Lecture 1

• Nuts and Bolts View of the Internet:
  • Billions of connected computing devices
    • Hosts = end systems
    • running networking apps at the internet’s “edge”
  • Packet Switches: forward packets (chunks of data) using routers
  • Communication Links - Fiber, Cooper
  • Networks - Collection of devices, routers, links managed by an organization
  • Internet - A network of networks (Interconnected ISPs)
  • Protocol - Languages to send anr receive messages (HTTP. TCP)
• A “Services” View of the Internet:
  • Infrastructure - provides services to applications (web, streaming, etc)
  • Programming Interface - “Hooks” allowing send/recieve apps to “connect” to use Internet transport service
• Network Protocols - define format, order of messages sent and recieved among network entities
• Network’s Edge:
  • Hosts - clients and servers
    • Physically speaking clients and servers are the same
    • Clients request data from servers
  • Servers often in data centers

Lecture 2

• Access Networks and Physical Media

  • How to connect end systems to edge routers
    • Residential access nets
    • Institutional access networks (school, company)
    • Mobile access networks (WiFi, 4G/5G)

• Internet at Home - DSL (Phased Out), 5G (15%), FTTH (20%), Cable (50%)

  • Access networks: Digital Subscription Line (DSL)

    • Use existing telephone line to central office DSLAM (DSL Access Multiplexer)

      

    • Connect your computer to a DSL modem - convert into digital signals with bits over the internet

  • What is a modem?

    • Modems are physical layer devices

      • They don’t read the data going across

      • They simply convert between different analog signal formats

        

  • What is a Router?

    • Routers are IP Layer Devices
    • They connect to and direct traffic properly to > 1 computers
    • They create an internal network so computers can communicate with each other without the internet (LAN)

  • Access networks: cable-based access

    • Frequency Division Multiplexing (FDM) - different channels transmitted in different frequency bands

      

  • Home Networks

    

• Wireless Access Networks

  • Shared wireless access networks connects end systems to router via base station aka “access point”
  • Wireless local area networks (WLANs)
    • Typically within or around building (100 feet)
    • 802.11 b/g/n WiFi: 11, 54, 450 Mbps transmission rate
    • b/g/n are protocols

• Access networks: Wide-are cellular access networks

  • Provided by mobile, cellular network operator
  • 4G, 5G

• Access networks: Enterprise Networks

  • companies. univeristies, etc
  • Mix of wired, wireless link technologies and routers
  • Ethernet: 100Mbps, 1Gbps, 10Gbps
  • WiFi: wireless access pointes at 11, 54, 450 Mbps

• Access Networks: Data Center Networks

  • High bandwidth links (10s to 100s Gbps) connect hundreds to thousands of servers together and to internet

• Rates:

  • 1 Kbps = 1 thousands bits per second
  • 1 Mbps = 1 million bits per second
  • 1 Gbps = 1 bilion bits per second

Hosts and Links

• Hosts: Send packets of data
  • Host Sending Function
    • Takes application message (text image video etc)
    • Broken into chunks (packets) of L bits
    • Transmits packet into access network at transmission rate R

Lecture 3

• Links: Physical Media
  • bit - propagates between transmitter/reiever pairs
  • physical link - what lies between transmitter and receiver
  • guided/unguided media - either through physical connection (fiber optic) or wireless
    • coaxial cable - two concentric copper conductors (100 Mbps per channel)
    • fiber optic cable - glass fiber carrying light pulses
      • each pulse a bit
      • high speed operation; low error rate (10-100s Gbps)
      • “full-duplex”
    • wireless radio - signal carried in various bands in electromagnetic spectrum
      • no physical “wire”
      • broadcast, “half-duplex” (sender to reciever)
      • propagation env effects - reflection, obstruction, interference; causes delays
    • radio link
      • wireless LAN (wifi): 10-100 Mbps; 10’s of ,eters
      • wide-area (e.g 4G cellular): 10’s Mbps over 10km
      • bluetooth: cable replacement; short distances, limited rates
      • terrestrial microwave
      • satellite - up to 45mbps per channel
• Delay Calculation

Lecture 4

• Traceroute program - provides delay measurement from source to router along end-to-end internet path towards destination (sees the round trip time) (sends 3 times)