Transformations of Networking — Part 1
- Transformations of Networking — Part 1 (this article)
- Transformations of Networking — Part 2
- Transformations of Networking — Part 3
- Transformations of Networking — Part 4
- Transformations of Networking — Part 5
The world of networking has changed immensely in the last 30 years. For a timeline, check out the Wikipedia 802.3 page.
But the interesting thing is there are intermediate steps from the first coaxial Ethernet, to today’s 10gbps fiber up-links. These intermediate steps have changed the networking world drastically, and have changed how we design networks in the first place. Armed with this knowledge, you can design excellent networks today, taking advantage of this new technology and most critically, not make the mistakes of the past.
Coaxial — The Wikipedia 10base2 Page — 1972
When Ethernet was first introduced, the infrastructure used coaxial copper media. This coaxial cable was limited in its uses, for a network had to created linearly. Each host was connected to the cable through a T-Connector, and any unused end points had to be capped with a Terminator.
There were further physical limitations. As the cable design was coaxial and shared, the connections had to be grounded at all points or the network stops. This makes this network design vulnerable to disruption from both accidental or malicious changes; even attempting to extend the network to another host, or remove a host would cause a temporary network failure. Lastly the length of the coaxial cable was limited to 185m, so the physical location of the host computers had to be in line with the network cable.
In addition to these physical characteristics, there were also logical limitations. Having all these computers on a single network was the primary goal of Ethernet, but as they were all connected to the same wire the designers had to come up with a solution to allow communication between all devices.
The mechanism for this is CSMA/CD (Carrier Sense Multiple Access with Collision Detection); see the Wikipedia Page for CSMA/CD. A common analogy for CSMA/CD is of a polite dinner party in the dark, where each participant at the table who wishes to speak must do so, and if the participant is interrupting someone else (a collision) he must wait for a random period of time before attempting to speak again. Thus the protocol allows every device to have a chance to speak at some point.
All of these issues really limited the network architect’s ability to build a network, and fault-tolerance wasn’t even a consideration at this stage.
The Hub and 10baseT — 1990
The Wikipedia Network Hub Page
10baseT and the hub freed networks from the limitations of coaxial cabling by creating a single location for all cables to come to — allowing network designers to create a star network design.
This design (effectively a star topology) allowed for much greater flexibility in the physical location of the network hosts, as each segment of the star is permitted to be up to 100m. Additionally, 10baseT was not held by the restrictions of coaxial cable — without the Terminators or T-Connectors 10baseT networks were not nearly as vulnerable to accidental mishaps as with 10base2.
This major change in networking topology allowed networks to expand laterally into offices, businesses, universities, and governments. Many people use hubs in their homes, and their simple design means that they’re still useful today for network analysis.
As networks became larger, it was increasingly necessary to have more addressing space for management of computers, servers and printers. Novell networking was prevalent in the 1980s and 1990s and their systems pushed the Layer 3 protocol IPX/SPX into common use. This legacy is still seen today, for some devices (particularly printers) ship with IPX/SPX enabled and running; although for the most part IPX/SPX has been superseded by IP.
In this way, hubs played their part in the transformation of networking from a quirky collection of computers at a university, to a resource that multinational corporations depend on for their bottom line. But that’s another story.
Summary
The hub arrived just in time for the personal computer revolution — it allowed companies to build more complicated networks and relieved network administrators from the restrictions of the coaxial cable. The simple design of the hub made inexpensive, rapid deployment of networking possible.
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