Planning and Installation GuideChapter 2: System Overview
remote site. Each of the servers handle 2,000 BHCC. In this case, both servers should be
provisioned with hardware that meets the medium tier of hardware requirements because
the system capacity and both server capacities fall within this tier.
When deploying servers for medium or large systems, please note that you must select an
operating system with support for expanded memory by using the Enterprise Editions of
either Microsoft Windows 2003 or 2008 Server. Busy Hour Call Completion (BHCC) and Busy Hour Call Attempts (BHCA)
Busy Hour Call Completion (BHCC) per system is the total number of calls in the system
during the busy hour, including internal and external calls and including calls terminated
to desk phones, softphones, trunks, or server applications such as voicemail. This includes
all traffic that can occur in the server - regular voice calls, workgroup calls, voicemail etc.
Busy Hour Call Attempts (BHCA) is the number of calls attempted at the busiest hour of
the day (peak hour). The higher the BHCA, the higher the stress on the network
processors. If a bottleneck in the network exists with a capacity lower than the estimated
BHCA, then congestion will occur resulting in many failed calls and customer
BHCC Limits for Server Tiers
Server requirements are specified in 3 tiers: servers for small systems that support up to 500
users, servers for medium sized systems that support up to 2,500 users, and servers for
large systems that support up to 10,000 users.
BHCC per server is based on the number of calls actually handled by the server during the
business hour, including workgroup calls in menus and queues, auto-attendant calls and
calls to the voicemail service.
Call Load Capacity for Switches
A ShoreTel system supports a maximum of 100 Voicemail Model Switches. There are no
restrictions concerning the allocation of switches among the sites defined by the system.
For ShoreGear Voicemail Model Switches, call load capacity is:
• 5400 BHCC when supporting 90 MGCP IP Phones or 90 SIP Trunks
• 3600 BHCC when supporting 90 SIP IP Phones or 90 SIP Trunks
BHCA Call Volume
The system supports 5,000 BHCA.
number of
users per
number of
users assigned
per Server
System BHCC
Maximum BHCC
per server
Reports run outside
business hours
Maximum BHCC
per server
Reports run during
business hours
Small 500 500 5,000 1,000 Not Recommended3
Medium 2,500 1,000 25,000 5,000 1,000
Large 10,000 1,000 50,000 10,000 5,000
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