An alternative: Pricing into BGP
Looking at the Border Pricing Protocol, one question can be asked: Why did we develop a new protocol inspired from BGP and did not integrate pricing features directly in BGP? It would be possible, since BGP proposes extensibility through its attributes.
A first answer could be it would add quite some complexity to BGP to add pricing mechanisms. Moreover, BPP is a protocol between Management Entities, which can be different from routers, when BGP works between border routers.
On the other hand, since BPP reproduces many BGP features, it might be a good idea to reuse them directly at the implementation level. In other words, it would be a big advantage to use the existing BGP infrastructure. It would also put the pricing mechanisms much closer to the routing information, which would facilitate some parts of the pricing process. The direct integration of Pricing in BGP also avoids the creation of a new protocol, therefore also not requiring the maintenance and the dealing other issues of a new protocol. Finally, it would bring the pricing information directly in routers, which may offer an interesting advantage in terms of scalability in the charging process.
Some features of BPP can not be reproduced, like the idea of having a request-based protocol or the support of multiple QoS architectures. Nevertheless, it would offer in its simplest version a simple implementation and not a lot of overhead. Each BGP update would only have to carry a price attribute (like it carries the next hop attribute for example) and routing tables would have a price field.