[ih] X.25

[Jack Haverty]

On 10/1/25 18:00, John Demco via Internet-history wrote:
> The growth of costs (especially due to international X.25 charges) was 
> a major motivation in....

When we linked the US and UK gateways over the X.25 public network, cost 
for international X.25 traffic was also a factor.  ARPA paid all the 
costs billed from the US connections, and the UK paid the costs for UK 
connections.   As with the traditional phone calls, the calling party 
was billed for the X.25 calls that they initiated.

So, ...

In the spirit of the management mantra "Management is the Art of Moving 
Your Expenses into Someone Else's Budget", we took advantage of how the 
Internet worked.  If an X.25 connection was already open, a gateway 
would just send datagrams out that connection.  If a connection was idle 
for a while (minute or so?), the connection was closed to avoid running 
up the bills.   That was the design, but everything was configurable of 
course.

Just as an experiment, at some point we configured the US gateway so 
that it had a very short timeout.  Basically it would open a connection, 
send the datagram that it had for that route through public X.25, and 
immediately close the connection.  Often the datagram to be sent when 
the route had been idle was a SYN for a new TCP connection.  A response 
would be returned by the destination to complete the 3-way handshake and 
then pass data for however long it took until the connection was closed.

So, the US side would be charged for a quick one-datagram connection, 
but the charges for long FTP or Telnet connections would mostly be 
billed to the UK side.

We didn't ourselves get any benefit from such a scheme; it just seemed 
like the right thing to do and was an interesting experiment.

Did anybody else play similar games while using the X.25 public network 
underneath their parts of the Internet?

/Jack

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