LAS VEGAS, NV. -- May 10, 1999 -- PSINet Inc. (NASDAQ:PSIX), the first and largest independent commercial Internet Service Provider (ISP), and Cisco Systems, Inc. (NASDAQ:CSCO) today announced that PSINet. InterSky - a business-grade and affordable wireless Internet access service has been certified as a Cisco Powered Network. This certification confirms the fact that PSINet InterSky is a reliable, secure and high-performance Internet access service for small or medium businesses. PSINet InterSky utilizes Cisco's industry-leading products as key components of the solution. PSINet and Cisco will also jointly market the new PSINet InterSky service under the Cisco Powered Network program.

PSINet InterSky offers an affordable, high-speed solution delivering wireless Internet services to thousands of small to medium businesses in a designated service area. The service has already been successfully launched in several cities including Ft. Myers and Naples, FL; Knoxville, Nashville and Memphis, TN; and Mobile, AL. PSINet InterSky is expected to be operational in 50 markets by the end of the year 2000.

"PSINet's commercial customers demand the highest quality and reliability from their Internet services," said Richard Frizalone, vice president of wireless Internet services for PSINet Inc. "Cisco's existing presence in the top markets worldwide complements the recent expansion of PSINet's core network. The integrated solution of PSINet InterSky provides innovative and unique business-grade service that directly competes with overpriced options currently available in second-tier markets."

In the past, the second-tier markets have been overlooked by existing telecommunications carriers because of the costs associated with delivering land-based local loop Internet services over legacy public switched telephone networks (PSTNs).

"PSINet has developed a truly global presence while maintaining a focus on key services and applications that directly meet the needs of businesses - no matter how large or small," stated Larry Lang, Cisco vice president of service provider marketing. "The PSINet InterSky customers will have access to a high level of network interoperability and performance, as well as New World advanced application services. Also as a certified Cisco Powered Network service, PSINet InterSky customer can be confident of receiving an industry-leading network service which is built on Cisco's high-performance, reliable and secure components."

Priced currently at $395 per month, PSINet InterSky is an ideal Internet service for most small and medium businesses within designated service areas. Customers in these markets typically have individual on-line service accounts -- operating at speeds of 56 Kbps or less -- that do not provide dedicated "always available" bandwidth. These dial-up services often lack the ability to link to a local-area network (LAN).

PSINet InterSky is not just a modem, but a wireless connection using Airdata WIMAN, Inc. technology for an entire office LAN. Connections are delivered using a cellular-type infrastructure similar to a wireless voice network. PSINet InterSky services are then linked directly into PSINet's global Internet backbone using Cisco router technologies. This integrated solution provides customers full network engineering and monitoring services, value-added applications, and service level agreements (SLAs) similar to those offered to other PSINet connectivity customers. By eliminating local telco charges and reducing the turn-up time for Internet connectivity, PSINet InterSky provides an attractive alternative to meet the needs of most small to medium-size businesses for cost-effective high speed Internet service.

PSINet's participation in the Cisco Powered Network program demonstrates the company's emphasis to provide industry-leading technology solutions and services. Cisco equipment and software are helping PSINet create a New World communications infrastructure for next-generation business productivity.

About PSINet

Headquartered in Herndon, VA, PSINet is a global facilities-based Internet data communications carrier focused on the business marketplace. PSINet offers a broad set of high-speed corporate LAN connectivity services supporting managed security and guaranteed Internet, intranet, electronic commerce, Web hosting services, and services for other carriers and ISPs. PSINet operates an international technologically advanced frame relay and ATM-based, IP-optimized network consisting of more than 525 points of presence (POPs) around the world serving primary markets in Belgium, Brazil, Canada, France, Germany, Hong Kong, Italy, Japan, the Netherlands, the Republic of Korea, Switzerland, the United States, and the United Kingdom.

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PSINet and the PSINet logo are registered trademarks and PSINet InterSky is a service mark of PSINet Inc. in the U.S. and other countries.

Cisco, Cisco Systems and the Cisco Systems logo are registered trademarks of Cisco Systems, Inc. in the US and certain other countries. All other trademarks mentioned in this document are the property of their respective owners.