Traditional network model
Before SIP and VoIP, enterprises connected their internal
PBX-based telephone systems to carriers via dedicated TDM
(Time Division Multiplexing) trunks. Companies paid for them
whether they were idle or overflowing, and incurred toll and
tariff charges, especially expensive for long-distance calls.
Today, many companies integrate voice and data over IP and
link their sites using IP WANs to reduce costs for communica-
tions within the enterprise. However traditional PSTN circuits
are still used to communicate with their customers and sup-
pliers, partners, and the outside world.
Transforming trunking with SIP
SIP trunks enable enterprises to carry their voice data over
a pure IP connection to carrier clouds, rather than through
separate circuits as has been the practice for decades. An
Enterprise SIP proxy peers with a Carrier SIP proxy, with the
Part 4: How SIP Transforms Enterprise Communications
35
Marveling at what a SIP trunk can carry
SIP technology can alter the way that a
retail business services its customers.
Suppose a retailer with a number of
store locations wants to offload the
task of handling phone calls from its
store employees so they can focus on
in-store customers, but the retailer
has no direct connectivity between its
call center and each store.
SIP-based trunking enables a reconfig-
uration of communications to address
the problem. Through SIP-based DID
mobility inbound service, the service
provider transports local calls to each
store over the SIP network directly to
the call center.
Without making any changes to the
local stores, the retailer is now able to
free up store employees to serve in-
store customers, improve customer
service over the phone by reducing
hold times and busy signals, and still
retain a local presence to its cus-
tomers through a local access
number. And with SIP trunking, the
call center can replace dozens of
TDM trunk lines with a single SIP link!
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