CSE 489 Week 1 Notes
CSE 489 Week 1 Notes CSE 489
Popular in Modern Networking Concepts
Popular in Computer Science and Engineering
This 14 page Class Notes was uploaded by Winnie Liang on Sunday January 31, 2016. The Class Notes belongs to CSE 489 at University at Buffalo taught by Dimitrios Koutsonikolas in Spring 2016. Since its upload, it has received 132 views. For similar materials see Modern Networking Concepts in Computer Science and Engineering at University at Buffalo.
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Date Created: 01/31/16
CSE 489/589 Modern Networking Concepts 01/26/2016 ▯ Instructor: Dimitrios Koutsonikolas ▯ Office: 311 Davis Hall, Office hours TTh 5-6pm email@example.com TTh, 2-3:20PM Hoch 114 ▯ www.cse.buffalo.edu/faculty/dimitrio/courses/cse4589_s16/index.html ▯ USERNAME: cse4589_s16 ▯ PASSWORD: 114hochspring2016 ▯ Grading: ▯ Midterm: 20% th ▯ Final: 20% on May 10 ▯ Homeworks/WireShark Labs: 20% ▯ 3 Programming Assignments: 40% (12%+12%+16%) ▯ Class Participation: 5% ▯ ▯ Network analysis tools: WireShark, iperf, traceroute ▯ C/C++ programming in Linux ▯ ▯ WORKLOAD: ▯ 5 written HW assignments (teams of 2 or 3) Due beginning of class – 1 late day (graded out of 90) ▯ 6 WireShark labs (teams of 2 or 3) – screenshot references ▯ 3 individual programming assignments – 4 late days to use up (afterwards, -10% each day) ▯ 1 midterm ▯ 1 cumulative final ▯ ~80 pgs of light reading per week ▯ ▯ “I read and understand the academic honesty policies” on all your assignments on the top or else will be ungraded ▯ ▯ HW0 – show up in office and introduce yourself (Friday 1/29, 4:00 pm), 1% bonus ▯ ▯ ▯ ▯ 1/26/16 Lecture ▯ Chapter 1 Introduction ▯ ▯ Overview: ▯ - what’s the internet? ▯ - what’s a protocol? ▯ - network edge; hosts, access net, physical media ▯ - network core: packet/circuit switching, Internet structure ▯ - performance: loss, delay, throughput ▯ - protocol layers, service models ▯ - design philosophy of the internet ▯ ▯ What’s the internet? ▯ Nuts and bolts: ▯ - millions of connected computing devices: hosts = end systems (hosts network applications ex. browsers) (PC, Server, wireless laptops, smart-phones) running network apps communication links (connects the system devices to rest of network ex. wireless links, wired links) o fiber, copper radio, satellite o transmission rate: bandwidth Packet switches: forward packets (chunk of data) o Routers and switches ▯ - Internet: “network of networks” Interconnected ISPs ▯ - protocols control sending, receiving of msgs eg. TCP, IP, HTTP, Skype, 802.11 ▯ - Internet standards – defines protocols in a form of way RFC: Request for comments – to ensure devices communicate w/ ea other IETF: Internet Engineering Task Force ▯ A service view: ▯ - Infrastructure that provides services to applications: Web, VoIP, email, games, ecommerce, social nets,.. ▯ - Provides programming interface to apps hooks that allow sending and receiving app programs to “connect” to Internet provides service options, analogues to postal service ▯ ▯ What’s a protocol? ▯ … specific msgs sent ▯ … specific actions taken when msgs received, or other events ▯ ▯ Human protocols: Network protocols: ▯ - “what’s the time?” - machines rather than humans ▯ - “I have a question” - all communication activity in Internet governed by protocols ▯ - introductions protocols define format, order of msgs sent and received among network entities, and actions taken on msg transmission, receipt, or other event What’s a protocol? A human protocol and a computer network protocol: 1/29/16 Lecture A closer look at network structure: - network edge: hosts: clients and servers servers often in data centers ▯ - access networks, physical media: wired, wireless communication links ▯ - network core: interconnected routers, network of networks ▯ ▯ ▯ THE NETWORK EDGE: - end systems (hosts): run application programs, eg. Web, email, at “edge of network” - client/server model client host requests, receives service from always-on server eg. Web browser/server; email client/server ▯ - peer-peer model: minimal (or on) use of dedicated servers eg. Skype, BitTorrent ▯ ▯ 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 o link transmission rate, aka link data rate, aka link capacity, aka link bandwidth ▯ Bandwidth(Hz) vs. Data Rate (bits/sec) - Any transmission system has a limited band of frequences - The width of the band limits the data rate that can be carried on the medium Shannon C = B*log2(I + S/N) Higher bandwidth higher data rate Data rate also depends on coding scheme ▯ PEOPLE USE BANDWIDTH AND DATA RATE INTERCHANGEABLY. ▯ ▯ Physical Media ▯ - bit: propagates between transmitter/receiver pairs ▯ - physical link: what lies between transmitter & receiver ▯ - guided media: signals propagate in solid media: copper, fiber, coax ▯ - unguided media: signals propagate freely eg. Radio ▯ - twisted pair(TP) ▯ - insulated copper wires ▯ ▯ Coxial cable: two concentric copper conductors, bidirectional, broadband: multiple channels on cable ▯ Fiber optic cable: ▯ - glass fiber carrying light pulses, each pulse