by Dinesh Thakur Category: Network Technologies

Integrated Services Digital Network is a telephone system network. It is a wide area network becoming widely available. Prior to the ISDN, the phone system was viewed as a way to transport voice, with some special services available for data. The key feature of the ISDN is that it integrates speech and data on the same lines, adding features that were not available in the classic telephone system.

 
by Dinesh Thakur Category: Network Technologies

1. TDM is the digital multiplexing technique.

2. In TDM, the channel/link is not divided on the basis of frequency but on the basis of time.

3. Total time available in the channel is divided between several users.

4. Each user is allotted a particular a time interval called time slot or time slice during which the data is transmitted by that user.

 
by Dinesh Thakur Category: Network Technologies

Client/Server Architecture The client/server architecture significantly decreased network traffic by providing a query response rather than total file transfer. It allows multi-user updating through a GUI front end to a shared database. Remote Procedure Calls (RPCs) or standard query language (SQL) statements are typically used to communicate between the client and server.



 
by Dinesh Thakur Category: Network Technologies

Frequency-Division Multiplexing (FDM) is a scheme in which numerous signals are combined for transmission on a single communications line or channel. It is analog multiplexing technique. Each signal is assigned a different frequency (sub channel) within the main channel. its requires channel synchronization. FDM multiplexing technique is based on orthogonality of sinusoids.

 
by Dinesh Thakur Category: Network Technologies

A communications device that multiplexes (combines) several signals for transmission over a single medium. A demultiplexer completes the process by separating multiplexed signals from a transmission line. Frequently a multiplexer and demultiplexer are combined into a single device capable of processing both outgoing and incoming signals. A multiplexer is sometimes called a mux.

 
by Dinesh Thakur Category: Network Technologies

Frame relay has evolved from X.25 packet switching and objective is to reduce network delays, protocol overheads and equipment cost. Error correction is done on an end-to-end basis rather than a link -to-link basis as in X.25 switching. Frame relay can support multiple users over the same line and can establish a permanent virtual circuit or a switched virtual circuit.



 
by Dinesh Thakur Category: Network Technologies

In Computer network, a proxy server is a server (a computer system or an application program) that acts as an intermediary for requests from clients seeking resources from other servers. A client connects to the proxy server, requesting some service, such as a file, connection, web page, or other resource, available from a different server.



 
by Dinesh Thakur Category: Network Technologies

X.25 is a standard used by many older public networks specially outside the U.S.

• This was developed in 1970s by CCITT for providing an interface between public packet-switched network and their customers.

 
by Dinesh Thakur Category: Network Technologies

The Token-Passing Protocol relies on a control signal called the token. A token is a 24-bit packet that circulates throughout the network from NIC to NIC in an orderly fashion. If a workstation wants to transmit a message, first it must seize the token. At that point, the workstation has complete control over the communications channel. The existence of only one token eliminates the possibility of signal collisions. This means that only one station can speak at a time.

 
by Dinesh Thakur Category: Network Technologies

Definition: Asynchronous Transfer Mode (ATM) also called cell relay (transferring data in cells of a fixed size) that is operates at the data link layer (Layer 2) of OSI Model over fiber or twisted-pair cable, a high-speed switched network technology based on ITU-T Broadband Integrated Services Digital Network (B-ISDN) standard, developed by the telecommunications industry to implement the next generation network. ATM was designed for use in WANs such as the public telephone system and corporate data networks, though it has also been applied to create super-fast LANs.

ATM can carry all kinds of traffic: voice, video and data simultaneously at speeds up to 155 megabits per second. It Convert voice, video data to packets and passing large packet data through the same medium. ATM is differing from TCP/IP because it use fixed channel routing protocol routes between two end points. A real-time low-latency application such as VoIP and video takes precedence on an ATM network.

What is Asynchronous Transfer Mode (ATM)?

Asynchronous Transfer Mode

ATM is a dedicated connection-oriented switching technology, in which switches create a virtual connection or virtual circuit between the sender and receiver of a call that permanent or switched for the duration of the call. It is a small-packet switched system or similar to circuit-switched network, which breaks down messages into very small, fixed length packets called cells generally organizes digital data into 53 bytes in length (48 bytes of data plus a 5-byte header).   ATM frame structure

An ATM header can have User-Network Interface (UNI) and Network-Node Interface (NNI) two formats.
User-Network Interface (UNI) used for communication between end systems.
Network-Node Interface (NNI) used for communication between switches.

Two type of connections are supported by ATM (Asynchronous Transfer Mode)

Point-to-point connections: It connects either unidirectional or bi-directional two end-systems.
Point-to-multipoint connections: It connects one unidirectional ATM to number of destination ATM.
It is different in packet sizes from Ethernet data or frames. ATM is a core protocol for SONET that is the backbone of ISDN. The advantage conferred by such small cells is that they can be switched entirely in hardware, using custom chips, which makes ATM switches very fast (and potentially very cheap).
The asynchronous part of the name refers to the fact that although ATM transmits a continuous stream of cells over a physical medium using digital signal technology, some cells may be left empty if no data is ready for them so that precise timings are not relevant. Every cell is encoding data with asynchronous time-division multiplexing (TDM) and it queued before being multiplexed over the transmission path.
Every cell are encodes data and processed within their time slot allocated to it. When cell time slot allocated is finished, the next cell starts same procedure. That’s why it's called asynchronous time-division multiplexing (TDM);
This is ATM's greatest strength, as it enables flexible management of the quality of service (QoS) so; an operator can offer different guaranteed service levels (at different prices) to different customers even over the same line. This ability will enable companies to rent virtual private networks based on ATM that behave like private leased lines but in reality share lines with other users.
Available ATM service: Generally four data bit rates are available for ATM services: constant bit rate (CBR), variable bit rate (VBR), available bit rate (ABR) and unspecified bit rate (UBR).



 

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About Dinesh Thakur

Dinesh ThakurDinesh Thakur holds an B.SC (Computer Science), MCSE, MCDBA, CCNA, CCNP, A+, SCJP certifications. Dinesh authors the hugely popular blog. Where he writes how-to guides around Computer fundamental , computer software, Computer programming, and web apps. For any type of query or something that you think is missing, please feel free to Contact us.