computer science

IBM VNET

IBM VNET is a computer science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand IBM VNET rather than just read about it. In short: VNET is an international computer networking system deployed in the mid-1970s and still in current, though greatly diminished, use. It was developed inside IBM and provided the main email and file-transfer backbone for the company throughout the 1980s and 1990s.

Key takeaways

IBM VNET belongs to computer science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect IBM VNET to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of IBM VNET from memory before moving on to harder problems.

Reference excerpt

VNET is an international computer networking system deployed in the mid-1970s and still in current, though greatly diminished, use. It was developed inside IBM and provided the main email and file-transfer backbone for the company throughout the 1980s and 1990s. Through it, a number of protocols were developed to deliver email amongst time sharing computers over alternative transmission systems. VNET was first deployed as a private host to host network among CP/67 and VM/370 mainframes beginning before 1975. It was based on RSCS, a virtual machine–based communications program and an inter machine protocol developed in IBM's Advanced Systems Development Division's Remote Service System (RSS) prototype which produced some of the technology in the IBM Tivoli product. At that time, RSCS used the Binary Synchronous Communications (BSC) protocol, not Systems Network Architecture (SNA), to support file to file transfer among virtual machine users. The first several nodes included Scientific Centers and Poughkeepsie, New York lab sites. RSCS-compatible communications code was subsequently developed for MVT/HASP, MVT/ASP and MVS mainframe operating systems. By September 1979, the network had grown to include 285 mainframe nodes in Europe, Asia, and North America. Unlike the Internet, VNET switched files among mainframes using a store and forward technique. Many of the early connections operated over dial-up phone lines at speeds of 1200 to 2400 bits per second. The addition of a 19.2 kbit/s trans-Atlantic satellite circuit in late 1977 was considered a major step forward. End users typically sent files between 100 and 100,000 bytes in length. The user could expect delivery within one minute to several hours. File delivery was acknowledged on a hop by hop basis but there was no end to end delivery confirmation. However, by the late 1970s an email application was developed that provided delivery confirmation as well as message archiving. What began as a research activity among engineers and scientists became, by 1980, a valuable business asset for many organizations within IBM. The first widely disruptive computer worm, "Christmas Tree EXEC" in December 1987, originated on BITNET and spread to this network.

Notes

References

External links Interview with VNET creator Edson Hendricks

Worked examples

Example 1 — a first encounter with IBM VNET

Start with the simplest possible case. Write down what IBM VNET claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to IBM VNET before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about IBM VNET ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of IBM VNET

In research: IBM VNET appears in computer science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses IBM VNET in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: IBM VNET is common in secondary-school and first-year university syllabi. It links to neighbouring topics Computer network stubs, IBM, VM (operating system), so understanding it makes those chapters shorter.
In everyday life: Look for IBM VNET outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study IBM VNET in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what IBM VNET means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain IBM VNET out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is IBM VNET in simple terms?

Why does IBM VNET matter?

Because it connects several computer science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study IBM VNET?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on IBM VNET.