how many bits of entropy do we need for load balancing?
nanog at jack.fr.eu.org
nanog at jack.fr.eu.org
Tue Dec 15 00:25:39 UTC 2020
o/
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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