Backhaul network
The intermediate links that carry traffic from a network's edge, such as cell sites or branch offices, back to its core; also the practice of routing remote traffic through a central site.
A backhaul network is the set of links that carries traffic from the edge of a network back to its core. In a mobile network it connects the base stations at cell sites to the operator’s core; elsewhere it links remote sites and access points to central aggregation points. The links may be fibre, copper, microwave radio or satellite. The ISC2 exam outline names backhaul networks under data communications in Domain 4.
Backhaul matters for security because its links often cross infrastructure the operator does not own. NIST SP 800-187, Guide to LTE Security, notes that confidentiality protection on the LTE backhaul is optional in the specifications and that an unprotected backhaul is open to eavesdropping. Encryption on the radio link does not carry over to the backhaul, which is one reason 4G traffic still needs end-to-end protection.
The word has a second, design sense: backhauling, sometimes called hairpinning, routes branch or remote traffic back to a central data centre for inspection before it goes out. That adds latency when the destination is a cloud service, which is one reason SD-WAN designs commonly send such traffic out locally.
Exam relevance: a scenario is likely to ask where protection stops on a carrier or remote-site path. Candidates are expected to treat backhaul as a separate segment that needs its own protection.