1 computer network architecture ece 156 fall 2011 romit roy choudhury dept. of ece and cs
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Computer Network Architecture
ECE 156 Fall 2011
Romit Roy ChoudhuryDept. of ECE and CS
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Course Logistics
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Welcome to ECE 156
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Welcome to ECE 156
Prerequisite: ECE 52Else, come and talk to me
Further courses: ECE 256: Wireless Networking and Mobile
Computing•Spring 2012
CPS 296: Hot Topics in Networked Systems CPS 214: Computer Network and Distributed
Systems
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Welcome to ECE 156
Course Website:http://www.ee.duke.edu/~romit/courses/f11/ece156-f11-networking.html
Most course related information will be posted on the website
Please check the course website frequently
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Welcome to ECE 156
Make up classes Will be occasionally necessary due to travel Would like to schedule on a case by case basis
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Welcome to ECE 156
Grading: Participation/Presentation: 10% Homework: 20% Programming Assignments: 20% 1 mid-term exam: 20% Final exam: 30%
Programming project may be in groups of 2 One of the exams is likely to be open book
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Finally
Academic honesty Please please please … A few points is not worth a tarnished career In the long run, GPA does not matter as much
as you think it does
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Course Summary(Very Briefly)
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Course information
Course materials: Text:
Computer Networking: A Top Down Approach Featuring the Internet, J. Kurose & K. Ross, Addison Wesley, 3rd ed., 2005, or higher
Class notes/slides Acknowledgment to Jim Kurose
Some supplementary reading material
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What is this course about?
Introductory (first) course in computer networking Undergrads, early MS students
learn principles of computer networking learn practice of computer networking Internet architecture/protocols as case study Real wireless networks as case studies Intro to next generation networking
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Course information By the time you are finished …
You understand variety of concepts (not just factoids)
Internet, HTTP, DNS, P2P, … Sockets, Ports, … Congestion Control, Flow Control, TCP, … Routing, Basic Graphs, Djikstra’s Algorithm, IP, … DSL Vs Cable, Aloha, CSMA, TDMA, Token, WiFi 802.11,
… Security, RSA, … Cellular Networks, Mobile Networks, Satellite Networks,
… Wireless Multihop Networks (ad hoc, mesh, WLANs) Sensor Networks …
If you understand 75% of these terms, you shouldn’t be hereIf you understand 75% of these terms, you shouldn’t be here
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What this Course Does Not Cover
Not a “communications” course Does not cover
Modulation schemes Transmitter/Receiver design Signal processing and antenna design Etc.
This is course on Understading, analysing, and (perhaps)
designing of protocols and algorithms in networking systems (wired Internet/Ethernet and wireless cell/WiFi)
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What’s the difference between
CommunicationsAnd
Networking
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Finally
I cannot / will not / should not be speaking alone in class Questions Comments Disagreements Debates … are highly encouraged
This course can be real fun
Whether it will be … Is up to you and me
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Hello! I am ECE 156
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Computer Network Architecture
Past, Present, and Future
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On the Shoulders of Giants
1961: Leonard Kleinrock published a work on packet switching
1962: J. Licklider described a worldwide network of computers called Galactic Network
1965: Larry Roberts designed the ARPANET that communicated over long distance links
1971: Ray Tomilson invents email at BBN
1972: Bob Kahn and Vint Cerf invented TCP for reliable packet transport
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On the Shoulders of Giants …
1973: David Clark, Bob Metcalfe implemented TCP and designed ethernet at Xerox PARC
1975: Paul Mockapetris developed DNS system for host lookup
1980: Radia Perlman invented spanning tree algorithm for bridging separate networks
Things snowballed from there on …
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What we have today is beyond any of the inventors’ imagination …
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And YOU are here
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And by “YOU” I mean …
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“Cool” internet appliances
World’s smallest web serverhttp://www-ccs.cs.umass.edu/~shri/iPic.html
IP picture framehttp://www.ceiva.com/
Web-enabled toaster +weather forecaster
Internet phones
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And Of Course people …
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InterNetwork
Millions of end points (you, me, and toasters) are connected over a network Many end points can be addressed by numbers Many others lie behind a virtual end point
Many networks form a bigger network
The overall strcture called the Internet With a capital I Defined as the network of networks
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Internet structure: network of networks
roughly hierarchical at center: “tier-1” ISPs (e.g., MCI, Sprint, AT&T,
Cable and Wireless), national/international coverage treat each other as equals
Tier 1 ISP
Tier 1 ISP
Tier 1 ISP
Tier-1 providers interconnect (peer) privately
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Tier-1 ISP: e.g., Sprint
Sprint US backbone network
Seattle
Atlanta
Chicago
Roachdale
Stockton
San Jose
Anaheim
Fort Worth
Orlando
Kansas City
CheyenneNew York
PennsaukenRelayWash. DC
Tacoma
DS3 (45 Mbps)OC3 (155 Mbps)OC12 (622 Mbps)OC48 (2.4 Gbps)
…
to/from customers
peering
to/from backbone
….
