GSRP: An Application-Level Protocol Supporting Asynchronous Communication

3A access paradigm is a key problem in the decoupling Grid environments, which has important impacts on how users utilize and operate Grid. It has gained much attention in research fields of Internet, Mobile Computing and Pervasive Computing. This paper designs and implements a protocol named Grid Service Request Protocol (GSRP) that supports the user 3A access paradigm. It provides integrated synchronous and asynchronous communication, and realizes session management and session migration.The separation of session states from session applications,and the separation of message representations from message transportations are two basic patterns of GSRP. The protocol manages session states by self-controlled intermediate component. The intermediate also acts as a proxy of session migration and asynchronous conversation. GSRP consists of two layers which are Application Session Layer (ASL) and Message Transport Layer (MTL). ASL provides interfaces to send and receive message for upper applications, and MTL responds to the encapsulation and distribution of messages. GSRP emphasizes the unilateral operation. Any command by users does not require association with other sides in session.Soft-connection and persistent handler are two innovative mechanisms in GSRP. The soft-connection is a logical circuit to send GSRP packets on reliable TCP connection. It can be bound by different TCP connection in different time. To end-users it is always a continuous and uninterrupted path. The persistent handler is a dumped structure to manage sessions on intermediates.This paper conducts relative experiments in the protocol's platform developed by JAVA. The intermediate overhead, asynchronous communication function, session migrating time and packet transfer time are tested and analyzed in detail by experiments. The paper also evaluates other mechanisms and characters of GSRP. Based on experiments and evaluation result, GSRP can enable any time, any where and on any device access of users in some extension.