文档介绍:: .
Distributed Syst Network protocol
Network 3
Data link protocol
Data link 2
Physical protocol
Physical 1
Network
Drawbacks
Focus on message-passing only
Often unneeded or unwanted functionality
Violates access transparency
4 / 52Communication Layered Protocols
Low-level layers
Recap
Physical layer: contains the specification and implementation of
bits, and their transmission between sender and receiver
Data link layer: prescribes the transmission of a series of bits into
a frame to allow for error and flow control
Network layer: describes how packets in a network of computers
are to be routed.
Observation
For many distributed systems, the lowest-level interface is that of the
network layer.
5 / 52Communication Layered Protocols
Transport Layer
Important
The transport layer provides the actual communication facilities for
most distributed systems.
Standard Internet protocols
TCP: connection-oriented, reliable, stream-oriented
communication
UDP: unreliable (best-effort) datagram communication
Note