Communication Networks and Services Introduction to Message & - - PowerPoint PPT Presentation
Communication Networks and Services Introduction to Message & Circuit Switching Communication Services & Applications l A web browsing application enables retrieval of information from a server. l Uses TCP reliable stream service
l A web browsing application enables retrieval of
l Uses TCP reliable stream service provided by the
Web server Retrieval of information from web servers
Real-time voice exchange with mobile users l Mobile phone application enables two-way
l Uses UDP datagram service provided by the
l Service: Basic information transfer capability
l Internet transfer of individual block of information l Internet reliable transfer of a stream of bytes l Real-time transfer of a voice signal
l Applications build on communication services
l E-mail & web build on reliable stream service l Voice Telephony builds on real-time transfer
l The equipment (hardware & software) and facilities
l Virtually invisible to the user; Represented by a cloud l Applications run on user or terminal devices Communication Network l Equipment
l Routers, servers,
switches, multiplexers, hubs, modems, access points …
l Facilities
l Copper wires, coaxial
cables, optical fiber
l Ducts, conduits,
telephone poles …
l Network architecture: the plan that specifies
l Architecture is driven by the network services l Overall communication process is complex l Network architecture partitions overall
l Courier: physical transport of the message
l Messenger pigeons, pony express, UPS, drones
l Telegraph: message is transmitted across a
l Drums, beacons, mirrors,, flags, semaphores… l Electricity, light
l Telegraph delivers message much sooner
l Claude Chappe, 1790s l Semaphore mimics person with flags
l Different angle combinations of arms
l Code for enciphering messages kept
l Signal could propagate 800 km in 3
l Network nodes were created
l Store-and-Forward Operation:
l Messages arriving on a line are
recorded
l Next-hop in route determined by
destination address of a message
l Each message carried by hand to
next line, and stored until operator is available for transmission
North line South line West line East line Network Node
l William Sturgeon Electro-magnet (1825)
l Electric current in a wire wrapped around a piece of
l Joseph Henry (1830)
l Current over 1 mile of wire to ring a bell
l Samuel Morse (1835)
l Pulses of current deflect electromagnet to generate
l Experimental telegraph line over 40 miles (1840)
l Signal propagates at the speed of light!!!
l Approximately 2 x 108 meters/second in cable
l Digital transmission
l Text messages converted into dots/dashes or zeros/ones
l Message Switching Service
l Messages contain source & destination addresses l Store-and-Forward: Messages forwarded hop-by-hop across
network
l Routing determines path followed according to destination
address
Switches Message Destination Source Message Message Message
l Alexander Graham Bell (1875) discovered voice
l Microphone converts voice pressure variation (sound)
l Loudspeaker converts electrical signal back into sound
l Telephone patent granted in 1876 l Bell Telephone Company founded in 1877 Signal for ae as in cat Microphone Loudspeaker analog electrical signal sound sound
l Signaling required to establish a call
l Flashing light and ringing devices to alert the
l Called party information to operator to establish
Signaling + voice signal transfer
l For N users to be fully connected directly l Requires N(N – 1)/2 connections l Requires too much space for cables l Inefficient & costly since connections not always on
1 2 3 4 N
. . .
l Patchcord panel switch invented in 1877 l Operators connect users on demand
l Establish circuit to allow electrical current to flow
l Only N connections required to central office
1 2 3 N – 1 N
Network selects route; Sets up connection; Called party alerted
Telephone network
Pick up phone Dial tone. Dial number Exchange voice signals
1. 2. 3. 4. 5.
Telephone network Telephone network Telephone network Telephone network Telephone network
Hang up.
