data communication & computer networks cs 1652 the slides are adapted from the publisher’s...
TRANSCRIPT
Data Communication & Computer Networks
CS 1652
The slides are adapted from the publisher’s material All material copyright 1996-2009
J.F Kurose and K.W. Ross, All Rights Reserved
Jack LangeUniversity of Pittsburgh
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Course Objectives
Understand modern data communication systems and computer networks Understand the key concepts How they are designed & implemented How they are operated How they are likely to evolve in the future
Course Approach Top-down : from what’s familiar to nuts and
bolts The Internet as the main focus Hands-on experience on networked systems 1-2
Administrativia
Instructor: Jack Lange Email: [email protected] Office: Sennott Square #5407 Office Hours: Weds. 2-4PM
Teaching Assistant: TBD
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Communication
Course homepage http://www.cs.pitt.edu/~jacklange/teaching/cs1652-f13/ Announcements, clarifications, corrections Additional resources for projects
Google Group http://groups.google.com/group/pitt-cs1652-
f13 [email protected] Private discussion group
• Open venue for class discussions and questions
Based on email (Pitt addresses)• Email me if you want to use a different one
TextBooks
Computer Networking: A Top-Down Approach James Kurose and Keith Ross Fifth/Sixth Edition, Addison Wesley, 2010
TCP/IP Illustrated, Volume I: The Protocols Richard Stevens Addison Wesley, 1994
Class meeting times
Lecture Tues/Thurs: 4:00-5:15PM Sennott Square, Rm. 6110
Lab Sessions Sennott Square, Rm. 5506 Periodically replace lectures Hands on exercises Answer project question Hopefully guest lectures
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Networking Lab
Sennott Square, Rm. 5506 16 Linux machines (Fedore Core 13) Login: Hopefully will be your Pitt login Available for projects
• Can use other machines, but…• Must work on lab equipment
Dual NICS 1 internal network interface to be used for projects 1 external network interface for external access
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Homework
Reading assignments Expected to read before each class
Homework 4 problem sets spaced over semester
Projects Web server (20%) TCP (50%) Routing (30%)
Check Syllabus!
Grading
GradingMidterm (20%)Final (20%)4 Homework (10%) 3 Projects (50%)
Late policySubmit by midnight of the due date10% penalty for every day late
Projects
Work in groups of 2 C/C++ is required
Lot of work, but will be worth it Build a TCP stack and a Web server that runs on it IP routing
Highly Recommended: OS or having some familiarity with Unix systems programming, preferably in C or C++ Minet is in C++ BUILDING software is 50% of the grade of this class
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Today’s topic Computer Networks Overview
What’s the Internet?• Nuts and bolts vs. service view
What’s a protocol?• A set of rules between communicating entities
Network edge/core• Hosts, access networks, physical media• Packet switching/circuit switching, Internet structure
Goal Get “feel” and terminology More depth, detail later in course
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What is the internet?
Flows, packets, and bits
Optical light, electricity, and radio waves
Servers, clients, and peers
Hosts, switches, and routers
What’s the Internet: Hardware view millions of
connected computing devices: hosts = end systems
Home network
Institutional network
Mobile network
Global ISP
Regional ISP
router
PC
server
wirelesslaptop
cellular smartphone
wiredlinks
access points
communication links
fiber, copper, radio, satellite
transmission rate = bandwidth
routers: forward packets (chunks of data)
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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
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What’s a protocol?a human protocol and a computer network
protocol:
Hi
Hi
Got thetime?
2:00
TCP connectionresponse
Get http://www.awl.com/kurose-ross
<file>
time
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TCP connection request
Where are we?
What’s the Internet? Nuts and bolts vs. service view
What’s the protocol? Network edge/core
Hosts, access networks, physical media Packet switching/circuit switching, Internet
structure
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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 Edge routers “uplink” to
core routers 1-20
The network edge:
end systems (hosts): run application programs e.g. Web, email at “edge of network”
client/server
peer-peer
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
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Traditionally where the action is
Internet structure: network of networks
roughly hierarchical at center: “tier-1” ISPs (e.g., Verizon, Sprint, AT&T,
NTT, Quest, Level3, Global Crossing, Tata, Savvis, TeliaSonera), 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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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
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 ISP is customer oftier-1 provider
Tier-2 ISPs also peer privately with each other.
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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
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!
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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Tier-1 ISP: e.g., Sprint
…
to/from customers
peering
to/from backbone
….
………
POP: point-of-presence
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What’s the Internet: Software-ish view
protocols control sending, receiving of msgs
e.g., TCP, IP, HTTP, Skype, Ethernet
Provides meaning
Internet standards RFC: Request for comments IETF: Internet Engineering Task
Force
Internet: “network of networks”
loosely hierarchical public Internet versus private
intranet
Home network
Institutional network
Mobile network
Global ISP
Regional ISP
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What’s the Internet: 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
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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?1-22
100 Mbps
100 Mbps
100 Mbps1 Gbps
server
Ethernetswitch
Institutionalrouter
To Institution’sISP
Ethernet Internet access
Typically used in companies, universities, etc 10 Mbps, 100Mbps, 1Gbps, 10Gbps Ethernet Today, end systems typically connect into
Ethernet switch1-32
Wireless access networks
shared wireless access network connects end system to router via base station aka “access
point”
wireless LANs: 802.11b/g (WiFi): 11 or 54 Mbps 802.11n: ~450Mbps
wider-area wireless access provided by telco operator ~1Mbps over cellular system
(EVDO, HSDPA, 3G) next up: WiMAX (10’s Mbps)
over wide area
basestation
mobilehosts
router
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telephonenetwork
DSLmodem
homePC
homephone
Internet
DSLAM
Existing phone line:0-4KHz phone; 4-50KHz upstream data; 50KHz-1MHz downstream data
splitter
centraloffice
Digital Subscriber Line (DSL)
Also uses existing telephone infrastruture up to 1 Mbps upstream up to 8 Mbps downstream dedicated physical line to telephone central office
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Cable Network Architecture: Overview
home
cable headend
cable distributionnetwork (simplified)
Typically 500 to 5,000 homes
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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 (next class):
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ONT
OLT
central office
opticalsplitter
ONT
ONT
opticalfiber
opticalfibers
Internet
Fiber to the Home (FTTH)
Optical links from central office to the home Two competing optical technologies:
Passive Optical Network (PON) – e.g. Verizon FIOS Active Optical Network (AON) – Switched Ethernet
Much higher Internet rates; fiber also carries television and phone services
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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
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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
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Physical media: coax, fiber
Coaxial cable: two concentric copper
conductors bidirectional baseband:
single channel on cable
• Digital signal legacy Ethernet
broadband: multiple channels on
cable
• Analog Signal 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
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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
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Summary
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The Internet can be defined as A set of hosts running distributed applications
communicating via routers Infrastructure providing popular services
Protocols define the message formats, orders, actions on transmission and reception
Access networks: at the network edge Residential (dial-up, DSL, Cable, FTTH) Institutional (Ethernet) Wireless (Wi-fi, WiMAX)