Computer Networking: A Top Down Approach ppt

1 Chapter 1 Introduction Computer Networking: A Top Down Approach
A note on the use of these Powerpoint 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: Computer Networking: A Top Down Approach 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 J.F Kurose and K.W. Ross, All Rights Reserved 7th Edition, Global Edition Jim Kurose, Keith Ross Pearson April 2016 Introduction

2 Introduction Prof. Sungwook Kim [김승욱] AS building 903
Tel : 02] TA : Joonsu Ryu [류준수] AS building 901

3 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

4 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

5 What’s the Internet: “nuts and bolts” view
smartphone PC server wireless laptop billions of connected computing devices: hosts = end systems running network apps mobile network global ISP regional ISP home network institutional communication links fiber, copper, radio, satellite transmission rate: bandwidth wired links wireless packet switches: forward packets [chunks of data] routers and switches router Introduction 5

6 “Fun” Internet-connected devices
Web-enabled toaster + weather forecaster IP picture frame Tweet-a-watt: monitor energy use Slingbox: watch, control cable TV remotely sensorized, bed mattress Internet refrigerator Internet phones Introduction

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

8 What’s the Internet: a service view
mobile network global ISP regional ISP home network institutional infrastructure that provides services to applications: Web, VoIP, , 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 Introduction

9 What’s a protocol? human protocols: network protocols:
“what’s the time?” “I have a question” introductions … specific messages sent … specific actions taken when messages received, or other events network protocols: machines rather than humans all communication activity in Internet governed by protocols protocols define format, order of messages sent and received among network entities, and actions taken on message transmission, receipt Introduction

10 What’s a protocol? a human protocol and a computer network protocol:
Hi TCP connection request Hi TCP connection response Got the time? Get 2:00 time Q: other human protocols? Introduction

11 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 11

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

13 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

14 Access network: digital subscriber line [DSL]
central office telephone network voice, data transmitted at different frequencies over dedicated line to central office DSL modem splitter DSLAM DSL access multiplexer 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

15 Access network: cable network
cable headend … cable modem splitter Channels V I D E O A T C N R L 1 2 3 4 5 6 7 8 9 frequency division multiplexing: different channels transmitted in different frequency bands Introduction

16 Access network: cable network
cable headend … data, TV transmitted at different frequencies over shared cable distribution network cable modem splitter cable modem termination system CMTS 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

17 to/from headend or central office
Access network: home network wireless devices to/from headend or central office often combined in single box wireless access point [54 Mbps] router, firewall, NAT cable or DSL modem wired Ethernet [1 Gbps] Introduction

18 Enterprise access networks [Ethernet]
institutional link to ISP [Internet] institutional router Ethernet switch institutional mail, web servers typically used in companies, universities, etc. 10 Mbps, 100Mbps, 1Gbps, 10Gbps transmission rates today, end systems typically connect into Ethernet switch Introduction

19 Wireless access networks
shared wireless access network connects end system to router via base station aka “access point” wide-area wireless access provided by telco [cellular] operator, 10’s km between 1 and 10 Mbps 3G, 4G: LTE wireless LANs: within building [100 ft.] 802.11b/g/n [WiFi]: 11, 54, 450 Mbps transmission rate to Internet to Internet Introduction

20 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 2 1 R: link transmission rate host L [bits] R [bits/sec] packet transmission delay time needed to transmit L-bit packet into link = = Introduction

21 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 Gbps Ethernet Category 6: 10Gbps Introduction

22 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 Gbps transmission rate] low error rate: repeaters spaced far apart immune to electromagnetic noise Introduction

23 Physical media: radio radio link types:
terrestrial microwave e.g. up to 45 Mbps channels LAN [e.g., WiFi] 54 Mbps wide-area [e.g., cellular] 4G cellular: ~ 10 Mbps satellite Kbps to 45Mbps channel [or multiple smaller channels] 270 msec end-end delay geosynchronous versus low altitude signal carried in electromagnetic spectrum no physical “wire” bidirectional propagation environment effects: reflection obstruction by objects interference Introduction

24 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 24

25 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

26 Packet-switching: store-and-forward
L bits per packet 3 2 1 source destination R bps R bps 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 one-hop numerical example: L = 7.5 Mbits R = 1.5 Mbps one-hop transmission delay = 5 sec end-end delay = 2L/R [assuming zero propagation delay] more on delay shortly … Introduction

27 Packet Switching: queueing delay, loss
R = 100 Mb/s D R = 1.5 Mb/s B E queue of packets waiting for output link 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

28 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 1 1 2 3 0111 destination address in arriving packet’s header Introduction

