[SIPForum-discussion] Standard SIP Replies

[Paul Kyzivat]

On 3/2/16 5:22 AM, Adnan Aziz wrote:
> Hi Everyone,
> I will be very thankful, if someone could reply the following questions
> regarding SIP.
>
>  1. Is it in SIP specification/standards to respond to the OPTIONS
>     packets from REGISTERED and UNREGISTERED users?

The spec typically expects *some* response to every valid request. 
However this gets bent in the case of server overload.

It doesn't require a *successful* response. You can certainly respond 
with 401 or 403 if you don't wish to respond to this client.

>  2. Is it in SIP specification/standards to respond to the INVITE
>     packets without any prior REGISTRATION?

Same as above.

Note that SIP was designed with the expectation that you only need to 
register to make a device with a transient address callable via an 
Address of Record. It wasn't expected that registration would be 
required for *sending* requests, or for receiving requests addressed to 
the actual URI of your device. Rather, outgoing requests might be 
challenged with 401 or 407 for credentials.

However some deployments (notably 3gpp IMS) have chosen to require 
registration before providing any service. That is their choice, it is 
not part of the basic sip specs.

>  3. Does the SIP standard also support the registration process using
>     INVITE packets instead of REGISTER packets?

No.

I'm curious what is motivating these questions? What are you trying to do?

	Thanks,
	Paul

> I shall be very thankful to you for your replies. Also please mention
> the rfc or other authentic reference to support the answers.
>
>
> Best Regards,
> Adnan
>
>
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