Chapter_1_v8.2.pptx

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 1996-2023 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? What is a picture,” introduction to protocol? terminology  Network edge: hosts, access more depth, detail network, physical media  Network core: packet/circuit later in course switching, internet structure  Performance: loss, delay, throughput  Protocol layers, service models  Security  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 (chunks of data) local or  routers, switches ISP Internet regional home network content Communication links provider network datacenter  fiber, copper, radio, satellite network  transmission rate: bandwidth Networks enterprise  collection of devices, routers, network links: managed by an organization Introduction: 1-3  “Fun” Internet-connected devices Tweet-a-watt: monitor energy use bikes Pacemaker & Monitor Amazon Echo Web-enabled toaster + IP picture frame weather forecaster Internet refrigerator Slingbox: remote cars control cable TV Security Camera AR devices sensorized, scooters bed mattress Fitbit Gaming devices Others? Internet phones diapers Introduction: 1-4 The Internet: a “nuts and bolts” view mobile network 4G  Internet: “network of national or global ISP networks” Interconnected ISPs Streaming  protocols are everywhere IP video Skype control sending, receiving of messages local or regional e.g., HTTP (Web), streaming video, ISP Skype, TCP, IP, WiFi, 4/5G, Ethernet home network content provider HTTP network Internet standards datacenter  network Ethernet RFC: Request for Comments IETF: Internet Engineering TCP enterprise Task Force network WiFi Introduction: 1-5 The Internet: a “services” 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 network “hooks” allowing sending/receiving apps to “connect” to, use Internet enterprise transport service network provides service options, Introduction: 1-6 What’s a protocol? Human Network protocols: protocols:  computers (devices) rather than  “what’s the time?” humans  “I have a question”  all communication activity in Internet governed by protocols  introductions Rules for: Protocols define the format, … specific messages sent … specific actions taken order of messages sent and when message received, received among network or other events entities, and actions taken on message 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 links network 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, 4G/5G) local or regional ISP home network content provider network datacenter network 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 Gbps 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 and wired 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/5G cellular networks rate 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 Access networks: data center networks mobile network  high-bandwidth links (10s to 100s national or global ISP Gbps) connect hundreds to thousands of servers together, and to Internet local or regional ISP home network content provider network datacenter network Courtesy: Massachusetts Green High Performance enterprise Computing Center (mghpcc.org) network Introduction: 1-20 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 host rate R R: link transmission rate link transmission rate, aka link capacity, aka time packet link needed to bandwidth transmission= transmit L-bit = L (bits) delay packet into link R (bits/sec) Introduction: 1-21 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: 1-22 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: 1-23 Links: physical media Wireless radio Radio link types:  signal carried in various  Wireless LAN (WiFi) “bands” in 10-100’s Mbps; 10’s of meters electromagnetic spectrum  wide-area (e.g., 4G/5G cellular) 10’s Mbps (4G) over ~10 Km  no physical “wire”  Bluetooth: cable replacement  broadcast, “half-duplex” short distances, limited rates (sender to receiver)  terrestrial microwave  propagation environment point-to-point; 45 Mbps channels effects:  satellite reflection up to < 100 Mbps (Starlink) obstruction by objects downlink Interference/noise 270 msec end-end delay (geostationary) Introduction: 1-24 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: 1-25 The network core mobile network  mesh of interconnected routers national or global ISP  packet-switching: hosts break application-layer messages into packets network forwards packets local or from one router to the next, regional ISP across links on path from home network content source to destination provider network datacenter network enterprise network Introduction: 1-26  Two key network-core functions routing Routing: algorithm  global action: Forwarding: local forwarding local forwardingtable determine source-  aka “switching” table header value output link 0100 3 destination paths  local action: 0101 0111 2 2 taken by packets move arriving 1001 1  routing algorithms packets from router’s input link to appropriate 1 router output link 3 2 1 1 01 destination address in arriving packet’s header Introduction: 1-27 routing Introduction: 1-28  forwarding forwarding Introduction: 1-29  