CS683- Security and Privacy: Overview of Computer Networking (1/2) Karim Eldefrawy keldefrawy@usfca.edu University of San Francisco
A Good Text Book (if you need one) 1/24/18 Introduction 1-2
Networking Overview: Roadmap overview : our goal: v what ’ s the Internet? v get “ feel ” and v what ’ s a protocol? terminology v network edge; hosts, access net, v overview of physical media computer v network core: packet/circuit networking switching, Internet structure v approach: v performance: loss, delay, throughput § use Internet as v security example v protocol layers, service models v history 1/24/18 Introduction 1-3
Networking Overview: Roadmap 1.1 what is the Internet? 1.2 network edge § end systems, access networks, links 1.3 network core § packet switching, circuit switching, network structure 1.4 delay, loss, throughput in networks 1.5 protocol layers, service models 1.6 networks under attack: security 1.7 history 1/24/18 Introduction 1-4
What ’ s the Internet: “ nuts and bolts ” view PC v millions of connected mobile network computing devices: server § hosts = end systems global ISP wireless laptop § running network apps smartphone home v communication links network regional ISP § fiber, copper, radio, wireless satellite links wired § transmission rate: links bandwidth v Packet switches: forward packets (chunks of data) institutional router network § routers and switches 1/24/18 Introduction 1-5
“ Fun ” internet appliances Web-enabled toaster + weather forecaster IP picture frame http://www.ceiva.com/ Tweet-a-watt: monitor energy use Slingbox: watch, control cable TV remotely Internet Internet phones refrigerator 1/24/18 Introduction 1-6
What ’ s the Internet: “ nuts and bolts ” view mobile network v Internet: “ network of networks ” § Interconnected Internet Service global ISP Providers (ISPs) v Protocols control sending, receiving of messages (msgs) and home data network regional ISP § e.g., TCP, IP, HTTP, Skype, 802.11 v Internet standards § RFC: Request for comments § IETF: Internet Engineering Task Force institutional network 1/24/18 Introduction 1-7
What ’ s the Internet: a service view mobile network v Infrastructure that provides services to applications: global ISP § Web, VoIP, email, games, e- commerce, social nets, … home v provides programming network regional ISP interface to apps § hooks that allow sending and receiving app programs to “ connect ” to Internet § provides service options, analogous to postal service institutional network 1/24/18 Introduction 1-8
What ’ s a protocol? human protocols: network protocols: v “ what ’ s the time? ” v machines rather than humans v “ I have a question ” v all communication activity v introductions in Internet governed by protocols … specific msgs sent … specific actions taken when msgs received, or protocols define format, order other events of msgs sent and received among network entities, and actions taken on msg transmission, receipt 1/24/18 Introduction 1-9
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://www.awl.com/kurose-ross 2:00 <file> time Q: other human protocols? 1/24/18 Introduction 1-10
Networking Overview: Roadmap 1.1 what is the Internet? 1.2 network edge § end systems, access networks, links 1.3 network core § packet switching, circuit switching, network structure 1.4 delay, loss, throughput in networks 1.5 protocol layers, service models 1.6 networks under attack: security 1.7 history 1/24/18 Introduction 1-11
A closer look at network structure: v network edge: mobile network § hosts: clients and servers global ISP § servers often in data centers home v access networks, physical network regional ISP media: wired, wireless communication links v network core: § interconnected routers § network of networks institutional network 1/24/18 Introduction 1-12
Access networks and physical media Q: How to connect end systems to edge router? v residential access nets v institutional access networks (school, university, company) v mobile access networks keep in mind: v bandwidth (bits per second) of access network? v shared or dedicated? 1/24/18 Introduction 1-13
Access net: digital subscriber line (DSL) central office telephone network DSL splitter modem DSLAM ISP voice, data transmitted at different frequencies over DSL access multiplexer dedicated line to central office v 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 v < 2.5 Mbps upstream transmission rate (typically < 1 Mbps) v < 24 Mbps downstream transmission rate (typically < 10 Mbps) 1/24/18 Introduction 1-14
