Information Technology Reference
In-Depth Information
connections between VoIP/IPT systems and analog or digital circuits. This allows
Vo I P/ I P T s y s t e m s t o i n t e g r a t e w i t h t h e P S T N , P BX s , a n d a n a l o g e n d p o i n t s .
The Cisco Unified Communications Manager (CUCM) fulfills the role of call processing.
The CUCM servers are the “brains” of the voice dial plan and are used to establish IPT
calls between IP phones. It provides a scalable and distributable VoIP call processing solu-
tion. CUCM performs the functions similar to traditional PBXs on older voice networks.
Service applications include IVR, Auto Attendant, and Unified Messaging (voice mail).
Cisco IP Contact Center (IPCC) is used for enterprise call center applications. In addition,
a standards-based Telephony Application Programming Interface (TAPI) allows third-party
companies to develop applications for CUCM.
The voice-enabled infrastructure provides services to support IPT voice, including Power
over Ethernet (PoE) and QoS. PoE allows a switch to detect a phone and provide it with
power so that power does not have to be provided everywhere that phones are present.
With this model, backup/redundant power can be provided from a centralized location. In
addition, when a switch detects a phone, it can put that phone in a separate VLAN from
other endpoints and allow QoS signaling from the phones. LAN switches and WAN
routers work together to provide queuing of data and end-to-end prioritization of VoIP
over other types of network traffic during times of congestion.
Ta ble 1 4 - 5 summarizes the IPT functional areas.
Ta b l e 1 4 - 5
IPT Functional Areas
IPT Functional Area
Description
Service applications
Unity, IVR, TAPI interface
Call processing
Cisco CUCM
Client endpoints
IP phones, digital and analog gateways
Vo i c e - e n a b l e d i n f r a s t r u c t u r e
Layer 2 and Layer 3 switches and routers
Design Goals of IP Telephony
The overall goal of IP telephony is to replace the traditional, highly complex, expensive,
and isolated TDM-based telephone systems and the required duplicate infrastructure with
simpler, more cost-effective IPT components using existing data infrastructure and lever-
aging integration to provide flexibility and cost savings along with robust features and
functionality. IPT also allows third-party software providers to develop new applications
for IP phone s.
Key
To p i c
The following summarizes the design goals for a VoIP network:
To u s e e n d - t o - e n d Vo I P b e t w e e n s i t e s
■
To m a k e Vo I P w i d e l y u s a b l e
■
■
