EECS 563 Fall 2021 Introduction to Communications Networks Victor S Frost Dan F Servey Distinguished Professor Electrical Engineering and Computer Science University of Kansas 2335 Irving Hill Dr Lawrence Kansas 66045 e mail vsfrost ku edu http www ittc ku edu frost Communications Landscape cid 31 Voice cid 31 Data E mail Web Network based applications Images Machine to Machine IoT cid 31 Video Streaming Broadcast Video on Demand Mobile cid 31 Wired wireless cid 31 Mobility cid 31 Separate Voice Internet Video networks have converged to An integrated packet network Introduction 1 Introduction 2 Drivers Customer Expectations cid 31 Sense of always connected cid 31 Instant response high bandwidth cid 31 Ubiquitous connectivity cid 31 Multimedia video support cid 31 Conferencing simultaneous communications with multiple users Drivers Customer Expectations cid 31 Mobility support cid 31 Personalized information services cid 31 Context sensitive information services cid 31 Absolutely secure private cid 31 Low cost Introduction 3 Introduction 4 The Value of the Net cid 31 Metcalf s Law The value of a network increases as the square of the number of connected users some say nlog n cid 31 The value of a network increases as the square of the access cid 31 The value of a network increases as the square of computing bandwidth power of end device cid 31 Number of connected users bandwidth user and device capabilities are increasing Value of the Net Introduction 5 Drivers Technology Traffic Growth cid 31 Internet still growing cid 31 Access rates increasing Cable DSL 10 s 100 Mb s FTTH 100 s to 1 Gb s Wireless Gb s cid 31 https www cisco com c en us solutions collateral execu tive perspectives annual internet report white paper c11 741490 html Trends March 2020 Compound Annual Growth Rate CAGR Introduction 6 Drivers Technology cid 31 Moore s Law Processing power doubles every 18 months Moore s Law has been true since 1965 cid 31 Gilder s Law The Law of Telecoms Total telecommunications system capacity b s triples every three years https www cisco com c en us solutions collateral executive perspectives annual internet report white paper c11 741490 html Trends Introduction 7 Global device and connection growth Connection Speeds https www cisco com c en us solutions collateral executive perspectives annual internet report white paper c11 741490 html Trends Introduction 8 Speed Record cid 31 July 14 2021 fastest internet speed achieving a data transmission rate of 319 Terabits per second Tb s cid 31 From https interestingengineering com japan shattered internet speed record 319 terabits cid 31 The new record was made on a line of fibers more than 1 864 miles 3 000 km long Drivers Others cid 31 Economic cid 31 Public Policy Regulatory spectrum Network Neutrality cid 31 Local Laws and Culture FCC opening of White Space to make use of additional Introduction 9 Introduction 10 Issues in Networking Sharing Example Printer 50 1 1 1 Link Rate R b s Internet Fiber D in meters D 2000m Business Campus Computer Center 55 5 Business Offices Introduction 11 Issues in Networking Sharing cid 31 What is shared Link capacity Buffers memory Processing Common address name space Introduction 12 Issues in Networking Sharing cid 31 R Peak rate link capacity b s cid 31 L Message Length Bytes cid 31 Packet clocking serving time sec L 8 bits R bits sec cid 31 One way propagation time sec D meters Propagation speed meters sec sec Propagation speed c speed of light 3x108 meters sec in free space Propagation speed 2x108 meters sec in fiber cid 31 For L 9kBytes R 100Mb s Packet clocking time 0 72 ms cid 31 For D 2km One way propagation time 10 us cid 31 Round trip time RTT 2 Not including switching forwarding and processing times Introduction 13 Issues in Networking Sharing cid 31 Assume each customer and printer is connected using Ethernet i e at 1 Gb s cid 31 How fast does the link between the offices and the computer center have to be to guarantee all the customers can use the 1 Gb s cid 31 R Rate 55 Gb s cid 31 Too expensive Introduction 14 Issues in Networking Sharing cid 31 Solution Gamble cid 31 Assume called packets Each host computer breaks up messages into smallish units Packets from each customer are sent to a waiting line buffer to wait their turn to use the link Packets arriving to a full buffer are discarded Discarded packets are retransmitted later cid 31 Customer information now experiences Queueing Delay waiting in line Loss cid 31 Network resources are shared e g Transmission capacity Addresses Buffer memory Introduction 15 Issues in Networking Sharing cid 31 Customer performance requirements Delay 100ms and Loss 10 cid 31 Assume customer traffic Quality of Service Specifications L bytes Average packet length 9000 bytes packets sec device Packets are generated at a rate of 2 per second device Input Traffic Specification cid 31 Using basic queueing theory R 8 6 Mb s 55 Gb s System size 7 packets System Design What happens when you lose your gamble See the current Internet performance https www fcc gov reports research reports measuring broadband america measuring fixed broadband tenth report Packet Loss Delay Introduction 16 Issues in Networking Sharing What happens when you lose your gamble Packet Loss Delay Delay Latency by ISP Packet Loss From Tenth Measuring Broadband America Fixed Broadband Report A Report on Consumer Fixed Broadband Performance in the United States FCC January 2021 https www fcc gov reports research reports measuring broadband america measuring fixed broadband tenth report Toc52871202 From https www fcc gov reports research reports measuring broadband america measuring fixed broadband eighth report Introduction 17 Issues in Networking Protocols cid 31 Protocols are the rules implemented as algorithms that govern the interactions between network elements e g Routing Media Access Resource Allocation cid 31 Protocols are algorithms implemented software or hardware cid 31 Protocols must run in real time Assume R 40 Gb s and L 1500 Bytes Router must process a packet in 0 3 s Introduction 18 Issues in Networking Protocols cid 31 Peer protocols Executed at both ends of the connection Run on geographically distributed network elements Use memory to save state Packet events arrival to change state based on data in packet headers Packets arrive asynchronously cid 31 Protocols must work with inaccurate or imperfect knowledge Packets are lost due to bit errors or traffic congestion