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

locate an appropriate gateway. In this case, the URL for the location of the SIP

proxy would look like:

sip:[email protected];user=phone

where the SIP proxy at proxy.gateway.comwill determine the gateway and

forward the request.

IANA ENUM Service Registrations

ENUM may also be used for other services besides SIP. Several ENUM services

have been registered with the IANA, as shown in Table 4.1.

The Domain Name System

The Internet Domain Name System (DNS) [10] is a scalable namespace used to

refer to resources on the Internet and in private networks. DNS names avoid

specifics such as IP addresses and port numbers.

Scalability for the huge size of the DNS is because of its distributed nature

and the use of caching.

Table 4.1 ENUM Services

ENUM SERVICE NAME SERVICE TYPE/SUBTYPE URI SCHEME

h323 h323 h323:

sip sip sip:, sips:

ifax ifax:mailto mailto:

pres pres pres:

web web:http http:

web web:https https:

ft ft:ftp ftp:

email email:mailto mailto:

fax fax:tel tel:

sms sms:tel tel:

sms sms mailto mailto:

ems ems:tel tel:

ems ems:mailto mailto:

mms mms:tel tel:

mms mms:mailto mailto:

58 Chapter 4