Cisco Cisco Unified Contact Center Enterprise 8.5(2) Leaflet
9-3
Cisco Unified Contact Center Enterprise 7.5 SRND
Chapter 9 Sizing Call Center Resources
Call Center Basic Traffic Terminology
Servers
Servers are resources that handle traffic loads or calls. There are many types of servers in a call center,
such as PSTN trunks and gateway ports, agents, voicemail ports, and IVR ports.
such as PSTN trunks and gateway ports, agents, voicemail ports, and IVR ports.
Talk Time
Talk time is amount of time an agent spends talking to a caller, including the time an agent places a caller
on hold and the time spent during consultative conferences.
on hold and the time spent during consultative conferences.
Wrap-Up Time (After-Call Work Time)
After the call is terminated (the caller finishes talking to an agent and hangs up), the wrap-up time is the
time it takes an agent to wrap up the call by performing such tasks as updating a database, recording
notes from the call, or any other activity performed until an agent becomes available to answer another
call. The Unified CCE term for this concept is after-call work time.
time it takes an agent to wrap up the call by performing such tasks as updating a database, recording
notes from the call, or any other activity performed until an agent becomes available to answer another
call. The Unified CCE term for this concept is after-call work time.
Average Handle Time (AHT)
AHT is the mean (or average) call duration during a specified time period. It is a commonly used term
that refers to the sum of several types of handle time, such as call treatment time, talk time, and queuing
time. In its most common definition, AHT is the sum of agent talk time and agent wrap-up time.
that refers to the sum of several types of handle time, such as call treatment time, talk time, and queuing
time. In its most common definition, AHT is the sum of agent talk time and agent wrap-up time.
Erlang
Erlang is a measurement of traffic load during the busy hour. The Erlang is based on having 3600
seconds (60 minutes, or 1 hour) of calls on the same circuit, trunk, or port. (One circuit is busy for one
hour regardless of the number of calls or how long the average call lasts.) If a contact center receives 30
calls in the busy hour and each call lasts for six minutes, this equates to 180 minutes of traffic in the busy
hour, or 3 Erlangs (180 min/60 min). If the contact center receives 100 calls averaging 36 seconds each
in the busy hour, then total traffic received is 3600 seconds, or 1 Erlang (3600 sec/3600 sec).
seconds (60 minutes, or 1 hour) of calls on the same circuit, trunk, or port. (One circuit is busy for one
hour regardless of the number of calls or how long the average call lasts.) If a contact center receives 30
calls in the busy hour and each call lasts for six minutes, this equates to 180 minutes of traffic in the busy
hour, or 3 Erlangs (180 min/60 min). If the contact center receives 100 calls averaging 36 seconds each
in the busy hour, then total traffic received is 3600 seconds, or 1 Erlang (3600 sec/3600 sec).
Use the following formula to calculate the Erlang value:
Traffic in Erlangs = (Number of calls in the busy hour
AHT in sec) / 3600 sec
The term is named after the Danish telephone engineer A. K. Erlang, the originator of queuing theory
used in traffic engineering.
used in traffic engineering.
Busy Hour Traffic (BHT) in Erlangs
BHT is the traffic load during the busy hour and is calculated as the product of the BHCA and the AHT
normalized to one hour:
normalized to one hour:
BHT = (BHCA
AHT seconds) / 3600, or
BHT = (BHCA
AHT minutes) / 60
For example, if the call center receives 600 calls in the busy hour, averaging 2 minutes each, then the
busy hour traffic load is (600 * 2/60) = 20 Erlangs.
busy hour traffic load is (600 * 2/60) = 20 Erlangs.
BHT is typically used in Erlang-B models to calculate resources such as PSTN trunks or self-service
IVR ports. Some calculators perform this calculation transparently using the BHCA and AHT for ease
of use and convenience.
IVR ports. Some calculators perform this calculation transparently using the BHCA and AHT for ease
of use and convenience.
Grade of Service (Percent Blockage)
This measurement is the probability that a resource or server is busy during the busy hour. All resources
might be occupied when a user places a call. In that case, the call is lost or blocked. This blockage
typically applies to resources such as voice gateway ports, IVR ports, PBX lines, and trunks. In the case
of a voice gateway, grade of service is the percentage of calls that are blocked or that receive busy tone
might be occupied when a user places a call. In that case, the call is lost or blocked. This blockage
typically applies to resources such as voice gateway ports, IVR ports, PBX lines, and trunks. In the case
of a voice gateway, grade of service is the percentage of calls that are blocked or that receive busy tone