Internet Overview - Electrical and Computer Engineering
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Transcript Internet Overview - Electrical and Computer Engineering
Lec 1: Internet Overview
ECE5650
Overview
1-1
Intenet
Physical Connectivity
Topology
Access network and physical media
Layered Internet Protocol Stack
History
Overview
1-2
What’s the Internet: “nuts and bolts” view
millions of connected
computing devices: hosts
= end systems
running network apps
communication links
router
server
workstation
mobile
local ISP
fiber, copper, radio,
satellite
transmission rate =
regional ISP
bandwidth
routers: forward packets
(chunks of data)
company
network
Overview
1-3
What’s the Internet: a service view
Distributed applications:
Web, email, games, e-commerce,
file sharing
Network protocols: used by
applications to control sending,
receiving of msgs:
TCP, IP, HTTP, FTP, PPP
Internet standards
• RFC: Request for comments
• IETF: Internet Engineering Task
Force
Communication services
provided to apps:
Connectionless unreliable
connection-oriented reliable
Overview
1-4
A closer look at network structure:
network edge:
applications and
hosts
network core:
routers
network of
networks
access networks,
physical media:
communication links
Overview
1-5
The network edge:
end systems (hosts):
run application programs
e.g. Web, email
at “edge of network”
Programs in end-systems use the
serivce of the Internet to send msgs
to each other
client/server model
• client host requests, receives service from
always-on server; e.g. web, email
peer-peer model:
• minimal (or no) use of dedicated servers
• e.g. Gnutella, KaZaA, Skype, BitTorrent
Overview
1-6
The Network Core
Physical connectivity of
local area networks
mesh of interconnected
routers
Logical connectivity: how
is data transferred
through net?
Overview
1-7
Internet structure: network of networks
roughly hierarchical
at center: “tier-1” ISPs or Internet backbone networks
(e.g., MCI, Sprint, AT&T, Cable and Wireless),
national/international coverage, connect to large tier-2 ISPs and
to all tier-1 ISPs and many customer networks.
Tier-1
providers
interconnect
(peer)
privately
Tier 1 ISP
Tier 1 ISP
NAP
Tier-1 providers
also interconnect
at public Network
Access Points
(NAPs).
Tier 1 ISP
Overview
1-8
Commercial Internet ISP
Connectivity
Roughly hierarchical
Divided into tiers
Tier-1 ISPs are also called
backbone providers, e.g.,
AT&T, Sprint, UUNet,
Level 3, Qwest, Cable &
Wireless
An ISP runs (private)
Points of Presence (PoP)
where its customers and
other ISPs connect to it
E.g., MCI has 4,500 PoP
called private peering
ISPs also connect at
(public) Network Access
Point (NAP)
called public peering
Overview
1-9
Internet structure: network of networks
“Tier-2” ISPs: smaller (often regional) ISPs
Connect to one or more tier-1 ISPs, possibly other tier-2 ISPs
NAPs (Network Access Points) are complex high-speed switching networks often
concentrated at a single building. Operated by 3rd party telecom or Internet backbone ISP-1.
PoPs (Points of Presence) are private group of routers within each ISP and used to connect it
(peer it) with other up/down/equal ISPs and is the new trend in connectivity.
Tier-2 ISPs also
peer privately with
each other,
Tier-2 ISP
Tier-2 ISP pays
Tier-2 ISP
interconnect at
tier-1 ISP for
public NAPs or
connectivity to
private POPs.
rest of Internet,
tier-2 ISP is
customer of
tier-1 provider
Tier 1 ISP
Tier 1 ISP
Tier-2 ISP
NAP
Tier 1 ISP
Tier-2 ISP
Tier-2 ISP
Overview
1-10
Internet structure: network of networks
“Tier-3” ISPs and local ISPs
last hop (“access”) network (closest to end systems)
local
ISP
Local and tier3 ISPs are
customers of
higher tier
ISPs
connecting
them to rest
of Internet
Tier 3
ISP
Tier-2 ISP
local
ISP
local
ISP
local
ISP
Tier-2 ISP
Tier 1 ISP
Tier 1 ISP
Tier-2 ISP
local
local
ISP
ISP
NAP
Tier 1 ISP
Tier-2 ISP
local
ISP
Tier-2 ISP
local
ISP
Overview
1-11
Internet structure: network of networks
a packet passes through many networks!
local
ISP
Tier 3
ISP
Tier-2 ISP
local
ISP
local
ISP
local
ISP
Tier-2 ISP
Tier 1 ISP
Tier 1 ISP
Tier-2 ISP
local
local
ISP
ISP
NAP
Tier 1 ISP
Tier-2 ISP
local
ISP
Tier-2 ISP
local
ISP
Overview
1-12
Tier-1 ISP: e.g., Sprint
Introduction
1-13
ATT Global Backbone IP Network
From http://www.business.att.com
Overview
1-14
MichNet: Statewide Backbone
Nation’s longest-
running regional
network
An 2.5 Gigabit
(OC48c) backbone,
with 24 backbone
nodes
Two diverse 2.5
gigabit (2x OC48) to
chicago
www.merit.edu/mn
Overview
1-15
Overview
1-16
Intenet
Physical Connectivity
Structure
Access network and physical media
Layered Internet Protocol Stack
History
Overview
1-17
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?
