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Re: Difference between ipp, ipps, http, https CUPS protocols?



On 12/11/19 8:38 AM, Kent West wrote:
> 
> On 11/11/19 10:40 AM, Brian wrote:
>> On Mon 11 Nov 2019 at 10:18:26 -0600, Kent West wrote:
>>
>>> Probably answered somewhere, but I've been DuckDuckGo-ing for the
>>> past two
>>> hours and can't find the answer.
>>>
>>> When adding a printer via the CUPS web interface (localhost:631) on my
>>> Debian box, Administration / Add Printer / Other Network Printers,
>>> there are
>>> four Internet Printing Protocol options:
>>>
>>> https
>>>
>>> ipp
>>>
>>> http
>>>
>>> ipps
>>>
>>> Which one do I want to select? What are the differences?
>> 'ls -l /usr/lib/cups/backend' tells you that it doesn't matter what
>> choice you make.
>>
> 
> lrwxrwxrwx 1 root root      3 Oct 31 02:44 http -> ipp
> lrwxrwxrwx 1 root root      3 Oct 31 02:44 https -> ipp
> -rwxr-xr-x 1 root root  80120 Oct 31 02:44 ipp
> lrwxrwxrwx 1 root root      3 Oct 31 02:44 ipps -> ipp
> 
> Thank you. That does tell me they are all the same.

It doesn't tell me that.

It tells me that they're all the same file, but an executable can find
out what name it was called with, and change its behaviour accordingly.
Busybox is an extreme example.

> It does not tell me
> why CUPS on Debian makes the other three options available (thereby
> confusing the person adding the printer). There must be some reason why
> a person would expect to choose X over Y; that's the difference I'm
> looking for.
> 
> But your answer certainly helps. I now know it doesn't matter which of
> these I select.

I would guess that the *s versions use TLS, but beyond that I don't
know. I'd agree with deloptes that it probably depends on what the
remote end can support.

Richard


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