Chapter_1_v8.1_AAST.pdf

CC431 Computer Networks Textbook (Required) Computer Networking: A Top-Down Approach 8th Edition Jim Kurose, Keith Ross Pearson, 2020 The book is available via Moodle / Kortext Introduction: 1-2 Course Organization Text: Kurose and Ross (8th editions) Have...

CC431 Computer Networks Textbook (Required) Computer Networking: A Top-Down Approach 8th Edition Jim Kurose, Keith Ross Pearson, 2020 The book is available via Moodle / Kortext Introduction: 1-2 Course Organization Text: Kurose and Ross (8th editions) Have the ppt with you during lectures to take notes 7th: 1 exam (20 marks each), 5 lab + 5 assignments/quizzes 12th: 1 exam (15 marks) + 5 quizzes Pre-final: 10 marks (lab project) Final: 40 marks Course Online Videos by Jim Kurose: http://gaia.cs.umass.edu/kurose_ross/ http://gaia.cs.umass.edu/kurose_ross/online_lectures.htm 1-3 Introduction Course Organization Lectures: Dr. Ahmed Bendary Teaching Assistant: Eng. Nourhan Tarek 2-4 Introduction  Course Structure Chapter-1: Introduction and Overview Chapter-2: Application Layer (HTTP, SMTP, etc.) application application transport transport Chapter-3: Transport Layer (UDP and TCP) network network linklink Chapter-4: Network Layer (Routing Algorithms, IP address, etc.) physical physical Layered Internet protocol stack Chapter-5: Link Layer (Switches, Multiple Access Protocols, etc.) 2-5 Introduction  Chapter 1 Introduction  Based on slides from the book website + Modifications by Prof. Waleed Fakhr and Prof. Yahya Mohasseb.  All material copyright 1996-2020 J.F Kurose and K.W. Ross, All Rights Reserved Introduction: 1-6 Chapter 1: introduction Chapter Goal: Get “feel,” “big picture,” introduction to terminology more depth, detail later in course Overview/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 Key architectural principles: protocol layering and service models Security Introduction: 1-7 History 1.1 What is the Internet? The Internet: a “nuts and bolts: ” view Billions of connected mobile network The Core computing devices: national or global ISP  hosts = end systems  running network apps at Internet’s “edge” Packet switches: forward local or packets (chunks of data) Internet regional ISP  routers, switches home network content Communication links provider Network network datacenter  fiber, copper, radio, satellite of network  transmission rate: bandwidth Networks Networks The Edge enterprise  collection of devices, routers, network links: managed by an organization 1.1 What is the Internet? The Internet: a “nuts and bolts: ” view Billions of connected mobile network computing devices: national or global ISP  hosts = end systems The Edge  running network apps at Internet’s “edge” Packet switches: forward local or packets (chunks of data) Internet regional ISP  routers, switches The Core home network content Communication links provider network datacenter  fiber, copper, radio, satellite network  transmission rate: bandwidth Network Networks of enterprise Networks  collection of devices, routers, network links: managed by an organization  1- The network edge: “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, The Edge scooters bed Others? mattress Gaming devices Internet phones Fitbit Introduction: 1-10 1.1 What is the Internet? The Internet: a “nuts and bolts” view mobile network Internet: “network of networks” 4G national or global ISP Interconnected ISPs Streaming  protocols are everywhere Skype IP video control sending, receiving of messages local or e.g., HTTP (Web), streaming video, regional ISP Skype, TCP, IP, WiFi, 4G, Ethernet home network content provider HTTP network datacenter  Internet “standards” network Ethernet IETF: Internet Engineering Task Force TCP RFC: Request for Comments enterprise network Introduction: 1-11 WiFi 1.1 What is the Internet? The Internet: a “services” view mobile network Infrastructure/Platform that provides national or global ISP programming (socket) interface to distributed applications Streaming i.e., provides services to applications: Skype video Web, streaming video, multimedia local or teleconferencing, email, games, e- regional ISP commerce, social media, inter-connected home network content appliances, … provider HTTP network datacenter Internet socket interface is a set of rules that network the sending program must follow so that the Internet can deliver the data to the destination program. enterprise network Introduction: 1-12 1.1.3 What’s a protocol? Human protocols: Rules