A variety of other applications have been developed other than audio and video ones. There are some public domain application examples that we will use to illustrate the direction in which applications appear to be evolving to accompany multimedia applications.
Imm is an image dissemination program from the University of Hawii. Wb is a shared whiteboard from LBL. Nte is a shared text editor from UCL and ISI. These are discussed in detail in chapter eight. The basic design principle used for them is an idea from Van Jacobson at LBL, called Lightweight Sessions, and nte services in chapter eight to illustrate this idea further. For now, we can see an example of the creation of a lightweight session next.
Figure 1.3 shows the time sequence involved in setting up a light-weight session between two sites. In this case, site A creates a session advertisement, and some time later starts sending a media stream even though there may be no receiver at that time. Some time later, site B joins the session, and starts to receive the traffic. At the earliest opportunity site B also makes an RSVP reservation to ensure the flow quality is satisfactory.
This is discussed throughout the book, and particularly in the interludes.
