Introduction to Computer Networks - CBEMC-2 PDF

CBEMC-2 Challenge-Based Learning: Introduction to Computer Networks Overview qHow the interconnected networks affect our daily life? qLANs, WANs and the Internet § Network Edge § Network Core qInternet Structure qNetwork Standardization Networks in our daily lives...

CBEMC-2 Challenge-Based Learning: Introduction to Computer Networks Overview qHow the interconnected networks affect our daily life? qLANs, WANs and the Internet § Network Edge § Network Core qInternet Structure qNetwork Standardization Networks in our daily lives https://dev.to/daniel37623600/how-to-make-a-social-networking-app-3mg1 https://www.opustech.co.uk/wp-content/uploads/2017/04/IoT-Graphic-red-2.jpg https://www.oysterconnect.com/blogs/wp-content/uploads/2019/10/The-Exam-Cram_-How-to-Manage-That- Last-Minute-Prep-Stress_-11.png The Internet 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 § routers, switches ISP home network content Communication links provider network datacenter § fiber, copper, radio, satellite network § transmission rate: bandwidth enterprise network “Fun” Internet-connected devices Pacemaker & Monitor Tweet-a-watt: monitor energy use Amazon Echo IP picture frame Web-enabled toaster + weather forecaster Internet refrigerator Slingbox: remote control cable TV Security Camera AR devices sensorized, bed Internet phones mattress Others? Fitbit The Internet q Internet: “network of mobile network 4G networks” national or global ISP § Interconnected ISPs q protocols are everywhere Skype IP Streaming video § control sending, receiving of messages local or regional § e.g., HTTP (Web), streaming ISP video, Skype, TCP, IP, WiFi, 4G, home network content Ethernet provider HTTP network datacenter q Internet standards Ethernet network § RFC: Request for Comments TCP § IETF: Internet Engineering Task enterprise Force network WiFi The Internet: Service view q Infrastructure that provides mobile network services to applications: national or global ISP § Web, streaming video, multimedia teleconferencing, email, games, e- commerce, social media, inter- Streaming video Skype connected appliances, … § provides programming interface to local or regional distributed applications: ISP “hooks” allowing sending/receiving apps home network content to “connect” to, use Internet transport HTTP provider network datacenter service network provides service options, analogous to postal service enterprise network Protocol qThree elements § Source/sender § Destination/receiver § Channel or media qAll communication activities in Internet are governed by protocol § Protocols define the format, order of messages sent and received among network entities, and actions taken on msg transmission, receipt Internet structure qNetwork edge mobile network 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 Internet structure qNetwork edge mobile network § Hosts: clients and servers national or global ISP servers often in data centers qAccess networks, physical media: § wired, wireless local or communication links regional ISP home network content provider network datacenter network enterprise network Internet structure qNetwork edge mobile network § Hosts: clients and servers national or global ISP servers often in data centers qAccess networks, physical media: § wired, wireless local or communication links regional ISP qNetwork Core home network content provider § Interconnected routers network datacenter network § Network of networks enterprise network Internet structure qHow to connect end systems to mobile network edge router? national or global ISP § Residential § Enterprise § Mobile carrier local or regional ISP home network content provider network datacenter network enterprise network Access networks: cable-based access qFrequency Division Multiplexing (FDM) § different channels transmitted in different frequency bands 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 Access networks: DSL qDigital Subscriber Line § use existing telephone line to central office DSLAM data over DSL phone line central office telephone goes to Internet network voice over DSL phone line goes to telephone net DSL splitter § 24-52 Mbps dedicated modem DSLAM downstream transmission rate voice, data transmitted ISP at different frequencies over DSL access § 3.5-16 Mbps dedicated dedicated line to central office multiplexer upstream transmission rate Wireless Access networks qShared wireless access network connects end system to router § via base station aka “access point” qWireless local area qWide-area cellular access networks (WLANs) networks § typically within or around building § provided by mobile, cellular (~100 ft) network operator (10’s km) § 802.11b/g/n (WiFi): 11, 54, 450 § 10’s Mbps Mbps transmission rate § 4G cellular networks (5G coming) to Internet to Internet Access networks: enterprise network § companies, universities, etc. § mix of wired, wireless link technologies, connecting a mix of switches and routers (we’ll cover differences Enterprise link to ISP (Internet) shortly) institutional router Ethernet institutional mail, § Ethernet: wired access at switch web servers 100Mbps, 1Gbps, 10Gbps § WiFi: wireless access points at 11, 54, 450 Mbps Host:sends packets of data qHost’s sending function § takes application message two packets, § breaks into smaller chunks, known as packets, L bits each of length L bits § transmits packet into access network at 2 1 transmission rate R § link transmission rate, aka link capacity, aka host link bandwidth R: link transmission rate packet time needed to L (bits) transmission = transmit L-bit = delay packet into link R (bits/sec) Network core qmesh of interconnected routers mobile network qpacket-switching: hosts break national or global ISP application-layer