🚀 go-pugleaf

conrad@disuns2.epfl.ch (Christian Conrad) writes: 
: hello, 
:  
: I'm performing a simulation on message transfers between T9000, through an
: IMS C104. Some questions occurred: 
: 1) It is said in the documentation that if the output link of the IMS C104
: is not free, then the packet is bufferized, but WHERE ? (input or output link
: of C104) 

I don't think this is exactly what the documentation says.

The important point to bear in mind here is that each connection between C104s
(and T9000s etc.) is completely flow-controlled at the *byte* level.  This
means that it is not actually necessary for a packet which cannot proceed to
be buffered entirely within one device.  It is possible for a packet to be
buffered half in the input buffer of the device receiving it and half in the
output buffer of the device transmitting it.  It is even possible for a
particularly long packet to be buffered over several devices.  This means that
the C104 can route packets of arbitrary length.  However the performance of
networks of C104s is improved by using packets which are sufficiently short
that they can be buffered in at most two devices, for example those used by
the T9000 (which are at most 32 bytes plus a header and terminator).

: 2) What happens if two packets from different sources try to reach the same
: busy destination ? They should both be bufferized, so how many buffers there
: are ? 

If two or more packets are routed to the same output, only one can proceed
(making the output `busy') and the others are all stalled as described above.

: A possible solution to these problems would be to have 32 buffers of 32
: bytes for each output link of the IMS C104, is it correct ? 

However another possible solution is to use a low-level flow-control technique
which makes it unnecessary for packets to be buffered by the receiving device.

: Thanks in advance for answers. 
:            		Christian Conrad 
: 			LSP, laboratoire de systemes peripheriques, EPFL
:               

You're welcome.

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Peter Thompson, INMOS Ltd JANET:    thompson@uk.co.inmos
1000 Aztec West           UUCP:     ukc!inmos!thompson
Bristol BS12 4SQ, U.K.    INTERNET: thompson@inmos.com
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