Worley, Ed. It represents the consensus of the IETF community. Johansson, et al. All rights reserved. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Table of Contents 1.
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Google Network Working Group J. Rosenberg Request for Comments: dynamicsoft Obsoletes: H. Please refer to the current edition of the "Internet Official Protocol Standards" STD 1 for the standardization state and status of this protocol. Distribution of this memo is unlimited. All Rights Reserved. It also uses DNS to allow a server to send a response to a backup client if the primary client has failed. This document describes those DNS procedures in detail. Table of Contents 1 Introduction SIP end systems are called user agents, and intermediate elements are known as proxy servers.
To do so, it communicates with proxy 1 in its domain domain A. Proxy 1 forwards the request to the proxy for the domain of the called party domain B , which is proxy 2. Proxy 2 forwards the call to the called party, UA 2. As part of this call flow, proxy 1 needs to determine a SIP server for domain B. The first is for proxy 1 to discover the SIP server in domain B, in order to forward the call for joe B.
The second is for proxy 2 to identify a backup for proxy 1 in the event it fails after forwarding the request. For the first aspect, proxy 1 specifically needs to determine the IP address, port, and transport protocol for the server in domain B. The choice of transport protocol is particularly noteworthy. Thus, clients need to be able to automatically determine which transport protocols are available. The proxy sending the request has a particular set of transport protocols it supports and a preference for using those transport protocols.
Proxy 2 has its own set of transport protocols it supports, and relative preferences for those transport protocols. Some form.
IETF RFC 3263 PDF
The implementation of these applications is complicated by the practices of participants: users may move between endpoints, they may be addressable by multiple names, and they may communicate in several different media - sometimes simultaneously. Numerous protocols have been authored that carry various forms of real-time multimedia session data such as voice, video, or text messages. For locating prospective session participants, and for other functions, SIP enables the creation of an infrastructure of network hosts called proxy servers to which user agents can send registrations, invitations to sessions, and other requests. SIP is an agile, general-purpose tool for creating, modifying, and terminating sessions that works independently of underlying transport protocols and without dependency on the type of session that is being established. SIP can also invite participants to already existing sessions, such as multicast conferences. Media can be added to and removed from an existing session.
Rosenberg Request for Comments: dynamicsoft Obsoletes: H. Please refer to the current edition of the "Internet Official Protocol Standards" STD 1 for the standardization state and status of this protocol. Distribution of this memo is unlimited. All Rights Reserved.