Packet-switching: store-and- forward L bits per packet 321 source destination R bps R bps  packet transmission delay: takes L/R One-hop numerical seconds to transmit (push out) L-bit example: packet into link at R bps  L = 10 Kbits  store and forward: entire packet must  R = 100 Mbps arrive at router before it can be  one-hop transmission transmitted on next link delay = 0.1 msec Introduction: 1-30  Packet-switching: queueing R = 100 Mb/s A C D B R = 1.5 Mb/s E queue of packets waiting for transmission over output link Queueing occurs when work arrives faster than it can be serviced: Introduction: 1-31 Packet-switching: queueing R = 100 Mb/s A C D B R = 1.5 Mb/s E queue of packets waiting for transmission over output link Packet queuing and loss: if arrival rate (in bps) to link exceeds transmission rate (bps) of link for some period of time:  packets will queue, waiting to be transmitted on output link  packets can be dropped (lost) if memory (buffer) in Introduction: 1-32 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  commonly used idle if not used in traditional telephone by call (no sharing) networks * Check out the online interactive exercises for more examples: h ttp://gaia.cs.umass.edu/kurose_ross/interactive Introduction: 1-33 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 time band, can transmit at max rate of that narrow band frequency Time Division Multiplexing (TDM) time divided  each into slots call allocated periodic slot(s), can transmit at time maximum rate of (wider) frequency band (only) during Introduction: 1-34 Packet switching versus circuit switching example:  1 Gb/s link ….. N  each user: users 1 Gbps link 100 Mb/s when “active” active 10% of time Q: how many users can use this network under circuit-switching and packet switching?  circuit-switching: 10 users  packet switching: with 35 Q: how did we get value 0.0004? users, probability > 10 active A: HW problem (for those at same time is less with course in probability only) than.0004 * * Check out the online interactive exercises for more examples: h ttp://gaia.cs.umass.edu/kurose_ross/interactive Introduction: 1-35 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 with packet-switching? “It’s complicated.” We’ll study various techniques that try to Q: make human packet switching analogies of as “circuit-like” reserved as possible. resources (circuit switching) versus on-demand allocation (packet switching)? Introduction: 1-36 Internet structure: a “network of networks” mobile network  hosts connect to Internet via national or global ISP access Internet Service Providers (ISPs)  access ISPs in turn must be interconnected local or so that any two hosts regional ISP (anywhere!) can send packets home network content to each other provider network datacenter  resulting network of networks network is very complex enterprise network evolution driven by economics, national policies Let’s take a stepwise approach to describe current Internet structure 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: 1-38 Internet structure: a “network of networks” Question: given millions of access ISPs, how to connect them together? access … access net access net … net access net access net … … access access net net connecting each access … … ISP to each other directly … doesn’t scale: O(N2) access access … net net access connections. net access net access net access … access … … net access net access net net Introduction: 1-39 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: 1-40 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 ISP A net net … … access net ISP B access net access net ISP C access net access net access … net access net access net … access net Introduction: 1-41 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 net access net … net access access net net IXP access access ISP A net net … … 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: 1-42 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 ISP A net net … … 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: 1-43 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 ISP A net net … … 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: 1-44  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, regional ISPs Introduction: 1-45 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: 1-46 How do packet delay and loss occur?  packets queue in router buffers, waiting for turn for transmission  queue length grows when arrival rate to link (temporarily) exceeds output link capacity  packet loss occurs when memory to hold queued packets fills up packet being transmitted (transmission delay) A B packets in buffers (queueing delay) free (available) buffers: arriving packets dropped (loss) if no free buffers Introduction: 1-47 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 link of router Introduction: 1-48 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  dtrans = L/R very Introduction: 1-49 Caravan analogy 100 100 km km ten-car toll booth toll booth toll booth caravan (aka link) (aka 10-bit  carpacket) ~ bit; caravan ~ packet;  time to “push” entire toll service ~ link transmission caravan through toll  toll booth takes 12 sec to booth onto highway = service car (bit transmission 12*10 = 120 sec time)  time for last car to  “propagate” at 100 km/hr propagate from 1st to  Q: How long until caravan is 2nd toll both: lined up before 2nd toll booth? 