Sierra Video VS User Manual download pdf (Page 33)

Tahoe Series 16

password is the one that must be sent in the “K” command to permit the router

configuration to be changed, while in the latter case the password that was used to lock

the output is the one that must be sent in the “K” command to permit the take to occur.

Refer to the “B” command and the “G ADMIN_PASSWORD” command (in a separate

document) for more information.

For example, the command:

** M197 K1777 !!

requests that password 1777 be stored as the current password for remote address 197.

The command:

** M197 Y7,9 !!

requests that output 7 be connected to input 9, using the password stored for remote

address 197 as the output lockout override password. The take will succeed if output 9 is

either not locked or is locked with password 1777. Otherwise, the take will fail.

“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 !!

1 2 ... 28 29 30 31 32 33 34 35 36 37 38 ... 77 78

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Sierra Video VS User Manual Page 33

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