IPv6 Stress

I was reading this article on seven IPv6 myths today and a random thought entered my head. The article seemed to stress that the only real difference that IPv6 makes in this world is extending the address space from 32-bits to 128-bits. This is a 4x increase in the address space currently used.

This instantly triggered a yellow-flag in my head. This also means that there will be a marked increase in the memory space on networking devices, coupled with an increase in memory bandwidth consumption on the said devices.

What many people may not know is that on a networking device like a router, routes need to be maintained for the duration of a connection. This is usually maintained as some sort of table in the memory. When a network packet comes into a router, its header is examined for the destination address. This is then used to look-up the route to take in the routing table. Then, the network packet is forwarded onto the route on its way to the destination.

So, an IPv6 routing table would need to quadruple its memory space requirements. This would not be so bad if we didn’t take the real-world performance of memory into account. It would also mean that the amount of memory transfers would be quadrupled as well, assuming similar table and lookup patterns.

While I have not researched into this, I do think that there is room for innovation here. We could possibly change the routing table structure by dropping off some of the bits or to partition it up into directories indexed by the significant bits of the address or to hash the IP addresses in such a way as to reduce memory requirements.

This may not mean much to a lot of people but if the route look-up process slows down by a factor of four, it will significantly affect the latency of the network even if its effects on throughput may be minimal. Latency is very important for certain applications, anything that requires near real-time feedback like first-person shooters.


Published by

Shawn Tan

Chip Doctor, Chartered Engineer, Entrepreneur, Law Graduate.

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