System Features; Response Time Control; Dynamic Buffering - Multitech MMH900 User Manual

Chapter 1 - Introduction & Description
1.5

System Features

1.5.1

Response Time Control

Response time control is the technique used by a mux to make sure that
no user experiences undue delays in performance due to a specific
channel using too much link time. This can occur if one of the channels
is performing a high volume batch function, such as a print dump or
program transfer.
There are a variety of priority control (response time) schemes in use by
different mux vendors. Some vendors use a switch selection approach
where each channel can be given a high, medium or low setting with the
low used for those channels requiring higher volume batch transfers.
There are also software-sensing response time techniques where the
microprocessor actually monitors channel activity, and when a high
volume is sensed, that channel is given a lower priority so it will not
crowd out the others.
The MultiMux response time control method is one where data is
transferred from each channel on a timed basis while limiting the amount
sent with each transmission.
This insures that interactive users will not experience undue delays but,
on the other hand, batch activity can still be accommodated. This,
combined with a Response Time command and the ability to shut off
channels not being used, gives the MultiMux a very efficient priority
control system.
1.5.2

Dynamic Buffering

A basic requirement of all muxes is some sort of buffering capability to
temporarily hold channel data while it is being assembled into a block. In
the early days, a mux was sometimes judged by the size of its buffers.
Large buffers are unnecessary in newer designs that include
sophisticated dynamic buffer allocation techniques where the amount of
buffer per channel is assigned on an as-needed basis.
In the MultiMux, each channel is assigned 1K of buffer, but in the case
where more buffer is needed, the MultiMux will start assigning additional
buffers from the channels not requiring it. In this way a single channel
can have up to 8K of buffer if required. When dynamic buffering is
combined with efficient flow control and the automatic transmission of
data from each channel at set intervals, as in the MultiMux, very smooth
operation for each user is the result.
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