REFERENCE MODELS FOR COMPUTER NETWORKS Much of this material is taken from some developed by Ron Wyllys. Two major approaches:

mustardpruneΔίκτυα και Επικοινωνίες

23 Οκτ 2013 (πριν από 3 χρόνια και 7 μήνες)

100 εμφανίσεις

REFERENCE MODELS FOR COMPUTER NETWORKS



Much of this material is taken from some developed by Ron Wyllys.




Two major approaches:


1.

The seven
-
layer OSI/ISO model


Open Systems Interconnection,
currently maintained by the International Organization for
St
andards.


2.

The five
-
layer TCP/IP model


Transmission Control
Protocol/Internet Protocol.

OSI/ISO



1.

Physical layer


controls electrical and mechanical aspects of data
transmission, e.g., voltage levels, cable lengths, and so on.



2.

Data
-
link layer


addres
ses the transmission of data frames (or
packets) over a physical link between network entities, includes
error correction.



3.

Network layer


establishes paths for data between computers and
determines switching among routes between computers, determines
ho
w to disaggregate messages into individual packets.



4.

Transport layer


deals with data transfer between end systems and
determines flow control.



5.

Session layer


creates and manages sessions when one application
process requests access to another applica
tions process, e.g.,
MSWord importing a spread sheet from Excel.



6.

Presentation layer


determines syntactic representation of data, e.g.,
agreement on character code like ASCII/Unicode.



7.

Application layer


establishes interface between a user and a host

computer, e.g., searching in a database application.

TCP/IP


1.

Physical layer


not really part of this model, since TCP and IP deal
with software; usually thought to refer to all hardware beneath the
network layer.


2.

Network or data link layer


defined by

whatever the Internet
Protocol will run over, e.g., a token
-
ring network.


3.

Internet or network layer


provides network addressing and
routing, providing a common address space and connecting
heterogeneous networks. IP runs here.


4.

Transport layer


manag
es data
-
consistency by providing a reliable
[two meanings!!] byte stream between nodes on a network. TCP and
User Datagram Protocol (UDP) run here.


5.

Process and applications layer


provides application services to
users and programs.