The value of tmnxOamPingCtlMtuStartSize specifies the size of the first
OAM Echo message sent as part of an 'mtuPing' test.
Setting this object to a non-zero value is a prerequisite for starting
an 'mtuPing' test. Its value must be less than or equal to the value
of tmnxOamPingCtlMtuEndSize.
An attempt to set this object from a non-zero value to zero will fail
with a wrongValue error.
Changing the message size is a method of checking the ability of an
SDP to support a particular path-mtu value. The size of the message
does not include the SDP encapsulation, VC-Label (if applied) or any
DLC headers or trailers.