What is the purpose of the OSI model?
The OSI model (as well as IEEE 802 and NDIS) were established to standardize the design and construction of computer networks for developers and hardware manufacturers. Standards allow hardware and software components from a variety of different vendors to operate together. Without standards, everything would be vendor-specific and interoperability would suffer.
Almost all vendors implement standards in slightly different ways. This is normally done to take advantage of unique functionality in their product that just won't fit neatly into the model. However, if a vendor strays too far from the standards, they risk creating a 'closed' or proprietary product that is not supported by the rest of the industry.
IBM mainframes use Systems Network Architecture (SNA) that is a set of layered protocols like the OSI model. However, the SNA layers are not directly comparable to the OSI model layers. This makes interoperability between PC-based networks and IBM mainframes more difficult.
Exam Tip. Certification candidates need to understand the OSI and IEEE models because they provide a framework from which many of the technical concepts are taught. This understanding can be a big help when troubleshooting network problems in the real world.