NonStop S-Series Planning and Configuration Guide (G06.25+)

HP NonStop S-Series Planning and Configuration Guide—523303-015
3-1
3 Topologies
This section introduces the concept of the tetrahedral topology and describes the
ServerNet topologies available on NonStop S-series servers.
Tetrahedral Topology
The pattern in which the enclosures of a NonStop S-series system are arranged and
cabled together is called a topology. For example, four enclosures can be arranged in
different topologies: straight line (inline), wye, square, or tetrahedral.
In a tetrahedral topology, the connections between the processor enclosures in the
system allow each of the four enclosures to communicate directly with every other
enclosure without passing the message through a second enclosure.
By comparison, in an inline topology, the first enclosure has to pass the message
through two enclosures to communicate with the last enclosure. In a wye topology, the
central enclosure can communicate directly with the outer enclosures, but the outer
enclosures cannot communicate directly with each other. In a square topology, an
enclosure can communicate directly with the two adjacent enclosures but not with the
opposite enclosure.
Note. I/O adapter module (IOAM) enclosures are supported by NonStop S76000 and later
NonStop S-series systems in Tetra 8 and Tetra 16 topologies.
Tetrahedral Topology 3-1
ServerNet Topologies 3-3
Tetra 8 Topology 3-4
Tetra 16 Topology 3-5
Topology Configuration Considerations 3-9
Comparing the Tetra 8 and Tetra 16 Topologies 3-11
Tetra 8 Topology Configurations 3-11
Tetra 16 Topology Configurations 3-12
Tetra 8 Topology Features 3-13
Tetra 16 Topology Features 3-13
ServerNet Topology Configuration 3-14
Where the ServerNet Topology Configuration Value Is Stored 3-14
The ServerNet Topology Configuration Value and CRU
Replacement
3-15
ServerNet Routing Tables 3-15