Hello Satya; In regards to item 1: * SDP is a session description standard, while RTP is a data bearer standard. * SDP is commonly used to describe an RTP session via signalling before, during and after this data stream has been established. RTP is the actual streaming data. * See RFC 4566 for more details on what SDP is and is not.
In regards to item 2: * "The Proxy-Authorization header field allows the client to identify itself (or its user) to a proxy that requires authentication. A Proxy-Authorization field value consists of credentials containing the authentication information of the user agent for the proxy and/or realm of the resource being requested." - RFC 3261, Section 20.28 * "A Proxy-Authenticate header field value contains an authentication challenge. The use of this header field is defined in [H14.33]. See Section 22.3 for further details on its usage." - RFC 3261, Section 20.27 * "Similarly, when a UAC sends a request to a proxy server, the proxy server MAY authenticate the originator before the request is processed. If no credentials (in the Proxy-Authorization header field) are provided in the request, the proxy can challenge the originator to provide credentials by rejecting the request with a 407 (Proxy Authentication Required) status code. The proxy MUST populate the 407 (Proxy Authentication Required) message with a Proxy-Authenticate header field value applicable to the proxy for the requested resource." - RFC 3261, Section 22.3 * In summary, Proxy-Authorization is sent by the UAC in response to a 407 Proxy Authentication Required Response that includes a Proxy-Authenticate header in order to authenticate the client with a proxy server that requires authentication. In regards to item 3: * The REFER method is used to redirect a session to a new destination. An example application of this would be call transfer. See RFC 3515 for more details. In regards to the first part of item 4: * In SIP, Call Hold is specified in the SDP payload of a SIP message. Generally this is in either an INVITE, UPDATE or Re-INVITE request, but it can also be in session progress responses, such as a 180 Ringing, or 183 Session Progress. * There are 2 ways of specifying a call should be placed on hold in SDP. - RFC 2543 states that the c: line should be set to 0.0.0.0 - See RFC 2543 Section B.5 for details. - RFC 3264 states that an a: line should be added and set to recvonly - See RFC 3264 Section 8.4 for details. In regards to the second part of item 4: * A Re-INVITE can be identified by the presence of a From: and To: tag being present in the INVITE request's headers. This indicates that it's involved with an existing dialog, and hence can be then identified as a Re-INVITE. See RFC 3261 Section 14 for more details. I hope this information proves to be helpful; Joel Gerber Eastlink -----Original Message----- From: sip-implementors-boun...@lists.cs.columbia.edu [mailto:sip-implementors-boun...@lists.cs.columbia.edu] On Behalf Of satya testing Sent: December-31-12 6:26 AM To: sip-implementors@lists.cs.columbia.edu Subject: [Sip-implementors] Doubt in sip hi what is difference between SDP and RTP ? What is difference between Proxy-authorization and proxy-authentication in SIP ? why we send REFER method ? how you identify a call hold &how you identify a re invite Regards Satya sundar rout _______________________________________________ Sip-implementors mailing list Sip-implementors@lists.cs.columbia.edu https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors _______________________________________________ Sip-implementors mailing list Sip-implementors@lists.cs.columbia.edu https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
