1. Automatic Subnet Numbering
Hilarie Orman

2. Layer Addressing Characteristics
Unique, uncorrelated addresses
Linear strings of nodes
Join points
Spanning tree
Layer 3
Address blocks grouped by contiguous bits
Mesh of routers
Configured topology over layer 2
Universal address space

3. Routers and Subnets without IP addrs, no routingX X X X X

4. IP Address Fixed prefix ARIN or non-routable Subnet number Host number
DHCP

5. X X X X X SubnetNumbers SUBNET 7 SUBNET8 SUBNET 5 SUBNET 6 SUBNET 4

6. Requirements Support initialize, join, leave, partition, rejoin
Utilize IPv4 addresses efficiently
Solve v6 and v4 assignments
Cooperate with DHCP
Minimal interference with ongoing end node connections
Be secure

7. X Central Authority Single point of failure
Request Subnet Number X
Reply
Subnet Number
Single point of failure
--- ameliorate with elections

8. Distributed Agreement ProtocolX X X
Router 1 needs
3 subnet numbers X
Router 2 needs
2 subnet numbers X

9. Distributed Protocol Problems
Might be slow at startup
Partitions due to failure require renumbering
Partition joins as part of network growth would be complicated
Authentication … via secure multicast keying?

10. Network Partition / Nodes Join
SUBNET 7
SUBNET 1
SUBNET 10 X
SUBNET8 X
SUBNET 2 X
SUBNET 9 X
SUBNET 3 X
SUBNET 10 X
SUBNET 4

11. X X X Node Mobility Prefix | subnet 1 | hostnum

12. Address Utilization Mobility makes subnet size difficult to predict
Simplest assignment method divides address space into N subnets of equal size
Must overprovision and waste
Dynamic subnet size adjustment
Difficult to synchronize

13. Automatic Numbering at Layer 3 Main Points
No end node mobility without mobile IP
Partition/rejoin might require reassigning end node addresses
Breaks connections
Sizing subnets is awkward