The Point-to-Point Protocol (PPP), as described in RFC 1661, provides an encapsulation protocol for transporting network layer traffic over point-to-point links, such as synchronous serial or Integrated Services Digital Network (ISDN).

Multilink PPP (MLP), as defined in RFC 1990, is a variant of PPP used to aggregate multiple WAN links into one logical channel for the transport of traffic. So it's impossible to bundle an incoming interface and outgoing (point to multipoint) interface in a logical channel.

yasemin.