tailieunhanh - Chapter 210 Instant Messaging on the Internet

Instant messaging is one of today’s most popular services. Many youngsters (and not-soyoung people) use the service to keep in touch with their relatives, friends, co-workers, etc. Millions of instant messages are sent every day. So, it will come as no surprise that such a popular service is already supported in the IMS. Instant messaging is the service that allows a user to send some content to another user in near-real time. | Chapter 21 Instant Messaging on the Internet Instant messaging is one of today s most popular services. Many youngsters and not-so-young people use the service to keep in touch with their relatives friends co-workers etc. Millions of instant messages are sent every day. So it will come as no surprise that such a popular service is already supported in the IMS. Instant messaging is the service that allows a user to send some content to another user in near-real time. Because of the real-time characteristics of instant messages the content is typically not stored in network nodes as often happens with other services such as email. The content in an instant message is typically a text message but can be an HTML page a picture a file containing a song a video clip or any generic file. The instant messaging service combines perfectly with the presence service since presence allows a user to be informed when other users become available . connect to the network . Then users can send instant messages to their friends and start some sort of messaging conversation. The im URI Like presence mail or AAA functions an instant messaging service can be identified by an im URI. Like the pres URI the im URI does not define the protocol used to access an instant message resource. So whenever SIP is the protocol used to send the instant message it is recommended to use sip or sips URIs. The syntax of the im URI is IM-URI im to headers to mailbox headers header header header hname hvalue hname urlc hvalue urlc An example of an im URI is im alice@ The 3G IP Multimedia Subsystem IMS Merging the Internet and the Cellular Worlds Third Edition Gonzalo Camarillo and Miguel A. Garcia-Martin 2008 John Wiley Sons Ltd. ISBN 978-0-470-51662-1 454 CHAPTER 21. INSTANT MESSAGING ON THE INTERNET Modes of Instant Messages There are two modes of operation of the instant message service depending on whether they are stand-alone instant messages or part of a session of instant .