Access net: cable network cable headend … cable splitter modem C O N V V V V V V D D T I I I I I I A A R D D D D D D T T O E E E E E E A A L O O O O O O 1 2 3 4 5 6 7 8 9 Channels frequency division multiplexing: different channels transmitted in different frequency bands 1/24/18 Introduction 1-15
Access net: cable network cable headend … cable splitter cable modem CMTS modem termination system data, TV transmitted at different frequencies over shared cable ISP distribution network v HFC: hybrid fiber coax § asymmetric: up to 30Mbps downstream transmission rate, 2 Mbps upstream transmission rate v network of cable, fiber attaches homes to ISP router § homes share access network to cable headend § unlike DSL, which has dedicated access to central office 1/24/18 Introduction 1-16
Access net: home network wireless devices to/from headend or central office often combined in single box cable or DSL modem router, firewall, NAT wireless access point (54 Mbps) wired Ethernet (100 Mbps) 1/24/18 Introduction 1-17
Enterprise access networks (Ethernet) institutional link to ISP (Internet) institutional router Ethernet institutional mail, switch web servers v typically used in companies, universities, etc… v 10 Mbps, 100Mbps, 1Gbps, 10Gbps transmission rates v today, end systems typically connect into Ethernet switch 1/24/18 Introduction 1-18
Wireless access networks v shared wireless access network connects end system to router § via base station a.k.a “ access point ” wide-area wireless access wireless LANs: § provided by telco (cellular) § within building (100 ft) operator, 10 ’ s km § 802.11b/g (WiFi): 11, 54 Mbps § between 1 and 10 Mbps transmission rate § 3G, 4G: LTE to Internet to Internet 1/24/18 Introduction 1-19
Host: sends packets of data host sending function: v takes application message or data two packets, L bits each v breaks into smaller chunks, known as packets , of length L bits v transmits packet into access 1 2 network at transmission rate R R: link transmission rate host § link transmission rate, a.k.a link capacity, a.k.a link bandwidth packet time needed to L (bits) = = transmission transmit L -bit R (bits/sec) delay packet into link 1/24/18 Introduction 1-20
Physical media v bit: propagates between transmitter/receiver pairs twisted pair (TP) v physical link: what lies between transmitter & v two insulated copper receiver wires v guided media: § Category 5: 100 Mbps, 1 Gpbs Ethernet § signals propagate in solid § Category 6: 10Gbps media: copper, fiber, coax v unguided media: § signals propagate freely, e.g., radio 1/24/18 Introduction 1-21
Physical media: coax, fiber coaxial cable: fiber optic cable: v two concentric copper v glass fiber carrying light conductors pulses, each pulse a bit v bidirectional v high-speed operation: v broadband: § high-speed point-to-point transmission (e.g., 10 ’ s-100 ’ s § multiple channels on cable Gpbs transmission rate) § HFC v low error rate: § repeaters spaced far apart § immune to electromagnetic noise 1/24/18 Introduction 1-22
Physical media: radio radio link types: v signal carried in electromagnetic spectrum v terrestrial microwave v no physical “ wire ” § e.g. ,up to 45 Mbps channels v bidirectional v LAN (e.g., WiFi) § 11Mbps, 54 Mbps v propagation environment effects: v wide-area (e.g., cellular) § reflection § 3G cellular: ~ few Mbps v satellite § obstruction by objects § Kbps to 45Mbps channel (or § interference multiple smaller channels) § 270 msec end-end delay § geosynchronous versus low altitude 1/24/18 Introduction 1-23
Networking Overview: Roadmap 1.1 what is the Internet? 1.2 network edge § end systems, access networks, links 1.3 network core § packet switching, circuit switching, network structure 1.4 delay, loss, throughput in networks 1.5 protocol layers, service models 1.6 networks under attack: security 1.7 history 1/24/18 Introduction 124
The network core v mesh of interconnected routers v packet-switching: hosts break application-layer messages into packets § forward packets from one router to the next, across links on path from source to destination § each packet transmitted at full link capacity 1/24/18 Introduction 1-25
Recommend
More recommend
