Computer Networking: A Top-Down Approach PDF 8th Edition

Chapter 1 Introductio n 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...

Chapter 1 Introductio n 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:  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!) Computer  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. Networking: A Top- For a revision history, see the slide note for this page. Down Approach Thanks and enjoy! JFK/KWR 8th edition Jim Kurose, Keith Ross All material copyright 1996-2020 Pearson, 2020 J.F Kurose and K.W. Ross, All Rights Reserved Introduction: 1-1 Chapter 1: introduction Chapter goal: Overview/roadmap:  Get “feel,” “big  What is the Internet? picture,” introduction to  What is a protocol? terminology  Network edge: hosts, access more depth, detail later network, physical media in course  Network core: packet/circuit  Approach: switching, internet structure use Internet as  Performance: loss, delay, throughput example  Security  Protocol layers, service models  History Introduction: 1-2 The Internet: a “nuts and bolts” view Billions of connected mobile network computing devices: national or global ISP  hosts = end systems  running network apps at Internet’s “edge” Packet switches: forward packets local or (chunks of data) ISP Internet regional  routers, switches home network content Communication links provider  fiber, copper, radio, network datacenter satellite network  transmission rate: bandwidth Networks enterprise  collection of devices, routers, network links: managed by an organization Introduction: 1-3  “Fun” Internet-connected devices Pacemaker & Monitor Tweet-a-watt: monitor energy use Amazon Echo IP picture frame Web-enabled toaster + weather forecaster Internet refrigerator Slingbox: remote control cable TV Security Camera AR devices sensorized, bed Internet phones mattress Others? Fitbit Introduction: 1-4 The Internet: a “nuts and bolts” view mobile network 4G  Internet: “network of national or global ISP networks”  Interconnected ISPs protocols are everywhere IP Streaming Skype video control sending, receiving of messages local or e.g., HTTP (Web), streaming regional ISP video, Skype, TCP, IP, WiFi, 4G, Ethernet home network content provider  Internet standards HTTP network datacenter network RFC: Request for Comments Ethernet IETF: Internet Engineering TCP Task Force enterprise network WiFi Introduction: 1-5 The Internet: a “service” view  Infrastructure that mobile network provides services to national or global ISP applications: Web, streaming video, Streaming video multimedia teleconferencing, Skype email, games, e-commerce, local or social media,  provides inter-connected programming regional ISP appliances, interface … to distributed home network content provider applications: HTTP network datacenter “hooks” allowing network sending/receiving apps to “connect” to, use Internet enterprise transport service network provides service options, Introduction: 1-6 What’s a protocol? Human protocols: Network protocols:  “what’s the time?”  computers (devices) rather than  “I have a question” humans  introductions  all communication activity in Internet governed by protocols … specific messages sent Protocols define the format, … specific actions order of messages sent and taken when message received among network received, or other events entities, and actions taken on msg transmission, receipt Introduction: 1-7 What’s a protocol? A human protocol and a computer network protocol: Hi TCP connection request Hi TCP connection response Got the time? GET http://gaia.cs.umass.edu/kurose_ro 2:00 ss time Q: other human protocols? Introduction: 1-8 Chapter 1: roadmap  What is the Internet?  What is a protocol?  Network edge: hosts, access network, physical media  Network core: packet/circuit switching, internet structure  Performance: loss, delay, throughput  Security  Protocol layers, service models  History Introduction: 1-9 A closer look at Internet structure mobile network Network edge: national or global ISP  hosts: clients and servers  servers often in data centers local or regional ISP home network content provider network datacenter network enterprise network Introduction: 1-10 A closer look at Internet structure mobile network Network edge: national or global ISP  hosts: clients and servers  servers often in data centers local or Access networks, physical regional ISP media: home network content provider  wired, wireless network datacenter network communication links enterprise network Introduction: 1-11 A closer look at Internet structure mobile network Network edge: national or global ISP  hosts: clients and servers  servers often in data centers Access networks, physical local or regional media: ISP home network content  wired, wireless communication provider network links datacenter network Network core:  interconnected routers enterprise network  network of networks Introduction: 1-12 Access networks and physical media Q: How to connect end mobile network systems to edge router? national or global ISP  residential access nets  institutional access networks (school, company)  mobile access networks (WiFi, local or 4G/5G) regional ISP What to look for: home network content provider network  transmission rate (bits per second) of access datacenter network network?  