The hottest SIP protocol specification RFC3261 Chi

2022-08-16
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SIP protocol specification RFC3261 Chinese share

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connect to sip protocol specification RFC3261 Chinese share-23, about invite response processing

13.2.2 processing invite responses

once an invite is passed to the client transaction of the invite, UAC will wait for the response of the invite. If the client transaction of this invite returns a timeout instead of a response, this response is tu. if it has received a 408 (req includes floor glue, rubber on electronic components, key components on rubber products, etc.; such as brake pipes, brake cups, brake pads, seals, etc. UEST timeout) response, it acts as a response, as discussed in section 8.1.3

13.2.2.1 1XX responses

before receiving one or more final responses, it may reach zero, one or more temporary responses. For an invite request, the temporary response can create early dialogs. If there is a tag in the to of the temporary response, and if the dialog ID of this response cannot match the existing dialog, a new dialog will be created, and the creation process is defined in section 12.1.2

13.2.2.2 3xx responses

a 3xx response can contain one or more contact headers, which provide new addresses, which are reachable addresses of the callee. According to the different 3xx status codes (section 21.3), UAC may choose to try these different new addresses

13.2.2.3 4xx, 5xx and 6xx responses

for invite messages, a single non-2xx final response may be received. 4xx, 5xx and 6xx responses may contain a contact header field value, which represents a location. Other information about the error is found here. Subsequent final responses (which arrive only under error conditions) must be ignored

after receiving the reply of non -2xx final response, all early dialogs will end

after receiving the non-2xx final response, the UAC core considers that the invite transaction has been completed. This invite client transaction will process acks generation (see section 17) for this response

13.2.2.4 2XX responses

because of the bifurcation agent, multiple 2XX responses of a single invite request will arrive at the UAC end. Each response is distinguished by the tag parameters in the to header. Each response represents a different dialog when doing the experiment of the same size test block. These dialogs have different dialog identifier identification messages

if the dialog identifier matches the dialog identifier of the current dialog in the 2XX response interrupt, this dialog must be migrated to the confirmed confirmation state, and the routing group of this dialog must be recalculated. Its algorithm is based on the 2XX response and processed according to the section 12.2.1.2 process. Otherwise, a new dialog in the confirmed state must be reconstructed, and the construction process is handled according to section 12.1.2

note that only a small part of the states need to be recalculated, which is route set. Other status parts in this dialog, such as the part with the highest serial number (remote or local), do not need to be recalculated. The calculation of the route set part is only for backward compatibility. RFC 2543 does not enforce the check of record route header in 1XX response, which is only supported in 2XX., Because in the early dialog, the mid dialog request may have been sent, and other modifications may have been performed, such as modifying the serial number. Therefore, we cannot update the status of the entire dialog

uac core must generate an ACK request for each 2XX received from the transaction layer. Except for cseq and header domain required for authentication, the header domain of ACK request is constructed in the same way as any in dialog (section 12). The serial number of cseq header must be the same as that confirmed by invite, but the cseq method must be ack. Like invite, ACK must contain the same security information. If 2XX contains an offer message (based on the above rule), this ack must pass an answer message in its message body. If the offer in the 2XX response is not accepted, the UAC core must generate a valid answer message in the ACK and send a bye immediately

once the ACK is built, use the processing flow in [4] to determine the destination address, port and transmission mode. However, in order to transport the process, the request will be passed directly to the transport layer, not to the customer transaction layer. This is because the UAC core handles the retransmission of ACK, not transaction layer processing. Each time the ACK arrives, the retransmission ack that triggers the 2XX final response must be passed to the client transport layer

after the first 2XX response is received, UAC core believes that the invite transaction has completed the timing of 64*t1 seconds. At this point in time, all early dialogs that do not switch to the created state will end. Once the invite transaction is considered to be completed by the UAC core, no more new 2XX responses will arrive

if any 2XX response is confirmed to invite, UAC core does not want to continue that dialog. Then, UAC must send a bye request to end this dialog. The processing method is discussed in section 15

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