Internet Communications Using SIP : Delivering VoIP and Multimedia Services With Session Initiation Protocol {2Nd Ed.}

Open protocols are used exclusively. As a consequence, servers can be dis-
tributed across the network and can be provided and operated by various par-
ties, using appropriate Internet security procedures, such as some form of
secure IP tunneling. All real-time communication servers use only SIP and
HTTP to communicate, as will be shown later in this chapter. No APIs are
required. This makes the architecture completely open and allows easy out-
sourcing for specialized or high-performance services, such as unified mes-
saging, instant messaging, or conferencing.
There is a loose coupling between service components. The service con-
troller only invokes various service components by providing call control and
leaves the detailed operation to the respective servers.
Dedicated servers also allow the use of application switching in high-traffic
service hosting centers such as routing Web, e-mail, and various SIP and RTP
communication flows to the appropriate servers.
Figure 19.3 Shows a network based services portal for e-mail, Web and voice.

Figure 19.3 Network based services portal.

Voice

SIP Clients

Web & mail

Users with various clients

isp

PBX

Mobile

PSTN

Web Portal

Portal Services

Full web multimedia

http://www.isp.com

Email Portal

Unified Messaging

[email protected]

sales.isp.com

directory.isp.com

ftp.isp.com

email.isp.com

hosting.isp.com

voicemail.isp.com

i-messenger.isp.com

agent.isp.com

conference.isp.com

media.isp.com

checkout.isp.com

Voice Portal

IVR and voice browsing

Enterprise

Gateway

Network

Gateway Portals are “invisible” to end user,

but have URLs for routing to services

800.isp.com

SIP Component Services 325