What is a synchronous data connection?

Synchronous data connection (SDLC) is a protocol that provides data transfer through a layer of two of what is called Systems Network Architecture (SN). The dreams were developed by IBM® at the age of 20, as a wide network for IBM® Mainframe, network hardware and remote terminals for IBM®. Compared to the SNA, the Open Systems InterConnect is used in the Internet protocol (IP), where network operations are separated into layers, each responsible for one aspect of communication in the network. Although similar in the concept, the layers of the SNI are not compatible with the OSI layers. The user would rent a line from the telephone company and then set his computer hardware to connect via this dedicated line.S such a reliable connection was the synchronous control protocol to manage the effort to manage each line and provide data communication network between computer user systems. AsThe proprietary protocol has been added to modems and computer systems developed by IBM®, which formed the SNA environment. Later IBM® shared the concept of control of synchronous data connection with standard organizations, which then developed a high -level data connection protocol (HDLC) that other hardware retailers began to use.

The synchronous data connection protocol was the first of its kind to provide transmissions based on the bytes that are responsible for identifying each data frame. In SDLC, data transfer is divided into frames that are streaming via connection. Each frame contains not only the data sent, but also a number of bytes that carry information about Address Romus, how to organize all frames in the correct order and ability of the system to double the frame, whether it will happen during its journey.

The first and last bytes of the SDLC frame are called symptomswhich are basically a frame cover, which indicates its beginning and end. Another or two bytes form an address. The inspection bytes, which may have more purposes depending on the type of frame, are governed by the address and can handle frames, stop transmission, check status, questioning, etc. The useful data load is governed by inspection bytes and data, but several bytes used for redundant sequence.

The environment of pursuit of data connection synchronous control is relatively simple, where each node in the network is identified as primary or secondary. The primary nodes are most likely Mainframe Computer, while secondary are terminals communicating with Mainframe. However, the network running under SDLC is capable of several different types of topologies.

There are only two computers in the point-to-point settings that communicate with each other: the only primary mainframe and a single secondary terminal. With multi -point, however, mainframe is responsible for libOrthole number of secondary terminals. Another topology is a loop configuration, where mainframe acts as something like a primary point in a circle, where the frames pass through the first or the last terminal in the circle. Then there is something called the HUB Go-Aead method that allows the outgoing channel to the mainstream computer and the incoming channel to the terminals.