After you complete the planning phase, you should begin working on the design phase of the IPT network. The goal of the design phase is to propose an IPT network design by using the information that is collected in the planning phase and the information that is provided by the customer in the RFP. You also need to collect additional information that is specific to IPT feature requirements. (Refer to Appendixes D, "IPT Design Phase: IP Phone Selection Questionnaire," and E, "IPT Design Phase: IPT Requirement Analysis Questionnaire," for the IPT Design Phase Questionnaires).
You should consider several different design alternatives before arriving at the final design. This proposed design should cater to the company's current and future IPT needs.
The design phase consists of the following high-level tasks, through which different critical areas of the network are designed based on IPT network needs:
Network infrastructure design
Design of call-processing infrastructure and applications
Software version evaluation
Design validation
Figure 2-1, the goal of the design phase is to complete the preceding four design phase tasks and provide the design document that proposes an IPT network design that satisfies the customer's needs. The design document should include the proposed IPT network architecture diagrams, recommended configurations for voice gateways, QoS recommendations for LAN/WAN, etc. Chapters 5, 6, and 7 cover the preceding four tasks involved in the design phase and explain the individual tasks with the help of the case study.
IPT network designers should review this design document with the voice network architecture team and infrastructure groups in the customer's organization to ensure that the proposed design meets their requirements.
The first task of the design phase is to enable the existing network infrastructure to support IPT. Chapter 5 discusses the network infrastructure design tasks and focuses on the following design areas:
Choosing the IPT deployment model
Designing an IP addressing scheme, voice VLANs for IPT network devices, and IP routing
Evaluating and selecting Cisco IP phone models
Designing DHCP and TFTP services for Cisco IP phones and other IPT endpoints in addition to the use of DNS services
Designing quality of service (QoS) in the LAN
Choosing the in-line power standard and determining the additional hardware needs on the switches and the power requirements
Designing the LAN and WAN infrastructure for resiliency
Sizing the WAN links and design of QoS in the WAN
The second task of the design phase is to choose and size the IPT components, review and make recommendations to integrate or migrate current telephony applications with or to new IPT applications based on customer's telephony requirements. Chapters 6 and 7 discuss the following design tasks:
Sizing the CallManager clusters
Sizing the voice gateways and gatekeeper
Preparing the IPT system to integrate or access the corporate Lightweight Directory Access Protocol (LDAP) directory
Choosing the right design steps to migrate or integrate with the legacy systems (PBX, key, voice mail, or unified messaging system)
Incorporating the fax and modem requirements in the IPT network
Deploying the conferencing and transcoding resources and sizing them based on the requirements
Recommending the security and network management solutions
Customizing and sizing the IPT applications such as Auto Attendant (AA) and call center application IP-ICD (Integrated Contact Distribution)
Designing and customizing the voice mail system
As with any other products, the Cisco IPT products have undergone many software revisions. New versions include bug fixes to the old versions and many new features. The heart of the Cisco IPT solution is Cisco CallManager. It interfaces with other applications as described in the preceding section to provide additional features and capabilities. You should refer to the Cisco CallManager Compatibility Matrix available on Cisco.com to ensure that all the software versions on the other IPT endpointssuch as IP Phones, voice gateways, and applicationsare compatible with the CallManager version chosen for the deployment. The Cisco CallManager Compatibility Matrix is available at http://www.cisco.com/univercd/cc/td/doc/product/voice/c_callmg/ccmcomp.
The final task of the design phase is to validate the proposed design by building a proof of concept (POC) lab and conducting the acceptance testing. The POC lab topology that you design should emulate the proposed network and must contain all the different IPT components that are proposed in the actual design.
This acceptance testing is necessary for a smooth rollout of IPT throughout the entire network. To ensure this, you, along with the customer technical team, should develop a test plan that clearly defines various unique test scenarios and then execute the test plan. Typical scenarios include testing the following:
Internal and external phone calls
Conference calls
IPT features that are deployed
Failover scenarios
Calls between the sites across the WAN
Call admission control feature
WAN circuit failure conditions
Recovery times for failures within the LAN
Access to voice mail and message notification
Voice-mail/PBX integration
Call routing and calling privileges
System restoration from the backup data
While you are going through this exercise, the time that you devote must be reasonable enough to cover all the test scenarios described in the test plan. Following are some clear advantages of going through this exercise:
Fix problems such as functionality issues, configuration errors, and design flaws that are discovered during the testing.
Make necessary changes in the design depending on the types of problems discovered.
Modify or adjust the procedures used to build the servers, deploy phones, migrate users, etc. based on the results. This ensures that the final deployment process is smooth and helps to make the IPT rollout faster.
Fine-tune and adjust the server configuration parameters during the testing phase to achieve minimal telephony service disruptions by conducting failover tests.
Ensure that all the critical elements are in proper working order.
Ensure smooth transition/migration to the proposed IPT design.