messages into packets § forward packets from one router to the next, across links on path from source local or to destination regional ISP § each packet transmitted at full link home network content capacity provider network datacenter network enterprise network Packet-switching qStore-and-forward L bits per packet 3 2 1 source destination R bps R bps Packet-switching qqueuing delay, loss R = 100 Mb/s A C D B R = 1.5 Mb/s E queue of packets waiting for output link Two key network-core functions routing routing algorithm algorithm Routing: Forwarding: local forwarding local forwarding table table global action: header value output link determine source- local action: move arriving packets 0100 0101 3 2 destination paths from router’s 0111 1001 2 1 taken by packets input link to routing algorithms appropriate router 1 output link 3 2 11 01 destination address in arriving packet’s header Circuit switching qend-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 Circuit switching: FDM and TDM qFrequency Division Multiplexing (FDM) 4 users § optical, electromagnetic frequencies frequency divided into (narrow) frequency bands § each call allocated its own band, can transmit at max rate of that narrow band qTime Division Multiplexing time (TDM) § time divided into slots frequency § each call allocated periodic slot(s), can transmit at maximum rate of (wider) frequency band, but only during its time slot(s) time Internet structure qHosts connect to Internet via access Internet Service Providers (ISPs) § residential, enterprise (company, university, commercial) ISPs qAccess ISPs in turn must be interconnected § so that any two hosts can send packets to each other qResulting network of networks is very complex § evolution was driven by economics and national policies Internet structure: a “network of networks” Question: given millions of access ISPs, how to connect them together? … access net access 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 net Internet structure: a “network of networks” Question: given millions of access ISPs, how to connect them together? … access net access net … access net access access net … … net access access net net connecting each access ISP to … … each other directly doesn’t scale: … access O(N2) connections. access … net net access net access net access net access … access … net access … net access net net Internet structure: a “network of networks” Option: connect each access ISP to one global transit ISP? Customer and provider ISPs have economic agreement. … … access net access 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 Internet structure: a “network of networks” But if one global ISP is viable business, there will be competitors …. access … access net access net … 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 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 access net 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 Internet structure: a “network of networks” … and regional networks may arise to connect access nets to ISPs access … access net access net … 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 Internet structure: a “network of networks” … and content provider networks (e.g., Google, Microsoft, Netflix) may run their own network, to bring services, content close to end users … … access net access net access net access access net net IXP access access ISP A net net … … 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 Internet structure: a “network of networks” q 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 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 Tier-1 ISP Network map: Sprint ) POP: point-of-presence to/from other Sprint PoPS links to peering networks … … … … … links to/from Sprint customer networks Performance q How do packet loss and delay occur? § packets queue in router buffers packets queue, wait for turn arrival rate to link (temporarily) exceeds output link capacity: packet loss packet being transmitted (transmission delay) A B packets in buffers (queueing delay) free (available) buffers: arriving packets dropped (loss) if no free buffers Performance q Packet delay: four sources dnodal = dproc + dqueue + dtrans + dprop Performance q “Real” Internet delays and routes § traceroute program: provides delay measurement from source to router along end- end Internet path towards destination. 3 probes 3 probes 3 probes Performance qPacket 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 Performance qThroughput § 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 server sends bits (fluid) into pipe (Rs bits/sec) (Rc bits/sec) Standards qInternet Standard § tested specification that is useful to and adhered to by those who work with the Internet § formalized regulation that must be followed qInternet Draft § working document with no official status (6-month lifespan) § Request for Comments Organizations qInternet Engineering Task Force (IETF) qIEEE References § Some content of these slides are adapted from Computer Networking: A Top-Down Approach (2013, Kurose). § Kurose, James F. (2013). Computer networking : a top-down approach. Pearson. TK5105.875.I57 K88 2013b § Forouzan, B. (2013). Data Communications and Networking, McGraw Hill. TK5105.F65 2013 Message from DPO "The information and data contained in the online learning modules, such as the content, audio/visual materials or artwork are considered the intellectual property of the author and shall be treated in accordance with the IP Policies of DLSU. They are considered confidential information and intended only for the person/s or entities to which they are addressed. They are not allowed to be disclosed, distributed, lifted, or in any way reproduced without the written consent of the author/owner of the intellectual property."