【轉】分散式計算的謬論

早在1994年 SUN 的小夥 Peter Deutsch就提出了分散式計算的七大謬論，後來被 James Gosling等完善:

Fallacies of Distributed Computing

1. 網路是可靠的
2. 網路延時為零
3. 頻寬是無限的
4. 網路是安全的
5. 網路拓撲不會改變
6. 肯定至少有一個管理員（在值班）
7. 傳輸開銷為零
8. 網路是同質的

The fallacies

The fallacies are summarized below:^[1]

1. The network is reliable.
2. Latency is zero.
3. Bandwidth is infinite.
4. The network is secure.
5. Topology doesn't change.
6. There is one administrator.
7. Transport cost is zero.
8. The network is homogeneous.

Effects of the fallacies

1. Ignorance of network latency, and of the packet loss it can cause, induces application- and transport-layer developers to allow unbounded traffic, greatly increasing dropped packets and wasting bandwidth.
2. Complacency regarding network security results in being blindsided by malicious users and programs that continually adapt to security measures.^[2]
3. Multiple administrators, as with subnets for rival companies, may institute conflicting policies of which senders of network traffic must be aware in order to complete their desired paths.
4. The "hidden" costs of building and maintaining a network or subnet are non-negligible and must consequently be noted in budgets to avoid vast shortfalls.
5. Ignorance of bandwidth limits on the part of traffic senders can result in bottlenecks over frequency-multiplexed media.

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