The IETF addresses a broad range of scenarios, but at least in laboratories and high tech. companies, access is via Local Area Networks, and backbone speeds are appreciable. Thus a more loose approach has evolved, although mechanisms for mapping this and optimising it for loweer speed networks are not ignored.
There are at least two separate mechanisms for naming multimedia content:
Mime (``Multi-purpose Internet Mail Extensions'') is used to wrap content that is retrieved from the World Wide Web, and typically transferred using SMTP (the Simple Mail Transfer Protocol, used for Internet E-mail) or HTTP (The Hyper-Text Transfer Protocol) used for Web server to browser communication. In either case, this is for non-realtime communication.
RTP Payload types indicate what media type and encoding is in use in a realtime Internet session.
Neither case has an explicit multiplexing and synchronisation protocol. Instead, in the MIME case, we retrieve all tyhe media, and then play hem using a single local clock. In the RTP case, each stream has a source timestamp, and external clock synchronisation can be used to playout separately sourced streams with lip synch. This is discussed more in chapter five.