America Online Inc and BBN Corp reached an expanded agreement to build America Online’s private dial-up network to meet future demand from Internet on-line customers. The four-year deal is worth an estimated $340m and requires Cambridge, Massachusetts research and network services house BBN, to deliver and support a minimum of 70,000 new modems and associated services each year. The agreement covers BBN’s provision of modems as well as its operation and maintenance of a portion of the company’ s AOLnet system – and it also includes a provision of telecommunications circuits bought from both local and inter-exchange carriers.