Hierarchical Distribution

Vance Shipley <>
Fri Apr 20 00:43:44 CEST 2001


Folks,

I came across Ericsson's 'Cello' product recently and found the 
description of it's "execution platform" quite interesting.  I
am left wondering if it might be Erlang/OTP based.  In any event
I'm interested in how Erlang/OTP could be used to implement the
distribution as it is described in the white paper:

	http://www.ericsson.com/review/1999_02/files/1999021.pdf


The hardware is made up of a number (1-50) of 19" rack mount chassis 
which they refer to as 'subracks'.  In each subrack there is a 
'main processor' (MP) board as well as a number (1-25) of 
'device boards'.  The device boards contain 'board processors' (BP)
and may also contain 'subordinate processors' (SP).

The logical topology uses a 'main processor cluster' (MPC).  The 
BPs are hierarchically under a single MP while the SPs are hierarchically 
under a single BP.

     +----------------------------+
     | MPC       +----+           |      +----+       +----+
     |           | MP |           |------| BP |  -----| SP |
     |           +----+          /|      +----+ /     +----+
     |   +----+          +----+ / |      +----+/      +----+
     |   | MP |          | MP |<--|------| BP |-------| SP |
     |   +----+          +----+ \ |      +----+\      +----+
     |                           \|      +----+ \     +----+
     |               +----+       |------| BP |  -----| SP |
     |               | MP |       |      +----+       +----+
     |               +----+       |
     +----------------------------+
                        
So in distribution terms BPs only know about a single MP, and possibly 
some SPs.  Each MP knows about all other MPs but only knows about it's
own BPs, and I guess not any SPs.

Can the standard net_kernel be configured in this way?

It seems to me that this architecture would improve the scalability of
the system as it has been said that an Erlang/OTP network can't grow too 
large because each node knows about each other node.  It would also cut
down on the traffic.  If SPs were in telephones for instance they might
come and go quite often.  There would be no sense in telling other nodes
(MPs, other BPs, other SPs) about them.

	-Vance









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