Transition from IPV4 to IPV6 : Dual Stack, Tunneling, Header Translation

Transition from IPV4 to IPV6:

1. Flag Day:

• Declare a day and make a rule to use IPV6 from that day; not a feasible idea

2. Dual stack operation: V6 nodes run in both V4 and V6 modes and use version field to decide which stack to use.
   1. Nodes can be assigned a V4 compatible V6 address

• Allows a host which supports V6 to talk V6 even if local routers only speak V4
• Signals the need for tunneling
• Add 96 D's to a 32-bit V4 address :e.g. ::10.0.0.1

2. Nodes can be assigned a V4 mapped V6 address

• Allows a host which supports both V6 and V4 to communicate with a V4 host
• Add 2 bytes of l's to V4 address then zero extend the rest: e.g. ::FFFF:10.0.0.1

Dual-stack IPv6/IPv4 implementations recognize a special class of addresses

1. V4 compatible V6 address

• Add 96 0’s (zero-extending) to a 32-bit v4 address e.g. ::10.0.0.1
• Enables IPv6 devices to communicate through IPv4 connected networks by embedding IPv4 address in its IPv6 address which can later be extracted by IPv4 routers to route through IPv4 networks.
• Deprecated in favor of IPv4-mapped IPv6 addresses.

1. V4 mapped V6 address

• Add 2 bytes of 1’s to v4 address then zero-extend the rest – e.g. ::ffff:10.0.0.1
• Used to represent the addresses of IPv4 nodes as IPv6 addresses to applications that are enabled for IPv6

3. Tunneling:

It is used to deal with networks where v4 router(s) sit between two V6 routers. Simply encapsulate V6 packets and all of their information in V4 packets until you hit the next V6 router.

Header Translation

1. Converting IPv6 Header to IPv4 and vice versa
2. Used to link IPv6 and IPv4 Networks
3. Some header fields may have lost during translation

• E.g. When converting IPv6 Packet to IPv4, the header information like Flow-label gets lost

References:

1. A.S. Tanenbaum, “Computer Networks”, 3rd Edition, Prentice Hall India, 1997.
2. W. Stallings, “Data and Computer Communication”, Macmillan Press, 1989.
3. Kurose Ross, “Computer Networking: A top-down approach”, 2nd Edition, Pearson Education
4. Larry L. Peterson, Bruce S. Davie, “Computer Networks: A Systems Approach”, 3rd Edition, Morgan Kaufmann Publishers