The IBM Cognos 8 Web server tier (tier 1.) contains one or more gateways. Web communication in IBM Cognos 8 is typically through gateways, which reside on one or more Web servers. A gateway is an extension of a Web server program that transfers information from the Web server to another server.
For failover, the gateway can be configured to know the location of multiple dispatchers.

Upon receiving a request, the IBM Cognos 8 gateway does the following:

encrypts passwords to ensure security

extracts information needed to submit the request to an IBM Cognos 8 server

attaches environment variables for the Web server

adds a default namespace to the request to ensure that the server authenticates the user in the correct namespace

passes requests to an IBM Cognos 8 dispatcher for processing