Frank and Frank -- 5 August 1991 -- B-I --------------------------------------- Network Working Group F. Solensky INTERNET-DRAFT F. Kastenholz Clearpoint Research Corp. August, 1991 Definition of Class E IP Addresses Status of this Memo This Internet Draft document will be submitted to the RFC editor for a standards document. Comments and suggestions are welcome and may be sent to the authors. Distribution of this memo is unlimited. Abstract This memo presents an extension to the method of classifying and assigning IP network numbers. It is intended to provide an temporary work-around to the imminent exhaustion of Class B network numbers until new architectures are developed [1]. It is a product of a "birds-of-a-feather" discussion held on July 21, 1991 at the twenty- first IETF conference held in Atlanta, GA. It should be noted that this document does NOT address the limitations inherent in the current routing architectures and technology. Specifically, the issue of scaling is not addressed. Background During the latter part of the 1980's, an ever-increasing number of organizations came to realize the advantage and importance of allowing their computer systems to interconnect with other systems and networks around the globe. While this is usually seen as a positive trend, it has not been without its drawbacks. One of the more immediate problems that this sudden growth has presented is a continuing heavy demand for Class B network numbers. While there are still a very large number of Class C addresses available, few organizations expect that their connectivity needs will be satisfied within the limitations of 254 IP addresses. The level of demand for Class B addresses can be illustrated by a short analysis of the data available. In the period between August 1990 and June 1991, the number of assigned Class B network numbers grew from 2533 to 5654 [2,3]. This averages out to an annual growth rate of over 123%. If this trend were to continue, the pool of available Class B network numbers would be depleted by October 1992. Solensky, Kastenholz [Page 1] INTERNET DRAFT AUGUST, 1991 While the authors acknowledge that a logistic or "s-shaped" curve would be a more realistic model, a projection based on this assmption would not be realistic until we have clearly passed the inflection point on the curve - the point at which the curve starts to climb less rapidly towards its upper limit. The data available at this time suggests that this leveling off has not yet occured: the annual growth rate in the allocation of Class B network numbers between 1983 and mid-1990 was only 78% [4], indicating that the growth rate is continuing to increase. Class E Network Numbers The entire Class E address space will be used for the assignment of new IP network numbers. Within the 28 bits available in Class E addresses, the first sixteen will define the network number and the remaining twelve will be the local address, as illustrated below. 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |1 1 1 1| NETWORK | Local Address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Class E address This approach has the advantage of allowing a more practical network size than the Class C address space (4094 addresses as compared to 254) while reducing the probability that large amounts of numbers would remain unused within the network. The network number 255.255.240.0 is reserved so that it does not conflict with the address reserved for IP broadcasts (255.255.255.255). Revisions to IP Address Classes A and C. The space for both Class A and C network numbers will be reduced. The low half of these address ranges - network number fields starting with "0" - will continue to be used in their present form, as illustrated. 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |0 0| NETWORK | Local Address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Revised Class A address Solensky, Kastenholz [Page 2] INTERNET DRAFT AUGUST, 1991 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |1 1 0 0| NETWORK | Local Address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Revised Class C address The upper half of these classes will be redesignated as classes F and G. These are illustrated below. 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |0 1| reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Class F address 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |1 1 0 1| reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Class G address This reduces the number of networks in each class to 126 and 1048574 respectively. It should be noted, however, the demand for numbers in these network classes has not been nearly as great as that for Class B. The reason for this is that by reserving the upper half of these address ranges, there will be sufficient numbering space available to develop alternative network number classifications should the need arise in the near future. This may include the restoration of their prior interpretations. For the sake of completeness, Class B and D addresses are also illustrated. The use of Class D or multicast addresses is specified in [5]. 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |1 0| NETWORK | Local Address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Class B address Solensky, Kastenholz [Page 3] INTERNET DRAFT AUGUST, 1991 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |1 1 1 0| multicast address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Class D address Conclusions It must be emphasized that this is intended only to be a work-around to the problem. It is by no means a "solution". While it defines a network classification that is four times the size of the original Class B space, this will only survive only two years if current growth rates continue. By that time, it is expected that the increased amount of network connectivity which has been exhibiting similar growth rates [4,6] will cause the computational intensity of keeping track of these routes to require an entirely different routing and addressing architecture for the Internet such as the one described in [5]. References: [1] "A New IP Routing and Addressing Architecture", J. Noel Chiappa. [2] "Internet Numbers", S. Kirkpatrick, M. Stahl, M. Recker, RFC 1166, SRI International, July 1990. [3] Internet Monthly Report, A. Westine [ed], June, 1991. [4] "Continued Internet Growth", Frank Solensky, Proceedings of the Eighteenth Internet Engineering Task Force, July 30-August 3, 1990. pages 59-61. [5] "Host Extentions for IP Multicasting", S. Deering, RFC 1112, SRI International, August 1989. [6] "Growth of the Internet", Mike St. Johns, Proceedings of the Thirteenth Internet Engineering Task Force, April 11-14, 1989, pages 244-248. Solensky, Kastenholz [Page 4] INTERNET DRAFT AUGUST, 1991 Authors' Address: Frank Solensky Frank Kastenholz Clearpoint Research Corp. 35 Parkwood Drive Hopkinton, MA 01748 Phone: (508) 435-2000 Email: solensky@clearpoint.com, kasten@clearpoint.com Solensky, Kastenholz [Page 5]