Throughout my early years as a consultant, when asynchronous transfer mode (ATM) was the rage and multiprotocol label switching (MPLS) was still at the outset, I handled numerous roles as a network architect alongside various carriers. During that period, I experienced first-hand problems that the new technologies posed to them.
The lack of true end-to-end automation made our daily tasks run into the night. Bespoke network designs due to the shortfall of appropriate documentation resulted in one that person knows all. The provisioning teams never fully understood the design. The copy-and-paste implementation approach is error-prone, leaving teams blindfolded when something went wrong.