shared or dedicated access among users? enterprise network Introduction: 1-13 Access networks: cable-based access cable headend … cable splitter modem C O V V V V V V N I I I I I I D D T D D D D D D A A R E E E E E E T T O O O O O O O A A L 1 2 3 4 5 6 7 8 9 Channels frequency division multiplexing (FDM): different channels transmitted in different frequency bands Introduction: 1-14 Access networks: cable-based access cable headend … cable splitter cable modem modem CMTS termination system data, TV transmitted at different frequencies over shared cable ISP distribution network  HFC: hybrid fiber coax asymmetric: up to 40 Mbps – 1.2 Gbs downstream transmission rate, 30-100 Mbps upstream transmission rate  network of cable, fiber attaches homes to ISP router homes share access network to cable headend Introduction: 1-15 Access networks: digital subscriber line (DSL) central office telephone network DSL splitter modem DSLAM voice, data transmitted ISP at different frequencies over DSL access dedicated line to central office multiplexer  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  24-52 Mbps dedicated downstream transmission rate  3.5-16 Mbps dedicated upstream transmission rate Introduction: 1-16 Access networks: home networks wireless devices to/from headend or central office often combined in single box cable or DSL modem WiFi wireless router, firewall, access NAT point (54, 450 wired Ethernet (1 Mbps) Gbps) Introduction: 1-17 Wireless access networks Shared wireless access network connects end system to router  via base station aka “access point” Wireless local area Wide-area cellular access networks (WLANs) networks  typically within or around  provided by mobile, cellular building (~100 ft) network operator (10’s km)  802.11b/g/n (WiFi): 11, 54,  10’s Mbps 450 Mbps transmission  4G cellular networks (5G rate coming) to Internet to Internet Introduction: 1-18 Access networks: enterprise networks Enterprise link to ISP (Internet) institutional router Ethernet institutional mail, switch web servers  companies, universities, etc.  mix of wired, wireless link technologies, connecting a mix of switches and routers (we’ll cover differences shortly)  Ethernet: wired access at 100Mbps, 1Gbps, 10Gbps  WiFi: wireless access points at 11, 54, 450 Mbps Introduction: 1-19 Host: sends packets of data host sending function:  takes application message  breaks into smaller chunks, two packets, known as packets, of length L bits each L bits  transmits packet into access 2 1 network at transmission rate R host R: link transmission rate link transmission rate, aka link capacity, aka link packet time needed to L (bits) bandwidth transmission= transmit L-bit = delay packet into link R (bits/sec) Introduction: 1-20 Links: physical media  bit: propagates between Twisted pair (TP) transmitter/receiver pairs  two insulated copper wires  physical link: what lies Category 5: 100 Mbps, 1 Gbps between transmitter & Ethernet receiver Category 6: 10Gbps Ethernet  guided media: signals propagate in solid media: copper, fiber, coax  unguided media: signals propagate freely, e.g., radio Introduction: 1-21 Links: physical media Coaxial cable: Fiber optic cable:  two concentric copper  glass fiber carrying light pulses, conductors each pulse a bit  high-speed operation:  bidirectional high-speed point-to-point  broadband: transmission (10’s-100’s multiple frequency channels Gbps) on cable  low error rate: 100’s Mbps per channel repeaters spaced far apart immune to electromagnetic noise Introduction: 1-22 Links: physical media Wireless radio Radio link types:  signal carried in  terrestrial microwave electromagnetic up to 45 Mbps channels spectrum  Wireless LAN (WiFi)  no physical “wire” Up to 100’s Mbps  broadcast and “half-  wide-area (e.g., cellular) duplex” (sender to receiver) 4G cellular: ~ 10’s Mbps  propagation environment  satellite effects: up to 45 Mbps per reflection channel obstruction by objects 270 msec end-end delay interference geosynchronous versus low-earth-orbit Introduction: 1-23 Chapter 1: roadmap  What is the Internet?  What is a protocol?  