The actual conversion process is provided through a function known as ENUM. This
function translates an E.164 telephone number into a SIP or TEL URI. The ENUM function
does not translate the identity into an IP address, however. This remains the function
of the Domain Name Server (DNS). We will talk more about these functions later.
Eventually, TEL URIs may disappear completely as we become more and more accustomed
to using SIP URIs for all communications. This is still a long way off, however,
and something we may not see for decades.
A subscription can have multiple identities as mentioned earlier. For example, I may
have one user identity for my e-mail, while maintaining a telephone number for my cell
phone. I may have yet another identity for business purposes, and one for personal use.
This is somewhat analogous with screen names with an ISP, where one account can
possess several screen names, yet all are billed under one subscription.
In today??™s networks, you use an ISP to provide e-mail service, and a telephone service
provider for wireless and wireline services. This is rapidly changing as service providers
are quickly moving to provide all services under one subscription, including video
service.
If you have an e-mail address, you already have a URI. The domain name identifies
who owns your subscription (your home network). For example, my personal e-mail
address is travisruss@aol.
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