Re: [AVT] draft-kerr-avt-vorbis-rtp-04

[Magnus Westerlund <[e-mail]>]

Hi Arthur,

I am not certain why you ask this question. When it comes to using a CRC 
for Vorbis, the problem is not really about all the possible choices, it 
is about documenting precisly which version one shall use. There is also 
advantages and disadvantages of using the same CRC as is used on the 
transport layer. The advantage is that the implementation may be 
available, however the disadvantage would be that any error that 
inflicted on the protected data is not detected with a second CRC if the 
first identical one fails to detecet. However this disadvantage does not 
appear to be an issue in the usage considered for the vorbis RTP payload 
format.

I haven't read RFC 3385 properly to see if it is guarranted to be a 
suitable reference. I do however get the impression that it is likely by 
pointing at the relevant sections. However it is also important to 
remeber to provide the definition for the data to perform the 
calculation over.

Cheers

Magnus

Arthur de Castro Callado wrote:
> Hi,
> 
> Can RFC 3385 be considered enough of a reference for CRC32 
> implementations, or is it desirable to have (create) another RFC defining 
> and naming all versions of CRC32 that MAY or SHOULD NOT be used in future 
> IETF standards?
> 
> Thanks,
> Arthur Callado.
> 
> On Tue, 18 Jan 2005, Linus Walleij wrote:
> 
> 
>>>I don't know if there is an RFC for CRC32 that you could simply 
>>>reference (after checking that it conforms to your implementation of 
>>>course).
>>
>>Now I know that there is RFC 3385 which carries an example 
>>implementation in Verilog, sort of awkward unless you're devising 
>>hardware implementations.
>>
>>I'd say that SHA-1 is better for any modern software implementation, but 
>>it's partly a matter of taste and opinion IMHO.
>>
>>
>>Linus Walleij
> 
> 
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-- 

Magnus Westerlund

Multimedia Technologies, Ericsson Research EAB/TVA/A
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