D Link Diagonal link
A Diagonal link connects a secondary (e.g. local or regional) STP (Signalling Transfer Point) pair to a primary (e.g. inter-network gateway) STP pair in a quad-link configuration. Secondary STPs within the same network are connected via a quad of D links. The distinction between a B link and a D link is rather arbitrary. For this reason such links may be referred to as B/D links.
