@section[Conclusion]
It is evident that whilst the Gateway has been performing well there are
three main limitations on its use.  These limitations are the speed of the X.25
line, the resiliance of the X.25 link and the available CPU within the Gateway.

Although the line speed appears to be adequate for the user load on the
Gateway, section 4.1.4 indicates the problems associated with a speed
limitation of 9.6 kb/s.  A further consequence in the normal running of 
the Gateway is the blocking effect caused by this line speed.  With only
half of the maximum number of active users, the time spent in the queue
awaiting transmission on the X.25 link could be in the order of two to 
three seconds.  Such a delay being imposed by a Gateway, a supposedly
transparent part of the network, is unacceptable.

The current resiliance of the X.25 link causes serious problems in a
service X.25 network.  It is a frequent occurance for an X.25 link to be
broken for a few seconds, for line failures, a monitor to be inserted or
by patching errors.  The X.25 protocol was designed to recover from such
errors and consequently the current position whereby all calls are lost on
a momentary break is not acceptable.

The CPU limitation of the gateway is not so much of a problem as it appears
on first sight.  From detailed measurements on EDNET, a user profile can be
obtained, from this it is quite clear that the packet throughput limitation
of the Gateway exceeds the theroughput which the maximum number of users can
produce as shown in section 4.1.4.

This situation could and will change if the current use of the Gateway changes.
If the Gateway is used for intensive File Transfer type traffic in conjunction
with an increase in the X.25 link speed then the dominating facter will then be
the power of the CPU in conjunction with the quantity of the high level
compiler used to produce the Gateway code.

From the above it is clear that the Gateway is a useful tool for allowing
a small number of users on a Local Area Network to access Wide Area
Network facilities.  The number of actual users of the LAN who can be readily
supported will depend on the proportion of users who wish to access
off-LAN facilities.  In the Edinburgh University environment, a very
high proportion of users access multiple machines, both multiple hosts,
but mainly specialist services, such as the Library machine, that the
University will only have one off.  Under these circumstances, as more
departments put in LANs to interlink their own machines there will be a
clear need for Gateways which can support a far higher line speed backed
by a more powerful CPU than the existing Gateway.