CSC 401 Data and Computer Communications Networks Computer Networks and The Internet Sec 1.1 and 1.2 Prof. Lina Battestilli Fall 2017
Outline Computer Networks and the Internet (Ch 1) 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 our goal: get feel and terminology more depth, detail later in course approach: use Internet as example NCSU CSC401 Lina Battestilli 2
Internet of Things (IoT) IP picture frame http://www.ceiva.com/ sensori zed, bed mattres s Web-enabled toaster + weather forecaster Tweet-a-watt: monitor energy use Internet refrigerator Gaming Console Internet phones NCSU CSC401 Lina Battestilli 3
What s the Internet: nuts and bolts view PC server wireless laptop smartphone millions of connected computing devices: hosts/end systems running network apps 2015: 5 billion devices, 3.2 billion users mobile network global ISP tablets IoTs home network regional ISP wireless links wired links communication links fiber, copper, radio, satellite transmission rate (bits/sec : bandwidth) router Link-layer switch Packet switch: forward packets (chunks of data) determine the route/path Similar to transportation network institutional network NCSU CSC401 Lina Battestilli 4
What s the Internet: nuts and bolts view Internet: network of networks Interconnected ISPs Hierarchical structure mobile network global ISP protocols control sending, receiving of msgs e.g., TCP, IP, HTTP, Skype, Ethernet home network regional ISP Internet standards RFC: Request for comments IETF: Internet Engineering Task Force IEEE 802 LAN/MAN Ethernet, WiFi institutional network ISP s managed independently, runs IP, naming/addressing NCSU CSC401 Lina Battestilli 5
Cisco Predictions 2016 Cisco Visual Networking Index: Forecast 2015 2020 By 2020, there will be nearly 4.1 billion global Internet users (more than 52 percent of the world's population), up from 3.0 billion in 2015. By 2020, there will be 26.3 billion networked devices and connections globally, up from 16.3 billion in 2015. Globally, the average fixed broadband connection speed will increase 1.9-fold, from 24.7 Mbps in 2015 to 47.7 Mbps by 2020. Globally, IP video will represent 82 percent of all traffic by 2020, up from 70 percent in 2015. Accessed Aug, 2016 http://www.cisco.com/c/en/us/solutions/service-provider/visual-networking-index-vni/index.html NCSU CSC401 Lina Battestilli 6
What s the Internet: a service view communication infrastructure enables distributed applications: Web, VoIP, email, games, e-commerce, file sharing communication services provided to apps: reliable data delivery from source to destination best effort (unreliable) data delivery B A Internet API: how a program running on one end system asks the Internet Infrastructure to deliver data to a specific destination program running on another end system Socket Interface! NCSU CSC401 Lina Battestilli 7
Postal Service API What is the API for Alice to send Bob a letter? 1. Alice puts the letter in a envelope 2. Alice writes Bob s full name, address, Zip code and writes in the center of the envelope 3. Alice seals the envelope and puts a stamp in upper right hand side of envelope 4. Alice drops the envelope in an official mail service mailbox Postal service provides many services: express, reception confirmation, ordinary use, etc NCSU CSC401 Lina Battestilli 8
What is a protocol? Protocols define format, order of msgs sent and received among network entities, and actions taken on msg transmission, receipt human protocols: what s the time? I have a question Introductions network protocols: machines rather than humans all communication activity in Internet governed by protocols NCSU CSC401 Lina Battestilli 9
What is a protocol? a human protocol and a computer network protocol: Hi Hi Got the time? 2:00 TCP connection request TCP connection response Get http://www.awl.com/kurose-ross <file> time NCSU CSC401 Lina Battestilli 10
Outline Computer Networks and the Internet (Ch 1) 1.2 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 NCSU CSC401 Lina Battestilli 11
A closer look at network structure: mobile network global ISP network edge: applications and hosts clients & servers home network regional ISP access networks, physical media: wired, wireless communication links institutional network network core: interconnected routers network of networks NCSU CSC401 Lina Battestilli 12
Access networks and physical media Connecting end systems to edge router home access nets enterprise access networks (school, company) mobile access networks keep in mind: bandwidth (bits per second) of access network? shared or dedicated? Mobile Home Enterprise NCSU CSC401 Lina Battestilli 13
Global View of Internet Users Data from 2015 from worldbank.org Households With Internet Access 44% Globally 31% in Developing Countries 78% in Developed Countries Leader: > 80% Sweden USA :DSL & Cable Europe: 90% DSL 14
Access net: Digital Subscriber Line (DSL) DSL modem splitter Central Office DSLAM telephone network Encoded in diff frequencies: 0-4KHz used for 2-way telephone 4-50kHz for medium speed upstream channel 50kHz-1MHz for highspeed downstream channel voice, data transmitted at different frequencies over dedicated line to central office DSL Access 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 < 2.5 Mbps upstream transmission rate (typically < 1 Mbps) < 24 Mbps downstream transmission rate (typically < 10 Mbps) DSL provider may purposefully limit rate (tier price, distance, wire) ISP DSL Standards developed by ITU NCSU CSC401 Lina Battestilli 15
Access net: Cable Network cable modem splitter cable headend Channels V I D E O V I D E O V I D E O V I D E O V I D E O V I D E O D A T A D A T A C O N T R O L 1 2 3 4 5 6 7 8 9 frequency division multiplexing: different channels transmitted in different frequency bands