………POP: point-of-presence
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Cables Laid Out in the Oceans
Optical Fiber cross-section
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Cable Connections carry 95% traffic (rest?)
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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
France telecome, Tiscali, etc. buys from Sprint
Tier 1 ISP
Tier 1 ISP
Tier 1 ISP
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 ISPs also peer privately with each other, interconnect at NAP
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Internet structure: network of networks
“Tier-3” ISPs and local ISPs (Time Warner, Earthlink, etc.) last hop (“access”) network (closest to end systems)
Tier 1 ISP
Tier 1 ISP
Tier 1 ISP
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
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Internet structure: network of networks
a packet passes through many networks! Local ISP (taxi) -> T1 (bus) -> T2 (domestic) -> T3 (international)
Tier 1 ISP
Tier 1 ISP
Tier 1 ISP
Tier-2 ISPTier-2 ISP
Tier-2 ISP Tier-2 ISP
Tier-2 ISP
localISPlocal
ISPlocalISP
localISP
localISP Tier 3
ISP
localISP
localISP
localISP
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Organizing the giant structure
Networks are complex!
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?
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Turn to analogies in air travel
a series of steps
ticket (purchase)
baggage (check)
gates (load)
runway takeoff
airplane routing
ticket (complain)
baggage (claim)
gates (unload)
runway landing
airplane routing
airplane routing
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ticket (purchase)
baggage (check)
gates (load)
runway (takeoff)
airplane routing
departureairport
arrivalairport
intermediate air-trafficcontrol centers
airplane routing airplane routing
ticket (complain)
baggage (claim
gates (unload)
runway (land)
airplane routing
ticket
baggage
gate
takeoff/landing
airplane routing
Layering of airline functionality
Layers: each layer implements a service layers communicate with peer layers rely on services provided by layer below
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Why layering?
Explicit structure allows identification, relationship of complex system’s pieces
Modularization eases maintenance, updating of system change of implementation of layer’s service
transparent to rest of system e.g., runway delay (wheels up time) depends
on clearence of destination runway … doesn’t affect rest of system
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Protocol “Layers”
Service of each layer encapsulated
Universally agreed services called PROTOCOLS
A large part of this course will focus on designing protocols for
networking systems
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Internet protocol stack
application: supporting network applications FTP, SMTP, HTTP, DNS …
transport: host-host data transfer TCP, UDP …
network: routing of datagrams from source to destination IP, BGP, routing protocols …
link: data transfer between neighboring network elements PPP, Ethernet, WiFi, Bluetooth …
physical: bits “on the wire” OFDM, DSSS, CDMA, Coding …
application
transport
network
link
physical
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Success of Layering
Protocol stack successful in Internet
Internet uses wired physical layer links Very reliable BER = 10-8
What about wireless networks Very unreliable due to channel fluctuations Due to co-channel interference Due to external noise
Does horizontal layering still hold ?
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Questions ?
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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