Multilink Point-to-Point Protocol (MPPP)

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MPPP which stands for Multilink Point to Point Protocol is a protocol for inverse multiplexing of Point-to-Point Protocol (PPP) communication links. Multilink Point-to-Point Protocol (MPPP) is an extension of the industry-standard PPP. MPPP can also be abbreviated as MP or MLP.

How it works

An ordinary dial-up modem connection to the Internet through an Internet service provider (ISP) usually uses PPP as its wide area network (WAN) data-link protocol, but sometimes the 56-Kbps speed provided by V.90 modems is insufficient. MPPP allows multiple physical dial-up links to be inverse multiplexed together to form a single high-bandwidth logical PPP connection between the dial-up client and the ISP. MPPP works by ordering the data frames from the client across the multiple PPP channels and recombining them at the ISP’s termination point, and vice versa. MPPP defines protocols for splitting the data stream into PPP packets, sequencing the packets, transmitting them over separate logical data links, and then recombining them at the receiving station.

MPPP is also supported by some ISDN terminal adapters to allow two 64-Kbps Integrated Services Digital Network (ISDN) channels to be inverse multiplexed together into a single 128-Kbps channel using the bonding protocol.

More channels can be aggregated for even greater bandwidth. Microsoft Windows 98 supports MPPP for both analog modems and ISDN terminal adapters.

In the Remote Access Service (RAS) of Windows NT, MPPP is known as RAS Multilink Channel Aggregation and supports the aggregation of two or more analog modems or ISDN terminal adapters (or a combination of both). RAS Multilink Channel Aggregation was originally based on Request for Comments (RFC) 1717 and is supported by Windows NT Server and Windows NT Workstation, although it is only supported for dial-out connections on Windows NT Workstation. Multilink in the Windows 2000 Routing and Remote Access feature supports RFC 1990, which obsoletes RFC 1717.

Multilink Point-to-Point Protocol (MPPP)

MPPP connections aggregated across multiple routers

An extension to MPPP called Multichassis Multilink Point-to-Point Protocol (MMP), which some vendors support, allows MPPP connections to be aggregated across multiple routers and network access servers (NAS’s) in a way that is transparent to the dial-up MPPP client. In other words, the client initiates an MPPP session but is actually connected to several MMP-enabled NAS’s at the ISP instead of only one NAS as in the usual scenario. MMP enables the data stream to be split, sequenced and recombined at several different points to provide a single logical connection between the client and the ISP.

Another extension to MPPP that some vendors support is called Multichannel PPP (MPP), which in addition to inverse multiplexing of PPP links also supports session and bandwidth management functions, including the dynamic addition or removal of channels without the need to reinitialize the link. Both the client and the server must support MPP for this to work.

Using MPPP for dial-up connection to the Internet

To use MPPP for a dial-up connection to the Internet, your ISP’s NAS must also support this protocol. RAS Multilink Channel Aggregation for Windows 98 or Windows NT functions best if all devices are of the same type (analog or ISDN) and operate at the same speed. When a Windows dial-up client attempts a multilink connection, it first establishes the primary connection using the first installed device, and then it successively aggregates each additional device.