In a multisite deployment, these are some of the possible issues:
- Quality issues: When real-time traffic such as voice or video travels over a packet-switching network such as an IP network, delay-sensitive packets must be given priority to avoid jitter, which results in decreased voice quality.
- Bandwidth issues: Cisco Unified Communications solutions can include voice and video streams, signaling traffic, management traffic, and application traffic, such as rich-media conferences. The additional bandwidth that is required when deploying a Cisco Unified Communications solution must be calculated and provisioned. These tasks ensure that classical data applications and Cisco Unified Communications applications do not overload the available bandwidth. You should optimize bandwidth consumption by eliminating unnecessary IP WAN traffic.
- Availability issues: When you deploy Cisco Unified Communications Manager with centralized call processing, IP phones register with the Cisco Unified Communications Manager over the IP WAN. If gateways in remote sites are using the MGCP as a signaling protocol, they also depend on the availability of Cisco Unified Communications Manager as a call agent. It is important to implement fallback solutions for IP phones and gateways in scenarios in which the connection to Cisco Unified Communications Manager is broken because of IP WAN failure.
- Dial plan issues: Directory numbers are usually unique per site, but they can overlap across multiple sites. Overlapping directory numbers and other issues, such as numbers that are not consecutive, must be solved by the design of a multisite dial plan. Various PSTN access codes in various countries are another example of dial plan issues.
- NAT and security issues: Cisco Unified Communications Manager and IP phones use IP primarily to communicate within the enterprise. The use of private IP addresses is very common within the enterprise. When the system should interact with a public IP network—for instance, when placing calls via an ITSP—then Cisco Unified Communications Manager and IP phone IP addresses must be translated to public IP addresses. This translation makes them visible on the Internet and, therefore, subject to attacks.