程序代写代做代考 FTP dns Java algorithm Chapter 1 Introduction

Chapter 1 Introduction
Computer
Networking: A Top
Down Approach
6th edition
Jim Kurose, Keith Ross Addison- Wesley March 2012
Introduction 1-1

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?
 what’s a protocol?
 network edge; hosts, access net,
physical media
 network core: packet/circuit switching, Internet structure
 performance: loss, delay, throughput
 security
 protocol layers, service models
 history
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
 packet switching, circuit switching, network structure 1.4 delay, loss, throughput in networks
1.5 protocol layers, service models
1.6 networks under attack: security
1.7 history
Introduction 1-3

What’s the Internet: “nuts and bolts” view
PC server
wireless laptop
smartphone
 hosts = end systems
 running network apps
mobile network
home network
institutional network
global ISP
regional ISP
millions of connected computing devices:
communication links
wireless links
wired links
 fiber, copper, radio, satellite
 transmission rate: bandwidth
router
Packet switches: forward packets (chunks of data)
 routers and switches
Introduction 1-4

“Fun” internet appliances
Web-enabled toaster +
IP picture frame http://www.ceiva.com/
weather forecaster
Tweet-a-watt: monitor energy use
Internet refrigerator
Internet phones
Slingbox: watch,
control cable TV remotely
Introduction 1-5

What’s the Internet: “nuts and bolts” view
 Internet: “network of networks”  Interconnected ISPs
 protocols control sending, receiving of msgs
mobile network
global ISP
 e.g., TCP, IP, HTTP, Skype, 802.11 home
 Internet standards
 RFC: Request for comments
 IETF: Internet Engineering Task Force
network
regional ISP
institutional network
Introduction 1-6

What’s the Internet: a service view
 Infrastructure that provides services to applications:
 Web, VoIP, email, games, e- commerce, social nets, …
 provides programming interface to apps
 hooks that allow sending and receiving app programs to “connect” to Internet
 provides service options, analogous to postal service
mobile network
home network
institutional network
global ISP
regional ISP
Introduction 1-7

What’s a protocol?
human protocols:
 “what’s 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
Introduction 1-8

What’s a protocol?
a human protocol and a computer network protocol:
Hi
Hi
Got the time?
2:00
TCP connection request
TCP connection response
Get http://www.awl.com/kurose-ross
Q: other human protocols?
time
Introduction 1-9

Chapter 1: roadmap 1.1 what is the Internet?
1.2 network edge
 end systems, access networks, links 1.3 network core
 packet switching, circuit switching, network structure 1.4 delay, loss, throughput in networks
1.5 protocol layers, service models
1.6 networks under attack: security
1.7 history
Introduction 1-10

A closer look at network structure:
 network edge:
 hosts: clients and servers
 servers often in data centers
 access networks, physical media: wired, wireless communication links
 network core: interconnected routers network of networks
mobile network
home network
institutional network
global ISP
regional ISP
Introduction 1-11

