There are many factors to consider when assessing the traffic and bandwidth requirements for Agent and Supervisor Desktops in a Unified CCE environment. While the VoIP packet stream bandwidth is the predominant contributing factor to bandwidth usage, other factors such as call control, agent
state signaling, Silent Monitoring, recording, and statistics must also be considered.
VoIP packet stream bandwidth requirements are derived directly from the voice codec deployed (G.729, G.711, and so forth), and can range from 4 kbps to 64 kbps per voice stream. Therefore, the contact center's call profile must be well understood because it defines the number of straight calls (incoming or outgoing), consultative transfers, and conference calls, and consequently the number of VoIP packet streams, that are active on the network. In general, the number of VoIP packet streams typically is slightly greater than one per agent, to account for held calls, Silent Monitoring sessions, active recordings, consultative transfers, and conference calls.
Call control, agent state signaling, Silent Monitoring, recording, and statistics bandwidth requirements can collectively represent as much as 25% to 50% of total bandwidth utilization. While VoIP packet stream bandwidth calculations are fairly straightforward, these other factors depend
heavily on implementation and deployment details and are therefore discussed further in the sections below.
Because WAN links are usually the lowest-speed circuits in a Cisco Unified Communications network, attention must be given not only to bandwidth, but also to reducing packet loss, delay, and jitter where voice traffic is sent across these links. G.729 is the preferred codec for use over the WAN because the G.729 method for sampling audio introduces the least latency (only 30 ms) in addition to any other delays caused by the network. The G.729 codec also provides good voice quality with good compression characteristics, resulting in a relatively low (8 kbps) bandwidth utilization per stream.
Consider the following QoS factors:
Total delay budget for latency, taking into account WAN latency, serialization delays for any local area network traversed, and any forwarding latency present in the network devices.
Impact of routing protocols. For example, Enhanced Interior Gateway Routing Protocol (EIGRP) uses quick convergence times and conservative use of bandwidth. EIGRP convergence also has a negligible impact on call processing and Unified CCE agent logins.
Method used for silently Monitoring and Recording agent calls. The method used dictates the bandwidth load on a given network link.
Cisco Unified Mobile Agent deployments that use QoS mechanisms optimize WAN bandwidth utilization.
Use advanced queuing and scheduling techniques in distribution and core areas as well.