Vaisala Hydromet Data Collection Platform - Manual (Page 204)

User's Guide ______________________________________________________________________
202 _________________________________________________________________ M210933EN-C
Physical and Logical Interfaces
The same physical communication device can be accessed via multiple
logical communication interfaces. This way, the same device can be
used to access different networks or services. These logical interfaces
can, in turn, be accessed through different application services, for
example, to send reports and log files.
The relationship between physical and logical interfaces and the
services using them are illustrated in
Figure 86 on page 202 .
0710-079 Figure 86 Relationship between Logical and Physical Interfaces
In the figure, the FTP service uses interface 1 as its primary connection
and interface 2 as a backup connection. Both these interfaces use device
1 as their physical interface. Even though both interfaces use the same
physical device, they can be connected to different networks, thereby
enabling the FTP application to, for example, access a backup FTP
server in case the primary FTP server is down. The secondary logical
interface for a service can also use another physical interface, creating
a backup mechanism if one communication device breaks down. The
different services can also use the same logical or physical interface as
another service.
TCP/IP communications channels (such as TCP sockets) are accessed
via virtual COM ports in the QML logger software. The virtual ports
map to the actual logical and physical interfaces, depending on the
configuration. The report or measurement configurations are created as
with earlier Lizard versions, with the difference being that the source or
FTP VCOM
Intf 1
NTP
Intf 2
Device 1
Intf 3
Device 2
Primary
Secondary
Service
Logical Interface
Physical Interface