there are several different types of bonding, hence your confusion. Some of them aren't bonding at all. The options (or at least some of them) are ...
1. Line bonding where the DSL system bonds two physical lines at the lowest level and presents as a single link to the layers above. Use by Be and Rutland Telecom.
2. Multilink PPP where a single IP address is provided and two circuits terminate at the same PPP server (need not be the same ISP end circuits but need to be provided by one provider with the multilnk capable kit). Often uses Cisco router at customer end.
3. VPN solutions where multilnk VPN routers pass traffic to each other over multiple links, appearing at both ends to be a single tunnel. May require expensive hardware eg Firebrick or similar. Operates at the IP level so can be over different ISPs or technologies
4. Sharedband (.com) routing traffic over 2 or more lines to a remote server that combines the traffic. Appears as a single IP address at the server end. Managed service.
5. Load balancing routers that fire traffic down two or more lines according to present rules or load. May limit a single application to one line, best suited to a multi-user situation to load balance users to lines.
All but the last should give you >180% of the slowest line for a single data stream, possibly more depending how they handle different line rates / latencies and the overhead load.
MaxDSL - goes as fast as it can and doesn't read the line checker first.
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