The value of tmnxL2tpTuMlpppShortSeqNumberRx specifies
if this system requests to receive short sequence numbers from the peer.
If the value of this object is 'always', this system includes
the Short Sequence Number Header Format Option in its LCP configuration
options.
If the value of this object is 'never', this system does not includes
the Short Sequence Number Header Format Option in its LCP configuration
options.
The value of this object is only relevant for tunnels where this system
performs the LNS role.