RFC 1753 (rfc1753) - Page 2 of 18

IPng Technical Requirements Of the Nimrod Routing and Addressing Architecture

RFC 1753         Nimrod Technical Requirements for IPng    December 1994


   While current day routing technologies do not yet have the
   characteristics and capabilities that generate these requirements,
   they also do not seem to be completely suited to routing in the
   next-generation Internet. As routing technology moves towards what is
   needed for the next generation Internet, the underlying fundamental
   laws and principles of routing will almost inevitably drive the
   design, and hence the requirements, toward things which look like the
   material presented here.

   Therefore, even if Nimrod is not the routing architecture of the
   next-generation Internet, the basic routing architecture of that
   Internet will have requirements that, while differing in detail, will
   almost inevitably be similar to these.

   In a similar, but more general, context, note that, by and large, the
   general analysis of sections 3.1 ("Interaction Architectural Issues")
   and 3.2 ("State and Flows in the Internetwork Layer") will apply to
   other areas of a new internetwork layer, not just routing.

   I will tackle the internetwork packet format first (which is
   simpler), and then the whole issue of the interaction with the rest
   of the internetwork layer (which is a much more subtle topic).

2. Packet Format

2.1 Packet Format Issues

   As a general rule, the design philosophy of Nimrod is "maximize the
   lifetime (and flexibility) of the architecture". Design tradeoffs
   (i.e., optimizations) that will adversely affect the flexibility,
   adaptability and lifetime of the design are not not necessarily wise
   choices; they may cost more than they save. Such optimizations might
   be the correct choices in a stand-alone system, where the replacement
   costs are relatively small; in the global communication network, the
   replacement costs are very much higher.

   Providing the Nimrod functionality requires the carrying of certain
   information in the packets. The design principle noted above has a
   number of corollaries in specifying the fields to contain that
   information.

   First, the design should be "simple and straightforward", which means
   that various functions should be handled by completely separate
   mechanisms, and fields in the packets. It may seem that an
   opportunity exists to save space by overloading two functions onto
   one mechanism or field, but general experience is that, over time,
   this attempt at optimization costs more, by restricting flexibility
   and adaptability.



Chiappa