Overview
1-18
Residential access: point to point access
Dialup via modem
Uses existing telephony infrastructure; Home is
connected to central office
up to 56Kbps direct access to router (often less)
Can’t surf and phone at same time: can’t be
“always on”central
office
home
PC
home
dial-up
modem
telephone
network
Internet
ISP
modem
(e.g., AOL)
Overview
1-19
ADSL: asymmetric digital subscriber line
up to 1 Mbps upstream (today typically < 256 kbps)
up to 8 Mbps downstream (today typically < 1 Mbps)
FDM: 50 kHz - 1 MHz for downstream
4 kHz - 50 kHz for upstream
0 kHz - 4 kHz for ordinary telephone
Existing phone line:
0-4KHz phone; 4-50KHz
upstream data; 50KHz-1MHz
downstream data
home
phone
Internet
DSLAM
telephone
network
splitter
DSL
modem
home
PC
central
office
Overview
1-20
Residential access: cable modems
HFC: hybrid fiber coax
asymmetric: up to 30Mbps downstream, 2
Mbps upstream
network of cable and fiber attaches homes to
ISP router
homes share access to router so
communication activity is visible to each
other.
deployment: available via cable TV companies
Overview
1-21
Residential access: cable modems
Diagram: http://www.cabledatacomnews.com/cmic/diagram.html
Overview
1-22
Cable Network Architecture: Overview
Typically 500 to 5,000 homes
cable headend
cable distribution
network (simplified)
home
Overview
1-23
Cable Network Architecture: Overview
cable headend
cable distribution
network (simplified)
home
Overview
1-24
Cable Network Architecture: Overview
server(s)
cable headend
cable distribution
network
home
Overview
1-25
Cable Network Architecture: Overview
FDM:
V
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Channels
cable headend
cable distribution
network
home
Overview
1-26
Company access: local area networks
company/univ local area
network (LAN) connects
end system to edge router
Ethernet:
shared or dedicated link
connects end system
and router
10 Mbs, 100Mbps,
Gigabit Ethernet
LANs: chapter 5
Overview
1-27
Wireless access networks
shared
wireless access network
connects end system to router
via base station aka “access point”
wireless LANs:
802.11a/b/g (WiFi): 11 Mbps ~54Mbps
802.11n: 100~200Mbps (theoretically
up to 300Mbps)
wider-area wireless access
provided by telco operator
3G ~ 384 kbps
• Will it happen??
WAP/GPRS in Europe
WiMAX
router
base
station
mobile
hosts
~100Mbps
~10 miles
Overview
1-28
Home networks
Typical home network components:
DSL or cable modem
router/firewall/NAT
Ethernet
wireless access
point
to/from
cable
headend
cable
modem
router/
firewall
Ethernet
wireless
laptops
wireless
access
point
Introduction
1-29
Physical Media
Bit: propagates between
transmitter/rcvr pairs
physical link: what lies
between transmitter &
receiver
guided media:
signals propagate in solid
media: copper, fiber, coax
Twisted Pair (TP)
two insulated copper
wires
Category 3: traditional
phone wires, 10 Mbps
Ethernet
Category 5:
100Mbps Ethernet
unguided media:
signals propagate freely,
e.g., radio
Introduction
1-30
Physical Media: coax, fiber
Coaxial cable:
Fiber optic cable:
conductors
bidirectional
baseband:
pulses, each pulse a bit
high-speed operation:
two concentric copper
single channel on cable
legacy Ethernet
broadband:
multiple channels on
cable
HFC
glass fiber carrying light
high-speed point-to-point
transmission (e.g., 10’s100’s Gps)
low error rate: repeaters
spaced far apart ; immune
to electromagnetic noise
Introduction
1-31
Physical media: radio
signal carried in
electromagnetic
spectrum
no physical “wire”
bidirectional
propagation
environment effects:
reflection
obstruction by objects
interference
Radio link types:
terrestrial microwave
e.g. up to 45 Mbps channels
LAN (e.g., Wifi)
11Mbps, 54 Mbps
wide-area (e.g., cellular)
3G cellular: ~ 1 Mbps
satellite
Kbps to 45Mbps channel (or
multiple smaller channels)
270 msec end-end delay
geosynchronous versus low
altitude
Introduction
1-32
Intenet
Physical Connectivity
Topology
Access network and physical media
Layered Internet Protocol Stack
History
Overview
1-33
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
A protocol is a set of rules that govens how
two or more communicating parties are
to interact. It defines:
- msg format
- order of msgs sent & received
- actions taken on msg transmission &
receipt
Overview
1-34
Protocol “Layers”
Networks are complex!
