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Re: Hashing function for PSAMP
Regarding PSAMP compliance, I was under the impression that the
agreement was (even If I could not find a trace of it, after looking
approx. 30 sec ;)):
If you want to be PSAMP compliant, you MUST implement at least one of
the "method" described in the draft.
So I concluded that one filtering or one sampling mechanism would be
Now, the discussion below is about a compulsory hash function.
Can we please clarify the situation regarding PSAMP compliance, so where
is/are the MUST(s):
- MUST implement one of the filtering or sampling mechanism (note:
hashing is a filtering function)?
- Or MUST implement one of the filtering and one of the sampling
mechanism (note: hashing is a filtering function)?
- Or MUST implement one of the filtering, sampling, or hashing mechanism?
- Or MUST implement one of the filtering, sampling, and hashing mechanism?
- Or something else?
From there, we will deduce if we even need a compulsory hash function...
Currently, the packet selection document has IPSX mandatory for packet
selection and CRC32 mandatory for packet digest.
The problem I see with this recommendation is that IPSX is not suitable
for IPv6. It does not sound like a good idea to have it mandatory for
Here are two alternatives:
1. Make IPSX mandatory for IPv4 packet selection and BOB mandatory
for IPv6 packet selection.
Then, with BOB implemented anyway, we should then replace CRC32
with BOB for packet digest, because both perform similarly and
there is no good reason for forcing implementors to support also
a third hash function.
2. Just make BOB mandatory for packet selection and packet digest.
This would simplify implementation, because only a single function
is required. For packet digest this should be OK, see 1.
A disadvantage is that BOB is slower than IPSX by factor 7.
An advantage is, that BOB is free of IPR, while IPSX is protected
by a patent.
Does anybody have a preferences for 1., 2., or the current choice?
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