Figure 6.1 SIP-enabled IP communication network
Endpoints and servers benefit from a long list of protocol features of SIP:
■■ Web-style and telephony-type addressing—SIP devices can use URIs that
are location-independent and URLs that point to a specific host.
Addresses can take the form of e-mail addresses or telephone numbers,
with clearly defined options for E.164 public telephone numbers and
private numbering plans.
■■ Registration—Devices connected to the network are registered so as to
route calls to and from the device. Users may register themselves using
their ID to get access to their particular information and services, inde-
pendent from the device registration. This is similar to e-mail access
from web kiosks or Internet cafes. Such dynamic routing to/from the
user is accomplished without needing “switch translations” or other
static routing tables to be managed.
■■ Security—SIP is designed to use the Internet security mechanisms pro-
tect sensitive signaling information from various types of attack. User
location and traffic patterns can be kept confidential. SIP security can
be quite complex and uses the advances in all generic IP security
mechanisms.
■■ Redirect—A SIP server can redirect a request to another address, similar
to the core function of the AIN.CALLED,
PRESENTITYMEDIA, MESSAGESSUBSCRIBEINVITEINVITE INVITEINVITEFORKINGNETWORK
PROXYGATEWAYS
PSTNMOBILEPBXLOCAL
PROXYLOCAL
PROXYNOTIFYCALLER,
WATCHERFRAME RELAY, ATM,
H.323, H.248NON-IP NETWORKSSIP Overview 99