Post on 08-Jan-2016
description
Overview 1-1
Lec 1: Internet Overview
ECE5650
Overview 1-2
Intenet
Physical Connectivity Topology Access network and physical media
Layered Internet Protocol Stack History
Overview 1-3
What’s 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)
local ISP
companynetwork
regional ISP
router workstation
servermobile
Overview 1-4
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 1-5
A closer look at network structure: network edge:
applications and hosts network core:
routers network of networks
access networks, physical media: communication links
Overview 1-6
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 1-7
The Network Core
Physical connectivity of local area networks mesh of interconnected
routers Logical connectivity:
how is data transferred through net?
Overview 1-8
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 ISP
Tier 1 ISP
Tier 1 ISP
Tier-1 providers interconnect (peer) privately
NAP
Tier-1 providers also interconnect at public Network Access Points (NAPs).
Overview 1-9
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 1-10
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 1 ISP
Tier 1 ISP
Tier 1 ISP
NAP
Tier-2 ISPTier-2 ISP
Tier-2 ISP Tier-2 ISP
Tier-2 ISP
Tier-2 ISP pays tier-1 ISP for connectivity to rest of Internet, tier-2 ISP is customer oftier-1 provider
Tier-2 ISPs also peer privately with each other, interconnect at public NAPs or private POPs.
Overview 1-11
Internet structure: network of networks
“Tier-3” ISPs and local ISPs last hop (“access”) network (closest to end systems)
Tier 1 ISP
Tier 1 ISP
Tier 1 ISP
NAP
Tier-2 ISPTier-2 ISP
Tier-2 ISP Tier-2 ISP
Tier-2 ISP
localISPlocal
ISPlocalISP
localISP
localISP Tier 3
ISP
localISP
localISP
localISP
Local and tier- 3 ISPs are customers ofhigher tier ISPsconnecting them to rest of Internet
Overview 1-12
Internet structure: network of networks
a packet passes through many networks!
Tier 1 ISP
Tier 1 ISP
Tier 1 ISP
NAP
Tier-2 ISPTier-2 ISP
Tier-2 ISP Tier-2 ISP
Tier-2 ISP
localISPlocal
ISPlocalISP
localISP
localISP Tier 3
ISP
localISP
localISP
localISP
Introduction 1-13
Tier-1 ISP: e.g., Sprint
Overview 1-14
ATT Global Backbone IP Network
From http://www.business.att.com
Overview 1-15
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 1-16
Overview 1-17
Intenet
Physical Connectivity Structure Access network and physical media
Layered Internet Protocol Stack History
Overview 1-18
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 1-19
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”
telephonenetwork Internet
homedial-upmodem
ISPmodem(e.g., AOL)
homePC
central office
Overview 1-20
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
telephonenetwork
DSLmodem
homePC
homephone
Internet
DSLAM
Existing phone line:0-4KHz phone; 4-50KHz upstream data; 50KHz-1MHz downstream data
splitter
centraloffice
Overview 1-21
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 1-22
Residential access: cable modems
Diagram: http://www.cabledatacomnews.com/cmic/diagram.html
Overview 1-23
Cable Network Architecture: Overview
home
cable headend
cable distributionnetwork (simplified)
Typically 500 to 5,000 homes
Overview 1-24
Cable Network Architecture: Overview
home
cable headend
cable distributionnetwork (simplified)
Overview 1-25
Cable Network Architecture: Overview
home
cable headend
cable distributionnetwork
server(s)
Overview 1-26
Cable Network Architecture: Overview
home
cable headend
cable distributionnetwork
Channels
VIDEO
VIDEO
VIDEO
VIDEO
VIDEO
VIDEO
DATA
DATA
CONTROL
1 2 3 4 5 6 7 8 9
FDM:
Overview 1-27
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 1-28
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 ~100Mbps ~10 miles
basestation
mobilehosts
router
Introduction 1-29
Home networks
Typical home network components: DSL or cable modem router/firewall/NAT Ethernet wireless access point
wirelessaccess point
