Mpd is a netgraph(4) based implementation of the multi-link PPP
protocol for FreeBSD.  It is designed to be both fast and flexible.
It handles configuration and negotiation in user land, while routing
all data packets strictly in the kernel.  It supports several of
the numerous PPP sub-protocols and extensions, such as:

      Multi-link PPP capability 
      PAP, CHAP, MS-CHAP and EAP authentication 
      PPP compression and encryption
      IPCP and IPV6CP parameter negotiation
      
Mpd have support for many link types:

      Serial port modem
      Point-to-Point Tunnelling Protocol (PPTP)
      Layer Two Tunnelling Protocol (L2TP)
      PPP over Ethernet (PPPoE)
      PPP over TCP
      PPP over UDP
      PPP over specified netgraph(4) node

Mpd also includes many additional features: 

      IPv4 and IPv6 support
      RADIUS authentication and accounting
      NetFlow traffic accounting
      Network address translation (NAT)
      Dial-on-demand with idle timeout 
      Multiple active connections running simultaneously 
      Dynamic demand based link management (also known as ``rubber bandwidth'') 
      Powerful chat scripting language for asynchronous serial ports 
      Pre-tested chat scripts for several common modems and ISDN TAs
      Clean device-type independent design 
      Comprehensive logging
      Telnet and HTTP control interfaces.

WWW: http://www.sourceforge.net/projects/mpd