Ethernet Switches & Routers

IPv4 Internet Routing Table Growth: No Signs of Deaggregation, Yet

by Greg.Hankins on ‎08-18-2011 01:18 PM (311 Views)

The remaining available IPv4 address pool and growth of the IPv4 Internet routing table is something that I've been watching closely.  We've seen two significant events this year already, that make running out of IPv4 addresses in the near future very real:

  • IANA (Internet Assigned Numbers Authority, the entity that controls numbers for protocols, the Country Code Top Level Domains and maintains the IP Address allocations) officially allocated the remaining five IPv4 /8s to the Regional Internet Registries (RIRs) on February 3, 2011.
  • APNIC (Asia Pacific Network Information Centre, the RIR that allocates IP and AS numbers in the Asia Pacific region) implemented a strict allocation policy for their last IPv4 /8 on April 15, 2011.

As IPv4 addresses become scarcer, it will have a significant impact on the Internet routing table size.  We're just not sure what exactly will happen though, because we've never been in this situation before.  One thing we do expect to happen, is that IPv4 addresses will be chopped up into smaller pieces, which is also known as deaggregation.  For example, someone might take a /23 address and divide it into two /24 addresses that will then both be carried in the Internet routing table.  The result is that the Internet routing table could grow rapidly and unpredictably in the future.

The good news is that while the Internet routing table has grown about 9.22% since the beginning of this year, the percentage of each prefix length in the table and the average prefix length has remained almost constant.  This means that the Internet routing table is still growing efficiently, and that there are no signs of large scale deaggregation... yet.

Let's take a look at two graphs that show the percentages of each prefix length distribution.  What we're looking for is a change in the distribution percentages, or in the average prefix length.  So far this year, the prefix distributions change only slightly compared to the historical ranges.

as6447-01-jan-2011-18-aug-2011-prefixes.png

AS6447 Internet Routing Table Statistics, Average Prefix Length 22.3747

Source: bgp.potaroo.net

as131072-01-jan-2011-18-aug-2011-prefixes.png

AS131072 Internet Routing Table Statistics, Average Prefix Length 22.3454

Source: bgp.potaroo.net

I'll be writing updates on the Internet routing table growth, so watch the Brocade Service Providers Forums for more news on this topic.  Click here for more information on Brocade's routing solutions.

References

Two sets of historical routing table data are publicly available that are used widely in IP routing table research:

Special thanks to Geoff Huston (APNIC) for his work and analysis tools, which are available at the BGP Routing Table Analysis Reports site.