[Simh] VAX XQ and wireless networking

[Sergey Oboguev]

I have not personally tried it, but here are few general remarks:

SIMH DEQNA/DELQA virtual devices talk 802.3, whereas WiFi (802.11) is different 
from 802.3 in frame structure and everything else. WiFi may superficially look 
like Ethernet (i.e. have similarly looking MAC address), but it is actually not, 
so naive binding of XQ to host WiFi interface would not work for that reason.

In addition, guest operating system software using DEQNA/DELQA will likewise be 
expecting 802.3 structured frames and protocol capabilities.

Therefore, some form of translation between 802.3 and 802.11 or tunneling of 
802.3 packets through 802.11 (or generic TCP/IP) would be required.

If all you want is to connect SIMH instance to exterior TCP/IP network via IP 
connectivity only (i.e. do not need VAXcluster, LAT or DECnet), then regular 
host OS level bridging of tap interface (or Windows interface such as loopback 
or wired Ethernet interfaces) to WiFi interface would be one thing to try. 
Bridging is likely to suffice to translate IP packets from 802.3 MAC envelope to 
802.11 and vice versa; that is it's purpose anyway.

If, on the other hand, you want to interconnect multiple SIMH instances over 
WiFi utilizing not only IP, but also other Ethernet based protocols such as 
VAXcluster or LAT or DECnet, host OS bridging may fail to translate those 
protocols. In the latter case you'd need to find a way to tunnel 802.3 packets 
over 802.11 or over generic TCP/IP. General approach would be to attach SIMH XQ 
to Linux tap device on one side and hook tap/tun's other side into tunneling 
software. VDE (http://wiki.virtualsquare.org/wiki/index.php/VDE) does just that, 
but I personally do not have experience using VDE. Furthermore, there is some 
direct VDE support in the latest version of SIMH (assuming the simulator 
executable is built with VDE option enabled). I have not personally tried using 
it, but at a glance at the code, it looks like it allows to connect XQ to 
VDE_SWITCH directly (using vde:port syntax), not requiring tap device as an 
intermediary.
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