draft-ietf-drums-smtpupd-04.txt

Abstract data types have proved to be a useful technique for structuring systems. In large systems it is sometimes useful to have different regions of the system use different representations for the abstract data values. A technique is described for communicating abstract values between such regions. The method was developed for use in constructing distributed systems, where the regions exist at different computers and the values are communicated over a network. The method defines a call-by-value semantics; it is also useful in nondistributed systems wherever call by value is the desired semantics. An important example of such a use is a repository, such as a file system, for storing long-lived data.

This thesis is about the efficiency of protocol layering. It examines the technique of protocol layering in an abstract way and finds two major sources of inefficiency in protocol implementations which are caused by the imposition on them of a layered structure. The conventional approach to making layered protocol' implementations run efficiently m for avoiding the sources of inefficiency discussed herein -- are all independent of the protocol specification, and thus all decrease the value of the protocol specification as a guide for implementing protocols.

INTRODUCTION The principal aim of the mail service transition plan is to provide orderly support for computer mail service during the period of transition from the old ARPANET protocols to the new Internet protocols. This plan covers only the transition from the current text computer mail in the ARPANET environment to text computer mail in an Internet environment. This plan does not address a second transition from text only mail to multimedia mail [10,11]. The goal is to provide equivalent or better service in the new Internet environment as was available in the ARPANET environment. During the interim period, when both protocol environments are in use, the goal is to minimize the impact on users and existing software, yet to permit the maximum mail exchange connectivity. It is assumed that the user is familiar with both the ARPANET and Internet protocol environments [1-8]. The Internet protocols are designed to be used in a diverse collection of networks including the ARPANET