Access net: Cable Network cable headend cable modem splitter coax Fiber Node fiber CMTS cable modem termination system data, TV transmitted at different frequencies over shared cable distribution network HFC: hybrid fiber & coax asymmetric: DOCSIS2.0: up to 42.8 Mbps downstream, 30.7 Mbps upstream DOCSIS 3.1: up to 912Mbps downstream, 216 Mbps upstream (yr 2013) 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 ISP need to coordinate transmission and avoid collisions!!! NCSU CSC401 Lina Battestilli 17
Access net: Fiber-To-The-Home (FTTH) Fiber Optics can offer much higher rates that twisted-pair copper wire or coaxial cable Telcos lay optical fiber from CO all the way to the homes e.g Direct fiber from CO to each home (way too expensive!) One fiber leaving CO and split into customer-specific fibers close to the home Active optical networks (AONs) Passive optical networks (PONs) used by Verizon FIOS UAE, South Korea, Hong Kong, Japan, Singapore, Taiwan, Lithuania, Sweden 30% NCSU CSC401 Lina Battestilli 18
Passive optical networks (PONs) 1 Gbps Rates? convert optical to electrical signals Each home has Optical Network Terminator (ONT) ONT is connected via optical fiber to neighborhood splitter Splitter combines < 100 homes into a single fiber back to CO At CO, Optical Line Terminator (OLT) All packets from OLT are replicated at the splitter NCSU CSC401 Lina Battestilli 19
Which Home Access Network? DSL Proponents Direct connection, Dedicated Capacity Rural Broadband Satelite 1Mpbs StarBand or HughesNet vs. Cable Proponents Reasonable dimensioned HFC network provides much faster transmission rates Fiber to the Home(FTTH) Dial-up Modem 56Kbps! NCSU CSC401 Lina Battestilli 20
Access net: home network wireless devices often combined in single box to/from headend or central office cable or DSL modem wireless access point (54 Mbps) router, firewall, NAT wired Ethernet (1 Gbps) Introduction 1-21
Enterprise Access Networks (Ethernet) 100Mpbs Ethernet switch 1 10 Gpbs institutional link to ISP (Internet) institutional router institutional mail, web servers typically used in companies, universities, etc 10 Mbps, 100Mbps, 1Gbps, 10Gbps transmission rates today, end systems typically connect into Ethernet switch Introduction 1-22
Wireless LANs Shared wireless access network connects end system to router via base station aka access point wireless LANs: within building (a few 10s of meters) from base 802.11b/g/n (WiFi): 11, 54, 450 Mbps transmission rate wide-area wireless access provided by telco (cellular) operator 10s of km from the base Uses the same wireless infrastructure used for cellular telephony between 1 and 10 Mbps 3G, 4G, LTE to Internet to Internet Introduction 1-23
Map of Access Points in Raleigh http://wigle.net/ Accessed Aug 2017 NCSU CSC401 Lina Battestilli 24
Physical media bit: propagates between transmitter/receiver pairs physical link: what lies between transmitter & receiver guided media: Cost: Cost of links is relatively minor compared to other networking costs Installation cost is orders of magnitude higher Builders install them in buildings before they are actually used. signals propagate in solid media: copper, fiber, coax unguided media: signals propagate freely, e.g., radio NCSU CSC401 Lina Battestilli 25
Host: sends packets of data host sending function: takes application message breaks into smaller chunks, known as packets, of length L bits transmits packet into access network at transmission rate R link transmission rate, aka link capacity, aka link bandwidth 2 host 1 two packets, L bits each R: link transmission rate packet transmission delay time needed to transmit L-bit packet into link = = L (bits) R (bits/sec)
twisted pair (TP) Physical media: twisted pair the dominant solution in high-speed LAN networking. two insulated copper wires (each 1mm thick) Twisting reduces the electrical interference from similar pairs close by Typically a bunch of pairs are bundled together in a cable with protective shield A wired pair is a single communication link UTP Category 5: 100 Mbps, 1 Gpbs Ethernet UTP Category 6a: 10Gbps at up to 100m NCSU CSC401 Lina Battestilli 27
coaxial cable: two concentric copper conductors Physical media: coax Special insulation and shielding bidirectional broadband: multiple channels on cable Shared medium: end systems share a cable with each receiving what was sent to them NCSU CSC401 Lina Battestilli 28
fiber optic cable: Physical media: fiber glass fiber carrying light pulses, each pulse a bit high-speed operation: high-speed point-to-point transmission (e.g., 10 s-100 s Gpbs transmission rate) low error rate: repeaters spaced far (100km) & hard to tap immune to electromagnetic noise Prevalent in the Internet Backbone High cost: transmitters, receivers, switches Optical Carrier (OC) standard link speeds OC-n ( n*51.8 Mbps), used in SONET OC-768 40Gbps NCSU CSC401 Lina Battestilli 29
Physical media: radio signal carried in electromagnetic spectrum no physical wire Bidirectional Propagation environment effects: Reflection: multipath fading Obstruction by objects: shadow fading, reduces the signal strength Interference: other transmissions and electromagnetic signals NCSU CSC401 Lina Battestilli 30
radio link types: terrestrial microwave Physical media: radio Short distance (e.g., wireless headsets, keyboards, etc.) Bluetooth ver4.0 ~24Mbps LAN (e.g., WiFi) 11Mbps, 54 Mbps, 72-150Mbps, wide-area (e.g., cellular) 3G: ~ 1 Mbps, 4G: potential 100Mbps satellite Kbps to 45Mbps channel (or multiple smaller channels) 270 msec end-end delay Geostationary vs. Low-Earth orbiting (LEO) NCSU CSC401 Lina Battestilli 31
References Some of the slides are identical or derived from 1. Slides for the 7 th edition of the book Kurose & Ross, Computer Networking: A Top-Down Approach, 2. Slides by Jim Kurose for his CSC453 course at Umass 3. Slides from Nick McKeown, CS144 at Stanford University NCSU CSC401 Lina Battestilli