for: Network protocols:  “what’s the time?” … specific messages sent  computers (devices) rather … specific actions taken when than humans  “I have a question” message received, or other  all communication activity in  introductions events Internet governed by protocols Hi TCP connection request Hi TCP connection response Got the GET http://gaia.cs.umass.edu/kurose_ross time? 2:00 time Introduction: 1-13 1.1.3 What’s a protocol? Protocols define the format, order of , and actions taken on messages sent and received among network entities CC331 Slides 1.2 - The network edge: end systems (hosts): run application programs e.g. Web browsing, email at “edge of network” peer-peer 1- client/server model  client host requests, receives service from always-on server client/server  e.g. Web browser/server; email client/server 2- peer-peer model:  minimal (or no) use of dedicated servers  e.g. Skype, BitTorrent 1-15 Introduction 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: 1-16 1.2 - The network edge: End Systems (Hosts) mobile network - Clients and Servers (often in data centers) national or global ISP Data Centers: engines behind the Internet applications Internet companies such as Google, Microsoft, Amazon, local or and Alibaba have built massive data centers regional ISP Example: Amazon Web Services (AWS) (Amazon data centers) home network content serve three purposes: provider network datacenter 1. Amazon e-commerce pages. network 2. Massively parallel computing infrastructures for Amazon- specific data processing tasks. 3. Cloud computing to other companies. enterprise network Introduction: 1-17 1.2 - The network edge: Data center networks: mobile network national or global ISP high-bandwidth links (10s to 100s 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 Computing Center (mghpcc.org) enterprise https://www.digitalinformationworld.com/2019/06/the-world-s- network most-creative-data-centers-infographic.html Introduction: 1-18 1.2 - The network edge: 1.2.1. Access Networks (network access technologies) mobile network — the network that physically connects an end national or global ISP system to the first router “edge router”. Q: How to connect end systems to edge router? (which connects subnet to other subnets)? local or regional ISP Residential access nets home network content Enterprise/institutional access networks (school, company) provider network Mobile access networks (WiFi, 4G/5G) datacenter network keep in mind:  bandwidth (bits per second) of access network? enterprise network  shared or dedicated? Introduction: 1-19 1.2 - The network edge: 1.2.1. Access networks: cable-based access cable headend … cable splitter modem DoCSIS Standard (Cable TV) C Not available in Egypt 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 1.2 - The network edge: 1.2.1. 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: 1-21 1.2 - The network edge: 1.2.1. Access networks: cable-based access cable headend … central office cable splitter modem Cable Modem Termination System (CMTS) data, TV transmitted at different frequencies over shared cable distribution network ISP  HFC: hybrid fiber coax Asymmetric: up to 40 Mbps – 1.2 Gbps downstream transmission rate, 30-100 Mbps upstream transmission rate  Fiber to the home (FTTH) attaches homes to ISP router Introduction: 1-22 1.2 - The network edge: 1.2.1. Access networks: Fiber to the home (FTTH) optical network terminator optical line terminator  Optical-distribution network (~ Gbps) active optical networks (AONs) and passive optical networks (PONs) Introduction: 1-23 1.2 - The network edge: 1.2.1. 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 access router, firewall, NAT point (54, 450 Mbps) wired Ethernet (1 Gbps) Introduction: 1-24 1.2 - The network edge: 1.2.1. Access networks: 5G fixed wireless Wireless and wired devices Using beam-forming technology, data is sent wirelessly from a provider’s base station to the a modem in the home without installing costly and failure-prone cabling Introduction: 1-25 1.2 - The network edge: 1.2.1. Access networks: enterprise networks LANs  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 802.11b/g/n: wireless access points at 11, 54, 450 Mbps (~100 ft) Wireless local area networks (WLANs) Enterprise link to ISP (Internet) institutional router Ethernet institutional mail, switch web servers Introduction: 1-26 1.2 - The network edge: 1.2.1. Access networks: Wireless access networks Shared wireless access network