11_Part 2-Lect-1-Intro_Computer networks and Internet.pdf

Kwame Nkrumah University of Science & Technology, Kumasi, Ghana COE 158 – Introduction to Python Programming and Computer Networks Department Electrical & Electronic Engineering College of Engineering...

Kwame Nkrumah University of Science & Technology, Kumasi, Ghana COE 158 – Introduction to Python Programming and Computer Networks Department Electrical & Electronic Engineering College of Engineering Introduction to Computer Networks and the Internet our goal: overview: what’s the Internet? get “feel” and what’s a protocol? terminology network edge; hosts, access net, more depth, physical media detail later network core: packet/circuit approach: switching, Internet structure – use Internet as performance: loss, delay, example throughput security protocol layers, service models history www.knust.edu.gh 1-2 Outline 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 www.knust.edu.gh Introduction 1-3 What’s the Internet: “nuts and bolts” view PC millions of connected mobile network server computing devices: wireless – hosts = end systems global ISP laptop – running network apps smartphone home ❖ communication links network regional ISP wireless ▪ fiber, copper, radio, links satellite wired links ▪ Different links transmit data at different rates ▪ transmission rate: bandwidth ▪ measured in institutional network bits/second www.knust.edu.gh 1-4  mobile network ❖ Packet switches: forward router packets (chunks of data) global ISP ▪ routers and link-layer switches ▪ link-layer switches used home network in access networks regional ISP ▪ Routers typically used in the network core route r ❖Route or path: sequence of route route communication links r r traversed between end institutional systems network www.knust.edu.gh  “Fun” internet appliances According to Statista, there are approximately 15.14 billion connected IoT devices as of 2023 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 refrigerator Internet phones www.knust.edu.gh 1-6 What’s the Internet: “nuts and bolts” view mobile network Internet: “network of networks” – Interconnected ISPs global ISP protocols control sending, receiving of msgs home – e.g., TCP, IP, HTTP, Skype, 802.11 network regional ISP Internet standards – RFC: Request for comments – IETF: Internet Engineering Task Force institutional network www.knust.edu.gh  Infrastructure that provides mobile network services to applications: – Web, VoIP, email, games, e- global ISP commerce, social networks, … home Distributed applications network regional ISP – since they involve multiple end systems that exchange data with each other – Internet applications run on end systems they do not run in the packet switches in the network core. institutional network www.knust.edu.gh  End systems attached to the Internet mobile network provide an Application programming interface (API) to apps global ISP – API is a set of rules that the sending program must follow so that the Internet home network can deliver the data to the destination regional ISP program – hooks that allow sending and receiving app programs to “connect” to Internet – provides multiple service options, analogous to postal service institutional network www.knust.edu.gh  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 time Q: other human protocols? www.knust.edu.gh  What’s a protocol? human protocols: network protocols: “what’s the time?” machines rather than humans “I have a question” all communication activity in introductions Internet governed by protocols … specific msgs sent … specific actions taken when msgs received, or other events Protocols define format, order of messages sent and received among network entities, and actions taken on message transmission, and/or receipt www.knust.edu.gh Outline 1.1 what is the Internet? 1.2 network edge ▪ end systems, access networks, links www.knust.edu.gh Introduction 1-12  A closer look at network structure: mobile network network edge: global ISP – End systems/hosts: clients and servers – Informally, clients tend to be home network desktop and mobile PCs, regional ISP smartphones etc. – Servers tend to be more powerful machines that store and distribute Web pages, stream video, relay e- mail, etc. – servers often in data centers institutional network www.knust.edu.gh  A closer look at network structure: mobile network ❖ access networks, physical global ISP media: wired, wireless communication links home network regional ISP ❖ network core: ▪ interconnected routers ▪ network of networks institutional network www.knust.edu.gh  Access networks and physical media An access network physically connects an end system to the first router or edge router on a path from the end system to any other distant end system Q: How to connect end systems to edge router? Residential or home access networks Enterprise or institutional access networks (school, company) Mobile access networks www.knust.edu.gh  Access networks and physical media Home access types: – DSL, Cable, (two most prevalent types) – FTTH , Dial-up , Satellite Enterprise access – Ethernet, WiFi – Ethernet(home access) keep in mind: bandwidth (bits per second) of access network? shared or dedicated? www.knust.edu.gh  Home 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 telephone line to central office DSLAM (Digital subscriber line access multiplexer) ▪ data over DSL phone line goes to Internet ▪ voice over DSL phone line goes to telephone net ❖ With DSL, a customer’s telco is also its ISP www.knust.edu.gh  Home access network : digital subscriber line (DSL) ❖ Voice and data encoded at frequencies (technique called frequency-division