6. Connection set up Information transfer Connection release
l Circuit switching service
l User signals for call setup and tear-down l Route selected during connection setup l End-to-end connection across network l Signaling coordinates connection setup
l Hierarchical Network
l Decimal numbering system l Hierarchical structure; simplified routing; scalability
l Signaling Network
l Intelligence inside the network
l Architecture (logical design) of networks
l Networks provide services to support applications l Networks are designed in layered architectures l Protocols govern operation of each layer l Focus on Internet Architecture
l Some aspects of physical design of network
l Broadband, WiFi, Ethernet, IP Routers, Sensors,
ECE 361 Computer Networks Winter 2019
Professor TAs Textbook Term Test (February 14, 2019 8-10 pm, Exam Centre, Room 100) 35% Labs (Labs 3 pts each) 15% Final Exam 50% Tutorial Lab Students will work in teams of 2; students are free to form teams from the same lab section. Time & Place Sayed Ehsan Etesami (mailto:ehsan.etesami@mail.utoronto.ca), Pooyan Habibi (mailto:pooyan.habibi@mail.utoronto.ca), Yihuan Huang (yihuan.huang@alum.utoronto.ca), Simona Marinova (mailto:simona.marinova@mail.utoronto.ca), Morteza Moghaddassian (mailto:m.moghaddassian@mail.utoronto.ca), Beibei Zhang (mailto:benjamin.zhang@mail.utoronto.ca)
Hamid Timorabadi LP371, lh.timorabadi@utoronto.ca (LEC 102) Communications Networks: Fundamental Concepts and Key Architectures, McGraw-Hill, Second Edition, by Leon-Garcia & Widjaja LEC101: TuWF 1pm, GB248; LEC102, TuThF, 9am, GB248 PRA101/102, Mon 3-6pm , PRA103/104, Mon noon-15:00am, GB243; TUT 101/103 Th 11am-noon, MY315/MY360; TUT102 Tu noon-1 pm Mark Distribution Closed Book; Formulas Provided Closed Book; Formulas Provided TA guides students through selected homework-related exercises; Homework solutions will be posted weekly
Date Lecture Topic (MWF) Reading Tutorial Lab
January 7, 2019 January 8, 2019 Introduction to Message & Circuit Switching; Course Overview January 9, 2019 Introduction to Packet Switching Networks January 11, 2019 Layered Network Architectures January 14, 2019 January 15, 2019 TCP/IP Architecture Overview January 16, 2019 HTTP January 18, 2019 Voice over IP; RTP and UDP January 21, 2019 January 22, 2019 Berkeley Sockets January 23, 2019 Digital Transmission January 25, 2019 Communications Media January 28, 2019 January 29, 2019 Error Detection: Check Sums & Polynomial Codes January 30, 2019 Stop-and-Wait ARQ February 1, 2019 Selective ARQ February 4, 2019 February 5, 2019 TCP Reliable Stream Service and Flow Control February 6, 2019 TCP Congestion Control February 8, 2019 Review for Midterm February 11, 2019 February 12, 2019 Packet Buffering and Statistical Multiplexing February 13, 2019 Packet Delay and Packet Loss Models February 15, 2019 Framing: HDLC, PPP, and Ethernet February 18, 2019 The schedule is subject to change because of unexpected events such as class cancellations, snowstorms, etc. WEEK 1 No Tutorial No Lab WEEK 2 Layered Architectures: Encapsulation; PRA02 Lab #1 WireShark Exercises WEEK 3 TCP & UDP PRA01/03/04 Lab #1 Wireshark Exercises WEEK 4 Bit Rates, Propagation Delay, Message Delays PRA02 Lab #2 TCP/IP Utilities Read Section 2.5 WEEK 5 ARQ Performance PRA01/03/04 Lab #2 TCP/IP Utilities Read Section 2.5 WEEK 6 Midterm on February 14, 2019 8-10 pm, Exam Centre, Room 100 Review Questions WEEK 7 Reading Week
