more depth, detail
later in course
approach:
descriptive
use Internet as example
Overview:
what’s the Internet what’s a protocol? network edge network core access net, physical media performance: loss, delay protocol layers, service models backbones, NAPs, ISPs history
communication infrastructure（基础设 施） enables distributed applications: WWW, email, games, e-commerce,
database., voting, file (MP3) sharing communication services provided: Connectionless（无连接） connection-oriented（面向连接） Internet does not provide that how long deliver the data from the sender to reciver
network protocols:
machines rather than humans
all communication activity in Internet governed by protocols
12/1/2020
School of Computer Science SNU. Juhou He
Chapter 1 Computer Networks and the Internet
Juhou He School of Computer Science
Shaanxi Normal University 2009.9.1
01.12.2020
1
Introduction
Our goal:
get context, overview, “feel” of networking
among network entities（网络实体）, and actions taken on message transmission, receipt .
12/1/2020
ol of Computer Science SNU. Juhou He
8
A closer look at network structure:
6
What’s a protocol?
12/1/2020
School of Computer Science SNU. Juhou He
7
What’s a protocol?
protocols define: format, order of messages sent and received
network edge: applications and hosts network core: routers network of networks access networks, physical media: communication links
12/1/2020
School of Computer Science SNU. Juhou He
Cyberspace（信息空间） [Gibson]:
“a consensual hallucination experienced daily by billions of
operators, in every nation, ...."
12/1/2020
School of Computer Science SNU. Juhou He
routers: forward packets
(chunks) of data thru network
12/1/2020
School of Computer Science SNU. Juhou He
3
What’s the Internet: “nuts and bolts” view
protocols: control sending,
pc’s workstations, servers PDA’s phones, toasters
running network applications communication links
coaxial cable,fiber optics, copper, radio, satellite
5
What’s a protocol?
human protocols: “what’s the time?” “I have a question” introductions
… specific msgs sent … specific actions taken when
msgs received, or other events
RFC: Request for comments IETF: Internet Engineering
Task Force
12/1/2020
School of Computer Science SNU. Juhou He
4
What’s the Internet: a service view
12/1/2020
School of Computer Science SNU. Juhou He
2
What’s the Internet: “nuts and bolts” view
millions of connected
computing devices: hosts, end-systems
receiving of msgs
e.g., TCP, IP, HTTP, FTP, PPP
Internet: “network of
networks”
loosely hierarchical(分层) public Internet versus private
intranet
Internet standards