+.SH 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.
+.LP
+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.
+.LP
+In circumstances the peer may send no endpoint discriminator or a
+non-unique value. The optional 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/pppd.tdb to match up links.
+.LP
+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. Currently, if the first pppd terminates (for example, because of
+a hangup or a received signal) the bundle is destroyed.