Communication Layered Protocols 1 2 1 Layers interfaces

Communication

Layered Protocols (1) 2 -1 Layers, interfaces, and protocols in the OSI model.

Layered Protocols (2) 2 -2 A typical message as it appears on the network. • Layering provides transparency and interoperability

Functionalities of Layers • Physical: Standardizes signaling interfaces • Data link: Organizes bits to form frames, detects and corrects transmission errors • Network layer: Routing (Internet protocol [IP]) • Transport layer: Reliability (retransmission, ordering of packets) • Session layer: Dialog control and synchronization • Presentation layer: Formats of messages and records • Application layer: Specific to applications (HTTP, FTP)

Client-Server TCP 2 -4 a) b) Normal operation of TCP. Transactional TCP.

Middleware Protocols • • • Resides in the application layer Provides protocols for supporting generic services Authentication protocols Commit protocols (Atomicity) Distributed locking Slightly adapted reference model

Middleware Protocols 2 -5 An adapted reference model for networked communication.

Remote Procedure Call • Send/receive do not conceal communication • Birrel and Nilsen designed first RPC protocol • Allowing programs to invoke procedures on other machines • Caller invokes the procedure and is suspended • Parameters are passed to callee, which executes the process and returns results • Caller continues with its execution • Hides communication