Increasing transmission speed by spreading the data over two or more lines. Bonded analog modems use two analog telephone lines to double transmission capacity, splitting data into two streams of 56 Kbps. In addition, if one modem fails, the transmission continues with the other modem. This "dual analog" method, also known as "modem bonding," uses the Multilink PPP protocol and must be supported by the ISP.

ISDN modems use channel bonding to split the data stream into two 64 Kbps channels, which use both lines in an ISDN BRI service (see ISDN). The DOCSIS 3.0 standard for cable modems supports a minimum of four cable channels bonded together to greatly increase subscribers' upstream and downstream speeds. See modem teaming.