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Issue 6.5

COLUMN

The Two Generals' Problem

The Fog Of Networking

Issue: 6.5 (July/August 2008)
Author: Charles Yeomans
Author Bio: Charles is a senior software engineer at Dakim, Inc.
Article Description: No description available.
Article Length (in bytes): 8,459
Starting Page Number: 40
Article Number: 6514
Related Link(s): None

Excerpt of article text...

The Two Generals' Problem is a classic example of the problems encountered when trying to communicate over an unreliable channel. If you write networking software, you will typically use unreliable channels, so you should understand the problem, and how to deal with it.

Suppose two generals want to coordinate an attack. The attack will fail unless both armies attack at the same time. The problem is how to agree on a time, given that they can only communicate by messenger.

So General A sends a messenger to General B. When General B receives the message, he sends a message back to General A confirming the attack time. But the only way General B knows that his response was received is for General A to send a reply by messenger...

...End of Excerpt. Please purchase the magazine to read the full article.