Sierra Video Ponderosa 3G Series Routing Switcher - Manual (Page 93)

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“M”: Set Remote Address
The command "M" is followed by a remote address value, and it sets the remote address
to be used by all remaining commands in the current command string. This command is
supported on larger routers. It would be used when a client/server software system on a
router control port permits multiple remote users to send commands to the router through
that control port. In such a system, the server software that talks to the control port can
insert an “M” command at the beginning of each command string it sends to the router on
behalf of its clients. The server would assign a different address to each of its clients. The
router uses the address to control access to and modification of protected resources. The
“M” command will typically work in conjunction with the “K” command, which allows a
password to be sent to the router. Some commands, such as those that allow
modification of router configuration settings, might require entry of an administrator
password before allowing the router configuration to be modified. The “K” command is
used to send the password, but the router must be able to record that password in
association with a particular remote user. The router would save the password as the one
established by the remote address specified in the “M” command. The examples below
show how this would work.
If the “M” command is not present in a control string received on a serial port, the address
assigned to the serial port itself is used as the address for all commands in that
command string.
The “M” command works on an honor system. There is nothing to keep a remote device
from forging a false address. This conforms with the philosophy of providing protection
mechanisms that are not designed to be totally hack-proof, but rather, are designed
under the assumption that controlling devices will honor the system. A dedicated hacker
can always hack into the system if he chooses. Note, however, that the server in a
client/server relationship can provide a great deal of added security for the system,
forcing the correct “M” command to be sent each time, and filtering out bogus “M”
commands received from clients.
When the router receives an “M” command in a command string, it echoes the same “M”
command in its response. This allows the server connected to the serial port to parse the
received response string and determine to which client it should route the response.
Normally the server will assign remote addresses to its clients. However, it should always
provide a way to send these addresses to the client, because the client needs to know its
address in order to know how to interpret some responses. By simply passing each “M”
response command received from the router back to the client, the server can let the
client know what its address is.
For example, the command:
** M139 K9664 !!
establishes password 9664 as the password for remote address 139. The response to
this command string would be:
** M139 OK !!
If remote address 13 later sends the command:
** M139 Y8,27 !!
to request that output 8 be connected to input 27, the router would check to see if output
8 has been locked. If so, the router compares the password of remote address 139
(which has previously been set to 96643) to the password that was used to lock output 8.
If they match, the connection request succeeds, but if they don’t match, output 8 is left
unchanged.