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   pppd    ( 8 )

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MULTILINK

Multilink PPP provides the capability to combine two or more PPP
       links between a pair of machines into a single `bundle', which
       appears as a single virtual PPP link which has the combined
       bandwidth of the individual links.  Currently, multilink PPP is
       only supported under Linux.

       Pppd detects that the link it is controlling is connected to the
       same peer as another link using the peer's endpoint discriminator
       and the authenticated identity of the peer (if it authenticates
       itself).  The endpoint discriminator is a block of data which is
       hopefully unique for each peer.  Several types of data can be
       used, including locally-assigned strings of bytes, IP addresses,
       MAC addresses, randomly strings of bytes, or E-164 phone numbers.
       The endpoint discriminator sent to the peer by pppd can be set
       using the endpoint option.

       In some circumstances the peer may send no endpoint discriminator
       or a non-unique value.  The bundle option adds an extra string
       which is added to the peer's endpoint discriminator and
       authenticated identity when matching up links to be joined
       together in a bundle.  The bundle option can also be used to
       allow the establishment of multiple bundles between the local
       system and the peer.  Pppd uses a TDB database in
       /var/run/pppd2.tdb to match up links.

       Assuming that multilink is enabled and the peer is willing to
       negotiate multilink, then when pppd is invoked to bring up the
       first link to the peer, it will detect that no other link is
       connected to the peer and create a new bundle, that is, another
       ppp network interface unit.  When another pppd is invoked to
       bring up another link to the peer, it will detect the existing
       bundle and join its link to it.

       If the first link terminates (for example, because of a hangup or
       a received LCP terminate-request) the bundle is not destroyed
       unless there are no other links remaining in the bundle.  Rather
       than exiting, the first pppd keeps running after its link
       terminates, until all the links in the bundle have terminated.
       If the first pppd receives a SIGTERM or SIGINT signal, it will
       destroy the bundle and send a SIGHUP to the pppd processes for
       each of the links in the bundle.  If the first pppd receives a
       SIGHUP signal, it will terminate its link but not the bundle.

       Note: demand mode is not currently supported with multilink.