connects end system to router  via base station aka “access point” Wireless local area networks (WLANs) Wide-area cellular access networks  typically within or around building (~100 ft)  provided by mobile, cellular network operator (10’s km)  802.11b/g/n (WiFi): 11, 54, 450 Mbps  10’s Mbps  4G cellular networks (5G coming) to Internet to Internet 1.2 - The network edge: A host sends packets of data through a link! host sending function:  takes application message two packets,  breaks into smaller chunks, L bits each known as packets, of length L bits  transmits packet into access 2 1 network at transmission rate R host link transmission rate, aka link R: link transmission rate capacity, aka link bandwidth time needed to L (bits) Packet transmission delay = transmit L-bit = Introduction: 1-28 packet into link R (bits/sec) 1.2 - The network edge: 1.2.2. Links: physical media  bit: propagates between Unshielded twisted pair (UTP) transmitter/receiver pairs  two insulated copper wires (10 Mbps)  physical link: what lies between Category 5: 100 Mbps, 1 Gbps Ethernet transmitter & receiver Category 6: 10Gbps Ethernet  guided media: signals propagate in solid media: copper, fiber, coax  unguided media: signals propagate freely, e.g., radio CC331 Slides Introduction: 1-29 1.2 - The network edge: 1.2.2. Links: physical media Coaxial cable: Fiber optic cable:  Glass fiber carrying light pulses  two concentric copper conductors  High-speed point-to-point  bidirectional transmission (10’s-100’s Gbps)  broadband:  Low error rate up to 100 kilometers : multiple frequency channels on cable repeaters spaced far apart 100’s Mbps per channel immune to electromagnetic noise very hard to tap CC331 Slides Introduction: 1-30 1.2 - The network edge: 1.2.2. Links: physical media Wireless radio Radio link types:  signal carried in various “bands” in  Wireless LAN (WiFi) electromagnetic spectrum 10-100’s Mbps; 10’s of meters  no physical “wire”  Wide-area Radio(e.g., 5G cellular) 10’s Mbps over ~10 Km  broadcast, “half-duplex” (sender to receiver)  Bluetooth: cable replacement  propagation environment effects: short distances, limited rates reflection  Terrestrial microwave obstruction by objects point-to-point; 45 Mbps channels Interference/noise  Satellite up to 45 Mbps per channel Introduction: 1-31 270 msec end-end delay 1.2 - The network edge: 1.2.2. Links: physical media Radio link types: Wireless radio  Wireless LAN (WiFi)  signal carried in various “bands” in electromagnetic spectrum 10-100’s Mbps; 10’s of meters  no physical “wire”  wide-area (e.g., 4G cellular)  broadcast, “half-duplex” (sender to receiver) 10’s Mbps over ~10 Km  Bluetooth: cable replacement  propagation environment effects: short distances, limited rates reflection  terrestrial microwave obstruction by objects point-to-point; 45 Mbps channels Interference/noise  satellite up to 45 Mbps per channel 270 msec end-end delay CC331 Slides Introduction: 1-32 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: 1-33 1.3 The network core mesh of interconnected routers mobile network national or global ISP packet-switching: hosts break application- layer messages into packets network forwards packets from one router to the next, across links on path local or regional ISP from source to destination each packet transmitted at full link home network content provider capacity network datacenter network Packet-switching is used in internet vs circuit-switching used in Telephone calls. enterprise network Introduction: 1-34 1.3 The network core Two key network-core functions Forwarding: Routing: routing algorithm “switching”  Global action (Decision): determine source- local local forwarding forwarding table table Local action: move header value output link destination paths taken arriving packets 0100 3 by packets. from router’s input 0101 0111 2 2  routing algorithms 1001 1 running in the link to appropriate background router output link 1 3 2 destination address in arriving Introduction: 1-35 packet’s header 1.4 Networks Wide Area Networks - Types of switched networks Communication Networks Broadcast Switched CC331 Slides Networks Networks Circuit Packet Switched Switched Network Network Virtual Datagram Circuit Network Network The network needs to be designed to route the traffic properly between sources/destinations and allocate suitable capacity on the links to avoid excessive delays (packet-switching) or blocking (circuit-switching).  