many “pieces”:
hosts
routers
links of various
media
applications
protocols
hardware, software
Layered Protocol
Modular approach to
network functionality
Examples:
• Taking an airplane trip
• Mailing service
Overview
1-35
Internet protocol stack
application: supporting network
applications
FTP, SMTP, HTTP
transport: process-process data
transfer
TCP, UDP
network: host-host data transfer
IP
link: data transfer between
neighboring network elements
application
transport
network
link
physical
PPP, Ethernet
physical: bits “on the wire”
Overview
1-36
source
message
segment Ht
datagram Hn Ht
frame
Hl Hn Ht
M
M
M
M
Encapsulation
application
transport
network
link
physical
Hl Hn Ht
M
link
physical
Hl Hn Ht
M
switch
destination
M
Ht
M
Hn Ht
Hl Hn Ht
M
M
application
transport
network
link
physical
Hn Ht
Hl Hn Ht
M
M
network
link
physical
Hn Ht
Hl Hn Ht
M
M
router
Overview
1-37
Characteristics of Layering
Layering positives:
Each layer relies on services from layer below
and exports services to layer above
Interface defines interaction
Hides implementation - layers can change
without disturbing other layers (black box)
Layering negatives: duplicate functionality and
inter-dependency.
Overview
1-38
Internet History
1961-1972: Early packet-switching principles
1961: Kleinrock - queueing
theory shows
effectiveness of packetswitching
1964: Baran - packetswitching in military nets
1967: ARPAnet conceived
by Advanced Research
Projects Agency
1969: first ARPAnet node
operational
1972:
ARPAnet demonstrated
publicly
NCP (Network Control
Protocol) first hosthost protocol
first e-mail program
ARPAnet has 15 nodes
Overview
1-39
Initial ARPANET
1965-1968
ARPANET plan,
implemented by BBN
(Bolt, Beranek,
Newman): packet switch
to build IMP
1969
ARPANET
commissioned: 4 nodes,
50kbps
Overview
1-40
Initial Expansion of the ARPANET
Dec. 1969
July 1970
Apr. 1972
Mar. 1971
Sept. 1972
Overview
RFC 527: ARPAWOCKY; RFC 602: The Stockings Were Hung by the Chimney with
Care
1-41
Internet History
1972-1980: Internetworking, new and proprietary nets
1970: ALOHAnet satellite
network in Hawaii
1973: Metcalfe’s PhD thesis
proposes Ethernet
1974: Cerf and Kahn – archi.
for interconnecting networks
Initially, named NCP
Later, split to TCP/IP
late70’s: proprietary
architectures: DECnet, SNA,
XNA
late 70’s: switching fixed
length packets (ATM
precursor)
1979: ARPAnet has 200 nodes
Cerf and Kahn’s internetworking
principles:
minimalism, autonomy - no
internal changes required to
interconnect networks
best effort service model
stateless routers
decentralized control
define today’s Internet architecture
2005 ACM Turing Award
“A protocol for packet network
interconnection”, IEEE Trans. on
Communications Technology,
vol.22(5), 627-641
Overview
1-42
Internet History
1980-1990: new protocols, a proliferation of networks
1983: deployment of
TCP/IP
1982: SMTP e-mail
protocol defined
1983: DNS defined
for name-to-IPaddress translation
1985: FTP protocol
defined
1988: TCP congestion
control
new national networks:
Csnet, BITnet,
NSFnet, Minitel
100,000 hosts
connected to
confederation of
networks
Overview
1-43
Internet History
1990, 2000’s: commercialization, the Web, new apps
Early 1990’s: ARPAnet
decommissioned
1991: NSF lifts restrictions on
commercial use of NSFnet
(decommissioned, 1995)
Late 1990’s – 2000’s:
more killer apps: instant
messaging, peer2peer file
sharing (e.g., BitTorrent,
YouTube)
1992, 1 million hosts
network security to
early 1990s: Web
forefront
hypertext [Bush 1945, Nelson Today:
1960’s]
400 million users, 150
countries
HTML, HTTP: Berners-Lee
backbone links running at 10
1994: Mosaic, later Netscape
Gbps
late 1990’s:
commercialization of the Web
Overview
1-44
Growth of the Internet
Number of Hosts on the
Internet:
Aug. 1981
213
Oct. 1984
1,024
Dec. 1987
28,174
Oct. 1990
313,000
Jul. 1993
1,776,000
Jul. 1996 19,540,000
Jul. 1999 56,218,000
Jul. 2004 285,139,000
Jan. 2005 317,646,000
Jul. 2005 353,284,000 About 2B users out of 6.8B people,
from 16M in 1995, 350M in 2000,1B in 2005
Overview
1-45
Summary
Physical Connectivity
Topology
Access network and physical media
Layered Internet Protocols
History
Overview
1-46