计算机网络chapter2,chapter2-6计算机网络

哈工大计算机学院李全龙Computer Networks 2: Application Layer 1Chapter 2: Application Layer

Our goals: conceptual, implementation aspects of network application protocols transport-layer service models client-server paradigm

peer-to-peer paradigm

learn about protocols

by examining popular application-level protocols

HTTP FTP

SMTP / POP3 / IMAP

DNS

programming network

applications

socket API

哈工大计算机学院李全龙Computer Networks 2: Application Layer 2

Some network apps

E-mail Web

Instant messaging Remote login P2P file sharing Multi-user network

games

Streaming stored video clips

Internet telephone Real-time video

conference

Massive parallel computing ……

哈工大计算机学院李全龙Computer Networks

2: Application Layer 3Creating a network app

Write programs that

run on different end systems and

communicate over a network.

e.g., Web: Web server software communicates with browser software

little software written for devices in network core

network core devices do not run user application code

application on end systems allows for rapid app

development, propagation

application transport network data link physical

application transport network data link physical

application transport network data link physical

哈工大计算机学院李全龙Computer Networks 2: Application Layer 4

Chapter 2: Application layer

2.1 Principles of

network applications 2.2 Web and HTTP 2.3 FTP

2.4 Electronic Mail

SMTP, POP3, IMAP

2.5 DNS

2.6 P2P file sharing 2.7 Socket programming

with TCP

2.8 Socket programming with UDP

哈工大计算机学院李全龙Computer Networks 2: Application Layer 5Application architectures

Client-server Peer-to-peer (P2P)

Hybrid of client-server and P2P

哈工大计算机学院李全龙Computer Networks 2: Application Layer 6

Client-server architecture

server:

always-on host

permanent IP address

server farms for scaling clients:

communicate with server

may be intermittently connected

may have dynamic IP addresses

do not communicate directly with each other