All efficient applications have the requirement for an efficient transport mechanism. For this reason, part of the initial focus of the LEAP protocol development effort has been on creating a general efficient transport mechanism. The resulting protocol is referred to as Efficient Short Remote Operations, or ESRO. ESRO is the efficient transport layer protocol for several LEAP applications. ESRO is a reliable connectionless transport mechanism, forming the foundation for the development of efficient protocols when TCP is too much and UDP is too little.
The need for efficient protocols extends across all aspects of wireless data communications, including e-mail, web browsing, and other applications. The LEAP architecture accommodates many of these applications based on the use of ESRO.
ESRO was published as RFC-2188 [25] in September of 1997. The ESRO protocol is publicly maintained and enhanced by ESRO.org at http://www.esro.org/. Patent free declarations have been made with respect to ESRO through the Free Protocols Foundation.
Considering that:
ESRO has been designed to address these specific needs.
The need to address the requirements that the ESRO protocol addresses has been well recognized for quite a long time. As early as 1995 such requirements were being discussed within the Internet research community. In particular, RFC-955 [3], entitled ``Towards a Transport Service for Transaction Processing Applications,'' demonstrates recognition of the need for ESRO. A more recent document, RFC-2757 [18], entitled ``Long Thin Networks,'' again recognizes the demand for such a protocol.
In the past, this unaddressed demand has given rise to a variety of product oriented proprietary solutions (as opposed to open protocols) which are often referred to as ``Middleware Products.'' This has been particularly widespread in the wireless industry. Often these solutions are vendor specific and do not scale.
The requirements and goals driving the ESRO protocol and system design include the following:
A description of ESRO includes references to a number of basic data communications concepts and ideas. Because of the informal, ad hoc, and often inconsistent terminology used within the Internet technical community, many of these concepts are referred to by a variety of different names throughout various documents and RFCs. Many of the RFCs mentioned below refer to ESRO-related concepts in an inconsistent manner.
In contrast to this, the ESRO specification uses the well defined and precise terminology of the ``Open Systems Interconnection Reference Model'' [19]. In this paper we will also adhere to the same precise terminology.
An example of the use of imprecise terminology is the term ``Transaction Processing.'' Various other protocol specifications refer to the concept of ``Remote Operations'' as ``Transaction Processing.'' In our terminology, however, Transaction Processing goes above and beyond Remote Operations, and also includes the concepts of Commitment, Concurrency and Recovery, and chained (related) Remote Operations which may be built on top of ESRO.