There are two modes of operation for Tivoli Enterprise Portal: Desktop mode, in which the Tivoli Enterprise Portal client is installed on your machine and runs as a desktop application. Browser mode, in which the thin client software is downloaded from the Tivoli Enterprise Portal Server to your machine the first time you log on to Tivoli Enterprise Portal from your browser, and thereafter when there are software updates. When using Tivoli Enterprise Portal in browser mode, you can start it from any machine by entering the URL for the Web server where the Tivoli Enterprise Portal Server is installed. Tivoli Enterprise Portal requires TCP/IP. IBM Tivoli products do not require a Domain Name System (DNS). If your Windows systems are running without DNS, make sure the \etc\hosts\ file of the local machine is up to date. 2.4 Communications Communications between components in the OMEGAMON infrastructure can use several different methods. The terminology is a little nonstandard as described here. TCP communications uses the User Datagram Protocol (UDP). When UDP is used, Remote Procedure Call (RPC) requests and responses flow as payload in user datagrams. UDP is generally favored for LANs because it is lighter weight. IP Pipe communications uses full-blown TCP/IP. Using TCP, RPC requests and responses stream between a point-to-point session. All concurrent RPC requests and responses for that instance of the product are multiplexed across this single link. IP.Spipe uses TCP/IP, RPC requests and responses. The default listening port is 3660. Systems Network Architecture (SNA) communications, as its name implies, uses standard SNA facilities. 2.5 Deployment scenarios In this section, we investigate three different deployment scenarios: Simple deployment with no firewall Simple deployment with a firewall Chapter 2. OMEGAMON XE architecture 25