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13 Simple Interprocessor Communication Protocol Specification
13.1 Application Scenario
The purpose of this protocol specification is to provide a framework which allows the
exchange of data and simple system control commands between single nodes of a multiprocessor system. Nodes in this
context are understood as computing nodes and controlling nodes (a physical node may be a mix of both). The exchange of
data and commands is structured into packets.
A target multiprocessor system for this protocol is understood as a "small to medium size" system:
-
the multiprocessor system is based on a message passing architecture with only local memory
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the protocol supports 256 different link addresses, this means the protocol is applicable to multiprocessor systems
consisting of e.g. 256 nodes each with one link (not very likely), 64 nodes each with four links, 32 nodes each with
8 links, etc ...
-
the interconnect network between the nodes is a 'flat' network, no hierarchical addressing is required and supported.
Especially 'header deletion' is not supported (since it is not required in such relatively small networks)
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multicast and broadcast messages are not supported, only 'simple' destination fields in ECSS-E-50-12A terminology
are provided
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the three previous addressing characteristics allow to reduce the size of the destination field of the packet header to
one byte
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the target system is physically small enough to fit into one box: the interconnect capabilities covers connections
between elements on a PC-board and between boards in a box (via a backplane or equivalent interconnect system).
Interconnect between boxes is not covered. This has one major implication: it is assumed that the electrical
environment within boxes is "clean" and no error is introduced on the links (e.g. by spikes, noise or HF
interference).
Experience with bus systems has shown that indeed data transfer can be regarded as reliable and parity checking is sufficient
to detect possible (very rare) transmission failures. In this case error recovery must be handled by some kind of control
program.
It is assumed that a SW kernel is running on the nodes of the system, providing resources for the execution for the major part
of the transaction level protocol functions. From the transaction level protocol functions, the specification scope of this
document covers the frame of the data transfers between two nodes and the coding and execution of a range of required
control commands. It is explicitly intended to specify only a minimum of transaction level functions and formats in order to
keep flexibility and broaden the application range.
In general, the basic design approach can be described as trading off functionality for conceptual and implementation
simplicity and speed.
SMCS332SpW
User Manual
– All Rights Reserved – Copyright per DIN 34 –
EADS Astrium GmbH, ASE2
Doc No: SMCS_ASTD_UM_100
Issue:
1.4
Updated: 9-Sep-2006
Page:
114 of 131
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