2.4.2 Layering

Networks are used to transmit messages between processes.

Protocols used to give messaging functionality

Table 2.2: Packets and messages

Packets in reality	Messaging abstraction
Limited Size	Arbitrary Size
Unordered (sometimes)	ordered
unreliable	reliable
machine to machine	process to process
Local Area Net	routed anywhere
Asynchronous	Synchronous
Insecure	Secure