What are examples of complex communication protocols that do not need a 7 layer OSI model to describe them?
TCP/IP is usually described as having 4 or 5 layers, depending on whom you ask, see RFC 1122. The Arpanet Reference Model (RFC 871) makes do with three layers.
Also, there is never a &quot;need&quot; to use the OSI model's 7 layers to describe a protocol. It's a mainly theoretical framework that comes in handy sometimes when communicating with others, but it is only as relevant as you want it to be (opinion warning here).