Avaya 4.2 System Capacity, Extension Capacity, Call Capacity, IP Office Unit Maximum Maximum VCM

1.3 System Capacity

System capacity can be separated into two aspects; the number of configurable phone extensions and the number of simultaneous IP phone calls.

Extension Capacity

The maximum number of H323 IP phones supported by an IP Office system is based on that system's maximum capacity for extensions of any type as listed in the table below. To find the capacity for IP phones remove the number of physical non-IP extensions installed on the system, ie. extension ports on the IP Office control unit and any external expansion modules.

IP Office Unit	Maximum	Maximum VCM
	Extensions	Channels
Small Office Edition	28 Total/16 IP[1]	3[2] or 16[2]
IP406 V2	190	30
IP412	360	60
IP Office 500	272	128

1.The maximum extension capacity is 28 for all phone types but only 16 may be IP phones.

2.Fixed non-adjustable capacity.

Call Capacity

There are a number of situations where the IP Office system needs to provide a voice compression channel in order for an IP phone to make calls. These channels are provided by Voice Compression Modules (VCMs) installed in the IP Office system. The number of VCM channels required and how long the channel is required will depend on a number of factors. For further details see Voice Compression 16.

A simple summary is:

∙A VCM channel is required during call setup.

∙The VCM channel is released if the call is to/from another IP device using the same compression codec (the supported VCM codecs are G711, G729 and G723a).

∙The VCM channel is used for the duration of the call when the call is to/from/via a non-IP device (extension or trunk line).

∙It should be remembered that VCM channels are also used for calls from non-IP devices to IP lines if those are configured in the IP Office system (IP, SIP and SES lines).

∙Calls from IP phones to the IP Office voicemail server use a VCM channel.

∙Note that on Small Office Edition systems with Embedded Voicemail, an additional channel is used for every call to voicemail.

H323 Install	Page 10
IP Office 4.2	15-601046 Issue 14j (10 March 2009)