computer science

Netsplit

Netsplit 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 Netsplit rather than just read about it. In short: In computer networking, specifically Internet Relay Chat (IRC), netsplit is a disconnection between two servers. A split between any two servers splits the entire network into two pieces.

Key takeaways

Netsplit 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 Netsplit to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Netsplit from memory before moving on to harder problems.

Reference excerpt

In computer networking, specifically Internet Relay Chat (IRC), netsplit is a disconnection between two servers. A split between any two servers splits the entire network into two pieces.

Cause and effects Consider the graph to the right, which represents the computer network. Each line represents an established connection. Therefore, the server C is connected directly to A, which is also connected to B and D.

If a disruption in the connection between C and A occurs, the connection may be terminated as a result. This can occur either by a socket producing an error, or by excessive lag in which the far server A anticipates this case (which is called a timeout). When the connection between A and C is severed, users who were connected to other servers that are no longer reachable on the network appear to quit. For example, if user Sara is connected to server A, user Bob is connected to server B, and user Joe is connected to C, and C splits, or disconnects, from A, it will appear to Joe as if Sara and Bob both quit (disconnected from the network), and it will appear to both Sara and Bob that Joe quit. However, Joe can still talk to anyone who is connected to the same server (in this case server C). This happens because the servers to which they are connected are informed of the change in the network status, and update their local information accordingly to display the change. Later, server C may relink (reconnect) to a server (or servers) on the network and the users who appeared to have quit will rejoin; the process of sending this updated information to all servers on the network is called a netburst (or sync).

Security issues

Occasionally, users will attempt to use netsplits to gain access to private channels. A denial-of-service attack can be used to cause a netsplit by overloading an IRC server's network connection or Internet infrastructure between two servers. If none of the channel users were on server C, a user could join a private channel and later gain access when the servers relink. This is commonly known as split riding or riding the split. Another typical netsplit-oriented IRC attack is Nickname Colliding. In this attack, a user on a split segment of the network would change nicknames to that of a user on the other side of the split network. Upon reconnection, the network would disconnect both users because only one nickname may be in use at one time. Modern IRC server software has largely eliminated this method, but servers using older software may still be vulnerable.

Appearance

Below are examples of a typical netsplit. When two servers split, a user sees this as large number of users quitting. After the servers are reconnected, a user sees the other users rejoining.

On GUI IRC clients

On command-line client IRC

To a user on a private network

References

Citations

Sources Hossein Bidgoli: The Internet Encyclopedia- Volume 2. Wiley 2004, ISBN 978-0-471-22204-0, p. 312-313

External links

Netsplit Manual (retrieved 2009–12–2)

Illustrations

Worked examples

Example 1 — a first encounter with Netsplit

Start with the simplest possible case. Write down what Netsplit 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 Netsplit 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 Netsplit 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 Netsplit

In research: Netsplit 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 Netsplit 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: Netsplit is common in secondary-school and first-year university syllabi. It links to neighbouring topics Computer errors, IRC, so understanding it makes those chapters shorter.
In everyday life: Look for Netsplit 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 Netsplit in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Netsplit 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 Netsplit out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Netsplit in simple terms?

In computer networking, specifically Internet Relay Chat (IRC), netsplit is a disconnection between two servers. A split between any two servers splits the entire network into two pieces.

Why does Netsplit 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 Netsplit?

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 Netsplit.