Re: [MMUSIC] RTSP "alt-ports" are not mentioned in the RFC.

[Magnus Westerlund <[e-mail]>]

On 2012-12-17 10:22, Harald Alvestrand wrote:
> On 12/13/2012 11:42 AM, Dushyant Joshi wrote:
>> Hello team,
>>
>> I could see RTSP alt-ports are not defined in either RFC 2326 or RFC 6064
> What is the point of defining an RTSP alt-port?

It appears to be old legacy. I assume the motivation was that it was
difficult to deploy on the <1024 port number and wanted an alternative
that still was prevented to be used by other services.

> 
> Usually, in port numbers, two is worse than one; one should either have
> a single port or have protocol/uri syntax to describe using any port.

The question is if this port number has any benefit at all. Any port
number for RTSP that isn't the default needs to be explicitly called out
in the URI anyway, thus I see little different between 8554 and 7892 for
example. If it is a matter of deploying security policies I would
believe that you need to coordinate that anyway. Or is this for the
cases of outbound policies where you want to say, general TCP isn't ok,
but RTSP is, but only to port 554 and 8554?

Still I think this is strange and I do question if even a informative
reference in the RTSP 2.0 spec is of benefit.

Cheers

Magnus

> 
>>
>> if you see IANA
>>
>> http://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xml
>>
>>
>> we have defined port 8554 as the alternate RTSP port
>>
>> rtsp            554/tcp    Real Time Stream Control Protocol
>> rtsp            554/udp    Real Time Stream Control Protocol
>> rtsp-alt        8554/tcp   RTSP Alternate (see port 554)
>> rtsp-alt        8554/udp   RTSP Alternate (see port 554)
>>
>> The RTSP 2.0 specification is still an Internet Draft and could add text.
>>   can we add this as an informative mentioning that there do exist an
>> alternative registered port.
>>
>> Regards,
>> Dushyant Joshi
>> 91-9886886757
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> 
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-- 

Magnus Westerlund

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