6-4
Cisco IP Telephony Solution Reference Network Design
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Chapter 6 Call Processing
Device Weights
BHCA Multiplier
The base weight of each device is calculated using 6 or fewer busy hour call attempts (BHCA). As the
quantity of BHCA increases, so also does the number of transactions the servers are required to process
and, therefore, the weight of the device on that platform. Each device requiring more than 6 BHCA has
a multiplier applied to its base weight. The multiplier is calculated by dividing the BHCA by 6 and
rounding up to the nearest whole number. For example, an IP phone that is making 15 BHCA would have
a multiplier of 3 (15/6 = 2.5, rounded up to 3). The total device weight of the IP phone with 15 BHCA
is equal to its base weight multiplied by 3.
illustrates the effect of the BHCA multiplier.
Note
The multiplier is applied only to station or client devices and not devices that are a media resource or
gateway.
Server Platforms
The total number of device weight units that a single Cisco CallManager can support depends on the
server platform, as indicated in
.
Table 6-3
Effect of BHCA Multiplier on Device Weights
0 to 6 BHCA
7 to 12 BHCA
13 to 18 BHCA 19 to 24 BHCA 25 to 30 BHCA
Multiplier
1
2
3
4
5
Device weight for example IP phone
1
2
3
4
5
Device weight for example CTI client port
2
4
6
8
10
Table 6-4
Maximum Number of Devices per Server Platform
Server Platform Characteristics
Maximum IP
Phones per Server
1
Maximum Device
Weight Units per
Server
High Availability
Platform
2
High Performance
Server
Cisco MCS-7845 (All models)
7500
10,000
Yes
Yes
Hewlett-Packard/Compaq DL380,
Dual CPU
All Cisco approved models
7500
10,000
Yes
Yes
Cisco MCS-7835 (All models)
Pentium III (733-1266MHz),
1-2GB RAM
2500
5000
Yes
No
Cisco MCS-7830
Pentium III (500MHz), 1GB RAM
1500
3000
Yes
No
Cisco MCS-7830
Pentium III (500MHz), 512MB RAM
500
1000
Yes
No
Cisco MCS-7825-1133
Pentium III (1.133GHz), 1GB RAM
1000
2000
No
No
Cisco MCS-7825-800
Pentium III (800MHz), 512MB RAM
1000
2000
No
No