1/3/2024 0 Comments Uri sip definition![]() O=root 1673140232 1673140232 IN IP4 10.135.0.1īesides Ringing the remove side might provide inband information such as early media before connection as in the example above. The remote side indicates Alerting state – the remote device is ringing. ![]() T1 can be modified and should be equal to the estimated maximum round trip time between client and server. Thus in total an SIP Client will by default try 32 seconds before cancelling a request which is called Timer B (64 times T1). Server replies immediately with Trying, to indicate that the message has been received and avoid re-transmissions from the client which would happen within 500 ms (the standard T1 Timer 1 for SIP) – 1000 ms (twice the previous timeout) – 2000 ms (1000 ms x 2) – 4000 ms (2000 ms x 2) up to 16000 milliseconds. SIP/2.0 100 trying - your call is important to us The second INVITE looks pretty much the same, but the CSeq value has increased and the authentication information is now present. The client acknowledges having received the authentication challenge. In this case the message is slightly different – 407 Proxy Authentication Required – to indicate that it is a Proxy requesting the authentication. Proxy-Authenticate: Digest realm="10.135.0.1", nonce="WWdAiVlnPjECocBoyYtBDshUs+RxMS+3"Īs in the case of the REGISTER message, the server will request authentication before accepting the request, as the initial INVITE does not contain any information needed for authentication. SIP/2.0 407 Proxy Authentication Required Content-Type: indicates that the SIP message includes also an SDP body which provides the information about the media supported by the calling part y.Supported: indicates that the User Agent supports Replaces (needed during transfers to replace an existing session) – 100rel (indicates support for the reliable transmission of provisional responses 1XX ).Contact: in this case Contact includes also +sip.instance or a unique identifier which allows the SIP Registrar / Proxy to easily detect duplicated registrations.Cseq: in case methods different from REGISTER are used, the number does not have to start with 1 so the User Agent picked 10691.The method is INVITE and the SIP URI requested is the number dialed: 001234567890 (a leading 0 is added by the phone to use the outgoing line this leading 0 might not be present, or – in countries like the United States – it might be substituted with 9).Via: SIP/2.0/UDP 10.135.0.12:5060 branch=z9hG4bKhye0bem20x.nx8hntĪllow: INVITE, CANCEL, BYE, ACK, REGISTER, OPTIONS, REFER, SUBSCRIBE, NOTIFY, MESSAGE, INFO, PRACK, UPDATE Let’s see in detail which data are exchanged and which headers are important to us during debug: INVITE SIP/2.0 The callee can interrupt the session at any time by sending a CANCEL. The callee can then either accept the call with OK or refuse it with an error. Before Ringing, a Trying is usually sent by the SIP Proxy to prevent the caller from retransmitting the message. The INVITE method containing SDP is sent to the called party which r eplies with a provisional message Ringing ( which indicates that the remote endpoint is ringing). Calls are started by means of the methods INVITE together with SDP (Session Description Protocol) which carry the information necessary to allow the endpoints of the calls to exchange audio in form of RTP (Real Time Protocol) packets.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |