ADSL2+ extends the capability of basic ADSL by doubling the number of downstream bits. The data rates can be as high as 24 Mbit/s downstream and 1.4 Mbit/s upstream depending on the distance from the DSLAM to the customer's home.
ADSL2+ is capable of doubling the frequency band of typical ADSL connections from 1.1 MHz to 2.2 MHz. This doubles the downstream data rates of the previous ADSL2 standard of up to 12 Mbit/s, but like the previous standards will degrade from its peak bitrate after a certain distance.
Also ADSL2+ allows port bonding. This is where multiple ports are physically provisioned to the end user and the total bandwidth is equal to the sum of all provisioned ports. So if 2 lines capable of 24 Mbit/s were bonded the end result would be a connection capable of 48 Mbit/s. Not all DSLAM Vendors have implemented this functionality. ADSL2+ port bonding is also known as g.998.x or g.Bond