29 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

30 Circuit switching: FDM versus TDM
4 users Example: FDM frequency time TDM frequency time Two simple multiple access control techniques. Each mobile’s share of the bandwidth is divided into portions for the uplink and the downlink. Also, possibly, out of band signaling. As we will see, used in AMPS, GSM, IS-54/136 Introduction

31 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 * ….. N users 1 Mbps link Q: how did we get value ? Q: what happens if > 35 users ? * Check out the online interactive exercises for more examples: Introduction

32 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

33 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 Introduction

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

35 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 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 net access net … access net Introduction

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

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

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

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

40 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 access net access net access net access net IXP access net access net ISP A … … Content provider network IXP ISP B access net access net ISP C access net access net access net regional net access net … access net access net … access net Introduction

41 Internet structure: network of networks
Tier 1 ISP Tier 1 ISP Google IXP IXP IXP Regional ISP Regional ISP access ISP access ISP access ISP access ISP access ISP access ISP access ISP access ISP 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

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

43 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 43

44 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 free [available] buffers: arriving packets dropped [loss] if no free buffers packets queueing [delay] B Introduction

45 Four sources of packet delay
propagation nodal processing queueing dnodal = dproc + dqueue + dtrans + dprop A B transmission 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

46 Four sources of packet delay
transmission A propagation B nodal processing queueing dnodal = dproc + dqueue + dtrans + dprop dtrans: transmission delay: L: packet length [bits] R: link bandwidth [bps] dtrans = L/R dprop: propagation delay: d: length of physical link s: propagation speed [~2x108 m/sec] dprop = d/s dtrans and dprop very different * Check out the online interactive exercises for more examples: * Check out the Java applet for an interactive animation on trans vs. prop delay Introduction 46

47 Caravan analogy cars “propagate” at 100 km/hr
toll booth ten-car caravan 100 km 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? 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 Introduction

48 Caravan analogy [more]
toll booth ten-car caravan 100 km 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, first car arrives at second booth; three cars still at first booth Introduction

49 Queueing delay [revisited]
R: link bandwidth [bps] L: packet length [bits] a: average packet arrival rate average queueing delay traffic intensity = La/R La/R ~ 0: avg. queueing delay small La/R -> 1: avg. queueing delay large La/R > 1: more “work” arriving than can be serviced, average delay infinite! La/R ~ 0 La/R -> 1 * Check online interactive animation on queuing and loss Introduction

50 “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

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

52 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 buffer [waiting area] packet being transmitted A B packet arriving to full buffer is lost * Check out the Java applet for an interactive animation on queuing and loss Introduction

53 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 file of F bits to send to client link capacity Rs bits/sec server sends bits [fluid] into pipe pipe that can carry fluid at rate Rs bits/sec] Rc bits/sec] link capacity Rc bits/sec Introduction

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

55 Throughput: Internet scenario
per-connection end-end throughput: min[Rc,Rs,R/10] in practice: Rc or Rs is often bottleneck Rs Rs Rs R Rc Rc Rc 10 connections [fairly] share backbone bottleneck link R bits/sec * Check out the online interactive exercises for more examples: Introduction

56 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 56

57 Protocol “layers” Question: 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

58 Organization of air travel
ticket [purchase] baggage [check] gates [load] runway takeoff airplane routing ticket [complain] baggage [claim] gates [unload] runway landing a series of steps Introduction

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

60 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

61 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, [WiFi], PPP physical: bits “on the wire” application transport network link physical Introduction

62 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

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

64 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 64

65 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

66 Bad guys: put malware into hosts via Internet
malware can get in host from: virus: self-replicating infection by receiving/executing object [e.g., 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

67 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] target 3. send packets to target from compromised hosts Introduction

68 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

69 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

70 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 70

71 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 program ARPAnet has 15 nodes Introduction

72 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

73 Internet history 1980-1990: new protocols, a proliferation of networks
1983: deployment of TCP/IP 1982: smtp 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

74 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, 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

75 Internet history 2005-present ~5B devices attached to Internet [2016]
smartphones and tablets aggressive deployment of broadband access increasing ubiquity of high-speed wireless access emergence of online social networks: Facebook: ~ one billion users service providers [Google, Microsoft] create their own networks bypass Internet, providing “instantaneous” access to search, video content, , etc. e-commerce, universities, enterprises running their services in “cloud” [e.g., Amazon EC2] Introduction

76 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

77 Chapter 1 Additional Slides
Introduction

78 copy of all Ethernet frames sent/received
packet capture [pcap] analyzer copy of all Ethernet frames sent/received Transport [TCP/UDP] Network [IP] Link [Ethernet] Physical application [www browser, client] OS