What is a computer network?
Definition of Computer Network
*Computer network is the product of the close combination of communication technology and computer technology
*Communication system model:
source------>sending device------>channel--------->receiving device--------->sink
noise source- ---------------------------|(noise source applied to the channel)
*Computer network is a kind of communication network.
The special feature is that both the source and the destination are computers.
*Definition of computer network: A computer network is a collection of interconnected and autonomous computers.
Autonomy – no master-slave relationship.
Interconnection – interconnection and intercommunication
% Communication link (interconnected medium)
Communication link is a channel, or called a medium. The specifics can be Is optical fiber, coaxial cable, twisted pair, wireless signal, etc.
how computers communicate
How to ensure interconnection when the distance is long and the number of computers is large?
* Interconnecting hosts via a switched network
In this way, only one link is required per host.
Each host can be connected to a switching node, which is a router or a switch in daily life.
What is the internet? (Composition Detail Angle)
#The world's largest Internet network
ISP (Internet Service Provider) interconnected "network of networks"
#A collection of millions of interconnected computing devices
Hosts (hosts) = end systems (end systems)
in common: can run various network applications
#Connection method
Communication link:
optical fiber, copper cable, radio, satellite, etc.
But it is impossible to directly connect all hosts through communication links. So packet switching is involved!
#packet switching: forwarding packets (packets):
using equipment: routers or switches
What is the internet? (service angle)
#Communication infrastructure that provides communication services for network applications
#Provide an application programming interface (API) for web applications
Q&A
Q: Can the Internet run smoothly with only hardware (host, link, switch...) connections? Can you guarantee the orderly delivery of application data?
A: No! !
We also learn to network protocol! !
What is a network protocol
Review of the past:
#Hardware (host, router, communication link, etc.) is the foundation of computer networks
# Data exchange in computer networks must abide by pre-agreed rules
Telecommunication
#Communication main subject is a "machine" rather than a person
#Exchange electronic or digital information
#All processes of computer networks must abide by certain/some rules----protocols
What is a network protocol
#Protocol is an important guarantee for the orderly operation of computer networks (like traffic rules)
#Definition of network protocol: network protocol (network protocol), referred to as protocol, is a rule, standard or agreement established for data exchange in the network
#Protocol specifies the format, meaning, sequence of information exchanged between communicating entities, and the "actions" taken for information received or events that occur
Three Elements of an Agreement
#Syntax (syntax)
structure or format of data and control information
signal level
#Semantics (semantics)
What kind of control information needs to be sent,
what actions to complete and what responses to make
Error control
#timing
sequence of events
speed matching
Protocol is an important part of computer network
#Protocol regulates all information sending and receiving processes in the network
eg TCP, IP, HTTP, SKype, 802.11
#Internet Protocol Standard
RFC: Request for Comments
Management: IETF (Internet Engineering Task Force)