1.3 The network core 1.3.1 Packet-switching: store-and-forward packet transmission delay: 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 = 10 Kbits L bits  R = 100 Mbps per packet 3 2 1  one-hop transmission delay R bps R bps = 0.1 msec source destination Introduction: 1-37 1.3 The network core 1.3.1 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: 1-38 1.3 The network core 1.3.1 Packet-switching: queueing 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) is full R = 100 Mb/s A C D B R = 1.5 Mb/s E queue of packets waiting for transmission over output link Introduction: 1-39 1.3 The network core 1.3.2 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 (minimal delay) circuit segment idle if not used by call (no sharing – less efficient) call setup required  commonly used in traditional telephone networks * Check out the online interactive exercises for more examples: http://gaia.cs.umass.edu/kurose_ross/interactive Introduction: 1-40 1.3 The network core 1.3.2 Circuit switching: FDM and TDM Frequency Division Multiplexing (FDM) 4 users  optical, electromagnetic frequencies divided frequency into (narrow) frequency bands  each call allocated its own band, can transmit at max rate of that narrow band time Time Division Multiplexing (TDM) frequency  time divided into slots  each call allocated periodic slot(s), can transmit at maximum rate of (wider) frequency band (only) during its time time slot(s) Introduction: 1-41 1.3 The network core 1.3.2 Circuit switching Numerical example How long does it take to send a file of 640,000 bits from host A to host B over a circuit-switched network? All links are 1.536 Mbps Each link uses TDM with 24 slots/sec 500 msec to establish end-to-end circuit  Solution:  Each circuit has a transmission rate of 1.536Mbps/24 = 64kbps.  So, it takes 640kb/64kbps = 10 sec. to transmit the file.  To this 10sec we add 0.5 sec, to get 10.5 seconds to send the file. 1-42 Introduction 1.3 The network core 1.3.2 Circuit switching – Comparison To Packet 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 users, Q: how did we get value 0.0004? probability > 10 active at same time is less than 0.0004 * A: HW problem (for those with course in probability only) * Check out the online interactive exercises for more examples: http://gaia.cs.umass.edu/kurose_ross/interactive Introduction: 1-43 1.3 The network core 1.3.2 Circuit switching – Comparison To Packet Switching Is packet switching a better in all cases?  Great for “bursty” data – sometimes has data to send, but at other times not resource sharing simpler, no call setup (Remember: for Datagram not for “Virtual Circuit”!)  But, excessive congestion possible! packet delay and loss due to buffer overflow protocols needed for reliable data transfer, congestion control Introduction: 1-44 1.3 The network core 1.3.3. Network of Networks hosts connect to Internet via access mobile network national or global ISP Internet Service Providers (ISPs) access ISPs in turn must be interconnected so that any two hosts (anywhere!) can send packets to each other local or resulting network of networks is very regional ISP complex home network content evolution driven by economics, provider network national rather than by performance datacenter network considerations. enterprise Let’s take a stepwise approach to network describe current Internet structure 1.3 The network core 1.3.3. Network of Networks Question: given millions of access ISPs, how to connect them together? access access net net access net access access net net access access net net access access net net access net access net access net access net access access net access net Introduction: 1-46 net 1.3 The network core 1.3.3. Network of Networks Question: given millions of access ISPs, how to connect them together? access access net net access net access access net net access access net net connecting each access ISP to each other directly doesn’t scale: Option 1: access access net O(N2) connections. net Full Connectivity Does NOT work access net access net access net access net access access net access net Introduction: 1-47 net  1.3 The network core 1.3.3. Network of Networks Question: given millions of access ISPs, how to connect them together? access access net net access net access access net net access access net net global Option 2: access ISP access net net Connect each access ISP to one global transit ISP (imaginary)? access net access Customer and provider ISPs access net have economic agreement. net access