Showing posts with label technology. Show all posts
Showing posts with label technology. Show all posts
Monday, 1 July 2013
What is top down implementation - peak concepts
What is Coupling - peak concepts
The
more connections between modules, the more dependent they are in the
sense that more knowledge about one module is required to understand or
solve the other module. Hence, the fewer and simpler the connections
between modules, the easier it is to understand one without
understanding the other. Coupling between modules is the strength of
interconnection between modules or a measure of independence among
modules.
To
solve and modify a module separately, we would like the module to be
loosely coupled with other modules. The choice of modules decides the
coupling between modules. Coupling is an abstract concept and is not
easily quantifiable. So, no formulas can be given to determine the
coupling between two modules. However, some major factors can be
identified as influencing coupling between modules.
Among
them the most important are the type of connection between modules, the
complexity of the interface, and the type of information flow between
modules. Coupling increase with the complexity and obscurity of the
interface between modules. To keep coupling low we would like to
minimize the number of interfaces per module and the complexity of each
interface. An interface of a module is used to pass information to and
from other modules. Complexity of the interface is another factor
affecting coupling.
The
more complex each interface is, higher will be the degree of coupling.
The type of information flow along the interfaces is the third major
factor-affecting coupling. There are two kinds of information that can
flow along an interface: data or control, Passing or receiving control
information means that the action of the module will depend on this
control information, which makes it more difficult to understand the
module and provide its abstraction. Transfer of data information means
that a module passes as input some data to another module and gets in
return some data as output.
What is Error Correction and Detection - peak concepts
Error Correction : Send
additional information so incorrect data can be corrected and accepted.
Error correction is the additional ability to reconstruct the original,
error-free data.
There are two basic ways to design the channel code and protocol for an error correcting system :
• Automatic Repeat-Request (ARQ) : The
transmitter sends the data and also an error detection code, which the
receiver uses to check for errors, and request retransmission of
erroneous data. In many cases, the request is implicit; the receiver
sends an acknowledgement (ACK) of correctly received data, and the
transmitter re-sends anything not acknowledged within a reasonable
period of time.
• Forward Error Correction (FEC) : The
transmitter encodes the data with an error-correcting code (ECC) and
sends the coded message. The receiver never sends any messages back to
the transmitter. The receiver decodes what it receives into the "most
likely" data. The codes are designed so that it would take an
"unreasonable" amount of noise to trick the receiver into
misinterpreting the data.
What is a Connection-Oriented Service - peak concepts
- In connection oriented service a connection is established between the communicating n+1entity using the service provided by the n-entity.
- The service users of connection oriented service undergo three different phases.
- Connection oriented service is modeled after the telephone system. When we make a phone call, we first establish a connection; then we talk or transfer information. And when we are done we hang up or drop the connection.
- Such a connection acts like a tube. The sender pushes bits from one end of the tube and the receive takes out from the other end.
- In connection oriented service, the order in which the bits are received is same as the order in which they are sent.
- During connection establishment, the sender, receiver and subnet negotiate certain parameters as quality of service required, maximum message size, and exchange of source and destination addresses.
Sunday, 30 June 2013
What is Peer-to-Peer Networks - peak concepts
- In the peer to peer computer network model we simply use the same Workgroup for all the computers and a unique name for each computer in a computer network.
- There is no master or controller or central server in this computer network and computers join hands to share files, printers and Internet access.
- It is practical for workgroups of a dozen or less computers making it common environments, where each PC acts as an independent workstation and maintaining its own security that stores data on its own disk but which can share it with all other PCs on the network.
- Software for peer-to-peer network is included with most modern desktop operating systems such as Windows and Mac OS.
- Peer to peer relationship is suitable for small networks having less than 10 computers on a single LAN.
What is Internet - peak concepts
What is Intranet - peak concepts
Intranet : An intranet is a set of interconnected networks or Internetworking, using the Internet Protocol and uses IP-based tools such as web browsers and ftp tools, that is under the control of a single administrative entity.
That administrative entity closes the intranet to the rest of the
world, and allows only specific users. Most commonly, an intranet is the
internal network of a company or other enterprise. A large intranet
will typically have its own web server to provide users with browseable information.
What is Database server - peak concepts
