In computer science Computer science or computing science is the study of the theoretical foundations of information and computation, and of practical techniques for their implementation and application in computer systems. It is frequently described as the systematic study of algorithmic processes that create, describe and transform information. According to Peter J, in particular networking A computer network is a group of computers that are connected to each other for the purpose of communication. Any computer network is classified on the basis of a wide variety of characteristics. This article provides a general overview of types and categories and also presents the basic components of a network, a session is a semi-permanent interactive information interchange, also known as a dialogue, a conversation or a meeting, between two or more communicating devices, or between a computer and user (see Login session In computing, a login session is the period of activity between a user logging in and logging out of a system). A session is set up or established at a certain point in time, and torn down at a later point in time. An established communication session may involve more than one message in each direction. A session is typically, but not always, stateful In computer science and automata theory, a state is a unique configuration of information in a program or machine. It is a concept that occasionally extends into some forms of systems programming such as lexers and parsers, meaning that at least one of the communicating parts needs to save information about the session history in order to be able to communicate, as opposed to stateless A stateless server is a server that treats each request as an independent transaction that is unrelated to any previous request communication, where the communication consists of independent requests with responses.
Communication sessions may be implemented as part of protocols and services at the application layer Application Layer is a term used in categorizing protocols and methods in architectural models of computer networking. Both the OSI model and the Internet Protocol Suite contain an application layer, at the session layer The Session Layer provides the mechanism for opening, closing and managing a session between end-user application processes, i.e. a semi-permanent dialogue. Communication sessions consist of requests and responses that occur between applications. Session Layer services are commonly used in application environments that make use of remote procedure or at the transport layer In computer networking, the Transport Layer is a group of methods and protocols within a layered architecture of network components within which it is responsible for encapsulating application data blocks into data units suitable for transfer to the network infrastructure for transmission to the destination host, or managing the reverse in the OSI model The Open System Interconnection Reference Model is an abstract description for layered communications and computer network protocol design. It was developed as part of the Open Systems Interconnection (OSI) initiative. In its most basic form, it divides network architecture into seven layers which, from top to bottom, are the Application,.
- Application layer examples:
- HTTP Hypertext Transfer Protocol is an application-level protocol for distributed, collaborative, hypermedia information systems. Its use for retrieving inter-linked resources, called hypertext documents, led to the establishment of the World Wide Web in 1990 by English physicist Tim Berners-Lee. There are two major versions, HTTP/1.0 that uses a sessions, which allow associating information with individual visitors
- A telnet Telnet is a network protocol used on the Internet or local area networks to provide a bidirectional interactive communications facility. Typically, telnet provides access to a command-line interface on a remote host via a virtual terminal connection which consists of an 8-bit byte oriented data connection over the Transmission Control Protocol ( remote login session
- Session layer The Session Layer provides the mechanism for opening, closing and managing a session between end-user application processes, i.e. a semi-permanent dialogue. Communication sessions consist of requests and responses that occur between applications. Session Layer services are commonly used in application environments that make use of remote procedure example:
- A Session Initiation Protocol The Session Initiation Protocol is a signaling protocol, widely used for controlling multimedia communication sessions such as voice and video calls over Internet Protocol (IP). The protocol can be used for creating, modifying and terminating two-party (unicast) or multiparty (multicast) sessions consisting of one or several media streams. The (SIP) based Internet phone Voice over Internet Protocol is a general term for a family of transmission technologies for delivery of voice communications over IP networks such as the Internet or other packet-switched networks. Other terms frequently encountered and synonymous with VoIP are IP telephony, Internet telephony, voice over broadband (VoBB), broadband telephony, call
- Transport layer example:
- A TCP The Transmission Control Protocol is one of the core protocols of the Internet Protocol Suite. TCP is one of the two original components of the suite (the other being Internet Protocol, or IP), so the entire suite is commonly referred to as TCP/IP. Whereas IP handles lower-level transmissions from computer to computer as a message makes its way session, which is synonymous to a TCP virtual circuit In telecommunications and computer networks, a virtual circuit , synonymous with virtual connection and virtual channel, is a connection oriented communication service that is delivered by means of packet mode communication. After a connection or virtual circuit is established between two nodes or application processes, a bit stream or byte stream, a TCP connection Connectivity, in the context of computer science, refers to the use of computer networks to link computers to one another, and provide information resources between computer systems and their final users. On a collective scale, connectivity may refer to the Internet bandwidth coming into and going out of a country, and the quality of the, or an established TCP socket.
In the case of transport protocols that do not implement a formal session layer (e.g., UDP The User Datagram Protocol is one of the core members of the Internet Protocol Suite, the set of network protocols used for the Internet. With UDP, computer applications can send messages, in this case referred to as datagrams, to other hosts on an Internet Protocol (IP) network without requiring prior communications to set up special transmission) or where sessions at the session layer are generally very short-lived (e.g., HTTP Hypertext Transfer Protocol is an application-level protocol for distributed, collaborative, hypermedia information systems. Its use for retrieving inter-linked resources, called hypertext documents, led to the establishment of the World Wide Web in 1990 by English physicist Tim Berners-Lee. There are two major versions, HTTP/1.0 that uses a), sessions are maintained by a higher level program using a method defined in the data being exchanged. For example, an HTTP exchange between a browser and a remote host may include an HTTP cookie In computing, a cookie is a small piece of text stored on a user's computer by a web browser. A cookie consists of one or more name-value pairs containing bits of information such as user preferences, shopping cart contents, the identifier for a server-based session, or other data used by websites which identifies state, such as a unique session ID In computer science, a session identifier, session ID or session token is a piece of data that is used in network communications to identify a session, a series of related message exchanges. Session identifiers become necessary in cases where the communications infrastructure uses a stateless protocol such as HTTP. For example, a buyer who visits, information about the user's preferences or authorization level.
Protocol version HTTP/1.1 Hypertext Transfer Protocol is an application-level protocol for distributed, collaborative, hypermedia information systems. Its use for retrieving inter-linked resources led to the establishment of the World Wide Web makes it possible to reuse the same TCP session for a sequence of service requests and responses (a sequence of file transfers) in view to reduce the session establishment time, while HTTP/1.0 Hypertext Transfer Protocol is an application-level protocol for distributed, collaborative, hypermedia information systems. Its use for retrieving inter-linked resources led to the establishment of the World Wide Web only allows a single request and response during one TCP session. However, this transport layer session mechanism should not be confused with a so-called HTTP session, since it does not last a sufficiently long time, and does not provide application level interactive services such as dynamic web pages.
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