For a long time, a ten-megabyte network was the only way to connect computers. Although this technology had a number of features (stub terminators, signal collisions, wave impedance matching ), it was it that was most widely used.
The equipment was relatively inexpensive, installation was simple, and a speed of 1.25 MB / s suited everyone. However, the amount of data transmitted became more and more every year, and the requirements for network equipment were tightened. Therefore, in the 90s, the outdated solution was replaced by Fast Ethernet technology. In developing the wishes of users and manufacturers were taken into account, the "childhood diseases" of the 10-Mbit network were overcome.
Fast Ethernet. Description
The time of the origin of technology can be considered 1992. It was then that a group of companies engaged in the creation of network equipment, including 3Com, SYNOptics and several others, created a special joint association called the "Fast Ethernet Alliance". His tasks included analysis of the developments of various manufacturers, which could be used to create a high-speed information transfer solution.
Moreover, the principles of the formation and transmission of data packets should not be too different from 10-megabit networks. This was necessary to maintain compatibility with CSMA / CD access.
In the same year, an association was formed at the IEEE Standardization Institute, whose task was to study the 100-megabyte access solutions offered by the companies. This was the beginning of the secret confrontation between companies and their developments. Each developer sought to ensure that his decision was taken as a standard.
As a result, as often happens, many had to sacrifice, choosing a compromise option. For example, the proposed 100VG-AnyLAN technology from HP and AT&T, which implements the completely new Demand Priority access principle, was rejected because it was not backward compatible with the existing 10Base solution.
The result of the work was the recognition in 1995 of a 100-megabyte Fast Ethernet solution as standard, which received the designation 802.3u.
Features
The main difference between Fast Ethernet and its predecessor - 10 Mbps Base-T - was a change in physical implementation.
In addition to compatibility with the previous solution, the main advantages of this technology include:
- increase the speed of data exchange up to 12.5 MB / s (those same 100 Mb);
- use of random access method;
- the possibility of using familiar solutions, since the function of creating star-shaped networks was preserved, and it was possible to use classic conductors: twisted pair and optical fiber.
Since in Fast Ethernet the frame format of data packets remained the same, this allowed for almost complete backward compatibility. So, even now, all network solutions for 100 Mbit and even 1 Gigabit provide for a 10-Mbit mode of operation (it can be set forcibly in the driver settings).
Nevertheless, there are differences. For example, the time intervals of frame transmission were reduced by almost 10 times (in fact, this allowed us to achieve such a high speed).
Segment Features
As an Ethernet option that does not use a coaxial cable, 100 Mbps Fast Ethernet involves connecting to all ends of the receiving device branches. It can be computer network cards , hubs and hubs (HUB). A limit is imposed on the line length, depending on the type of conductor used. So, for the twisted pair of the fifth category, the permissible distance is 100 meters, but the optical fiber makes it possible to work from 400 m (half duplex) to 2 km.
Although the number of repeaters (repeater) is also limited, this does not prevent the creation of complex network diagrams due to the multiport nature of such devices.