Goldman Sachs has invested $50 million for a minority stake in Perimeter eSecurity, a Milford, Conn.-based provider of managed network security services. Part of the capital will be used to provide liquidity for prior Perimeter Internetworking shareholders, which include Total Technology Ventures, the ASTRI Group, Connecticut Innovations, 1to1 Venture Partners and Redstone7.com. The company raised just under $5 million over two rounds in 2000 and 2001. The latter deal included a post-money valuation of around $10 million. www.perimeterusa.com