Chapter1_Computer Networks and the Internet

Chapter 1: Introduction
Our goal:
get “feel” and
Overview:
what’s the Internet?
what’s a protocol? network edge; hosts, access
terminology more depth, detail later in course approach: use Internet as example
Introduction
1-2
Chapter 1: roadmap
1.1 What is the Internet? 1.2 Network edge
end systems, access networks, links
1.3 Network core
circuit switching, packet switching, network structure
Introduction 1-11
A closer look at network structure:
network edge:
applications and hosts access networks, physical media: wired, wireless communication links
networks”

loosely hierarchical public Internet versus private intranet
Institutional network
Introduction
1-7
1.1.2 What’s the Internet: a service view
COMPUTER NETWORKING
A Top Down Approach , 4th edition.
Jim Kurose, Keith Ross
张雪 E-mail: snow_wonder@ Tel: 86223623 Office：A302 网络教研室
Introduction
1-1
end systems, access networks, links
1.3 Network core
circuit switching, packet switching, network
structure
1.4 Delay, loss and throughput in packetswitched networks 1.5 Protocol layers, service models
that interconnects millions of computing devices throughout the world. A nuts-and-Bolts description A services description
Introduction
1-4
1.1.1 What’s the Internet: “nuts and bolts” view

Introduction
1-13
1.2.1 Client and Server Programs
client/server
model(C/S)


client host requests, receives service from always-on server Server host provides service e.g. Web browser/server; peer-peer email client/server client/server
Internet standards RFC: Request for comments IETF: Internet Engineering Task Force
Mobile network Global ISP
Home network Regional ISP

Internet: “network of
Goal: data transfer

between end systems
same as before!
App’s using TCP:
HTTP (Web), FTP (file
UDP - User Datagram
Protocol [RFC 768]: connectionless unreliable data transfer no flow control no congestion control
Get /kurose-ross
2:00
<file>
time Q: Other human protocols?
Introduction 1-10
Chapter 1: roadmap
1.1 What is the Internet? 1.2 Network edge
1.4 Delay, loss and throughput in packetswitched networks 1.5 Protocol layers, service models
Introduction 1-3
1.1 What’s the Internet?
The Internet is a computer network
Home network Regional ISP
Institutional network
TCP/IP

e.g., TCP, IP, HTTP, SMTP, ARP, ICMP, RIP
Introduction 1-6
1.1.1 What’s the Internet: “nuts and bolts” view
network core:
interconnected routers network of networks

Introduction
1-12
1.2 The network edge:
end systems (hosts):
Computers and other devices connected to the Internet run application programs e.g. Web, email at “edge of network”
Introduction 1-8
infrastructure enables
1.1.3 What’s a protocol?
human protocols: “what’s the time?” “I have a question” introductions network protocols: machines rather than humans all communication activity in Internet governed by protocols
Goal: data transfer
between end systems handshaking: setup (prepare for) data transfer ahead of time

TCP service [RFC 793]

reliable, in-order bytestream data transfer
Introduction 1-9
1.1.3 What’s a protocol?
a human protocol and a computer network protocol: Hi Hi
Got the time?
TCP connection request TCP connection response
Introduction 1-15
TCP - Transmission

congestion control:

Control Protocol

Internet’s reliable data transfer service
Network edge: best effort (unreliable) data transfer service
transfer), Telnet (remote login), SMTP (email)
App’s using UDP:
PC server
millions of connected
Mobile network Global ISP
wireless laptop cellular handheld
hosts = end systems running network apps communication links
Internet through ISP (Internet Service Provider)


Protocols controlling the
sending and receiving of information within the Internet.

Local ISP Regional ISP
fiber, copper, radio, satellite transmission rate = bandwidth routers: forward packets (chunks of data)

computing devices:
Home network Regional ISP

Hello, hello back human protocol set up “state” in two communicating hosts