A key issue in the scalability of HIPPI-SONET networks is the manageability of HIPPI routing. HIPPI routing can be done one of two ways: source routing or logical routing. We first used source routing because the size of the network, both in terms of end hosts as well as HIPPI switches, was small (under 10 hosts and 4 switches). As the network grew in size, source routing became inadequate and we turned to logical routing. This technique involves building switch routing tables and assigning HIPPI addresses (called I-fields) that are location independent.
Since there are no HIPPI routing protocols and no automatic means of configuring and updating host and switch tables, the configuration effort was substantial. We conclude that to build a large network from HIPPI bridges, dynamic routing update protocols as well as ARP servers to map network addresses to link-layer addresses are required.