can have a value of 255.
0.12.16.89 - No Class A network can have an address of 0.
255.9.56.45 - No network address can be 255.
10.34.255.1 - No network address can be 255.

Network/Netmask specification

Sometimes you may see a network interface card (NIC) IP address specified in the following manner:

192.168.1.1/24

The first part indicates the IP address of the NIC which is "192.168.1.1" in this case. The second part "/24" indicates the netmask value meaning in this case that the first 24 bits of the netmask are set. This makes the netmask value 255.255.255.0. If the last part of the line above were "/16", the netmask would be 255.255.0.0.

MatherBoard

The Motherboard is the connecting device by which each part of the computer communicates with the other parts .The motherboard is made up of several components.

Major parts of motherboard :