Vaisala Hydromet Data Collection Platform - Manual (Page 219)

Chapter 5 __________________________________________ Configuring TCP/IP-Based Telemetry
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IP header compression is an algorithm which reduces the amount of
redundant header data. Using it is recommended whenever operating
over a RS-232 line, that is, with modem and null modem connections.
Authentication
QML supports two authentication methods: Password Authentication
Protocol (PAP) and Challenge Authentication Protocol (CHAP). These
can be used with modem and null modem connections.
PAP is very simple protocol where user credentials are transmitted in
plain text, making it insecure. CHAP is more secure as it does not
transmit user credentials over the link. It is the preferred authentication
option to use with the QML logger.
Outgoing user credentials are stored in parameter set of the
communication interface used, for example, parameter set netifX:
S:00000001: netif0:username = pppuser
S:00000001: netif0:password = userppp
For incoming authentication, there is a separate parameter set reserved,
named pppclients. For example, below are listed the user credentials
for users router1 and router2:
S:00000001: pppclients:router1:password = userppp
S:00000001: pppclients:router2:password = r2pass
Authentication can also be configured to be required both ways. For
example, when the QML logger is authenticating to remote computer,
it can simultaneously request the remote computer to authenticate itself
to QML. This option is set on by the communication interface
parameter auth_both. If bidirectional authentication is required, you
need to set outgoing credentials for the communication interface used
and incoming credentials in the pppclients parameter set.
NOTE Microsoft has its own version of CHAP called MS-CHAP, which is
not supported by QML. PAP is currently the only possibility for
authenticating the QML logger when connecting to a Windows PC.
When connecting from Windows PC to QML, also CHAP can be used.