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?
Introduction 1-12

Access net: digital subscriber line (DSL)
central office
DSLAM
DSL access multiplexer
telephone network
DSL splitte modem
r
voice, data transmitted at different frequencies over dedicated line to central office
ISP
 use existing telephone line to central office DSLAM  data over DSL phone line goes to Internet
 voice over DSL phone line goes to telephone net
 < 2.5 Mbps upstream transmission rate (typically < 1 Mbps)  < 24 Mbps downstream transmission rate (typically < 10 Mbps) Introduction 1-13 Access net: cable network cable headend ... cable splitter modem O VVVVVV N IIIIIIDDT DDDDDDAAR EEEEEETTO OOOOOOAAL 123456789 Channels C frequency division multiplexing: different channels transmitted in different frequency bands Introduction 1-14 Access net: cable network cable splitter modem data, TV transmitted at different frequencies over shared cable distribution network cable headend ... CMTS cable modem termination system ISP  HFC: hybrid fiber coax  asymmetric: up to 30Mbps downstream transmission rate, 2 Mbps upstream transmission rate  network of cable, fiber attaches homes to ISP router  homes share access network to cable headend  unlike DSL, which has dedicated access to central office Introduction 1-15 Access net: home network wireless devices often combined in single box to/from headend or central office cable or DSL modem router, firewall, NAT wired Ethernet (100 Mbps) wireless access point (54 Mbps) Introduction 1-16 Enterprise access networks (Ethernet) institutional link to ISP (Internet) institutional router Ethernet institutional mail, switch web servers  typically used in companies, universities, etc  10 Mbps, 100Mbps, 1Gbps, 10Gbps transmission rates  today, end systems typically connect into Ethernet switch Introduction 1-17 Wireless access networks  shared wireless access network connects end system to router  via base station aka “access point” wireless LANs:  within building (100 ft)  802.11b/g (WiFi): 11, 54 Mbps transmission rate to Internet wide-area wireless access  provided by telco (cellular) operator, 10’s km  between 1 and 10 Mbps  3G, 4G: LTE to Internet Introduction 1-18 Host: sends packets of data host sending function:  takes application message  breaks into smaller chunks, known as packets, of length L bits  transmits packet into access network at transmission rate R  link transmission rate, aka link capacity, aka link bandwidth two packets, L bits each 21 R: link transmission rate host packet transmission delay = time needed to transmit L-bit packet into link = L (bits) R (bits/sec) 1-19 Physical media  bit: propagates between transmitter/receiver 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 5: 100 Mbps, 1 Gpbs Ethernet  Category 6: 10Gbps Introduction 1-20 Physical media: coax, fiber coaxial cable:  two concentric copper conductors  bidirectional  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 Gpbs transmission rate)  low error rate:  repeaters spaced far apart  immune to electromagnetic noise Introduction 1-21 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: ~ few Mbps  satellite  Kbps to 45Mbps channel (or multiple smaller channels)  270 msec end-end delay  geosynchronous versus low altitude Introduction 1-22 Fiber Options:  FTTN / FTTLA (fiber-to- the-neighborhood)  FTTC / FTTK (fiber-to-the- curb)  FTTB (fiber-to-the-building)  FTTH (fiber-to-the-home) Info and graphic from Wikipedia.org Introduction 1-23 Chapter 1: roadmap 1.1 what is the Internet? 1.2 network edge  end systems, access networks, links 1.3 network core packetswitching, circuitswitching,networkstructure 1.4 delay, loss, throughput in networks 1.5 protocol layers, service models 1.6 networks under attack: security 1.7 history Introduction 1-24 The network core  mesh of interconnected routers  packet-switching: hosts break application-layer messages into packets  forward packets from one router to the next, across links on path from source to destination  each packet transmitted at full link capacity Introduction 1-25 Packet-switching: store-and-forward L bits per packet source 321 destination  takes L/R seconds to transmit (push out) L-bit packet into link at R bps  store and forward: entire packet must arrive at router before it can be transmitted on next link  end-end delay = 2L/R (assuming zero propagation delay) one-hop numerical example:  L = 7.5 Mbits  R = 1.5 Mbps  one-hop transmission delay = 5 sec more on delay shortly ... R bps R bps Introduction 1-26 Packet Switching: queueing delay, loss A B R = 100 Mb/s C R = 1.5 Mb/s queue of packets waiting for output link D E queuing and loss:  If arrival rate (in bits) to link exceeds transmission rate of link for a period of time:  packets will queue, wait to be transmitted on link  packets can be dropped (lost) if memory (buffer) fills up Introduction 1-27 Two key network-core functions routing: determines source- destination route taken by packets  routing algorithms forwarding: move packets from router’s input to appropriate router output routing algorithm local forwarding table header value output link 0100 0101 0111 1001 3 2 2 1 3 dest address in arriving packet’s header 1 2 Network Layer 4-28 Alternative core: circuit switching end-end resources allocated to, reserved for “call” between source & dest:  In diagram, each link has four circuits.  call gets 2nd circuit in top link and 1st circuit in right link.  dedicated resources: no sharing  circuit-like (guaranteed) performance  circuit segment idle if not used by call (no sharing)  Commonly used in traditional telephone networks Introduction 1-29 Circuit switching: FDM versus TDM FDM frequency TDM frequency Example: 4 users time time Introduction 1-30 Packet switching versus circuit switching packet switching allows more users to use network! example:  1 Mb/s link  each user: • 100 kb/s when “active” • active 10% of time circuit-switching:  10 users packet switching:  with 35 users, probability > 10 active at same time is less than .0004 *
N
users
* Check out the online interactive exercises for more examples
Introduction 1-31
1 Mbps link
Q: how did we get value 0.0004? Q: what happens if > 35 users ?

