3Com 3C13618 Command Reference Manual page 214

Description
Using the virtualbaudrate command, you can configure the virtual baudrate on the
interface. Using the undo virtualbaudrate command, you can cancel the virtual
baudrate on the interface.
By default, virtual baudrate is not set on the interface.
Virtual baudrate is used for the load balancing and flow control among MP links, and it
is just a parameter for flow balancing of the system, without affecting the real baudrate
of the physical port. When the virtual baudrate is not set on the interface, the system will
fulfill the traffic load distribution according to the baudrate on hardware port (as to the
synchronous serial interface working in the DTE mode, the baudrate is considered as
64000 bps). When the virtual baudrate is set on the interface, the system will fulfill the
traffic load distribution according to its virtual baudrate. The higher the interface
baudrate (or virtual baud rate), the bigger the allocated loading data flow to the
interface.
Generally speaking, If the links bound in MP channel have the identical features and
baudrate, there is no need to set the virtual baudrate for the interfaces. If the features or
operating mode of links bundled in MP channel are different, then it is necessary to set
the virtual baudrate for the interfaces.
The transmission efficiency of the asynchronous serial interface is lower than that of the
synchronous serial interface with the identical baudrates. When binding the
asynchronous serial interface and the synchronous serial interface into one MP
channel, it is need to set the virtual baudrate on the asynchronous serial interface,
which may be about 70 percentage of the physical port baudrate. For example, the
asynchronous serial interface baudrate is 115200 bps, then the virtual baudrate of this
port can be set as 80640 bps.
It is recommended that the virtual baudrate should not be higher than the real baud rate
of the physical port.
If the virtual baudrate of an interface is set as 1 to 63, the preference of the interface will
be set as the lowest. Only when there is no interface available with higher preference
level, MP channel chooses this interface to transmit data.
For related commands, see ppp mp.
Example
# Set the virtual baud rate of the interface Serial0 as 1048576 (1M) bps.
[3Com-Serial0]virtualbaudrate 1048576
Link Layer Protocol
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