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Chapter 1
Introduction
Computer
Networking: A
Top Down
Approach
6 th edition Jim Kurose, Keith Ross Addison-Wesley March 2012 A note on the use of these ppt slides: We’re making these slides freely available to all (faculty, students, readers). They’re in PowerPoint form so you see the animations; and can add, modify, and delete slides (including this one) and slide content to suit your needs. They obviously represent a lot of work on our part. In return for use, we only ask the following: (^) If you use these slides (e.g., in a class) that you mention their source (after all, we’d like people to use our book!) (^) If you post any slides on a www site, that you note that they are adapted from (or perhaps identical to) our slides, and note our copyright of this material. Thanks and enjoy! JFK/KWR All material copyright 1996- J.F Kurose and K.W. Ross, All Rights Reserved
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
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 Packet switches: forward packets (chunks of data) routers and wired links wireless links router mobile network global ISP regional ISP home network institutional network smartphone PC server wireless laptop
“Fun” internet appliances
IP picture frame http://www.ceiva.com/ Web-enabled toaster + weather forecaster Internet phones Internet refrigerator Slingbox: watch, control cable TV remotely Tweet-a-watt: monitor energy use
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 global ISP regional ISP home network institutional network Introductio n 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
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
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 global ISP regional ISP home network institutional network
Access net: digital subscriber line (DSL) central office ISP telephone network DSLAM voice, data transmitted at different frequencies over dedicated line to central office 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 DSL modem splitter DSL access multiplexer
Access net: cable network cable modem splitter
cable headend Channels V I D E O V I D E O V I D E O V I D E O V I D E O V I D E O D A T A D A T A C O N T R O L 1 2 3 4 5 6 7 8 9 equency division multiplexing: different channels transmitte different frequency bands
Access net: home network to/from headend or central office cable or DSL modem router, firewall, NAT wired Ethernet (100 Mbps) wireless access point (54 Mbps) wireless devices often combined in single box
Enterprise access networks (Ethernet) (^) typically used in companies, universities, etc (^) 10 Mbps, 100Mbps, 1Gbps, 10Gbps transmission rates (^) today, end systems typically connect into Ethernet switch Ethernet switch institutional mail, web servers institutional router institutional link to ISP (Internet)
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 R: link transmission rate host 2 1 two packets, L bits each 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
