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