net access access net access net Introduction: 1-48 net 1.3 The network core 1.3.3. Network of Networks Question: given millions of access ISPs, how to connect them together? Option 3: global ISP is a viable business! access access net net access Multiple competing global ISP access net access net net access access net net ISP A access net ISP B access net access ISP C net access net access net access net access access net access net Introduction: 1-49 net 1.3 The network core 1.3.3. Network of Networks Question: given millions of access ISPs, how to connect them together? Option 4: connected ISPs Internet exchange point access access net net access net access access net net IXP access access net net ISP A access net IXP ISP B access net access ISP C net access net access net peering link access net access access net access net Introduction: 1-50 net 1.3 The network core 1.3.3. Network of Networks Question: given millions of access ISPs, how to connect them together? Option 4: connected ISPs Points of presence (PoPs): A group of one or more routers (at the same location) in the provider’s network where customer ISPs can connect into the provider ISP. A customer network leases a high-speed link from a third-party telecommunications provider to directly connect one of its routers to a router at the PoP. Exists in all levels of the hierarchy (except for access ISP). Multi-homing: (except for tier-1 ISPs) Any ISP may choose to connect to two or more provider ISPs. e.g., multihome with two regional ISPs, or with two regional ISPs and a tier-1 ISP. Peering: nearby ISPs at the same level of the hierarchy can peer, that is, they can directly connect their networks together so that all the traffic between them passes over the direct connection (typically settlement-free) rather than through upstream to reduce some costs. Internet Exchange Point (IXP): a third-party meeting point where multiple ISPs can peer together. Introduction: 1-51 1.3 The network core 1.3.3. Network of Networks Question: given millions of access ISPs, how to connect them together? Option 5: access access net net Regional networks connect access net access access nets to ISPs access net net IXP access access net net ISP A access net IXP ISP B access net access ISP C net access net access net regional ISP access net access access net access net Introduction: 1-52 net 1.3 The network core 1.3.3. Network of Networks Question: given millions of access ISPs, how to connect them together? Option 6: Content-provider networks (Google/Microsoft etc) may run their access access net net own network, to bring services, content close to end users access net access access net net IXP access access net net ISP A Content provider network access net IXP ISP B access net access ISP C net access net access net regional ISP access net access access net access net Introduction: 1-53 net  1.3 The network core 1.3.3. 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: 1-54 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: 1-55 1.4 Delay, Loss & Throughput in Packet-Switched Networks How do packet delay and loss occur? packets queue in the router buffer, 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: 1-56 Task 1:  https://media.pearsoncmg.com/aw/ecs_kurose_compnetwork_7/cw /content/interactiveanimations/transmission-vs-propogation- delay/transmission-propagation-delay-ch1/index.html  Work the transmission versus propagation delay Java applet for all the possible cases and make a 1 page report. Introduction 2-57 1.4 Delay, Loss & Throughput in Packet-Switched Networks How do packet delay and loss occur? dnodal = dproc + dqueue + dtrans + dprop transmission A propagation B nodal processing queueing dproc: nodal processing  check bit errors dqueue: queueing delay  determine output link  time waiting at output link for transmission  typically < microsecs  depends on congestion level of router Introduction: 1-58 1.4 Delay, Loss & Throughput in Packet-Switched Networks How do packet delay and loss occur? transmission A propagation B nodal processing queueing dnodal = dproc + dqueue + dtrans + dprop dtrans: transmission delay: dprop: propagation delay:  L: packet length (bits)  d: length of physical link  R: link transmission rate (bps)  s: propagation speed (~2x108 m/sec)  dtrans = L/R  dprop = d/s dtrans and dprop Introduction: 1-59 very different 1.4 Delay, Loss & Throughput in Packet-Switched Networks Packet delay - Caravan analogy 100 km 100 km ten-car caravan toll booth toll booth toll booth (aka 10-bit packet) (aka link)  car ~ bit; caravan ~ packet; toll  time to “push” entire caravan service ~ link transmission through toll booth onto highway =  toll booth takes 12 sec to service car 12*10 = 120 sec (bit transmission time)  time for last car to propagate from  “propagate” at 100 km/hr 1st to 2nd toll both: 100km/(100km/hr) = 1 hr  Q: How long until caravan is lined up before 2nd toll booth?  