The Directors Cut

IPng discussions reached a climax at the Toronto meeting of the IETF in July when the IPng area directors made recommendations for the features of IPng, selecting what they believe to be the most appropriate aspects of the four main contenders for IPng. The main features of IPv6 (IP version 6, the protocol that will support IPng) are:

• 128 bit addresses. Even given the Internets exponential growth rate (it is doubling in size each year) and the potential for whole new markets, such as UPC (universal personal communications) and energy managements systems (where every appliance becomes a potential internet `node'), 128 bit addresses should provide adequate addressing capability for any network limited to this planet.

  One of the lessons of IPv4 is that while an address space that is partitioned into sub-addresses is administratively powerful it does not give an optimal usage of addresses. IPv6 has about 4 billion billion times the address space of IPv4. Allowing for the lowered utilisation of a partitioned address space 128-bit addresses give between 1500 and 500 billion addresses per square meter of the earths' surface (depending on how pessimistic you are about the effect of address partitioning.)

• New address classes including topology based addresses and sub-classes of addresses for NSAP, IPX, IPv4 and local use addresses. In addition more flexibility has been introduced into multicast addresses.

• A simpler header, allowing faster routing. Over recent years the increase in transmission bandwidth has meant that for many networks it is now CPU power, not transmission bandwidth, that limits the throughput of a network. As a consequence simpler protocols that require less processing are being developed, even if less useful information per byte is sent on the line.

• Much greater flexibility in the format and number of options fields, including a mechanism that allows most options to remain unread at most routers.

• Support for authentication and privacy mechanisms. IPv4 does not provide strong authentication or privacy, although this can be provided by an Internet application, like Kerberos. The IPv6 options include support for both authentication and privacy. Although the protocol does not impose particular authentication and privacy mechanisms it is expected that keyed MD5 will be used for authentication and DES CBC will be used for privacy.

  The ability to support arbitrary security and privacy mechanisms gives both future-proofing and allows more general export of the protocol from countries (like the US) which place limits on the export of security mechanisms.

• Improved facilities for specification of the type of source that generated the packet. This allows packets to be processed in a manner most appropriate to the requirements of the particular usage. For example real-time traffic, say from a video-phone, should be delivered with a low latency even at the cost of higher packet loss, where as data traffic should be delivered with the lowest possible packet loss rate.

 
Figure 1: The Old and the New