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Chapter 1: Introduction

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Chapter 1: Introduction Our goal: get feel and terminology more depth, detail later in course approach: use Internet as example Overview: what s the Internet – PowerPoint PPT presentation

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Title: Chapter 1: Introduction

1
Chapter 1 Introduction

Our goal
get feel and terminology
more depth, detail later in course
approach
use Internet as example

Overview
whats the Internet
whats a protocol?
network edge
network core
access net, physical media
Internet/ISP structure
performance loss, delay
protocol layers, service models
network modeling

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
1.4 Delay, loss and throughput in packet-switched
networks
1.5 Protocol layers, service models
1.6 Networks under attack security
1.7 History

3
Whats the Internet nuts and bolts view

millions of connected computing devices hosts
end systems
running network apps

communication links
fiber, copper, radio, satellite
transmission rate bandwidth

routers forward packets (chunks of data)

4
Cool internet appliances
Internet gaming, chatting
Web-enabled toaster weather forecaster
Radio Frequency Identification (RFID)
Internet phones
5
Whats the Internet nuts and bolts view

protocols control sending, receiving of msgs
e.g., TCP, IP, HTTP, Skype, Ethernet
Internet network of networks
loosely hierarchical
public Internet versus private intranet
Internet standards
RFC Request for comments
IETF Internet Engineering Task Force

6
Whats the Internet a service view

communication infrastructure enables distributed
applications
Web, VoIP, email, games, e-commerce, file sharing
communication services provided to apps
reliable data delivery from source to destination
best effort (unreliable) data delivery
Provide a comment playground for everyone

7
Whats a protocol?

human protocols
whats the time?
I have a question
introductions
specific msgs sent
specific actions taken when msgs received, or
other events

network protocols
machines rather than humans
all communication activity in Internet governed
by protocols

protocols define format, order of msgs sent and
received among network entities, and actions
taken on msg transmission, receipt
8
Whats a protocol?

a human protocol and a computer network protocol

Hi
TCP connection request
Hi
9
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
1.4 Delay, loss and throughput in packet-switched
networks
1.5 Protocol layers, service models
1.6 Networks under attack security
1.7 History

10
A closer look at network structure

network edge applications and hosts

access networks, physical media wired, wireless
communication links

network core
interconnected routers
network of networks

11
The network edge

end systems (hosts)
run application programs
e.g. Web, email
at edge of network

client/server model
client host requests, receives service from
always-on server
e.g. Web browser/server email client/server

peer-peer model
minimal (or no) use of dedicated servers
e.g. Skype, BitTorrent, Joost

12
Network edge connection-oriented service (TCP)

Goal data transfer between end systems
handshaking setup (prepare for) data transfer
ahead of time
Hello, hello back human protocol
set up state in two communicating hosts
TCP - Transmission Control Protocol
Internets connection-oriented service

TCP service RFC 793
reliable, in-order byte-stream data transfer
loss acknowledgements and retransmissions
flow control
sender wont overwhelm receiver
congestion control
senders slow down sending rate when network
congested

13
Network edge connectionless service (UDP)

Goal data transfer between end systems
same as before!
UDP - User Datagram Protocol RFC 768
connectionless
unreliable data transfer
no flow control
no congestion control
No need to setup

Apps using TCP
HTTP (Web), FTP (file transfer), Telnet/ssh
(remote login), SMTP (email)
Apps using UDP
streaming media, teleconferencing, DNS, Internet
telephony

14
Access networks and physical media

Q How to connect end systems to edge router?
residential access nets
institutional access networks (school, company)
mobile access networks
Keep in mind
bandwidth (bits per second) of access network?
shared or dedicated?

15
Residential access point to point access

Dialup via modem
up to 56Kbps direct access to router (often less)
Cant surf and phone at same time cant be
always on

DSL digital subscriber line
up to 1 Mbps upstream (today typically lt 256
kbps)
up to 8 Mbps downstream (today typically lt 1
Mbps)
Why asymmetric ? Why not 0 bps for upstream?
FDM 50 kHz - 1 MHz for downstream
4 kHz - 50 kHz for upstream
0 kHz - 4 kHz for ordinary
telephone

16
Residential access cable modems

HFC hybrid fiber coaxial cable
asymmetric up to 30Mbps downstream, 2 Mbps
upstream
deployment available via cable TV companies
homes in neighborhood share access to router

Cable modem compared to DSL
Pro Higher bandwidth (30 vs. 8 2 vs. 1)
Con Shared medium with neighbors

17
Residential access cable modems
Diagram http//www.cabledatacomnews.com/cmic/diag
ram.html
18
Cable Network Architecture Overview
Typically 500 to 5,000 homes
cable headend
home
cable distribution network (simplified)
19
Cable Network Architecture Overview
cable headend
home
cable distribution network
20
Cable Network Architecture Overview
cable headend
home
cable distribution network (simplified)
21
Cable Network Architecture Overview
FDM (more shortly)
cable headend
home
cable distribution network
22
Company access local area networks