Manual:MLPPP over single and multiple links
Multi-Link Point to Point Protocol (Multi-Link PPP or MLPPP) is a method of splitting, recombining, and sequencing data across multiple logical data links.
Large packets are actually split into bits and sent evenly down ALL logical data links. This is done instantaneously with NO loss of bandwidth. It is important to understand that other end of the link needs to use the same protocol to recombine your data.
To enable Multi-link PPP over single link you must specify MRRU option. If both sides support this feature there are no need for MSS adjustment (in firewall mangle). Study shows that MRRU is less CPU expensive that 2 mangle rules per client. MRRU allows to divide packet to multiple channels therefore increasing possible MTU and MRU (up to 65535 bytes)
Under Windows it can be enabled in Networking tag, Settings button, "Negotiate multi-link for single link connections". Their MRRU is hard coded to 1614.