Internetworking

• Heterogeity is inevitable
• No single network technology is the best for all needs
• Internet
  • Connect physics networks and software to make the resulting system appear homogeneous
• Internet is formed by networks, routers, and hosts
  • Router is a device using to connect two networks that may use different technologies

o       A router can connect networks that have

o       Different Technology

o       Different Connection Media

o       Different address schemas and sizes

o       Different print formats

o       Protocol software used in internet is designed by layers

o       One software module for each layer

o       The set of modules is known as a “stack” or “protocol stack”

o       Layering Principle

o       Software implementing layer N at the destination receives exactly the message sent by software implementing layer N at the source.

• The internet is a collection of:
  • Networks
  • Routers interconnecting networks
  • Hosts interconnecting networks

• Hosts send IP packets
• Routers forward IP packets to the destination
• Hosts receive the IP packets and pass the IP to the corresponding application depending on the port number.
• Internet Protocols
  • Known as TCP/IP

• Ethernet Layers
  • Physical – Basic Network Card
  • Network Interface – Define media access (MAC) format of packet and addressing
  • Internet – Facilitate to send packets across the internet (multiple routers)
  • Transport – Transports data from an application in one computer to an application in another computer.  It does not need to be reliable.
  • Application Layer – Everything else
• Internet Protocol – IP
  • Implements “Layer 3: Internet Layer”
  • Defines – Internet Addressing
  • Packet format
  • Routing
• IP Addressing
  • Abstraction
  • Independent of hardware addressing
  • 4 bytes long (32 bits)
  • Unique IP address for each host is one unique IP address for each interface.

• Midterm Review
  • History of Internet
  • What is a network?
  • How the network is used?
  • Transmission media
    • Signals
      • Electricity
      • Light
      • RF
      • Sound
    • Media
      • Copperwire, optical fiber, air
  • Types of encoding
    • Analog – Continuous signal, susceptible to noise
    • Digital – Discrete Signal, less susceptible to noise
    • RS232 – Serial Line
      • One bit after another
      • +15V = 0, -15V = 1
    • Start bit / end it
    • Speeds 9.6, 14.4 kbps
    • Limited Distance
  • Carrier Wave
    • Used for long distances
    • Forms of Modulation
      • Frequency
      • Amplitude
      • Phase
  • Modems
    • Modulator / Demodulator
    • Used to modulate a carrier wave to send data for long distances
  • Network Parameters
    • Propagation Delay – Time required for signal to across media
    • Bandwidth – Max number of times/second a signal changes
    • Throughput – Number of bits/second that can be transmitted
  • Nyquist Teorem
    • Relates Bandwidth and throughput
    • Does not consider noise
    • D = 2B log₂K
      • D – Througput (bits/sec)
      • B – Bandwidth (Hz)
      • K – Number values used to encode data. Usually 2
    • This sets a maximum theoretical limit that is difficult to achieve because of noise
  • Shannons Theorem
    • Also relates throughput and bandwidth
    • It considers noise
      • C = B log₂(1+S/N)
        • C – Throughput
        • B – Bandwidth
        • S – Power of signal
        • N – Power of noise
      • It is a more practical limit
  • Multiplexing
    • Sending multiple signals in the same channel
    • Time Division Multiplexing
    • Frequency Division Multiplexing
    • Packet Switching – Divides data into small units before transmitting
      • Allows Fair access
      • It makes the delay smaller
  • How to handle errors
    • Parity bit
      • Use the 7 bit to represent the number of 1’s that are in the byte
      • Even Parity
        • Set 7^th bit to 1 or 0 to make the number of 1’s in the byte even
      • Odd parity
        • Set 7^th bit to 1 or 0 to make the number of 1’s in the byte odd
    • Check Sum
      • It treats data as a sequence of words and computes the arithmetic sum in the sequence and stores checksum in the header
      • Receiver computes the checksum again and checks in the packet.
    • CRC – The probability of having an error undetected is smaller than checksum.
  • Local Area Networks
    • LAN / WAN / MAN
    • Locality principle of LANS
    • Network topology
      • Star
      • Ring
      • Bus
    • Ethernet
      • CSMA/CD
        • Explain each part
        • Exponential back off
      • CSMA/CA
        • Wireless Networs
      • Network Addressing
        • Unicast
        • Broadcast Ethernet
        • Multicast
        • Broadcast Ethernet
        • Promiscuous Mode
        • Ethernet Frame Format
      • Ethernet Types
        • Thicknet, Thinnet, Twisted Pair
        • Fast and Gigabit Ethernet
      • Examples of ring topology
        • Token Ring
        • FDDI
      • Star Topolgy
        • ATM
      • Extending Networks
        • Repeaters, Bridge, Hub, Switch
      • WAN’s and routing
        • Router
        • Next Hub Forwarding
        • Routing Table
        • Link State, Distance Vector
      • Connection Oriented and Connectionless Networks
        • ATM – Oriented
        • Ethernet / IP – Connectionless Networks
      • Delay and Utilization
        • D = D / 1 – U
      • Causes for delay
      • Protocols and layering
        • ISO 7 layer, reference models, internet layering
        • Memorize ISO 7  Layers
        • Memorize Internetworking Layers
• Study Notes
• Study Example Exams
• Study Project Code

• Not On Midterm

• IP protocol – layer 3
• IP is independent of hardware where it runs
• IP is a layer implemented in software
• IP defines
  • Internet addressing (4 bytes (octets) address size)
  • Packet Format
  • Routing
• IP is unreliable.  The reliability is implemented by TCP.
• However the Internet will do its best to deliver the packet
• IP is a “best effort” delivery protocol
• IP was designed this way to be the “least common denominator” of the networking hardware available
• IP has been implemented on
  • Ethernet SNA, Token Ring, Pronet, Serial Lines, Appletalk, ATM, FDDI, Radio
• The RFC’s (Request for Comments) are documents publicly available that describe the TCP/IP protocols
• There is an RFC for every IP implementation in every networking hardware available
  • IP on Ethernet
  • IP on Serial line (PPP, SLRP)
  • IP on ATM etc.
• IP addressing
  • Just an abstraction
  • You give a different number to every interface in a host

• Hosts that have more than 1 IP address, multiple network interfaces, are called multi-homed hosts
• Hosts connected to the same network have the same prefix in the IP address
  • Prefix – Identifies the Network
  • Suffix – Identifies the host in that network
• A global authority assigns unique prefixes to different networks
• A local administrator assigns a unique suffix, host number, to each host
• How big should the prefix network number be?
• There are different kinds of network numbers (prefixes) depending on the number of hosts that the network

Class A

 Class B

 Class C

Class D 

Class E