Internet Architecture and IP version 4 IP version 6 IPv4: was the first version of Internet Protocol

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  • Set # 05

    Network Layer

    Delivered By: Engr Tahir Niazi

    Internet Architecture and Protocol

  • Layer 3: Internet Protocol

     Logical address for computers on network

     Fragmentation and reassembly control

     Datagram service

     IP makes use of "best efforts" service

    – Connectionless

    – Similar to postal service

  • Layer 3: Internet Protocol  Advantages

    – Simplicity and less overhead

    – Upper layers can build more reliable service (TCP)

    – Adequate for many networks

    – Hop-by-hop routing is resilient

     Disadvantages

    – “Best efforts” allows no inherent Quality of Service (QoS)

    – Hop-by-hop routing allows no traffic engineering

    – IPv4 address space

  • IP Functions:  Encapsulates TCP and UDP Segments

     Common logical interface to different networks

     Universal 32-bit address notation (IPv4)

     Connectionless network protocol

  • IPv4 Address Structure:

  • Example:

     Since I is in the range 128 ≤ I < 192 we know this is a Class B


     We can write the address in a form that is a network address by

    putting 0s in the host part:

    Usually done with subnets – see later

  • Public & Private IP addresses

     Reserved for private intranets

    – -

    – -

    – -

     Used within organisations and within the home

     Use NAT (Network Address Translation) at edge of private

    domain (e.g in ADSL router) if need to connect to Internet.

     Loopback range used for testing: 127.x.x.x

  • Subnets:

     Use some of the bits in the host identifier field to distinguish

    between multiple networks called subnets

     More flexibility and the smaller subnets are easier to manage -

    also reduces the traffic on individual subnets

     Subnet mask is applied at the Network Layer. 1s define the subnet and

    0s the host Hosts apply the subnet mask to the destination


     If it is in the same network (subnet) ARP used to find MAC

    address; if not forwarded to a router

  • Subnet Example:

  • More Subnet Examples:

  • More Subnet Examples:

  • Price of Subnetting:

     Lose available number of addresses for hosts

    – The very first IP address within the network range identifies

    the network, can no be assigned to any host

    – The very last IP address within the network range is the

    broadcast address can not be assigned to any host

  • Exercise 1: Subnetting based on Networks

  • 3 Steps: 1. Determine number of networks and convert to binary

    2. Reserve bits in subnet mask and find the increment

    3. Use increment to find the network range.

  • Solution:

  • Exercise 2: Subnetting based on Hosts

  • Solution Ex: 2

  • Exercise:  An organisation has purchased class C address, and

    would like to use it to address his 9 networks

     Find upper range and lower range using following IP address

    and subnet mask (also find few next subnets)

    - Net id =, Subnet mask =

    - Net id=, Subnet Mask =

     An organisation has purchased this address, and

    would like to use to accommodate 220 hosts

  • Advance Subnetting: VLSM

  • Solution

  • Solution

  • VLSM Exercise: (IP =

  • NAT: Network Address Translation:

     Multiple computers, one internet connection

     NAT allows multiple devices to “share” the same public IP


     NAT glues two worlds together

    – DHCP server: assigns private IP addresses

    – DHCP client: gets public IP address

     NAT swaps public/private addresses on packets

  • How NAT works?

  • Public and Private IP address Mapping:

  • IPv4 and IPv6:

     There are currently two versions

     IP version 4

     IP version 6


     was the first version of Internet Protocol to be widely used, and

    accounts for most of today’s Internet traffic. There are just over

    4 billion IPv4 addresses. While that is a lot of IP addresses, it is

    not enough to last forever.

  • IPv6:

     IPv6 is a newer numbering system that provides a much larger

    address pool than IPv4. It was deployed in 1999 and should meet

    the world’s IP addressing needs well into the future.

    Difference b/w IPv4 & IPv6:

     The major difference between IPv4 and IPv6 is the number of IP

    addresses. There are 4,294,967,296 IPv4 addresses. In contrast,

    there are 340,282,366,920,938,463,463,374,

    607,431,768,211,456 IPv6 addresses.

     Many other like IP sec, Simpler header, no broadcast

  • Continue…..

  • IPv4 Header

  • IPv6 Header

  • Migration between IPv4 & IPv6

     Tunnelling

     Dual Stack Router

  • Summary:

     IP protocol

     Public and Private IP address

     Subnetting

     Variable length subnet mask

     Network address Translation

     IPv4 and IPv6

  • Q & A