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

Figure 4.5. Originating calls from a PBX of from the PSTN using ENUM

Figure 4.6 Using ENUM for IP-IP communications

Switch

PSTN

Internet Gateway

SIP-2

Phone number to reach any

device on IP or PSTN

PC can use presence,

phone number or URL to

reach any device on IP

or PSTN

SIP-1

DNS

ENUM

query

AOR to

Contact

Addresses

Generic

ENUM

enabled

Gateway

Switch

Calls will be routed by

default over IP

ENUM-SIP

inside

Switch Switch

Telco PSTN Telco/PBX

Gateway

The IN returns to the

switch the address of the

ENUM gateway if it exists,

otherwise the call is routed

over the PST.

Internet

SIP-1 SIP-2

DNS

PBX

ENUM

query

AOR

mapping to

Contact

Addresses

DNS and ENUM 75