Cisco High Speed Serial Interface NM-1HSSICisco High Speed Serial 1HSSI NM 1HSSI HSSI Description: The NM 1HSSI is a single port, high speed network module that provides connectivity to a Wide Area Network. Demand for high capacity corporate backbones, high speed Internet access, Virtual Private Networks (VPNs), and trunking connections for service provider internetworking has led to an increase demand for clear channel DS3 and E3 connections. Compatible with: 3600 3640