1.1.1. Components of a SIP Network

SIP
Proxy Server
PSTN
Gateway
Router
NAT
Provisioning
Server
PC
PC
Application
Server
PSTN
ISP
Gateway
PST
GN
ateway
P
Net
rivate IP
work
PSTN
Subscriber
Service Database

Provider

Billing
Server

Domain

Application
Server
Broadband
Modem

Subscriber

Domain

Phone
Adapter
IPNetwork
IP Teleph
subscribe
up to two
interface
device to
the servic
Home/SO
between . If the ISP provides only one
irects

(Internet)

Figure 1 -- Components of a SIP IP Telephony Network
ony Gateway (PHONE ADAPTER): The PHONE ADAPTER is a small device that sits at the
r’s premises. It converts between analog telephone signals and IP Telephony signals. It has
RJ-11 ports where standard analog telephones can be directly attached, and an RJ-45
for the Ethernet connection to the home or business LAN. Intelligence can be built into this
provide a wide range of features to the subscribers in association with the other elements in
e. The PHONE ADAPTER functions as a SIP User Agent (UA).
HO Routers with NAT Functionality: A home/SOHO router is used for routing IP packets
the subscriber’s private network and the ISP’s public network
public IP address to the subscriber, the devices attached to the private network will be assigned
private IP addresses and the router will perform network address translation (NAT) on packets sent
from the private network to the public network via the router. Home routers offer the following
features:
• An R-J45 WAN interface for connection to the ISP’s public network and one or more RJ-45
LAN interfaces for connection to the subscriber’s private network. The router d
packets between the private network and the public network.
• A PPPoE client to connect with the ISP through a DSL modem.
• A DHCP client where the router will obtain an IP address, subnet mask, default router
assignment, etc., for its WAN interface from a DHCP server on the public network.
• A DHCP server for auto-assignment of private IP addresses, subnet mask, and default
router assignment to devices attached to the private network, i.e. computers, IP Telephony
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