Backhaul

TODO: improve this page (notably, add figures to explain how backhaul and peering/transit get together)

Backhaul is the process of transporting subscribers' data between their location and the core network of the ISP; by extension, it also designate the network infrastructure needed to achieve this task. A backhaul network is sometimes also called a Middle-mile network.

Backhaul can be a difficult problem, especially when a ISP has subscribers at very different locations.

Example of backhaul infrastructures are:

• When using DSL, the telephone network (copper wires) is used as the underlying support. Usual components are DSLAM, BAS. See also a figure of a DSL backhaul infrastructure
• Wireless links
• VPN, which might not be considered as a real backhaul infrastructure
• Fiber infrastructure?

DIY ISPs basically have three classes of solutions for their backhaul:

• completely relying on an existing infrastructure, where a third-party handles all the backhaul and bring the traffic directly to the core network of the DIY ISP. This kind of service is often called Bitstream access. This is the easiest way to cover large regions, but might be expensive. Some big operators might also be reluctant to provide bitstream offers to small structures.
• reusing part of an existing infrastructure, by deploying some hardware (DSLAM, etc)
• deploying their own backhaul network from the ground up (very often using wireless links, as it is the cheapest solution; but deploying fiber is sometimes possible, like B4RN in the UK)

Which one to choose is heavily dependent on the technology, the geographical and financial scale of the DIY ISP, and the availability of affordable offers from resellers. For instance, a very localised ISP might want to deploy hardware (DSLAM, fiber switches) even if it is quite expensive; on the other end, a regional-scale ISP may not afford to deploy hardware in dozens of locations if there are only a few users connected at each location.

• Deploying hardware is difficult
• Bitstream offers are often very expensive

• in France, some regions build their own fiber network, and then provide affordable bitstream access to any interested operators (which is really great for DIY ISPs)

• Ubiquiti hardware: cheap and efficient