1IntroductionEECS 563 Fall 2021Introduction to Communications Networks Victor S. FrostDan F. Servey Distinguished Professor Electrical Engineering and Computer ScienceUniversity of Kansas2335 Irving Hill Dr.Lawrence, Kansas 66045e-mail: [email protected]://www.ittc.ku.edu/~frost2IntroductionCommunications Landscape Voice Data: E-mail, Web, Network based applications, Images, Machine-to-Machine, IoT Video, Streaming, Broadcast, Video on Demand, Mobile Wired & wireless  Mobility Separate Voice/Internet/Video networks have converged to:An integrated packet network3IntroductionDrivers: Customer Expectations Sense of always connected Instant response, high bandwidth Ubiquitous connectivity Multimedia (video) support Conferencing (simultaneous communications with multiple users)4IntroductionDrivers: Customer Expectations Mobility support Personalized information services Context sensitive information services Absolutely secure & private Low-cost5IntroductionThe Value of the Net Metcalf’s Law: The value of a network increases as the square of the number of connected users [some say nlog(n)] The value of a network increases as the square of the access bandwidth The value of a network increases as the square of computing power of end device Number of connected users, bandwidth/user and device capabilities are increasing  Value of the Net 6IntroductionDrivers: TechnologyTraffic Growth Internet still growing Access rates increasing Cable/DSL ~ 10’s-100 Mb/s FTTH ~100’s to 1 Gb/s  Wireless  Gb/s https://www.cisco.com/c/en/us/solutions/collateral/executive-perspectives/annual-internet-report/white-paper-c11-741490.html#Trends - March 2020Compound Annual Growth Rate — CAGR7IntroductionDrivers: Technology Moore’s Law Processing power doubles every 18 months Moore’s Law has been true since ~1965 Gilder’s Law (The Law of Telecoms) Total telecommunications system capacity (b/s) triples every three yearsGlobal device and connection growthhttps://www.cisco.com/c/en/us/solutions/collateral/executive-perspectives/annual-internet-report/white-paper-c11-741490.html#Trends8IntroductionConnection Speedshttps://www.cisco.com/c/en/us/solutions/collateral/executive-perspectives/annual-internet-report/white-paper-c11-741490.html#Trends9IntroductionSpeed Record July 14, 2021 “fastest internet speed, achieving a data transmission rate of 319 Terabits per second (Tb/s)” From https://interestingengineering.com/japan-shattered-internet-speed-record-319-terabits “The new record was made on a line of fibers more than 1,864 miles (3,000 km) long.”10IntroductionDrivers: Others Economic Public Policy/Regulatory FCC opening of “White Space” to make use of additional spectrum Network Neutrality Local Laws and Culture11IntroductionIssues in Networking: SharingExample: 150Business Offices155BusinessCampus Computer CenterLink Rate = R b/sPrinterD in metersD = 2000mInternetFiber1512IntroductionIssues in Networking: Sharing What is shared: Link capacity Buffers (memory) Processing Common address (name) space13IntroductionIssues in Networking: Sharing R = Peak rate (link capacity) b/s L=Message Length (Bytes) Packet clocking (serving) time (sec) = L*8 (bits)/R (bits/sec) One way propagation time (sec)= D (meters)/(Propagation speed (meters/sec) = sec Propagation speed = c = speed of light = 3x108meters/sec (in free space) Propagation speed = ~2x108meters/sec (in fiber) For L=9kBytes & R=100Mb/s Packet clocking time = 0.72 ms For D = 2km One way propagation time=  = 10 us Round trip time (RTT) = 2(Not including switching, forwarding, and processing times)14IntroductionIssues in Networking: Sharing Assume each customer and printer is connected using Ethernet, i.e. at 1 Gb/s 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. R= Rate = 55 Gb/s Too expensive15IntroductionIssues in Networking: Sharing Solution: Gamble Assume: Each host computer breaks up messages into ‘smallish’ units called packets 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 Customer information now experiences: Queueing Delay, waiting in line Loss Network resources are shared, e.g., Transmission capacity Addresses Buffer (memory)16IntroductionIssues in Networking: Sharing Customer performance requirements: Delay < 100ms and Loss < 10% Assume customer traffic: L (bytes) =Average packet length = 9000 bytes  packets/sec/device) = Packets are generated at a rate of 2 per second/device Using basic queueing theory R = 8.6 Mb/s << 55 Gb/s System size > 7 packetsWhat happens when you lose your gamble:- Packet Loss-Delay See the current Internet performance @https://www.fcc.gov/reports-research/reports/measuring-broadband-america/measuring-fixed-broadband-tenth-reportQuality of Service SpecificationsInput Traffic SpecificationSystem Design17IntroductionIssues in Networking: SharingWhat happens when you lose your gamble:-Packet Loss- Delay From: https://www.fcc.gov/reports-research/reports/measuring-broadband-america/measuring-fixed-broadband-eighth-reportFrom: Tenth Measuring Broadband America Fixed Broadband ReportA Report on Consumer Fixed Broadband Performance in the United States, FCC, January 2021https://www.fcc.gov/reports-research/reports/measuring-broadband-america/measuring-fixed-broadband-tenth-report#_Toc52871202Packet LossDelayLatency by ISP18IntroductionIssues in Networking: Protocols Protocols are the rules, implemented as algorithms, that govern the interactions between network elements, e.g., –Routing– Media Access– Resource Allocation Protocols are algorithms implemented software or hardware Protocols must run in “real time” Assume R = 40 Gb/s and L = 1500 Bytes – Router must process a packet in 0.3 s19IntroductionIssues in Networking: Protocols 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