IPv6 Packet

IPv6 Packet

1. Limitations of IPv4

   • Issues:
     • IPv4 address depletion
       • Limited number of unique public addresses
     • Lack of end-to-end connectivity
       • NAT
         • Network Address Translation
       • Public IPv4 address is shared
         • IPv4 address of internal network is hidden
     • Increased network complexity
       • NAT extended IPv4 lifespan
         • But, it is a translation mechanism to IPv6
         • Creates complexity, latency and difficult troubleshooting

2. IPv6 Overview

   • IETF
     • Internet Engineering Task Force
     • Concered with IPv4 issues
     • Development of IPv6
       • Improvements:
         • Increased Address Space
           • 128-bit hierachical
         • Improved Packet Handling
           • Simpler header
         • Eliminates need of NAT
           • Not need to use NAT for public/private IPv4 address.

3. IPv4 Packet Header Fields in the IPv6 Packet Header

   • Simplified IPv6 header
   • IPv4 header
     • Consists of:
       • Length of 20 octets
         • Up to 60 bytes
       • 12 basic header fields
   • IPv6 Header
     • Consists of:
       • Length of 40 octets

4. IPv6 Packet Header

   • Source IPv6 Addresss
     • 128-bit field
   • Hop Limit
     • 8-bit field
       • Replaces TTL
     • Value decremented by 1 for each router forwarding
       • If reaches zero, the packet is discarded
     • Eliminates Header Checksum
   • Next Header
     • 8-bit field
       • Equivalent to IPv4 protocol field
     • Indicates type of carried packet
       • Passing to appropiate upper layer protocol
   • Payload Length
     • 16-bit field
     • Length of data portion
       • Does not include IPv6 header length
   • Flow Label
     • 20-bit field
     • Packets with the same flow label, recieve the same type of handling by routers
   • Traffic Class
     • 8-bit field
       • Equivalent to DS
   • Destination IPv6 Address
     • 128-bit field
   • Version
     • 4-bit binary set to 0110
   • May contain EH
     • Extension Headers
       • Provides optional network layer information
       • Placed between IPv6 header and payload
       • Used for fragmentation, security, to support mobility and more.