A: 62 minutes Introduction: 1-60 1.4 Delay, Loss & Throughput in Packet-Switched Networks Packet delay - Caravan analogy 100 km 100 km ten-car caravan toll booth toll booth (aka 10-bit packet) (aka router)  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: 1-61 Packet queueing delay (revisited)  a: average packet arrival rate average queueing delay  L: packet length (bits)  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 small La/R ~ 0  La/R → 1: avg. queueing delay large  La/R > 1: more “work” arriving is more than can be serviced - average delay infinite! Introduction: 1-62 La/R → 1 Task 2: Packet Loss https://media.pearsoncmg.com/aw/ecs_kurose_compnetwork_7/cw/content/interactiveanimations/queuing -loss-applet/index.html Run the Queuing and Loss Applet for emission rate = transmission rate = 350 packets/sec, explain exactly what will happen and comment (repeat for both= 500 packets/sec) Repeat for emission rate=500 and transmission rate=350 Repeat for emission rate=350 and transmission rate=500. 1-63 Introduction “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: 1-64 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-fa5-1-0.gw.umass.edu 4 jn1-at1-0-0-19.wor.vbns.net (204.147.132.129) 16 ms 11 ms 13 ms 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 a transatlantic fiber-optic 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: 1-65 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: 1-66  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 carry linkthat pipe capacity can carry Rsfluid bits/sec at rate Rfluid c bits/sec at rate serverserver, sends with bits (fluid) into pipe (Rs bits/sec) (Rc bits/sec) file of F bits to send to client Introduction: 1-67 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 link on end-end path that constrains end-end throughput Introduction: 1-68 Throughput: network scenario  per-connection end- Rs end throughput: Rs Rs min(Rc,Rs,R/10)  in practice: Rc or Rs is R often bottleneck Rc Rc 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: 1-69 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 Protocol “layers” and reference models Networks are complex, Question: is there any with many “pieces”: hope of organizing  hosts structure of network?  routers and/or our discussion  links of various media of networks?  applications  protocols  hardware, software Introduction: 1-71 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: 1-72 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: 1-73 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: 1-74 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 source to destination network IP, routing protocols link  link: data transfer between neighboring network elements physical Ethernet, 802.11 (WiFi), PPP  physical: bits “on the wire” Introduction: 1-75  Services, Layering and Encapsulation M application Application exchanges messages to implement some application application service using services of transport layer Ht M transport Transport-layer protocol transfers M (e.g., reliably) from transport one process to another, using services of network layer network  transport-layer protocol encapsulates network application-layer message, M, with link transport layer-layer header Ht to create a link transport-layer segment Ht used by transport layer protocol to physical implement its service physical source destination Introduction: 1-76  Services, Layering and Encapsulation M application application Ht M transport Transport-layer protocol transfers M (e.g., reliably) from transport one process to another, using services of network layer network Hn Ht M network Network-layer protocol transfers transport-layer segment [Ht | M] from one host to another, using link layer services link link  network-layer protocol encapsulates transport-layer segment [Ht | M] with physical network layer-layer header Hn to create a physical network-layer datagram source Hn used by network layer protocol to destination implement its service Introduction: 1-77  Services, Layering and