wirelesslaptops
router/firewall
cablemodem
to/fromcable
headend
Ethernet
Introduction 1-30
Physical Media
Bit: propagates betweentransmitter/rcvr pairs
physical link: what lies between transmitter & receiver
guided media: signals propagate in solid
media: copper, fiber, coax
unguided media: signals propagate freely,
e.g., radio
Twisted Pair (TP) two insulated copper
wires Category 3: traditional
phone wires, 10 Mbps Ethernet
Category 5: 100Mbps Ethernet
Introduction 1-31
Physical Media: coax, fiber
Coaxial cable: two concentric copper
conductors bidirectional baseband:
single channel on cable legacy Ethernet
broadband: multiple channels on
cable HFC
Fiber optic cable: glass fiber carrying
light pulses, each pulse a bit
high-speed operation: high-speed point-to-point
transmission (e.g., 10’s-100’s Gps)
low error rate: repeaters spaced far apart ; immune to electromagnetic noise
Introduction 1-32
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
Overview 1-33
Intenet
Physical Connectivity Topology Access network and physical media
Layered Internet Protocol Stack History
Overview 1-34
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
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
Overview 1-36
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 PPP, Ethernet
physical: bits “on the wire”
application
transport
network
link
physical
Overview 1-37
messagesegment
datagram
frame
sourceapplicatio
ntransportnetwork
linkphysical
HtHnHl M
HtHn M
Ht M
M
destination
application
transportnetwork
linkphysical
HtHnHl M
HtHn M
Ht M
M
networklink
physical
linkphysical
HtHnHl M
HtHn M
HtHnHl M
HtHn M
HtHnHl M HtHnHl M
router
switch
Encapsulation
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
Overview 1-39
Internet History
1961: Kleinrock - queueing theory shows effectiveness of packet-switching
1964: Baran - packet-switching 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 host-host protocol
first e-mail program ARPAnet has 15 nodes
1961-1972: Early packet-switching principles
Overview 1-40
Initial ARPANET
1965-1968 ARPANET plan,
implemented by BBN (Bolt, Beranek, Newman): packet switch to build IMP
1969 ARPANET
commissioned: 4 nodes, 50kbps
Overview 1-41
Initial Expansion of the ARPANET
Dec. 1969 Mar. 1971July 1970
Apr. 1972 Sept. 1972RFC 527: ARPAWOCKY; RFC 602: The Stockings Were Hung by the Chimney with Care
Overview 1-42
Internet History
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
1972-1980: Internetworking, new and proprietary nets
Overview 1-43
Internet History
1983: deployment of TCP/IP
1982: SMTP e-mail protocol defined
1983: DNS defined for name-to-IP-address translation
1985: FTP protocol defined
1988: TCP congestion control
new national networks: Csnet, BITnet, NSFnet, Minitel
100,000 hosts connected to confederation of networks
1980-1990: new protocols, a proliferation of networks
Overview 1-44
Internet History
Early 1990’s: ARPAnet decommissioned
1991: NSF lifts restrictions on commercial use of NSFnet (decommissioned, 1995) 1992, 1 million hosts
early 1990s: Web hypertext [Bush 1945,
Nelson 1960’s] HTML, HTTP: Berners-Lee 1994: Mosaic, later
Netscape late 1990’s:
commercialization of the Web
Late 1990’s – 2000’s: more killer apps: instant
messaging, peer2peer file sharing (e.g., BitTorrent, YouTube)
network security to forefront
Today: 400 million users, 150
countries backbone links running at
10 Gbps
1990, 2000’s: commercialization, the Web, new apps
Overview 1-45
Number of Hosts on the Internet:
Aug. 1981 213Oct. 1984 1,024Dec. 1987 28,174 Oct. 1990 313,000 Jul. 1993 1,776,000Jul. 1996 19,540,000Jul. 1999 56,218,000Jul. 2004 285,139,000Jan. 2005 317,646,000Jul. 2005 353,284,000 About 2B users out of 6.8B people,
from 16M in 1995, 350M in 2000,1B in 2005
Growth of the Internet
Overview 1-46
Summary
Physical Connectivity Topology Access network and physical media
Layered Internet Protocols History