February 25, 2019 February 26, 2019 Aloha Random Access February 27, 2019 CSMA/CD & CSMA/CA March 1, 2019 Ethernet LANs March 4, 2019 March 5, 2019 Spanning Tree Protocol & VLANs March 6, 2019 WIFI LANs March 8, 2019 LTE Cellular Mobile Networks March 11, 2019 March 12, 2019 Router and Switch Design March 13, 2019 Routing Tables: Datagrams & Virtual Circuits March 15, 2019 Packet Scheduling and Quality of Service March 18, 2019 March 19, 2019 Distance Vector Routing March 20, 2019 Link-State Routing March 22, 2019 MPLS and SDN March 25, 2019 March 26, 2019 Segment Routing March 27, 2019 IPv6 and CIDR March 29, 2019 DHCP, NAT, and IP mobility April 1, 2019 April 2, 2019 Cryptographic Algorithm Overview April 3, 2019 Private Key and Public Key Cryptography April 5, 2019 TLS , HTTPS, SSH April 8, 2019 April 9, 2019 Course Review April 10, 2019 Course Review April 12, 2019 Review Questions PRA01/03/04 Lab #3 UDP Sockets PRA02 Lab #3 UDP Sockets WEEK 10 WIFI & LTE PRA01/03/04 has Lab #5 OpenFlow Pt- Pt & Multipoint WEEK 8 Statistical Multiplexing PRA01/03/04 Lab #4 TCP Sockets WEEK 14 WEEK 11 Routers & Switches PRA02 Lab #4 TCP Sockets WEEK 12 Routing Protocols WEEK 9 MAC & Ethernet WEEK 13 IP Topics PRA02 has Lab #5 OpenFlow Pt-Pt & Multipoint Circuits
l Early computer systems very expensive l Time-sharing methods allowed multiple terminals
l Remote access via telephone modems l Needed to share expensive lines
Host computer Terminal Terminal . . . Terminal Modem Modem Telephone Network
l Multiplexer allows a line to carry frames that contain
l Frames are buffered at multiplexer until line becomes
l Address in frame header identifies terminal l Header carries other control and error checking
CRC Information Header Header Information CRC Host computer Terminal Terminal . . . Terminal Multiplexer Frame
l National & international terminal-oriented networks l Routing was very simple (to/from host) l Each network typically handled a single application
New York City San Francisco Chicago Atlanta
. . . . . . . . . T T . . . T
l As cost of computing dropped, terminal-oriented
l Needed flexible computer networks
l Interconnect computers as required l Support many applications
l Application Examples
l File transfer between arbitrary computers l Execution of a program on another computer l Multiprocess operation over multiple computers
Larry Roberts: ARPANET Vint Cerf & Bob Kahn: TCP/IP Tim Berners-Lee: World-Wide Web
l Network should support multiple applications
l Transfer arbitrary-size messages l Low-delay short messages for interactive
l But in store-and-forward operation, long messages
l Packet switching
l Network transfers packets using store-and-forward l Packets have maximum length l Break long messages into multiple packets
l ARPANET testbed led to many innovations
Packet Switch Packet Switch Packet Switch Packet Switch Packet Switch Message Packet 3 Packet 2 Packet 1 Message Host generates message Source packet switch converts message to packet(s) Packets transferred independently across network Destination packet switch delivers message Destination packet switch reasembles message
Packet Switch Packet Switch Packet Switch Packet Switch Packet Switch Packets header includes source & destination addresses Packet switches have table with next hop per destination No connection setup prior to packet transmission Routing tables calculated by packet switches using distributed algorithm Packet Hdr
Dest: Next Hop: xyz abc wvr edf
Routing is highly nontrivial in large mesh networks
l Different packet switching networks emerged
l Wired, satellite, radio packet networks
l Each network has its protocols and uses
l Internetworking protocols invented to enable
l Internet: a network of networks
l Routers (gateways) interconnect networks l Host computers prepare IP packets and transmit
l Each network has own addresses & protocols l Routers forward IP packets across networks l Best-effort IP transfer service, no retransmission
Net 1 Net 2 Router
l Hierarchical address: Net ID + Host ID l IP packets routed according to Net ID l Routers compute routing tables using
G G G G G G Net 1 Net 5 Net 3 Net 4 Net 2 H H H H
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