Encapsulation M application application Ht M transport transport network Hn Ht M network Network-layer protocol transfers transport-layer segment [Ht | M] from one host to another, using link layer services link Hl Hn Ht M link Link-layer protocol transfers datagram [Hn| [Ht |M] from host to neighboring host, using network-layer services physical physical  link-layer protocol encapsulates network datagram [Hn| [Ht |M], with link-layer header source Hl to create a link-layer frame destination Introduction: 1-78  Services, Layering and Encapsulation M application M application message Ht M transport Ht M transport segment network Hn Ht M Hn Ht M network datagram link Hl Hn Ht M Hl Hn Ht M link frame physical physical source destination Introduction: 1-79  message M source application Encapsulation: an segment datagram Hn Ht Ht M M transport network end-end view 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: 1-80 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: 1-81 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: 1-82 Bad guys: put malware into hosts via Internet  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. DDoS attacks Introduction1-83 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: 1-84 Bad guys: fake identity IP spoofing: injection of packet with false source address A C src:B dest:A payload B Introduction: 1-85 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 botnet) 3. send packets to target target from compromised hosts Introduction: 1-86 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: 1-87 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: 1-88 Internet history 1961-1972: Early packet-switching principles  1961: Kleinrock - queueing  1972: theory shows effectiveness of ARPAnet public demo packet-switching NCP (Network Control Protocol)  1964: Baran - packet-switching first host-host protocol in military nets first e-mail program  1967: ARPAnet conceived by ARPAnet has 15 nodes Advanced Research Projects Agency  1969: first ARPAnet node operational Internet history 1972-1980: Internetworking, new and proprietary networks  1970: ALOHAnet satellite Cerf and Kahn’s internetworking network in Hawaii principles:  1974: Cerf and Kahn -  minimalism, autonomy - no architecture for interconnecting internal changes required to networks interconnect networks  best-effort service model  1976: Ethernet at Xerox PARC  stateless routing  late70’s: proprietary  decentralized control architectures: DECnet, SNA, XNA define today’s Internet architecture  1979: ARPAnet has 200 nodes Introduction: 1-90 Internet history 1980-1990: new protocols, a proliferation of networks  1983: deployment of TCP/IP  new national networks: CSnet,  1982: smtp e-mail protocol BITnet, NSFnet, Minitel defined  100,000 hosts connected to  1983: DNS defined for name- confederation of networks to-IP-address translation  1985: ftp protocol defined  1988: TCP congestion control Introduction: 1-91 Internet history 1990, 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 forefront (decommissioned, 1995)  est. 50 million host, 100 million+  early 1990s: Web users hypertext [Bush 1945, Nelson 1960’s] HTML, HTTP: Berners-Lee  backbone links running at Gbps 1994: Mosaic, later Netscape late 1990s: commercialization of the Web Introduction: 1-92 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)  ~18B devices attached to Internet (2017) Introduction: 1-93 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, overview, packet-switching versus circuit- switching vocabulary, “feel” Internet structure of networking  performance: loss, delay, throughput  more depth,  layering, service models detail, and fun to  security follow!  history Introduction: 1-94 Additional Chapter 1 slides Introduction: 1-95  ISO/OSI reference model Two layers not found in Internet application protocol stack! presentation  presentation: allow applications to interpret meaning of data, e.g., encryption, session compression, machine-specific conventions transport  session: synchronization, checkpointing, network recovery of data exchange link  Internet stack “missing” these layers! physical these services, if needed, must be implemented in application The seven layer OSI/ISO reference model needed? Introduction: 1-96 Wireshark application (www browser, packet email client) analyzer application OS packet Transport (TCP/UDP) Network (IP) capture copy of all Ethernet frames Link (Ethernet) (pcap) sent/received Physical Introduction: 1-97