Sockets Direct Protocol

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The Sockets Direct Protocol (SDP) is an agreement ( protocol ) for the exchange of data between computers. This is a byte stream transport protocol that mimics the Transmission Control Protocol (TCP).

SDP provides the application (the user ) with a uniform socket interface . Based on this mapping of the standard socket operations to operations of the InfiniBand architecture, socket-based applications can use the advantages of the InfiniBand architecture (IBA) without further adjustments. An SDP Upper Layer Protocol (ULP) can now transmit data in a message-oriented manner via a byte stream interface with a reliable InfiniBand connection (InfiniBand's Reliable Connection).

A distinction is made between the following two methods for the actual transmission:

  • The buffer copy mechanism uses private buffers to transfer the data. For this it is necessary that the data is first copied from the main memory into a private buffer and then can be transferred to another node .
  • With the zero-copy mechanism, on the other hand, the data is transferred between a DMA and an RDMA buffer with RDMA read / write. It is therefore possible to access memory areas of a remote node directly without having to make a copy of the memory area beforehand.

SDP was specified by the InfiniBand Trade Association (IBTA) .