In computer networking, the Message Session Relay Protocol (MSRP) is a protocol for transmitting a series of related instant messages in the context of a communications session. An application instantiates the session with the

Session Description Protocol The Session Description Protocol (SDP) is a format for describing multimedia communication sessions for the purposes of announcement and invitation. Its predominant use is in support of streaming media applications, such as voice over IP (VoIP) ...

(SDP) over

Session Initiation Protocol The Session Initiation Protocol (SIP) is a signaling protocol used for initiating, maintaining, and terminating communication sessions that include voice, video and messaging applications. SIP is used in Internet telephony, in private IP telepho ...

(SIP) or other rendezvous methods. The MSRP protocol is defined i
RFC 4975
MSRP messages can also be transmitted by using intermediaries peers, by using the relay extensions defined i
RFC 4976
MSRP is used in the

RCS RCS may refer to: Organisations *Racing Club de Strasbourg Alsace * Radio Corporation of Singapore *Radcliffe Choral Society * Rawmarsh Community School *Red Crescent Society *Red Cross Society * Representation of Czechs and Slovaks, a football t ...

context, especially for the

instant messaging Instant messaging (IM) technology is a type of online chat allowing real-time text transmission over the Internet or another computer network. Messages are typically transmitted between two or more parties, when each user inputs text and trigge ...

file transfer File transfer is the transmission of a computer file through a communication channel from one computer system to another. Typically, file transfer is mediated by a communications protocol. In the history of computing, numerous file transfer protocol ...

and

photo sharing Image sharing, or photo sharing, is the publishing or transfer of digital photos online. Image sharing websites offer services such as uploading, hosting, managing and sharing of photos (publicly or privately). This function is provided through ...

features.

Protocol design

MSRP syntax is similar to other IETF text based protocols such as SIP,

HTTP The Hypertext Transfer Protocol (HTTP) is an application layer protocol in the Internet protocol suite model for distributed, collaborative, hypermedia information systems. HTTP is the foundation of data communication for the World Wide Web, ...

and

RTSP The Real Time Streaming Protocol (RTSP) is an application-level network protocol designed for multiplexing and packetizing multimedia transport streams (such as interactive media, video and audio) over a suitable transport protocol. RTSP i ...

. MSRP requires a reliable transport layer, like TCP. Each message is either a request or a response and uses URIs; a message contains headers and a body that can carry any type of data, including binary information. The first 2 headers must be To-Path and From-Path and the last must be Content-Type; this significantly reduces the complexity of parsers. Messages must also end with 7 dash ('-') characters, followed by a transaction identifier which appears in the first line; these are followed by a continuation flag, which is a single character and end of line (CRLF). This last line at the end of messages makes it rather simple to find and detect the message boundaries. An MSRP URI has a scheme (which is "msrp" or "msrps"), authority, as defined by RFC 3986, which holds the IP/domain name and possibly the port, an optional session identifier, the transport and additional optional parameters. For example: msrp://atlanta.example.com:7654/jshA7weztas;tcp * msrp is the scheme * atlanta.example.com:7654 is the authority * jshA7weztas is the session identifier * tcp is the transport

Usage in SIP

MSRP can be used within a SIP session: * to do

in a one-to-one or one-to-many mode * to do an attachment

* to do some

(e.g., Image Share) based on prior exchange of capabilities between the user endpoints MSRP session is set up through SIP's offer-answerRFC 3264, ''An Offer/Answer Model with the Session Description Protocol (SDP)'', IETF, The Internet Society (2002) model. The SDP m-line media type is ''message'' and the protocol is either ''TCP/MSRP'' for MSRP over TCP and ''TCP/TLS/MSRP'' for MSRP over secure TLS. Furthermore, the MSRP URI is specified in a ''path'' attribute. A full SDP example, as provided by the RFC: v=0 o=alice 2890844526 2890844527 IN IP4 alice.example.com s= - c=IN IP4 alice.example.com t=0 0 m=message 7394 TCP/MSRP * a=accept-types:text/plain a=path:msrp://alice.example.com:7394/2s93i9ek2a;tcp The address and port are contained in the c- and m-lines, but also in the path attribute on an a-line. Generally, other media types use the c-line and m-line to describe the address and port, but the MSRP RFC 4975 section 8.1 says the path attribute is the authoritative source for MSRP.

References

{{Instant messaging Application layer protocols VoIP protocols

Protocol design

Usage in SIP

See also

References