Answers in this category:
What does the [H14.17] in RFC 2543 stand for?
Do callers need to know the location of the Location Server?
What is the difference between a call leg and a call id?
What is the difference between tag and branch-id?
How can one recognize a retransmitted, duplicate or looped request?
What is the relationship between the From, Contact, Via and Record-Route/Route headers?
How are URLs compared?
What's the difference between the request URIs tel:+12125551212 and sip:12125551212@gw.com?
Do I always need a proxy or redirect server?
How does a caller find its local registrar?
How do I ensure registrar reliability?
Are ACK requests retransmitted?
How are BYE requests routed?
Can I CANCEL requests other than the first INVITE?
How does a caller find its proxy server?
What's the difference between a stateless and a stateful proxy server?
Why can a forking SIP proxy not be stateless?
How does a caller find the remote SIP client of the callee?
How does SIP get through a firewall?
Does SIP do keep-alive?
Why does SIP not have a Content-Transfer-Encoding header?
I want SIP to be more compact. What can I do?
What are the different addresses in SIP?
The BNF for header <put your favorite header here> allows a parameter to appear more than once. What does this mean?
Can the request URI include a port number and/or transport parameter?
Transport in Via
What should I do if my re-INVITE fails?
How long can SIP host names be?
Can a User Agent also act as a Registrar?
Can I remove an m= line from SDP in response or re-INVITE?
I'm a UAC. I sent an INVITE, and then decide I want to hang up before getting a final response. Do I send BYE or CANCEL?
I'm a proxy, and I forked a request, and forwarded multiple 200 OK upstream. Now, I get an ACK. What do I do with it?
If I get a new SDP body in the ACK, and I don't like the media type, how can I indicate its unacceptable to me?
Can a SIP UA register with multiple registrars?
Is it possible for a UA to make a call to itself, and have the result be two separate calls on the same machine?
Does a UAS use the request-URI or To field to determine if a call is for it?
How are SIP parsers implemented?
Is it possible to use Hide with Record-Route?
How does a proxy handle a method other than the standard INVITE, ACK, BYE, etc.?
Why does a proxy server doing TCP need to be stateful?
In computing the Content-Length, does the newline in a body count as one byte or two (CR vs. CR-LF)?
Can a proxy fork a non-INVITE request? If yes, what happens if it gets multiple responses?
Should responses be sent to the host specified in Via? Is From ever used for sending responses?
Once a SIP registrar gets a REGISTER request, how does it update the Location Server with the contact information?
Is a SIP URI without a user name valid?
Is there a specific order for header fields?
When is a CANCEL used?
What do I need to do to use SRV records?
Why does SIP/SDP allow for multiple codecs to be used for the same media stream?
What are spirals? Why does a proxy care?
What's the difference between loose and strict source routing?