The report describes a modeling library for analysis and optimization of distributed service systems: enterprise computing infrastructure, E-commerce and E- service systems. The library uses a small number of basic notions, such as service, server, cluster (of servers), clients and message, which allow us to describe, analyze and optimize various system configurations and deployment of services among servers. The service requests and responses are modeled by messages traveling in the system and using the system common resources, such as network bandwidth and cache space. Clients send their requests for services to servers, which either return responses or may issue secondary requests for other services. The messages can form complex activities such as transactions (sessions). To find optimal deployments of services among servers, different partition policies can be used including partitions based on genetic algorithms. The Systems of Servers is built on top of the Communicating Structures Library (CSL), a basic library for modeling large-scale distributed systems [1,2]. In its turn, it is a base for more specialized libraries that target specific classes of service systems. All these libraries are part of the System Factory [4], a modeling environment for system integration and customization. 19 Pages