100km/(100km/hr) = 1 hr Introduction: 1-50 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: 1-51 Packet queueing delay (revisited)  a: average packet arrival rate average queueing  L: packet length (bits) delay  R: link bandwidth (bit transmission rate) L. a arrival rate of bits “traffic : R service rate of bits intensity” traffic intensity = La/R 1  La/R ~ 0: avg. queueing delay La/R ~ 0 small  La/R -> 1: avg. queueing delay large  La/R > 1: more “work” arriving La/R -> 1 is more than can be serviced - Introduction: 1-52 “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: 1-53 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 2 border1-rt-fa5-1-0.gw.umass.edu (128.119.3.145) 1 ms 1 ms 2 ms 3 delay measurements 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 11 renater-gw.fr1.fr.geant.net (62.40.103.54) 112 ms 114 ms 112 ms looks like delays 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: 1-54  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 publisher’s website) of queuing and loss Introduction: 1-55  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: 1-56 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: 1-57 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: 1-58 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: 1-59 Network security  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!  We now need to think about: how bad guys can attack computer networks how we can defend networks against attacks how to design architectures that are immune to attacks Introduction: 1-60 Network security  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!  We now need to think about: how bad guys can attack computer networks how we can defend networks against attacks how to design architectures that are immune to attacks Introduction: 1-61 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: 1-62 Bad guys: fake identity IP spoofing: injection of packet with false source address A C src:B dest:A payload B Introduction: 1-63 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 3. send packets to botnet) target target from compromised hosts Introduction: 1-64 Lines of defense:  authentication: proving you are who you say you are cellular networks provides hardware identity via SIM card; no such hardware assist in traditional Internet  confidentiality: via encryption  integrity checks: digital signatures prevent/detect tampering  access restrictions: password-protected VPNs  firewalls: specialized “middleboxes” in access and core networks:  off-by-default: filter incoming packets to restrict senders, receivers, applications  detecting/reacting to DOS attacks … lots more on security (throughout, Chapter 8) Introduction: 1-65 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: 1-66 Protocol “layers” and reference models Networks are complex, Question: is there with many “pieces”: any hope of  hosts organizing structure  routers of network?  links of various media  and/or our  applications discussion of networks?  protocols  hardware, software Introduction: 1-67 Example: organization of air travel end-to-end transfer of person plus baggage ticket (purchase) ticket (complain) baggage (check) baggage (claim) gates (load) gates (unload) runway takeoff runway landing airplane routing airplane routing airplane routing How would you define/discuss the system of airline travel?  a series of steps, involving many services Introduction: 1-68 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 service  via its own internal-layer actions  relying on services provided by layer below Introduction: 1-69 Why layering? Approach to designing/discussing complex  systems: explicit structure allows identification, relationship of 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 Introduction: 1-70 Layered Internet protocol stack  application: supporting network applications HTTP, IMAP, SMTP, DNS application application  transport: process-process data transfer TCP, UDP transport 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: 1-71  Services, Layering and Encapsulation M Application exchanges messages to implement applicatio some application service using services of applicatio transport layer Ht M n Transport-layer protocol transfers M (e.g., n reliably) from one process to another, using services of network layer transport  transport-layer protocol transport encapsulates application-layer message, M, with transport layer- network network layer header Ht to create a transport-layer segment link Ht used by transport layer link protocol to implement its service source physical physical destination Introduction: 1-72  Services, Layering and Encapsulation M applicatio applicatio Ht M n Transport-layer protocol transfers M (e.g., n reliably) from one process to another, using services of network layer Hn Ht M transport Network-layer protocol transfers