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Most large companies today have a SNA-compatible mainframe installed as a central nerve in the information system. However, there has been an evolution within the corporate enterprise network (Figure 1). (Figure 1 omitted) Ten years ago there was a totally IBM dominated hierarchical SNA environment with the mainframe as a single source processor, and users were attached to the mainframe with unintelligent terminals through cluster controllers. Through the last decade a desktop computer revolution has taken place. Many users wanted a PC on their own desk to perform personal productivity tools such as spreadsheets, business graphics and word processing. However, a connection to the central mainframe was still required and the users were therefore equipped with 3270 emulation software and hardware.
In the last five years departmental servers have been installed to serve the desktop computers in a client/server relationship. This has instigated the birth of workgroup computing. All the departmental workgroups have been islands of computing not sharing data with the existing mainframe environment. The concept of the nineties is to link all these workgroups into a large corporate enterprise network with the use of bridges. Today the trend is towards peer-to-peer computing with the PCs connected to departmental servers, which again often act as bridges to the central host environment. The applications and databases are distributed between the workgroups with global availability.
SEGMENTATION OF NETWORKS
The implementation of local bridges (Figure 2) arises from the need to optimize workgroup performance.(Figure 2 omitted) This is achieved through segmentation (splitting one large network out into smaller separate workgroups or segments, each connected to each other by a high speed local bridge. This can be achieved without the usual worry about bottlenecks and delays due to bridging.
The bridge's performance and low latency time allows the user to have a good response time whether connected to a local server or connected to a server via a bridge. Wire speed local bridges, such as the 16/4 source-routing box bridge developed by Olicom, can...