Review: RFC 4984 - Report from the IAB Workshop on Routing and Addressing

This document is a report on the proceedings of the workshop on Routing and addressing held in 2006. It points on major limitations of today's internet (IPv4 and IPv6) and the features to keep in mind when redesigning tomorrow's internet.

The following paragraph presents a brief summery of the major problems:

The Scalability of the Routing System: the growth of the routing tables (Routing Information Base (RIB)) results from adding more address prefixes in the table. This growth is due to the natural growth of the internet and the de-aggregation of address prefixes. This de-aggregation is caused mainly by multihoming and traffic engineering.

Multihoming is when a host is served with more than one Internet Service Provider (ISP). This provides a host usually running critical applications more reliance. In case of failure of the primary ISP, the host can switch to another ISP. This solution avoids the single point of failure and allows the host to continue serving its clients.
Consider a network C with a prefix from an Internet Provider P1. When C multihomes with a second provider P2 then both P1 and P2 should announce globally that C can be reached from P1 and P2. This causes prefix de-aggregation since it is not provided by P2. So P2 updates its RIB with the prefix of C provided by P1. P2 informs C prefix globally this means that other routers will update their RIB too.
This operation causes the growth of RIB tables by adding additional de-aggregated prefix entries.

Traffic engineering: is used for load balancing, it allows packets to use or avoid network paths. When a path is overloaded traffic engineering allows routers to deliver packets using another paths. This operation causes to add more de-aggregated prefixes to the routing tables. Sometimes it is used for political reasons. The traffic of one government is not allowed to transit through routers of an other government.

Large numbers of mobile networks: with the increasing number of mobile devices, users can now access internet from almost anywhere even on planes as Boieng announced. Today each mobile network can be announced by a prefix, actual routers handles several thousands of mobile networks prefixes.
There is an open question regarding the impact of global routing if the number of such networks increases (e.g. on planes, trains, ships).

Mobile hosts: Billions of gadgets, sensors can become online in the next several years. The current solutions use home agents, so from routing perspective it is considered like stationary hosts.
However if another solution was proposed with a clear separation between identity-location than there might be some impact. This is why further investigation is needed.

The overloading of IP address semantics: IP address is used as an identifier and a locater while we should split the identity from location. When a host moves its position, its identity remains the same while its location changes.
In the multihoming example, a prefix is used to locate and identify a network.
Though an IP address must be used only to locate a host based on network topology.

IPv6: It is believed that IPv4 address space (32 bits) restrained the growth of the RIB tables. The deployment of IPv6 with a larger address space (128 bits) might cause the growth of RIB tables by a factor of 4.

Hardware limitations: the growth of RIB tables increases the need to build more powerful routers to handle this growth. However the costs of silicon is dominated by the actual fabrication hosts. The silicon used in core routers is produced in low volume (1.000 - 10.000) unit per year while the microprocessors volume is in millions per year. This places the router silicon under the cost curve.
The increase in bandwidth forced router manufacturers to increase
silicon technology but now the hardware is near to its limits. This means that the hardware will not keep up with the increase of bandwidth.
In routers, DRAM is used for storing the routing table entries, the DRAM access speed must grows faster to keep up with the extension of the RIB entries.
More entries means more access speed to maintain a certain level of performance.
There is also the Heat and Power Factor actually transistors consume power even when it is Idle. The smaller and hotter the transistors, the larger the current, so powerful routers need cooling technology and at present the air cooling is starting to be a limiting factor.



Link to the RFC 4984