Network Fundamentals Lecture 1 PDF

Network Fundamentals Lecture 1 Introduction INSEARCH CRICOS provider code: 00859D I UTS CRICOS provider code: 00099F Insearch Limited is a cont...

Network Fundamentals Lecture 1 Introduction INSEARCH CRICOS provider code: 00859D I UTS CRICOS provider code: 00099F Insearch Limited is a controlled entity of the University of Technology Sydney (UTS), and a registered private higher education provider of pathways to UTS. 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 local or packets (chunks of data) Internet regional ISP  routers, switches 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: 1-2 “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 Gaming devices Others? Internet phones Fitbit Introduction: 1-3 The Internet: a “nuts and bolts” view mobile network 4G  Internet: “network of networks” national or global ISP Interconnected ISPs  protocols are everywhere Skype IP Streaming video control sending, receiving of messages local or regional ISP e.g., HTTP (Web), streaming video, Skype, TCP, IP, WiFi, 4G, Ethernet home network content provider HTTP network datacenter  Internet standards network Ethernet RFC: Request for Comments IETF: Internet Engineering Task enterprise TCP Force network WiFi Introduction: 1-4 The Internet: a “services” view  Infrastructure that provides mobile network services to applications: national or global ISP Web, streaming video, multimedia teleconferencing, email, games, e- Streaming commerce, social media, inter- Skype video connected appliances, … local or regional ISP  provides programming interface to distributed applications: home network content provider “hooks” allowing sending/receiving HTTP network datacenter network apps to “connect” to, use Internet transport service provides service options, analogous enterprise to postal service network Introduction: 1-5 What’s a protocol? Human protocols: Network protocols:  “what’s the time?”  computers (devices) rather than humans  “I have a question”  all communication activity in Internet  introductions governed by protocols Rules for: Protocols define the format, order of … specific messages sent messages sent and received among … specific actions taken network entities, and actions taken when message received, or other events on message transmission, receipt Introduction: 1-6 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_ross 2:00 time Q: other human protocols? Introduction: 1-7  A closer look at network structure:  network edge: mobile network hosts: global ISP Clients (laptop, iPad, phone) servers, cloud Access networks: home network Home: Ethernet, WiFi regional ISP functional Institution: Ethernet, WiFi Wired: Ethernet, Cable, DSL, fibre media Wireless: WiFi, mobile  network core: interconnected routers network of networks institutional network Introduction: 1-8 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: 1-9 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 Access networks, physical media: regional ISP wired, wireless communication links 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 media: regional ISP wired, wireless communication links home network content provider network datacenter Network core: network  interconnected routers  network of networks enterprise network Introduction: 1-11 Access networks and physical media Q: How to connect end systems mobile network national or global ISP to edge router? 1. residential access nets 2. institutional access networks (school, company) local or 3. mobile access networks (WiFi, 4G/5G) regional ISP What to look for: home network content provider  transmission rate (bits per second) of access network datacenter network network?  shared or dedicated access among users? enterprise network Introduction: 1-12 Access network: digital subscriber line (DSL) central office telephone network DSL splitter modem DSLAM ISP voice, data transmitted at different frequencies over DSL access dedicated line to central office multiplexer  use existing dedicated telephone line to central office DSLAM data over DSL phone line goes to Internet voice over DSL phone line goes to telephone net  < 2.5 Mbps upstream transmission rate (typically < 1 Mbps)  < 24 Mbps downstream transmission rate (typically < 10 Mbps) 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 network: home network wireless devices to/from headend or central office often combined in single box what about NBN? cable or DSL modem wireless access router, firewall, NAT point (54 Mbps) wired Ethernet (1 Gbps) 1-16 Enterprise access networks (Ethernet) institutional link to ISP (Internet) institutional router Ethernet institutional mail, switch web servers  typically used in companies, universities, etc.  10 Mbps, 100Mbps, 1Gbps, 10Gbps transmission rates  today, end systems typically connect into Ethernet switch 1-17 Wireless access networks Shared wireless access network connects end system to router  via base station aka “access point” Wireless local area networks Wide-area cellular access networks (WLANs)  provided by mobile, cellular network  typically within or around operator (10’s km) building (~100 ft)  10’s Mbps  802.11b/g/n (WiFi): 11, 54, 450  4G(LTE) cellular networks Mbps transmission rate  5G to Internet to Internet Introduction: 1-18 Host: sends packets of data host sending function:  takes application message  breaks into smaller chunks, two packets, known as