1. Chapter 20. Network Layer: IP
Internetworking
IPv4
IPv6
Transition from v4 to v6
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Communication Networks, KWU

2. Communication Networks, KWUIP
Network layer protocol for the Internet
Unreliable datagram protocol: Best-effort service
Packets in the IP layer is also called datagrams
No error control or flow control
Only an error detection mechanism
Delivery of a packet with no guarantees
Connectionless protocol
Each datagram (packet) is handled independently
Each packet can follow different route to the destination
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Communication Networks, KWU

3. Communication Networks, KWU
IP Datagram
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Communication Networks, KWU

4. Communication Networks, KWU
IP: Multiplexing
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Communication Networks, KWU

5. Communication Networks, KWU
IP: Fragmentation
MTU (Maximum Transfer Unit)
Identification
Flags (3 bits)
DF: the 2nd bit, Do not Fragment bit
MF: the 3rd bit, More Fragment bit
Fragmentation offset: the value of the offset if measured in units of 8 bytes
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Communication Networks, KWU

6. IP Fragmentation: Example
Original packet length = packet header (20 bytes) + payload (4000 bytes)
MTU of the link = 1420 bytes
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Communication Networks, KWU

7. Communication Networks, KWU
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Communication Networks, KWU

8. Communication Networks, KWU
IP: Header Checksum
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Communication Networks, KWU

9. Communication Networks, KWU
IPv6
Larger address space – hexadecimal colon notation
Better header format
New options
Allowance for extension
Support for resource allocation
Support for more security
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Communication Networks, KWU

10. IPv6: Abbreviated Address
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Communication Networks, KWU

11. IPv6: Transition from IPv4
Huge number of systems on the Internet
The transition from IPv4 to IPv6 cannot happen suddenly
Three strategies devised by the IETF
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Communication Networks, KWU

12. Transition Strategies: Dual Stack
It is recommended that
all hosts have a dual stack
before migrating completely to version 6
The source host queries the DNS to determine which version to use
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Communication Networks, KWU

13. Transition Strategies: Tunneling
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Communication Networks, KWU

14. Transition Strategies: Header Translation
When the majority of the Internet has moved to IPv6
IPv6 sender and IPv4 receiver
Spring 2010
Communication Networks, KWU