Instant message (IM) technologies allow people to talk online real time . To s end a message , you need to open up a small window where you and your friend can type in messages that both of you can see. Most of the popular instant-messaging programs provide a variety of features:

• Instant messages - Send notes back and forth with a friend who is online
• Chat - Create your own custom chat room with friends or co-workers
• Web links - Share links to your favorite Web sites
• Images - Look at an image stored on your friend's computer
• Sounds - Play sounds for your friends
• Files - Share files by sending them directly to your friends
• Talk - Use the Internet instead of a phone to actually talk with friends
• Streaming content - Real-time or near-real-time stock quotes and news

There are many IM systems, such as AOL IM, Yahoo IM and MSN IM, which use different technologies and they are often not compatible with each other. There have been several attempts to create a unified standard for instant messaging: IETF's SIP (Session Initiation Protocol) and SIMPLE (SIP for Instant Messaging and Presence Leverage), APEX (Application Exchange), Prim (Presence and Instant Messaging Protocol), and the open XML-based XMPP (Extensible Messaging and Presence Protocol), more commonly known as Jabber.Most attempts at creating a unified standard for the major IM providers (AOL, Yahoo! and Microsoft) have failed and each continues to use its own proprietary protocol.

The popular instant messaging protocols include the following:

• Extensible Messaging and Presence Protocol (XMPP): is an open Extensible Markup [XML] protocol for near-real-time messaging, presence, and request-response services. Although XMPP is not wedded to any specific network architecture, to date it usually has been implemented via a client-server architecture wherein a client utilizing XMPP accesses a server over a TCP connection, and servers also communicate with each other over TCP connections. A server acts as an intelligent abstraction layer for XMPP communications. Most clients connect directly to a server over a TCP connection and use XMPP to take full advantage of the functionality provided by a server and any associated services. Multiple resources may connect simultaneously to a server on behalf of each authorized client. The recommonded port for connections between a client and a server is 5222.
• Session Initiation Protocol for IM and Presence Leveraging Extensions ( SIMPLE): SIMPLE specifies a set of profiles and extensions to SIP, an Internet telephony protocol, in order to enable IM/presence. SIP has signaling methods such as INVITE and BYE to start and end a call or session. SIMPLE adds a new request method called MESSAGE to send a one-shot IM, called pager-mode IM. SUBSCRIBE is used to request presence information to be sent to the requester, while NOTIFY is used to transport the presence information. Longer IM sessions, in which participants exchange multiple messages over time, are signaled using INVITE and a transport protocol called Message Session Relay Protocol (MSRP). With SIMPLE, MSRP is used to transport the text of IMs, just as with SIP RTP is used to transport voice packets in an IP phone call.
• Jabber: Jabber is an open, XML-based protocol for instant messaging and presence. Jabber-based software is deployed on thousands of servers across the internet and is used by over ten million people worldwide. A key concept of the Jabber system is that of transports , also known as gateways , which allow users to access networks using other protocols - such as AIM and ICQ, MSN Messenger and Windows Messenger, SMS or E-mail.
• Common Profile for Instant Message (CPIM): CPIM defines common agreement and message formats on both Instant Messaging and Presence services. to achieve interoperation of IM systems.
• Internet Relay Chat Protocol (IRCP): IRCP allows communications between two clients, one to many (all) clients, client to server, and server to server. This protocol provides the technical foundation for most of the Internet instant message and chat systems. The IRC protocol has been developed on systems using the TCP/IP network protocol, although there is no requirement that this remain the only environment in which it operates. The IRC protocol is a text-based protocol, with the simplest client being any socket program capable of connecting to the server.

Instant Message (IM) Technology Overview

Related Terms: IMPP, IRCP, CPIM, SIMPLE, XMPP, XMP, SIP, Jabber