multiplexing): ❖ A high-speed downstream channel, in the 50 kHz to 1 MHz band ❖ A medium-speed upstream channel, in the 4 kHz to 50 kHz band ❖ An ordinary two-way telephone channel, in the 0 to 4 kHz band ❖ Approach makes the single DSL link appear as if there were three separate links ❖ That is a telephone call and an Internet connection can share the DSL link at the same time ❖ Data transmission rates [ITU 2003] ❖ < 2.5 Mbps upstream transmission rate (typically < 1 Mbps) ❖ < 24 Mbps downstream transmission rate (typically < 10 Mbps) ❖ Asymmetric access ❖ May purposefully limit residential data rates due to tiered services (different rates, available at different prices) or maximum rate limited distance between home and CO www.knust.edu.gh  Home access network: cable network ❖ Internet access using the cable TV company existing cable infrastructure ❖ fiber optics connect the cable head end to neighborhood-level junctions ❖ Traditional coaxial cable is then used to reach individual houses and apartments. ❖ Each neighborhood junction typically supports 500 to 5,000 homes Using frequency division multiplexing: different channels transmitted in different frequency bands to carry variety of services including analog//digital TV, video on demand, telephony a dn internet traffic www.knust.edu.gh Home access network : cable network 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 42.8 Mbps downstream transmission rate, 30.7 Mbps upstream transmission rate ❖ 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 www.knust.edu.gh  Home access network : fiber to the home (FTTH) ❖ Provides an optical fiber path from the PON FTTH architecture CO directly to the home ❖ several competing technologies for optical distribution active optical networks (AONs) passive optical networks (PONs). ❖ Each home has an an optical network terminator (ONT), connected by dedicated optical fiber to a neighborhood splitter ❖ The splitter combines a few homes onto a single, shared optical fiber, which connects to an optical line terminator (OLT) in the telco’s CO www.knust.edu.gh  Home access network : fiber to the home (FTTH) PON FTTH architecture ❖ The OLT, providing conversion between optical and electrical signals, connects to the Internet via a telco router ❖ Home users connect a home router (typically a wireless router) to the ONT and access the Internet via this home router ❖Data transmission rates [ITU-T G.984] ❖From155 Mbps upstream transmission rate up to 2.5 Gb/s) ❖From155 Mbps downstream transmission rate up to 2.5 Gb/s) FTTH provide Internet access rates in the gigabits per second range www.knust.edu.gh Enterprise access networks (Ethernet LAN) institutional link to ISP (Internet) institutional router Ethernet institutional mail, switch web servers typically used in companies, universities, etc ❖ 100Mbps, 1Gbps, 10Gbps transmission rates ❖ today, end systems typically connect into Ethernet switch www.knust.edu.gh  Access net: home network (Ethernet LAN) wireless devices to/from headend or central office often combined in single box cable or DSL modem wireless access router, firewall, NAT point (54 Mbps) wired Ethernet (100 Mbps) Combine broadband residential access (i.e., cable modems or DSL) with these inexpensive wireless LAN technologies to create powerful home networks www.knust.edu.gh  Wireless access networks shared wireless access network connects end system to router – via base station aka “access point” wireless LANs: wide-area wireless access ▪ within building (100 ft) ▪ provided by telco (cellular) ▪ 802.11b/g (WiFi): 11, 54 Mbps operator, 10’s km transmission rate ▪ between 10 Mbps – 20 Gbps ▪ 4G(LTE), 5G, 6G to Internet to Internet www.knust.edu.gh  Host: sends packets of data host sending function: takes application message breaks into smaller chunks, two packets, known as packets, of length L L bits each bits transmits packet into access network at transmission rate R 2 1 – link transmission rate, aka link capacity, aka R: link transmission rate link bandwidth host packet time needed to L (bits) transmission = transmit L-bit = R (bits/sec) delay packet into link www.knust.edu.gh  Physical media bit: propagates between transmitter/receiver pairs physical link: what lies twisted pair (TP) between transmitter & two insulated copper receiver wires guided media: – Category 5: 100 Mbps, 1 – signals propagate in Gpbs Ethernet solid media: copper, – Category 6: 10Gbps fiber, coax unguided media: – signals propagate freely, e.g., radio www.knust.edu.gh  Physical media: coax, fiber coaxial cable: fiber optic cable: ❖ glass fiber carrying light two concentric copper pulses, each pulse a bit conductors ❖ high-speed operation: bidirectional ▪ high-speed point-to-point broadband: transmission (e.g., 10’s-100’s Gpbs transmission rate) – multiple channels on cable ❖ low error rate: – HFC ▪ repeaters spaced far apart ▪ immune to electromagnetic noise www.knust.edu.gh  Physical media: radio signal carried in radio link types: electromagnetic spectrum ❖ terrestrial microwave ▪ e.g. up to 45 Mbps channels no physical “wire” ❖ LAN (e.g., WiFi) bidirectional ▪ 11Mbps, 54 Mbps propagation environment ❖ wide-area (e.g., cellular) effects: ▪ 3G cellular: ~ few Mbps – reflection ❖ satellite ▪ Kbps to 45Mbps channel (or – obstruction by multiple smaller channels) ▪ 270 msec end-end delay objects ▪ geosynchronous versus low – interference altitude www.knust.edu.gh  Kwame Nkrumah University of Science & Technology, Kumasi, Ghana Computer Networking: A Top Down Approach THE END 6th edition Jim Kurose, Keith Ross Addison-Wesley March 2012 All material copyright 1996-2012 J.F Kurose and K.W. Ross, All Rights Reserved