The level of handshake required for managing a connection

Abstract

A connection between two hosts across a widearea network may consist of many sessions over time, each called an incarnation. A connection is synchronized using a connection establishment protocol, based on a handshake mechanism, to allow reliable exchange of data. This paper identifies the precise level of handshake needed under different assumptions on the nodes and on the network, using a formal model for connection management. In particular, the following parameters are studied: the size of the memory at the nodes, the information retained between incarnations, and the existence of time constraints on the network. Among the results we obtain are: (1) If both nodes have bounded memory, no incarnation management protocol exists. (2) If the nodes have unbounded memory, then a two-way handshake incarnation management protocol exists. (3) If the nodes have unbounded memory, and the server does not retain connection-specific information between incarnations, then a three-way handshake incarnation management protocol exists. On the other hand, a two-way handshake incarnation management protocol does not exist, even if some global information is retained. (4) If a bound on maximum packet lifetime (MPL) is known, then a two-way handshake incarnation management protocol exists, in which the server does not retain connection-specific information between incarnations.

Exon: An Oblivious Exactly-Once Messaging Protocol

“…Indeed, Attiya et al [3] proved that if the nodes have unbounded memory, a three-way handshake oblivious protocol exists, whereas a two-way handshake oblivious protocol does not exist. The same paper proved also that if a bound on maximum packet lifetime (MPL) exists and is known, then a two-way handshake oblivious protocol is possible, but at least MPL must elapse between the time two consecutive incarnations are established-which is impractical in most networked applications.…”

“…The protocol most related to Exon is Attiya's three-way handshake oblivious unbounded memory protocol [3], in also only requiring a single integer as node state between incarnations. But Attiya's protocol is classically connection based, with API-visible full-duplex connections, which prevents safely ensuring exactly-once message delivery, as the receiving side can concurrently close the connection, preventing delivery.…”