In today's networks, backbone routers must keep track of every route in the Internet. So, the size of routing tables is outpacing the rate of growth of memory technology. To reduce this size, more layers of subnets can be created but they could take up more of the address space in the packet header.
And IPng's 32-byte address space could prove inadequate.
One solution to prevent an address shortage is to use a
The catch of this scheme is its processing complexity which can drag down network performance. But variable-length addresses add very little to processing overhead. One example of this approach is based on connectionless network protocol (CLNP).