A different communication model

The communication model commonly used to design recovery rollback is datagram oriented: a packet is sent at some time to a destination, and it is received at a later time.

The cause-effect relation binds the state of the source process when it sends the packet, and the state of the destination process when it receives the packet.

This model is adequate to describe IP communication, by nature lightweight: the application of a dynamic checkpoint selection algorithm at this point has an unsustainable impact.

Instead, we propose a session oriented protocol, where the cause-effect relation binds instances of complex synchronization protocols, that we call sessions.


A number of communication protocols induce syncronization actions: the simplest is probably TCP, with the 3-way handshake, but sessions are explicitely indicated by RFC2543 for "multimedia conferences, Internet telephone calls and multimedia distribution".

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International Symposium on Computers and Communications