Internet Video Series, Part 1


Episode 09, Segment 02 of 04


Class "C" (Small Commercial Grade) Internet Services

If you've seen our "OSI Seven Layer Vocabulary of Modern Internetworking" movie here on, then you also know that layer four of this architecture makes provision to address many, many different application services inside each computer.  Internet addressing commonly makes provision for selecting among up to 65,535 TCP processes and up to 65,535 UDP style processes for networking within each computer.  Very, very few computers will ever be expanded and exploited to the point where they use up all of that process addressing space.  But that addressing system works splendidly on the Internet, and so any of over 33 million potential processes can be running anywhere in a Class C address space, and each of those processes can address any other process anywhere else out in the entire world wide Internet. 

After a small business makes a commitment to purchase a Class C address space from a commercial grade Internet service provider, they must then purchase a commercial grade router.  This is a fairly expensive and sophisticated device costing on the order of several hundred to several thousand American dollars.  The dominant supplier of business class routers in the industry is "Cisco".  The business class router will provide an Ethernet connection that can feed all of the computers in a local area network, and it's typically expanded by a combination of hubs, or switches.  You can learn more about hubs and switches here on by visiting our Ethernet section and looking for short movies with those corresponding titles. 

After installing the router and an appropriate assortment of hubs and switches, all of the computers constituting the small businesses local area network are then given IP addresses from among the group of 256 Internet addresses represented by the Class C address space, and are connected through the hubs and switches back through the router, and to one another. 

For the sake of simplicity, this diagram illustrates only two computers, but as many as 253 computers can be interconnected in this way.  In common internet parlance, we would say that each of these two hundred fifty three computers is directly connected to the Internet.  Each can run any combination of network clients or network server processes. Each of those processes can address any other computer with it's processes directly connected to the Internet.  So, in this fully developed, business oriented, class C connection situation, there are multiple computers per router (up to two hundred and fifty three) and there are multiple processes per computer (more than one hundred thirty thousand) for a grand total potentially of more than 33 million network oriented processes on this small network all of which can simultaneously address the world wide internet and speak with any other process anywhere else.  It's really powerful.  For most people it's "overkill". 

Any of these network processes can be clients, with processes originating inside the lan and accessing internet services or servers, constantly listening for conversations originating out on the Internet accessing to access local services.  Every time you install an additional computer on this kind of network another one hundred thirty one thousand new local network processes either clients or servers, can potentially interact with the world wide Internet. 

Episode 09, Segment 03 of 04