a bit ▯ - high-speed operation ▯ - low error rate ▯ Radio: signal carried in electromagnetic spectrum, no physical wire, bidirectional, propagation environment events: reflection, obstruction by objects, interference ▯ ▯ Access networks: ▯ How to connect end systems to edge router? ▯ - residential access nets ▯ - institutional access networks (school, company) ▯ - mobile access networks ▯ ▯ Access net: digital subscriber line (DSL) ▯ ▯ BOTH voice and data transmitted over the same line ▯ - 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 ▯ Upstream transmission rate (Mbps) is lower than downstream transmission rate!! ▯ ▯ Access net: cable network ▯ Frequency division multiplexing: different channels transmitted in different frequency bands ▯ ▯ - HFC: hybrid fiber coax: asymmetric, higher downstream transmission rate is greater than 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 ▯ - ALL DATA reaches every house. Two houses accessing same channel, they share BANDWIDTH. ▯ Home Network: ▯ ▯ ▯ Enterprise access Networks (Ethernet) – used in companies, universities ▯ - today, end systems typically connect into Ethernet switch ▯ ▯ Wireless access networks ▯ - shared wireless access network connects end system to router via base station aka “access point” ▯ - wireless LANS: within building (100ft) (between 600 Mbps) ▯ - wide-area wireless access: provided by telco(cellular) operator, 3G, 4G: LTE (Between 1-10 Mbps) ▯ ▯ Next Topic: ▯ NETWORK CORE: 1) packet switching, 2) circuit switching, network structure ▯ - packet switching – internet; ▯ - circuit switching – telephone network ▯ The Network Core – a mesh of interconnected ROUTERS ▯ How is data transferred though net? ▯ - circuit switching: dedicated circuit per call: telephone net ▯ - packet-switching: data sent thru net in discrete “chunks” ▯ ▯ ▯ Network Core: Circuit Switching (COMMON IN TRADITIONAL TELEPHONE NETWORKS) ▯ - end- end resources allocated to, reserved for “call” between source and destination: ▯ - in diagram, each link has 4 circuits: call gets 2 nd circuit in top link and st 1 circuit in right link ▯ - dedicated resources: no sharing of RESOURCES circuit-like performance ▯ - Call set-up required ▯ - Advantage: guaranteed performance and much more intelligent than package switching; Disadvantage: extra delays before we can start talking on the phone ▯ ▯ - network resources (eg. Bandwidth) divided into ‘pieces’ pieces allocated to calls resource piece idle if not used by owning call (no sharing) dividing link bandwidth into “pieces”: frequency division, time division ▯ ▯ Circuit switching: FDM vs. TDM (frequency division multiplexing vs. time division multiplexing) ▯ FDM: 4 users, they each receive ¼ of the transmission rate ▯ TDM: 4 users, they each receive full of transmission rate but at different quarter time frames (1/4 time therefore delay) ▯ ▯ ▯ Question: How long does it take to send a file of 640,000 bits from host A to host B over a circuit-switched network? ▯ - all link speeds: 1.536 Mbps ▯ - each link uses TDM with 24 slots/frame ▯ - 500msec to establish end-to-end circuit ▯ CHECK SOLVED PROBLEM IN NOTES ▯ ▯ Network Core: Packet Switching ▯ - each end-to-end data stream divided into packets user A, B packets share network resources each packet uses full link bandwidth resources uses as needed NO GUARANTEED PERFORMANCE: no bandwidth division into “pieces; no dedicated allocation; no resource reservation ▯ ▯ - resource contention: aggregate resource demand can exceed amount available congestion: packets queue, wait for link use store and forward: packets move one hop at a time (moves one at a time) o node receives complete packet before forwarding EXTRA DELAYS ▯ ▯ Packet-switching: store-and-forward ▯ ▯ - takes L/R seconds to transmit (push out) packet of L bits on to link at R bps ▯ - store and forward: entire packet must arrive at router before it can be transmitted on next link ▯ - delay = 3L / R (assuming zero propagation delay) ▯ ▯ ▯ Packet Switching: Statistical Multiplexing ▯ - sequence of A & B packets has no fixed timing pattern bandwidth shared on DEMAND: statistical multiplexing. ▯ - TDM: each host gets same slot in revolving TDM frame ▯ ▯ ▯ queuing and loss: ▯ - IF arrival rate (In bits/sec) to link exceeds transmission rate of link for a period of time: packets will queue, waited to be transmitted on link packets can be dropped(lost) if memory (buffer) fills up ▯ ▯ Packet switching makes more efficient sharing of a link than circuit switching ▯ ▯ Packet switching vs. circuit switching ▯ Packet switching allows more users to use network!!! ▯ ▯ ▯ CHECK SOLVED PROBLEM IN NOTES ( ON THE MIDTERM Q#1!!!!!!!!!!!!!) ▯ ▯ Is packet switching a “slum dunk winner?” ▯ - great for bursty data resource sharing simpler, no call setup ▯ - excessive congestion possible: packet delay and loss protocols needed for reliable data transfer, congestion control - How to provide circuit- like behavior? Bandwidth guarantees needed for audio/video apps Still an unsolved problem (ch. 7) ▯ ▯ ▯ ▯ ▯
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