sustrik@250bpm.com

Applications Internet Engineering Task Force Publish Subscribe PUB SUB distribution SP This document defines a scalability protocol used for distributing data to arbitrary number of subscriber nodes.

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The publish/subscribe protocol can be run on top of any SP mapping, such as, for example, SP TCPmapping. Also, given that SP protocols describe the behaviour of entire arbitrarily complex topology rather than of a single node-to-node communication, several underlying protocols can be used in parallel. For example, publisher can send a message to intermediary node via TCP. The intermediate node can then forward the message via PGM etc.

+---+ TCP +---+ PGM +---+ | |----------->| |---------->| | +---+ +---+ +---+ | | PGM +---+ +------------>| | +---+

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End-to-end functionality is built on top of hop-to-hop functionality. Thus, an endpoint on the edge of a topology contains all the hop-by-hop functionality, but also implements additional functionality of its own. This end-to-end functionality acts basically as a user of the underlying hop-by-hop functionality.

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TODO: Do we want any loop avoidance in PUB/SUB?

New SP endpoint types PUB and SUB should be registered by IANA. For now, value of 32 should be used for PUB endpoints and value of 33 for SUB endpoints. IANA should eventually also register and issue numbers for different message matching algorithms.

The mapping is not intended to provide any additional security to the underlying protocol. DoS concerns are addressed within the specification.