x: In full duplex session, both the network elements that have established a session for interaction can communicate or send data at the same time. Some of the popular session layer protocols are session initiation protocol (SIP) and AppleTalk session protocol (ASP). Session layer software in most scenarios is more of a set of tools rather than a specific protocol. For instance RPC (remote procedure call) usually associated with the session layer for communication between remote systems gives more of a set of APIs (application program interfaces) for working on remote sessions and SSH (secure shell), another protocol associated with session layer also gives the implemented the ability to establish secure sessions. While the term session is usually used for communication over a short duration between ele- ments, the term connection is used for communication that takes place for longer durations. Let us consider a typical scenario of how a session layer works when handling a single application. The Web page displayed by a Web browser can contain embed- ded objects of media, text, and graphics. This graphic file, media file, and text con- tent file are all separate files on the Web server. If the browser is a pure application object that cannot handle multiple objects together then a separate download must be started to access these objects. So the Web browser opens a separate session to the Web server to download each of these individual files of the embedded objects in the Web page. The session layer performs the function of keeping track of what packets and data belong to what file. This is required SO that the Web page can be displayed correctly by the Web browser. 10.7 Presentation Layer This is the sixth lowest layer (L6) in the ISO/OSI model. The role of the presentation layer is to ensure that communication between applications in two different systems occur even when the data representation format is not the same. As the name sug- gests, a common syntax or format that the two interacting systems can underst