Packet switching versus circuit switching
is packet switching a “slam dunk winner?”
 great for bursty data
 resource sharing
 simpler, no call setup
 excessive congestion possible: packet delay and loss
 protocols needed for reliable data transfer, congestion
control
 Q: How to provide circuit-like behavior?
 bandwidth guarantees needed for audio/video apps  still an unsolved problem (chapter 7)
Q: human analogies of reserved resources (circuit switching) versus on-demand allocation (packet-switching)?
Introduction 1-32

Internet structure: network of networks
 End systems connect to Internet via access ISPs (Internet Service Providers)
 Residential, company and university ISPs  Access ISPs in turn must be interconnected.
 So that any two hosts can send packets to each other  Resulting network of networks is very complex
 Evolution was driven by economics and national policies
 Let’s take a stepwise approach to describe current Internet structure

Internet structure: network of networks
Question: given millions of access ISPs, how to connect them together?
access net
access net
access net
access net
access net
access net
access net
access net
access net
access net
access net
access net
access net
access net
access net
access net

Internet structure: network of networks
Option: connect each access ISP to every other access ISP?
access net
access net
access net
access net
access net
access net
access net
access net
connecting each access ISP to each other directly doesn’t scale: O(N2) connections.
access net
access net
access net
access net
access net
access net
access access net
net

Internet structure: network of networks
Option: connect each access ISP to a global transit ISP? Customer and provider ISPs have economic agreement.
access net
access net
access net
access net
access net
access net
access net
access net
access net
access net
global ISP
access net
access net
access net
access net
access net
access net

Internet structure: network of networks
But if one global ISP is viable business, there will be competitors ….
access net
ISP A
access net
access net
access net
access net
access net
access net
access net
access net
access net
ISP B
access net
access net
ISP C
access net
access access net
net
access net

Internet structure: network of networks
But if one global ISP is viable business, there will be competitors …. which must be interconnected
access net
access net
Internet exchange point
access net
access net
access net
access net
access net
access net
ISP A
access net
IXP
access net
IXP
ISP B
peering link
access access net
net
access net
access net
ISP C
access net
access net

Internet structure: network of networks
… and regional networks may arise to connect access nets to ISPS
access net
ISP A
access net
access net
access net
access net
access net
access net
access net
access net
IXP
access net
IXP
access net
access net
ISP C
ISP B
regional net
access access net
net
access net
access net

Internet structure: network of networks
… and content provider networks (e.g., Google, Microsoft, Akamai ) may run their own network, to bring services, content close to end users
access net
ISP A
access net
access net
access net
access net
access net
access net
access net
access net
IXP
access net
ISP B
Content provider network
IXP
ISP B
regional net
access access net
net
access net
access net
access net
access net

Internet structure: network of networks
Tier 1 ISP Tier 1 ISP
Google
IXP
IXP IXP
Regional ISP Regional ISP
access access access access ISP ISP ISP ISP
access access access access
 at center: small # of well-connected large networks
 “tier-1” commercial ISPs (e.g., Level 3, Sprint, AT&T, NTT), national &
international coverage
 content provider network (e.g, Google): private network that connects
it data centers to Internet, often bypassing tier-1, regional ISPs
Introduction 1-41
ISP ISP ISP
ISP

Tier-1 ISP: e.g., Sprint
POP: point-of-presence
to/from backbone peering
……
to/from customers
Introduction 1-42

… …

Chapter 1: roadmap 1.1 what is the Internet?
1.2 network edge
 end systems, access networks, links
1.3 network core
 packet switching, circuit switching, network structure 1.4 delay, loss, throughput in networks
1.5 protocol layers, service models
1.6 networks under attack: security
1.7 history
Introduction 1-43