Network edge: hosts, access network, physical media  Network core: packet/circuit switching, internet structure  Performance: loss, delay, throughput  Security  Protocol layers, service models  History Introduction: 1-24 The network core  mesh of interconnected mobile network national or global ISP routers  packet-switching: hosts break application-layer messages into packets local or regional forward packets from one ISP router to the next, across home network content provider links on path from source network datacenter network to destination each packet transmitted at full link capacity enterprise network Introduction: 1-25  Packet-switching: store-and- forward L bits per packet 321 source destination R bps R bps  Transmission delay: takes L/R seconds to transmit (push out) L-bit packet into One-hop numerical link at R bps example:  Store and forward: entire packet must  L = 10 Kbits arrive at router before it can be  R = 100 Mbps transmitted on next link  one-hop transmission  End-end delay: 2L/R (above), delay = 0.1 msec assuming zero propagation delay Introduction: 1-26 Packet-switching: queueing delay, loss R = 100 Mb/s A C D B R = 1.5 Mb/s E queue of packets waiting for output link Packet queuing and loss: if arrival rate (in bps) to link exceeds transmission rate (bps) of link for a period of time:  packets will queue, waiting to be transmitted on output link  packets can be dropped (lost) if memory (buffer) in Introduction: 1-27  Two key network-core functions routing Routing: algorithm  global action: Forwarding: local forwarding local forwardingtable determine table header value output link  local action: 0100 3 source- move arriving 0101 0111 2 2 destination paths packets from 1001 1 taken by packets router’s input  routing link to algorithms appropriate 1 router output 3 2 link 01 11 destination address in arriving packet’s header Introduction: 1-28 Alternative to packet switching: circuit switching end-end resources allocated to, reserved for “call” between source and destination  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 and TDM Frequency Division Multiplexing (FDM) 4 users frequency  optical, electromagnetic frequencies divided into (narrow) frequency bands  each call allocated its own band, can transmit at max rate time of that narrow band Time Division Multiplexing frequency (TDM)  time divided into slots  each call allocated periodic slot(s), can transmit at maximum rate of (wider) frequency band, time but only during its time slot(s) Introduction: 1-30 Packet switching versus circuit switching Is packet switching a “slam dunk winner”?  great for “bursty” data – sometimes has data to send, but at other times not resource sharing simpler, no call setup  excessive congestion possible: packet delay and loss due to buffer overflow protocols needed for reliable data transfer, congestion control  Q: How to provide circuit-like behavior? bandwidth guarantees traditionally used for audio/video applications Q: human analogies of reserved resources (circuit switching) versus on-demand allocation (packet switching)? Introduction: 1-31 Internet structure: a “network of networks”  Hosts connect to Internet via access Internet Service Providers (ISPs) residential, enterprise (company, university, commercial) 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: 1-32 Internet structure: a “network of networks” Question: given millions of access ISPs, how to connect them together? access … access net access net … net access access net net access access net net … … access access net net access net access net access net access … net access net access net … access net Introduction: 1-33 Internet structure: a “network of networks” Question: given millions of access ISPs, how to connect them together? access … access net access net … net access access net … … net access access net net connecting each access … … ISP to each other directly … access access doesn’t scale: O(N2) … net net access connections. net access net access net access … … net access net access net … access net Introduction: 1-34 Internet structure: a “network of networks” Option: connect each access ISP to one global transit ISP? Customer and provider ISPs have economic agreement. access … access net access net … net access access net net access access net net … … global access net ISP access net access net access net access net access … net access net access net … access net Introduction: 1-35 Internet structure: a “network of networks” But if one global ISP is viable business, there will be competitors …. access … access net access net … net access access net net access access net net ISP A … … access net ISP B access net access net ISP C access net access net access … net access net access net … access net Introduction: 1-36 Internet structure: a “network of networks” But if one global ISP is viable business, there will be competitors …. who will want to be connected Internet exchange point access … access access net net … net access access net net IXP access access net net ISP A … … access net IXP ISP B access net access net ISP C access net access net peering link access … net access net access net … access net Introduction: 1-37 Internet structure: a “network of networks” … and regional networks may arise to connect access nets to ISPs … … access access net access net net access access net net IXP access access net net ISP A … … access net IXP ISP B access net access net ISP C access net access net regional ISP access … net access net access net … access net Introduction: 1-38 Internet structure: a “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 access net net IXP access access net net ISP A … … Content provider network access net IXP ISP B access net access net ISP C access net access net regional ISP access … net access net access net … access net Introduction: 1-39  Internet structure: a “network of networks” Tier 1 ISP Tier 1 ISP Google IXP IXP IXP Regional ISP Regional ISP access access access access access access access access ISP ISP ISP ISP ISP ISP ISP 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 networks (e.g., Google, Facebook): private network that connects its data centers to Internet, often bypassing tier-1, regionalIntroduction: ISPs 1-40  Internet structure: a “network of networks” Tier-1 ISPs are global transit ISP. There are approximately a dozen tier-1 ISPs, including Level 3 Communications, AT&T, Sprint, and NTT. Note that the tier-1 ISPs do not pay anyone as they are at the top of the hierarchy. There may be multiple competing regional ISPs in a region. In such a hierarchy, each access ISP pays the regional ISP to which it connects, and each regional ISP pays the tier-1 ISP to which it connects. The amount that a customer ISP pays a provider ISP reflects the amount of traffic it exchanges with the provider. To reduce these costs, a pair of nearby ISPs at the same level of the hierarchy can peer. When two ISPs peer, it is typically settlement-free, that is, neither ISP pays the other. By peering with each other directly, the two ISPs can reduce their payments to their provider ISPs. Introduction: 1-41 Internet Exchange Points (IXP) An Internet Exchange Points (IXP) (typically in a standalone building with its own switches) is a meeting point where multiple ISPs can connect and/or peer together. An IXP earns its money by charging each of the the ISPs that connect to the IXP a relatively small fee, which may depend on the amount of traffic sent to or received from the IXP. There are over 400 IXPs in the Internet today Introduction: 1-42 content-provider networks Google is currently one of the leading examples of such a content-provider network. Google has over 50–100 data centers distributed across North America, Europe, Asia, South America, and Australia. Some of these data centers house over one hundred thousand servers. The Google data centers are all interconnected via Google’s private TCP/IP network, which spans the entire globe but is nevertheless separate from the public Internet. The Google private network attempts to “bypass” the upper tiers of the Internet by peering (settlement free) with lower-tier ISPs, either by directly connecting with them or by connecting with them at IXPs. The Google network also connects to tier-1 ISPs, and pays those ISPs for the traffic it exchanges with them. Introduction: 1-43 Chapter 1: roadmap  What is the Internet?  What is a protocol?  Network edge: hosts, access network, physical media  Network core: packet/circuit switching, internet structure  Performance: loss, delay, throughput  Security  Protocol layers, service models  History Introduction: 1-44 How do packet loss and delay occur? packets queue in router buffers  packets queue, wait for turn  arrival rate to link (temporarily) exceeds output link capacity: packet loss packet being transmitted (transmission del A B packets in buffers (queueing delay) free (available) buffers: arriving packets dropped (loss) if no free buffers Introduction: 1-45 Packet delay: four sources transmission A propagation B nodal processingqueueing dnodal = dproc + dqueue + dtrans + dprop dproc: nodal dqueue: queueing delay processing  time waiting at output link for  check bit errors transmission  determine output  depends on congestion level of link router  Introduction: 1-46 Packet delay: four sources transmission A propagation B nodal processingqueueing dnodal = dproc + dqueue + dtrans + dprop dprop: propagation delay: dtrans: transmission delay:  d: length of physical link  L: packet length (bits)  s: propagation speed (~2x108  R: link transmission rate m/sec) (bps) dtrans and dprop  dprop = d/s * Check out the online interactive exercises:  dtrans = L/R very http://gaia.cs.umass.edu/kurose_ross Introduction: 1-47 Caravan analogy 100 100 km km ten-car toll booth toll booth caravan (aka router) (aka 10-bit  cars“propagate” packet) at 100  time to “push” entire km/hr caravan through toll  toll booth takes 12 sec to booth onto highway = service car (bit transmission 12*10 = 120 sec time)  car ~ bit; caravan ~ packet  time for last car to  Q: How long until caravan is propagate from 1st to lined up before 2nd toll 2nd toll both: booth? 