packets, of length L bits L bits each  transmits packet into access 2 1 network at transmission rate R link transmission rate, aka link host capacity, aka link bandwidth R: link transmission rate packet time needed to L (bits) transmission = transmit L-bit = delay packet into link R (bits/sec) Introduction: 1-19 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 Ethernet between transmitter & Category 6: 10Gbps Ethernet receiver  guided media: signals propagate in solid media: copper, fiber, coax  unguided media: signals propagate freely, e.g., radio Introduction: 1-20 Links: physical media Coaxial cable: Fiber optic cable:  two concentric copper conductors  glass fiber carrying light pulses, each pulse a bit  bidirectional  high-speed operation:  broadband: high-speed point-to-point multiple frequency channels on cable transmission (10’s-100’s Gbps) 100’s Mbps per channel  low error rate: repeaters spaced far apart immune to electromagnetic noise Introduction: 1-21 Links: physical media Wireless radio Radio link types:  signal carried in various  Wireless LAN (WiFi) “bands” in electromagnetic 10-100’s Mbps; 10’s of meters spectrum  wide-area (e.g., 4G cellular)  no physical “wire” 10’s Mbps over ~10 Km  broadcast, “half-duplex”  Bluetooth: cable replacement (sender to receiver) short distances, limited rates  propagation environment effects:  terrestrial microwave reflection point-to-point; 45 Mbps channels obstruction by objects  satellite Interference/noise up to 45 Mbps per channel 270 msec end-end delay Introduction: 1-22 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 local or regional ISP router to the next, across links on path from source to destination home network content provider each packet transmitted at full link network datacenter network capacity enterprise network Introduction: 1-23 Host: sends packets of data host sending function:  takes application message two packets,  breaks into smaller chunks, known as L bits each packets, of length L bits  transmits packet into access network at transmission rate R 2 1 link transmission rate, aka link R: link transmission rate capacity, aka link bandwidth host Higher R  Faster: measured in Delay packet time needed to L (bits) transmission = transmit L-bit = delay packet into link R (bits/sec) 1-24  Packet-switching: store-and-forward L bits per packet 3 2 1 source destination R bps R bps  transmission delay: takes L/R seconds to transmit One-hop numerical example: (push out) L-bit packet into link at R bps  L = 10 Kbits  store and forward: entire packet must arrive at  R = 100 Mbps router before it can be transmitted on next link  one-hop transmission delay  End-end delay: 2L/R(above), assuming zero = 0.1 msec propagation delay (more on delay shortly) Introduction: 1-25 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 router fills up Introduction: 1-26  Two key network-core functions routing algorithm Routing: Forwarding: local local forwarding forwarding table table  global action: header value output link determine source-  aka “switching” 0100 3 destination paths  local action: 0101 2 move arriving 0111 1001 2 1 taken by packets packets from  routing algorithms router’s input link 1 to appropriate router output link 3 2 destination address in arriving packet’s header Introduction: 1-27 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 * Check out the online interactive exercises for more examples: http://gaia.cs.umass.edu/kurose_ross/interactive Introduction: 1-28 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 of that narrow time band Time Division Multiplexing (TDM) frequency  time divided into slots  each call allocated periodic slot(s), can transmit at maximum rate of (wider) time frequency band (only) during its time slot(s) Introduction: 1-29 Internet structure: 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 The goal is to interconnect the access ISPs so that all end access access net systems can send packets to net access net each other access net access net access net access access net access net net 1-30 Internet structure: a “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: access access net O(N2) connections. net access net access net access net access net access access net access net net Introduction: 1-31 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 net access net access access net net access access net net global access net ISP access net access net access net access net access net access access net access net net Introduction: 1-32 Internet structure: a “network of networks” But if one global ISP is viable business, there will be competitors …. access access net net access net access 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 net Introduction: 1-33 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 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 net Introduction: 1-34 Internet structure: a “network of networks” … and regional networks may arise to connect access nets to ISPs 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 regional ISP access net access access net access net net Introduction: 1-35 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 access net 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 ISP C net access net access net regional ISP access net access access net access net net Introduction: 1-36  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: 1-37