How do loss and delay occur?
packets queue in router buffers
 packet arrival rate to link (temporarily) exceeds output link
capacity
 packets queue, wait for turn
packet being transmitted (delay)
A
B
packets queueing (delay)
free (available) buffers: arriving packets dropped (loss) if no free buffers
Introduction 1-44

Four sources of packet delay
transmission
B
A
propagation
nodal processing
queueing
dnodal = dproc + dqueue + dtrans + dprop
dproc: nodal processing  check bit errors
 determine output link  typically < msec dqueue: queueing delay  time waiting at output link for transmission  depends on congestion level of router Introduction 1-45 Four sources of packet delay transmission B A propagation nodal processing queueing dprop: propagation delay:  d: length of physical link  s: propagation speed in medium (~2x108 m/sec) dnodal = dproc + dqueue + dtrans + dprop dtrans: transmission delay:  L: packet length (bits)  R: link bandwidth (bps)  dtrans = L/R  dprop = d/s * Check out the Java applet for an interactive animation on trans vs. prop delay dtrans and dprop very different Introduction 1-46 Caravan analogy ten-car caravan 100 km toll toll 100 km booth  time to “push” entire caravan through toll booth onto highway = 12*10 = 120 sec  time for last car to propagate from 1st to 2nd toll both: 100km/(100km/hr)= 1 hr  A: 62 minutes  cars “propagate” at 100 km/hr  toll booth takes 12 sec to service car (bit transmission time)  car~bit; caravan ~ packet  Q: How long until caravan is lined up before 2nd toll booth? booth Introduction 1-47 Caravan analogy (more) 100 km 100 km ten-car caravan toll booth toll booth  suppose cars now “propagate” at 1000 km/hr  and suppose toll booth now takes one min to service a car  Q: Will cars arrive to 2nd booth before all cars serviced at first booth?  A: Yes! after 7 min, 1st car arrives at second booth; three cars still at 1st booth. Introduction 1-48 Queueing delay (revisited)  R: link bandwidth (bps)  L: packet length (bits)  a: average packet arrival rate  La/R ~ 0: avg. queueing delay small  La/R -> 1: avg. queueing delay large
 La/R > 1: more “work” arriving
traffic intensity = La/R
than can be serviced, average delay infinite!
* Check out the Java applet for an interactive animation on queuing and loss
La/R -> 1
La/R ~ 0
Introduction 1-49
average queueing delay

“Real” Internet delays and routes  what do “real” Internet delay & loss look like?
 traceroute program: provides delay measurement from source to router along end- end Internet path towards destination. For all i:
 sends three packets that will reach router i on path towards destination
 router i will return packets to sender
 sender times interval between transmission and reply.
3 probes 3 probes
3 probes
Introduction 1-50

“Real” Internet delays, routes traceroute: gaia.cs.umass.edu to www.eurecom.fr
3 delay measurements from
gaia.cs.umass.edu to cs-gw.cs.umass.edu
1 cs-gw (128.119.240.254) 1 ms 1 ms 2 ms
2 border1-rt-fa5-1-0.gw.umass.edu (128.119.3.145) 1 ms 1 ms 2 ms
3 cht-vbns.gw.umass.edu (128.119.3.130) 6 ms 5 ms 5 ms
4 jn1-at1-0-0-19.wor.vbns.net (204.147.132.129) 16 ms 11 ms 13 ms
5 jn1-so7-0-0-0.wae.vbns.net (204.147.136.136) 21 ms 18 ms 18 ms
6 abilene-vbns.abilene.ucaid.edu (198.32.11.9) 22 ms 18 ms 22 ms
7 nycm-wash.abilene.ucaid.edu (198.32.8.46) 22 ms 22 ms 22 ms
8 62.40.103.253 (62.40.103.253) 104 ms 109 ms 106 ms
9 de2-1.de1.de.geant.net (62.40.96.129) 109 ms 102 ms 104 ms
10 de.fr1.fr.geant.net (62.40.96.50) 113 ms 121 ms 114 ms
11 renater-gw.fr1.fr.geant.net (62.40.103.54) 112 ms 114 ms 112 ms
12 nio-n2.cssi.renater.fr (193.51.206.13) 111 ms 114 ms 116 ms
13 nice.cssi.renater.fr (195.220.98.102) 123 ms 125 ms 124 ms
14 r3t2-nice.cssi.renater.fr (195.220.98.110) 126 ms 126 ms 124 ms
15 eurecom-valbonne.r3t2.ft.net (193.48.50.54) 135 ms 128 ms 133 ms 16 194.214.211.25 (194.214.211.25) 126 ms 128 ms 126 ms
17 * * *
18 * * *
19 fantasia.eurecom.fr (193.55.113.142) 132 ms 128 ms 136 ms * Do some traceroutes from exotic countries at www.traceroute.org
trans-oceanic link
* means no response (probe lost, router not replying)
Introduction 1-51