100km/(100km/hr) = 1 hr Introduction: 1-48 Caravan analogy 100 100 km km ten-car toll booth toll booth caravan (aka router) (aka 10-bit packet)  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: 1-49 Packet queueing delay (revisited) average queueing  R: link bandwidth (bps) delay  L: packet length (bits)  a: average packet arrival rate traffic intensity = 1  La/R ~ 0: avg. queueing delay La/R small La/R ~ 0  La/R -> 1: avg. queueing delay large  La/R > 1: more “work” arriving is more than can be serviced - La/R -> 1 average delay infinite! Introduction: 1-50 “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 (with time-to-live field value of i) router i will return packets to sender sender measures time interval between transmission and reply 3 probes 3 probes 3 probes Introduction: 1-51 Real Internet delays and 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 3 delay measurements 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 to border1-rt-fa5-1- 4 jn1-at1-0-0-19.wor.vbns.net (204.147.132.129) 16 ms 11 ms 13 ms 0.gw.umass.edu 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 trans-oceanic link 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 looks like delays 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 decrease! Why? 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 * * * * means no response (probe lost, router not replying) 19 fantasia.eurecom.fr (193.55.113.142) 132 ms 128 ms 136 ms * Do some traceroutes from exotic countries at www.traceroute.org Introduction: 1-52  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: 1-53  Throughput  throughput: rate (bits/time unit) at which bits are being sent from sender to receiver instantaneous: rate at given point in time average: rate over longer period of time link capacity pipe that can link capacity pipe that can server sends R carry bits/sec carry Rc bits/sec server, with fluid s at rate fluid at rate bits file of F bits to (fluid) send to client (Rs bits/sec) into (Rc bits/sec) pipe Introduction: 1-54 Throughput Rs < Rc What is average end-end throughput? Rs bits/sec Rc bits/sec Rs > Rc What is average end-end throughput? Rs bits/sec Rc bits/sec bottleneck link onlink end-end path that constrains end-end throughput Introduction: 1-55 Throughput: network scenario  per-connection Rs end-end Rs Rs throughput: min(Rc,Rs,R/10) R  in practice: Rc or Rs Rc Rc is often bottleneck Rc * Check out the online interactive exercises for more examples: http://gaia.cs.umass.edu/kurose_ross/ 10 connections (fairly) share backbone bottleneck link R bits/sec Introduction: 1-56 Chapter 1: roadmap  What is the Internet?  What is a protocol?  Network edge: hosts, access network, physical media  Network core: packet/circuit switching, internet structure  Performance: loss, delay, throughput  Security  Protocol layers, service models  History Introduction: 1-57 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: 1-58 Bad guys: malware  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 or distributed denial of service (DDoS) attacks Introduction: 1-59 Bad guys: denial of service 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 target 3. send packets to botnet) target from compromised hosts Introduction: 1-60 Bad guys: packet interception 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 our end-of-chapter labs is a (free) packet-sniffer Introduction: 1-61 Bad guys: fake identity IP spoofing: send packet with false source address A C src:B dest:A payload B … lots more on security (throughout, Chapter 8) Introduction: 1-62 Chapter 1: roadmap  What is the Internet?  What is a protocol?  Network edge: hosts, access network, physical media  Network core: packet/circuit switching, internet structure  Performance: loss, delay, throughput  Security  Protocol layers, service models  History Introduction: 1-63 Protocol “layers” and reference models Networks are complex, with many “pieces”: Question:  hosts is there any hope of  routers organizing  links of various media structure of  applications network?  