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Interface Message Processor ( IMP ) is a special purpose Computer. The Processor plays a vital role in Host-to-Host communication. IMP is placed between Host Computers.  IMP helps Hosts to exchange information. IMPs ( Interface Message Processors ) form a group. The group dedicates itself towards reliable transmission of Packets. _________________________ Note: An Interface Message Processor can be supposed to have a face. Firstly this supposed face of IMP is in the direction of the first Host, which sends the  message. Secondly, this face is turned towards the other Host.  Now, the IMP,  with its face turned around, communicates with this other Host.  Transformed message from IMP is communicated to this Host. __________________________ Message ( a piece of information ) sent from the Host ( source of information  ) is transformed into Packets. Transformation of the message into Packets is performed by an IMP. These Packets are forwarded to the receiver H...

Wide-Area Network is a Network of Computers spread across cities,  countries, continents, and the world. The Network is present over a wide area indeed. WAN can be thought to be an information system. This information system is based on Computers. These Computers are somehow connected. A LAN ( Local Area Network ) may be connected on WAN ( Wide-Area Network). LANs are marked by Personal Computers ( PCs ) or microcomputers. These Personal Computers ( PCs ) become a part of WAN. Mainframe Computers may also be connected on WAN. WAN supports Mainframe Computers as well. WAN Computers use communication media to connect with each other. Communication media is used to share information. Communication media supported by WAN are: A ) Lines or Trunks  B ) Satellites  C) Microwave D) Medium and Long Range Radio Waves WAN communication takes time. Information travels from one Computer to another. There is some delay in this communication process. It is natural because such activity ...

Packet means a segment of information. This segment of information has a size. Yes, the size is that of the information that lies in the packet. We know that the size of information is expressed in bytes.  Information travels through Networks in the form of packets. In a particular collection all the packets have equal size. If we talk of packets elsewhere, then size may be different.  Packets can be sent over telecommunications lines. Such activities result in assured delivery of packets to the receiver. Yes, such transportation over physical links is reliable.  At a time only one packet can be sent over a telecommunications line. When the line becomes free, the next packet can be sent. When a packet is sent over a communication line, communication may succeed or fail. The success or failure of the communication process is related to transmission of previous and subsequent packets. This is true in cases where communication uses physical connections such as telecommunicat...

Multi-Tier Architecture of Computers is focused on multi-level arrangement of computing units. It is our goal to study how Computers are used levelwise. According to capacity and requirements we place Computers in three different tiers. The different requirements that should be met primarily by the Computers at three levels are: 1 ) 1st Tier: Satisfactory Speed and Memory Capacity  2 ) 2nd Tier: High Processing Speed 3 ) 3rd Tier: Large Storage ____________________________ First Tier: The Computer at the First Tier starts the communication process. In the First Tier there is a user Computer. It is also called Client Computer ( Thin Client). The Client needs service. It frames its requirement(s). The requirement is forwarded to the Computer at the Second Tier. After forwarding its requirement, the Client Computer waits for the response ( reply ). The response ( reply ) is expected from the Second Tier Computer to which service request has been forwarded.  ______________________...

A Communication Subnetwork ( Subnet ) is a typical subpart of a Network. The Subnetwork Computers are of high capacity. The subnetwork activities are carefully monitored. Advanced Computers are used as nodes. These are called Hosts. Such Computers are interconnected with communication links forming a Communication Subnetwork.  Subnetwork Computers have high speed and large storage. Such Computers may have additional processors, besides the main processing unit. The data to be processed may be of complex nature. The size of data handled here is large. Intensive operations are performed to process data. It must be said that Advanced Processors are of much use here. Inflow of data to the Communication Subnetwork from outside causes the size of data to be large. Data from outside  has to be handled by the Subnetwork. The memory capacity of Subnetwork Computers is well suited for large size data. Subnetwork links may distribute the inflow of data to several Subnetwork Computers. Th...

The term Transmission hints at movement. It can be said that Transmission means moving a bunch of information units  in a certain time. Transmission may be fast, or it may be slow. Fast Transmission is a guarantee of Network user satisfaction. Slow Transmission means problems. It is the objective of Network design to ensure fast transmission. Fast Transmission comes at a premium. Slow transmission has a penalty. It is undesirable.  Transmission is of information. An information source can be a transmitter.Such information source is the origin of transmission.  Networks help in information transmission. It helps to carry information from the transmitter to a receiver. The receiver is at the end-point.  If Transmission is slow, it is painful. Slow Transmission creates problems. In case of slow transmission, the receiver will have to wait for long for the next information. Suppose a receiver has fast receiving speed. If a transmitter has many things to transmit, the slo...

Network is a multipurpose connected structure. They are established to meet certain goals.  We know institutions and organisations have to serve. They have to carry their mission forward. In general Networks are designed with following goals: Sharing: The physical structure of the Network allows itself to be shared. Sometimes a Network line allows a number of information to pass out. This is because the Network line is able to carry more than one information at a time. Its capacity to carry information is really appreciable. There is a scope that idle Networks can be shared. Sharing of Network by many users helps in communication. It makes life easy. Because many users get Network benefits, they can collectively invest. This brings down  the financial burden. Maintenance of Information Flow: Network maintains the flow of Information.  Many types of disturbances affect information, when it is traveling. A Network protects information. Anything ( like interference from some...