Packet loss
 queue (aka buffer) preceding link in buffer has finite capacity
 packet arriving to full queue dropped (aka lost)
 lost packet may be retransmitted by previous node,
by source end system, or not at all
A
B
buffer (waiting area)
packet being transmitted
* Check out the Java applet for an interactive animation on queuing and loss
Introduction 1-52
packet arriving to full buffer is lost

Throughput
 throughput: rate (bits/time unit) at which bits transferred between sender/receiver
 instantaneous: rate at given point in time  average: rate over longer period of time
server, with
link capacity
link capacity
server sends bits
pipe that can carry
pipe that can carry
file of F bits
R bits/sec
s fluid at rate
R bits/sec
c fluid at rate
(fluid) into pipe
to send to client
Rs bits/sec)
Rc bits/sec)
Introduction 1-53

Throughput (more)
 Rs < Rc What is average end-end throughput? Rs bits/sec Rc bits/sec  Rs > Rc What is average end-end throughput?
Rc bits/sec
bottleneck link
link on end-end path that constrains end-end throughput
Rs bits/sec
Introduction 1-54

Throughput: Internet scenario
 per-connection end-
end throughput: Rs min(Rc,Rs,R/10) Rs
Rs
R
Rc
 in practice: Rc or Rs is often bottleneck
Rc
Rc
10 connections (fairly) share backbone bottleneck link R bits/sec
Introduction 1-55

Chapter 1: roadmap 1.1 what is the Internet?
1.2 network edge
 end systems, access networks, links
1.3 network core
 packet switching, circuit switching, network structure 1.4 delay, loss, throughput in networks
1.5 protocol layers, service models
1.6 networks under attack: security
1.7 history
Introduction 1-56

Protocol “layers” Networks are complex,
with many “pieces”:
 hosts
 routers
 links of various
media
 applications
 protocols
 hardware, software
Question:
is there any hope of organizing structure of
network?
…. or at least our discussion of networks?
Introduction 1-57

Organization of air travel
ticket (purchase) baggage (check) gates (load) runway takeoff airplane routing
ticket (complain) baggage (claim) gates (unload) runway landing airplane routing
 a series of steps
airplane routing
Introduction 1-58

Layering of airline functionality
ticket (purchase) ticket (complain) ticket
baggage (check) baggage (claim baggage
gates (load) gates (unload) gate
runway (takeoff) runway (land) takeoff/landing
airplane routing airplane routing airplane routing airplane routing airplane routing
departure intermediate air-traffic arrival airport control centers airport
layers: each layer implements a service
 via its own internal-layer actions
 relying on services provided by layer below
Introduction 1-59

Why layering?
dealing with complex systems:
 explicit structure allows identification, relationship of complex system’s pieces
 layered reference model for discussion
 modularization eases maintenance, updating of
system
 change of implementation of layer’s service transparent to rest of system
 e.g., change in gate procedure doesn’t affect rest of system
 layering considered harmful?
Introduction 1-60

Internet protocol stack
 application: supporting network applications
 FTP, SMTP, HTTP
 transport: process-process data
transfer
 TCP, UDP
 network: routing of datagrams from source to destination
 IP, routing protocols
 link: data transfer between
neighboring network elements  Ethernet, 802.111 (WiFi), PPP
 physical: bits “on the wire”
application
transport
network
link
physical
Introduction 1-61

