how many bits of entropy do we need for load balancing?

nanog at nanog at
Tue Dec 15 00:25:39 UTC 2020


Small of out topic

On 12/14/20 7:16 PM, Lawrence Wobker wrote:
A “perfect” balancing algorithm would be crypto grade hash generation 
with a large output, and a true modulo operation to select which member 
we use.
There are 3 kind of hashing algorithm

The first one is used to check the sanity of input, against bit-swapping 
error for instance
See CRC for instance
Those algorithm are deadly fast, but also dumb as hell

The second one is used for cryptographic purposes
While the output distribution is supposed to be quite good, its most 
important aspect lies here: it is hard to craft an input matching a 
specific hash
See sha256 for instance

The last one combines both speed and output distribution
See xxhash for instance

Unless you have a specific security thing in mind, you shall never use a 
crypto-grade hash algorithm

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