transport-layer transport segment [Ht | M] from one host to another, using link layer services network  network-layer protocol network encapsulates transport-layer link segment [Ht | M] with network link layer-layer header Hn to create a source physical network-layer datagram physical destination Hn used by network layer protocol to implement its service Introduction: 1-73  Services, Layering and Encapsulation M applicatio applicatio Ht M n n Hn Ht M transport Network-layer protocol transfers transport-layer transport segment [Ht | M] from one host to another, using Hl Hlink layer services network n Ht M network Link-layer protocol transfers datagram [Hn| [Ht |M] from host to neighboring host, using network-layer services link  link-layer protocol encapsulates link network datagram [Hn| [Ht |M], with source physical link-layer header Hl to create a physical destination link-layer frame Introduction: 1-74  Encapsulation Matryoshka dolls (stacking dolls) messagesegment datagram frame Credit: https://dribbble.com/shots/7182188-Babushka-Boi Introduction: 1-75  Services, Layering and Encapsulation message M applicatio M applicatio segment n Ht M Ht M n datagram Hn Ht M Hn Ht M transport transport frame Hl Hn Ht M Hl Hn Ht M network network link link source physical physical destination Introduction: 1-76  source Encapsulation: message M application an end-end view segment Htt M transport datagram Hn Ht M network frame Hl Hn Ht M link physical link link physical physical switch destination Hn Ht M network Hl Hn Ht M link Hn Ht M M application Ht M transport physical Hn Ht M network Hl Hn Ht M link router physical Introduction: 1-77 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: 1-78  Internet history 1961-1972: Early packet-switching principles  1961: Kleinrock - queueing  1972: theory shows effectiveness ARPAnet public demo 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  Internet history 1972-1980: Internetworking, new and proprietary networks  1970: ALOHAnet satellite network in Hawaii Cerf and Kahn’s internetworking principles:  1974: Cerf and Kahn -  minimalism, autonomy - no architecture for internal changes required interconnecting networks to interconnect networks  1976: Ethernet at Xerox PARC  best-effort service model  late70’s: proprietary  stateless routing architectures: DECnet, SNA,  decentralized control XNA define today’s Internet  1979: ARPAnet has 200 nodes architecture Introduction: 1-80  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: 1-81  Internet history 990, 2000s: commercialization, the Web, new applications  early 1990s: ARPAnet late 1990s – 2000s: decommissioned  more killer apps: instant  1991: NSF lifts restrictions messaging, P2P file sharing on commercial use of NSFnet  network security to (decommissioned, 1995) forefront  early 1990s: Web  est. 50 million host, 100 hypertext [Bush 1945, Nelson 1960’s] million+ users HTML, HTTP: Berners-Lee 1994: Mosaic, later Netscape  backbone links running at late 1990s: commercialization of Gbps the Web Introduction: 1-82  Internet history 2005-present: scale, SDN, mobility, cloud  aggressive deployment of broadband home access (10-100’s Mbps)  2008: software-defined networking (SDN)  increasing ubiquity of high-speed wireless access: 4G/5G, WiFi  service providers (Google, FB, Microsoft) create their own networks bypass commercial Internet to connect “close” to end user, providing “instantaneous” access to social media, search, video content, …  enterprises run their services in “cloud” (e.g., Amazon Web Services, Microsoft Azure)  rise of smartphones: more mobile than fixed devices on Internet (2017)  ~15B devices attached to Internet (2023, statista.com) Introduction: 1-83 Chapter 1: summary We’ve covered a “ton” of material!  Internet overview  what’s a protocol? You now have:  network edge, access network, core  context, packet-switching versus circuit- overview, switching vocabulary, Internet structure “feel” of  performance: loss, delay, networking throughput  more depth,  layering, service models detail, and fun to  security follow!  history Introduction: 1-84 Additional Chapter 1 slides Introduction: 1-85  ISO/OSI reference model Two layers not found in Internet protocol stack! application  presentation: allow applications to presentation interpret meaning of data, e.g., session encryption, compression, machine- specific conventions transport  session: synchronization, network checkpointing, recovery of data link exchange  Internet stack “missing” these layers! physical these services, if needed, must be The seven layer OSI/ISO implemented in application reference model needed? Introduction: 1-86  Services, Layering and Encapsulation M applicatio M applicatio message Ht M n Ht M n segment Hn Ht M Hn Ht M transport transport datagram Hl Hn Ht M network Hl Hn Ht M network frame link link source physical physical destination Introduction: 1-87 Wireshark application (www browser, packet email client) analyzer application OS packet Transport (TCP/UDP) capture copy of all Network (IP) Ethernet frames Link (Ethernet) (pcap) sent/received Physical Introduction: 1-88