410 Chapter 11: Designing a Unity Solution
should deﬁne this, but there are other support considerations as well. For instance, if you
do a phased migration as a part of your design, indicate any speciﬁc support requirements
for that design. Who do subscribers call for problems? Who do your tech support engineers
contact for operational issues during each phase of the migration? How does moving from
legacy voice messaging to uniﬁed messaging affect how subscribers are supported? Your
usage analysis should indicate a considerable number of support issues and concerns that
you need to address in your design, implementation, and operations. Document the expec-
tations and any support or operational standards that each Unity server should adhere to.
Criteria for Implementation
When you have your high-level and low-level design documents ﬁnalized and signed off
on, you will want to start extracting the low-level information to put together your imple-
mentation plan. Your design documentation should provide all the information that you
need to devise a sound implementation plan. As stated earlier, if it does not, you probably
need to go back and revise your design.
For more information regarding implementation, see Chapter 16, “Installation.”
This chapter discussed the Unity design process from start to ﬁnish. It took you step by step
through the key steps of the initial stage, the presales stage.
In the planning stage, you really ﬁnd out about how a Unity pilot might go. In this stage,
you gather all your data through capacity planning, site surveys, and usage analysis. The
planning stage is essential for putting together a sustainable design for Unity.
The design phase is split in two. The ﬁrst part involves restating your preliminary design by
deﬁning the high-level design. The high-level design also should reference all your source
data so that you have a recorded audit trail up to this point in the process. The second part
involves the low-level design detail.
Your ﬁnal goal is to use all the data collected from the planning stage along with your high-
level design to develop your low-level design.
Because the low-level design is your goal, it should be detailed. It should cover every
important aspect of a Unity server installation, including placement next to the messaging
servers that it services and all server-speciﬁc details, such as server names, IP addresses,
accounts used to access the server, and conﬁguration details. The low-level design should
contain all information necessary to develop an implementation plan for any Unity deploy-
ment, large or small. This includes both detailed documentation and detailed diagrams for
each Unity installation.