« Finally, Martin Kafai Lau asked if work should be done to merge the IPv4 and IPv6 FIB (forwarding information base) trees. The FIB tree is the data structure that represents routing tables in the Linux kernel. Miller explained that the two trees are not semantically equivalent: while IPv6 does source-address lookup and routing, IPv4 does not. We can't remove the source lookups from IPv6, because "people probably use that". According to Alexander Duyck, adding source tables to IPv4 would degrade performance to the level of IPv6 performance, which was jokingly referred to as an incentive to switch to IPv6.
« More seriously, Sowa argued that using the same compressed tree IPv4 uses in IPv6 could make sense. People may want to have source routing in IPv4 as well. Miller argued that the kernel is optimized for 32-bit addresses in IPv4, and conceded that it could be scaled to 64-bit subnets, but 128-bit addresses would be much harder. Sowa suggested that they could be limited to 64 bits, as global routes that are announced over BGP usually have such a limit, and more specific routes are usually at discrete prefixes like /65, /127 (for interconnect links) or /128 for (for point-to-point links). He expressed concerns over the reliability of such an implementation so, at this point, it is unlikely that the data structures could be merged. What is more likely is that the code path could be merged and simplified, while keeping the data structures separate. » https://lwn.net/Articles/719297/ _______________________________________________ homenet mailing list homenet@ietf.org https://www.ietf.org/mailman/listinfo/homenet