ISO/OSI reference model
 presentation: allow applications to interpret meaning of data, e.g., encryption, compression, machine-specific conventions
 session: synchronization, checkpointing, recovery of data exchange
 Internet stack “missing” these layers!
 these services, if needed, must be implemented in application
 needed?
application
presentation
session
transport
network
link
physical
Introduction 1-62

source
Encapsulation
application
transport
network
link
physical
message segment
M
Ht
M
datagram frame
Hn
Ht
M
Hl
Hn
Ht
M
link
physical
switch
destination
network
Hn
Ht
M
application
transport
network
link
physical
link
Hl
Ht
M
M
Hn
M
physical
Ht
Hn
Ht
M
router
Hl
Hn
Ht
M
Hn
Ht
M
Introduction 1-63

Chapter 1: roadmap 1.1 what is the Internet?
1.2 network edge
 end systems, access networks, links 1.3 network core
 packet switching, circuit switching, network structure 1.4 delay, loss, throughput in networks
1.5 protocol layers, service models
1.6 networks under attack: security
1.7 history
Introduction 1-64

Network security
 field of network security:
 how bad guys can attack computer networks
 how we can defend networks against attacks
 how to design architectures that are immune to attacks
 Internet not originally designed with (much) security in mind
 original vision: “a group of mutually trusting users attached to a transparent network”
 Internet protocol designers playing “catch-up”
 security considerations in all layers!
Introduction 1-65

Bad guys: put malware into hosts via Internet
 malware can get in host from:
 virus: self-replicating infection by receiving/executing
object (e.g., e-mail attachment)
 worm: self-replicating infection by passively receiving object that gets itself executed
 spyware malware can record keystrokes, web sites visited, upload info to collection site
 infected host can be enrolled in botnet, used for spam. DDoS attacks
Introduction 1-66

Bad guys: attack server, network infrastructure
Denial of Service (DoS): attackers make resources (server, bandwidth) unavailable to legitimate traffic by overwhelming resource with bogus traffic
1. select target
2. break into hosts around
the network (see botnet)
3. send packets to target from compromised hosts
target
Introduction 1-67

Bad guys can sniff packets
packet “sniffing”:
 broadcast media (shared ethernet, wireless)
 promiscuous network interface reads/records all packets (e.g., including passwords!) passing by
A
C
src:B
dest:A
payload
B
 wireshark software used for end-of-chapter labs is a (free) packet-sniffer
Introduction 1-68

Bad guys can use fake addresses
IP spoofing: send packet with false source address
A
C
src:B
dest:A
payload
B
… lots more on security (throughout, Chapter 8)
Introduction 1-69

Chapter 1: roadmap 1.1 what is the Internet?
1.2 network edge
 end systems, access networks, links
1.3 network core
 packet switching, circuit switching, network structure 1.4 delay, loss, throughput in networks
1.5 protocol layers, service models
1.6 networks under attack: security
1.7 history
Introduction 1-70

Internet history
1961-1972: Early packet-switching principles
 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 public demo
 NCP (Network Control Protocol) first host-host protocol
 first e-mail program
 ARPAnet has 15 nodes
Introduction 1-71

Internet history
1972-1980: Internetworking, new and proprietary nets
 1970: ALOHAnet satellite network in Hawaii
 1974: Cerf and Kahn – architecture for interconnecting networks
 1976: Ethernet at Xerox PARC
 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
Introduction 1-72

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-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
Introduction 1-73

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)
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, P2P file sharing
 network security to forefront
 est. 50 million host, 100 million+ users
 backbone links running at Gbps
Introduction 1-74

Internet history
2005-present
 ~750 million hosts
 Smartphones and tablets
 Aggressive deployment of broadband access
 Increasing ubiquity of high-speed wireless access
 Emergence of online social networks:  Facebook: soon one billion users
 Service providers (Google, Microsoft) create their own networks
 Bypass Internet, providing “instantaneous” access to search, emai, etc.
 E-commerce, universities, enterprises running their services in “cloud” (eg, Amazon EC2)
Introduction 1-75

Introduction: summary
covered a “ton” of material!
 Internet overview
 what’s a protocol?
 network edge, core, access network
 packet-switching versus circuit-switching
 Internet structure
 performance: loss, delay,
throughput
 layering, service models
 security
 history
you now have:
 context, overview, “feel” of networking
 more depth, detail to follow!
Introduction 1-76