More Networking Fundamentals

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More Networking Fundamentals

• ECIS469 Strategies and Technologies for the
  Internet

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The Internet Protocol Suite

• Developed independently of OSI
• Also known as TCP/IP Protocol suite
• Transmission control protocol/internet protocol
• Can be approximately mapped to the OSI model with
  some stretching
• Consists of four layers that runs over a fifth
  layer (hardware layer)
• Application, transport, Internet, Network
  Interface

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TCP/IP Internet Protocol Suite

• Development funded by research money from ARPA
• Provide rules for communication
• Message formats
• How computers respond when receiving message
• How errors are handled
• Rules are independent of network hardware
• Protocols describe network services

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Network Services

• At the application level
• Email
• FTP
• Remote Login (telnet)
• Network level services
• Connectionless packet delivery
• Reliable stream transport
• Forms a connection and sends data one packet at
  a time waiting for acknowledgement

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Distinguishing features of TCP/IP

• Network technology independence
• Defines unit of data transmission (datagram) and
  specifies how to send it on a particular network
• Universal Interconnection
• Each computer assigned a universally recognized
  address
• Datagram carries source and destination addresses
• End-to-End Acknowledgements
• Between sender and receiver and not between
  sender and each intermediate device
• Application Protocol Standards
• Not just for network services

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Internet Protocol Suite
OSI Layer
Application
Application Presentation Session
e.g. FTP
Messages or Streams
Transport
Transport
Transmission Control
Transport Protocol Packet
Internet
Network
Internet Protocol
IP Datagram
Network Interface
Data Link
Data link frames
Hardware Layer
Physical
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TCP/IP Internet Layering Model

• Application Layer
• Invoke application programs that access services
  available on the internet
• Passes data in the required form to transport
  layer for delivery
• Transport Layer
• Provides for end-to-end communication between
  applications
• Regulates flow if data
• Ensures reliable transport (checks for errors and
  ensures packets arrive in sequence)
• Internet Layer
• Accepts request from transport layer to transmit
  packets and gets destination information
• Encapsulates packet into IP datagram and fills in
  header
• Uses routing algorithm to determine whether to
  deliver directly or through a router
• Passes datagram on to network interface
• Network Interface Layer
• Accepts IP datagrams and send over network

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Two approaches to Network Communication

• Circuit-Switched (connection-oriented)
• Like the telephone service
• Telephone call establishes a connection/circuit
• From originating phone to local switching office
• Across trunk lines
• To destination switching office
• To destination phone
• Microphone sampled repeatedly and voice digitized
• Digitized signal sent to receiver phone at
  guaranteed rate of 64Kbps
• Advantage No other network activity can reduce
  capacity
• Disadvantage Fixed circuit cost charge the
  same regardless of whether you talk or not.

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Another approach

• Packet-switched (connectionless)
• Typically used to connect computers
• Data broken into small packets which are then
  multiplexed
• Packet (usually only 100s of bytes)
• Data
• Source and destination information
• Packets delivered by network hardware and then
  reassembled by software
• Advantage concurrent sending of data by multiple
  computers
• Disadvantage as activity rises, there is less
  network capacity

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Internet Architecture

• Machines connected to local networks
• How about connecting two networks?
• Physically, two LANs are connected by a common
  computer that is linked to both
• Physical connection not enough
• Two networks must be willing to communicate
• Connected by an IP Gateway (or IP Router)

Network 2
Network 1
Router
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More complex internet connections
Network 3
Network 2
Network 1
R1
R2

• When more than two networks involved, router must
  know topology of networks beyond immediate
  connection
• In above example, R1 must transfer all packets
  destined for Networks 2 and 3
• Imagine 1000s of such networks routing becomes
  complex
• Routers are small machines with little disk
  storage and memory
• Trick is that routers use the destination network
  for routing, NOT the destination host.
• This is achieved through IP addressing schemes

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IP Addresses

• Universal identifiers
• Communication system said to provide universal
  communication service if it allows any host
  computer to communicate with any other host
• Needs globally accepted method of identifying
  each host
• Names, addresses, routes

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Classes of IP Addresses

• IP address uniquely identifies a node or host
  connection to the internet.
• Configured by software not hardware specific
• An IP address is a 32 bit binary number
• Represented as 4 octets separated by decimal
  points (dotted quad notation)
• Each octet takes values from 0-255.

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IP Addressing

• According to the current IP protocol (IPv4), the
  address is broken down into two parts
• The network identifier
• The host identifier
• IPv4 also specifies 5 classes of IP addresses
• Classes A through E
• Can be identified through the values of the first
  octet in the dotted quad notation

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Classes of IP Addresses

• Class A
• Only used by a small handful of networks
• Network must have more than 216 hosts (65,536)
• Uses 7 bits for netid and 24 bits for hostid.
• Class B
• Intermediate sized networks with between 28 (256)
  and 216 hosts
• 14 bits to netid and 16 bits to hostids
• Class C
• Small sized networks with less than 28 (256)
  hosts
• 21 bits to netid and 8 bits to hostids
• Routers use the netid portion to determione where
  to send packets

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Identifying Network Classes

• In binary
• Class A networks start with a 0
• Class B networks start with 10
• Class C networks start with 110
• Class D networks start with 1110
• Class E networks start with 11110
• In decimal notation, if the first octet is
  between
• 1-126, it is Class A
• 128-191, it is Class B
• 192-223, it is Class C
• 224-239, it is Class D
• 240-255, it is Class E

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Who decides?

• Internet Assigned Names Authority (IANA)
  allocates addresses to RIR (Regional Internet
  Registry) based on need.
• Regional Internet Registries
• APNIC (Asia Pacific region)
• ARIN (Americas and Sub-Saharan Africa)
• LACNIC (Latin America and some Caribbean Islands
  )
• RIPE NCC (Europe, the Middle East, Central Asia,
  and African countries located north of the
  equator )

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Some IP Assignments

• 3.0.0.0 GE
• 9.0.0.0 IBM
• 12.0.0.0 ATT
• 19.0.0.0 Ford Motor Co.
• 55.0.0.0 Boeing
• Now, there is no class-based assignment
• CIDR Classless Inter Domain Routing
  pronounced cider (also called supernetting)

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Mapping IP Address to Physical Address

• According to TCP/IP, internet behaves like a
  virtual network
• Uses IP addresses for each host
• Two machines can only communicate if they know
  each others physical network address
• IP address must be mapped to correct physical
  address
• Known as the Address Resolution Problem

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Address Resolution Problem

• Address Resolution Protocol allows a host to find
  the physical address of a target host on the same
  physical network, given only the targets IP
  address
• Done through dynamic binding

A
Y
X
B
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IPng (IPv6)

• IPv4 has been virtually unchanged for 3 decades
• Why change the rules?
• New computer and communication technologies
• New applications
• Increases in size and load
• New government policies
• Main motivation imminent address space
  exhaustion

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IPv6 Main Characteristics

• Similarities
• More like an extended IPv4
• Still supports connectionless delivery, allows
  sender to chooses size of datagram, allows
  specification of number of allowable hops
• Differences
• Larger Address Space quadrupled from 32 bits to
  128 bits
• Flexible Header format
• Improved options (including control information)
• Support for resource allocation (for real time
  data)
• Protocol extension in future