protocols  hardware, software …. or at least our discussion of networks? Introduction: 1-64 Example: organization of air travel ticket (purchase) ticket (complain) baggage (check) baggage (claim) gates (load) gates (unload) runway takeoff runway landing airplane routing airplane routing airplane routing airline travel: a series of steps, involving many services Introduction: 1-65 Example: organization of air travel ticket (purchase) ticketing service ticket (complain) baggage (check) baggage service baggage (claim) gates (load) gate service gates (unload) runway takeoff runway service runway landing airplane routing routing service airplane routing airplane routing layers: each layer implements a Q: describe in service words the service  via its own internal-layer actions provided in each  relying on services provided by layer layer above below Introduction: 1-66 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 in layer's service implementation: transparent to rest of system e.g., change in gate procedure doesn’t affect rest of system  layering considered harmful?  layering in other complex systems? Introduction: 1-67 Internet protocol stack  application: supporting network applications IMAP, SMTP, HTTP application  transport: process-process data transfer TCP, UDP transport  network: routing of datagrams from network source to destination IP, routing protocols link  link: data transfer between neighboring network elements physical Ethernet, 802.11 (WiFi), PPP  physical: bits “on the wire” Introduction: 1-68  source message M application Encapsulation segment Ht M transport datagram Hn Ht M network frame Hl Hn Ht M link physical link physical switch destination Hn Ht M network M application Hl Hn Ht M link Hn Ht M Ht M transport physical Hn Ht M network Hl Hn Ht M link router physical Introduction: 1-69 Chapter 1: roadmap  What is the Internet?  What is a protocol?  Network edge: hosts, access network, physical media  Network core: packet/circuit switching, internet structure  Performance: loss, delay, throughput  Security  Protocol layers, service models  History Introduction: 1-70  Internet history 1961-1972: Early packet-switching principles  1961: Kleinrock - queueing  1972: theory shows ARPAnet public demo effectiveness of packet- switching NCP (Network Control  1964: Baran - packet- Protocol) first host-host switching in military nets protocol  1967: ARPAnet conceived first e-mail program by Advanced Research ARPAnet has 15 nodes Projects Agency  1969: first ARPAnet node operational Introduction: 1-71  Internet history 1972-1980: Internetworking, new and proprietary nets  1970: ALOHAnet satellite network in Hawaii Cerf and Kahn’s  1974: Cerf and Kahn - internetworking principles: architecture for interconnecting  minimalism, autonomy - networks no internal changes  1976: Ethernet at Xerox PARC required to interconnect networks  late70’s: proprietary  best-effort service model architectures: DECnet, SNA,  stateless routing XNA  decentralized control  late 70’s: switching fixed length packets (ATM precursor) define today’s Internet  1979: ARPAnet has 200 nodes architecture Introduction: 1-72  Internet history 1980-1990: new protocols, a proliferation of networks  1983: deployment of  new national networks: TCP/IP CSnet, BITnet, NSFnet,  1982: smtp e-mail Minitel protocol defined  100,000 hosts connected to  1983: DNS defined for confederation of networks name-to-IP-address translation  1985: ftp protocol defined  1988: TCP congestion control Introduction: 1-73  Internet history 990, 2000s: commercialization, the Web, new applications  early 1990s: ARPAnet late 1990s – 2000s: decommissioned  more killer apps: instant  1991: NSF lifts restrictions on messaging, P2P file sharing commercial use of NSFnet  network security to (decommissioned, 1995) forefront  early 1990s: Web  est. 50 million host, 100 hypertext [Bush 1945, Nelson 1960’s] HTML, HTTP: Berners-Lee million+ users 1994: Mosaic, later Netscape  backbone links running at late 1990s: commercialization Gbps of the Web Introduction: 1-74  Internet history 005-present: more new applications, Internet is “everywhere  ~18B devices attached to Internet (2017) rise of smartphones (iPhone: 2007)  aggressive deployment of broadband access  increasing ubiquity of high-speed wireless access: 4G/5G, WiFi  emergence of online social networks: Facebook: ~ 2.5 billion users  service providers (Google, FB, Microsoft) create their own networks bypass commercial Internet to connect “close” to end user, providing “instantaneous” access to search, video content, …  enterprises run their services in “cloud” (e.g., Amazon Web Services, Microsoft Azure) Introduction: 1-75 Chapter 1: summary We’ve covered a “ton” of material!  Internet overview  what’s a protocol? You now have:  network edge, access network,  context, core overview, packet-switching versus circuit- vocabulary, switching “feel” of Internet structure networking  performance: loss, delay,  more depth, throughput detail, and fun to  layering, service models follow!  security  history Introduction: 1-76