Microsoft® Windows Server™ 2003 White Paper
Other TCP/IP Applications
NLB uses TCP/IP as its published protocol, so it should route any TCP/IP application requests correctly. If the application requires repeated connections to a server, then you can change the Affinity setting of NLB to keep the application returning to the same server in the farm. This will probably negatively affect scaling.
NLB is also nice as you can add or remove servers to a cluster while the cluster is running. This allows you to expand or contract a farm dynamically as the application needs to scale out. This also allows you to reconfigure servers in the cluster without taking the entire cluster down.
Windows Server 2003 provides tremendous flexibility because you cannot only scale out but also scale up. Scaling up allows you to scale an application on a single server by adding resources such as more memory, faster disk, and more and/or faster processors as shown in the following figure.
Windows Server 2003 can scale from one processor to 32 (Datacenter Edition), resulting in a tremendous amount of room to grow on a single system.
Implementing a Scalable Architecture17