This document discusses pre-installation considerations for Sametime 8.5.1. It covers directories, availability requirements, video/audio needs, SSL certificates, business requirements, client versions, proxy decisions, embedded applications, and the Sametime system level architecture. The architecture includes virtual places, real-time transport protocol, session initiation protocol, extensible messaging and presence protocol, and telephony conferencing services. It is possible to install the community component without the Sametime server component but some functionality may be limited. The document emphasizes understanding pre-installation requirements and the Sametime architecture.