DRAG DROP
Drag each phrase from the left, and place it in the appropriate column on the right. Phrases can be used more
than once.
Select and Place:

Answer:

Explanation:
Internet telephony service providers (ITSPs) enable their customers to communicate with the outside world by
connecting a Voice over IP (VoIP) network with the public switched telephone network (PSTN). Using an ITSP
allows a business to reduce network management overhead and complexity by combining voice and data
services on a single IP-based network. ITSPs enable companies with many locations to transmit voice and data
to other branches over a single connection. Using a single network for both data and voice also allows network
administrators to configure Quality of Service (QoS) features that can adjust the bandwidth available for data
based on the bandwidth required for voice traffic. Because voice traffic is sent in real time, quality is critical.
Traditional PSTN connections require separate lines for voice and data. Telephony providers connecting to the
PSTN require 64 Kbps of dedicated bandwidth for each voice line. Therefore, PSTN circuits are sold in blocks
of 64-Kbps lines. Conversely, bandwidth from an ITSP can be purchased in only enough quantity to support the
customer’s bandwidth requirements. In addition, the audio codecs and compression methods used by ITSPs for
VoIP networks can reduce the amount of per-call bandwidth required and, therefore, support more
simultaneous calls, ITSPs typically use Session Initiation Protocol (SIP) to connect VoIP calls, although some
ITSPs use H.323. SIP is an Internet Engineering Task Force (IETF)>standard call signaling protocol. Although
the text-based signaling used by SIP is easier to understand and troubleshoot than the signaling used by H.323,
SIP uses more bandwidth than binary-based signaling methods like H.323 use. H.323 is an International
Telecommunication Union (ITU)-standard, peer-to-peer call signaling protocol. H.323 requires more processor
and memory resources than SIP.
The PSTN uses Signaling System 7 (SS7) to provide signaling for call setup and teardown. SS7 is a voice
signaling protocol that is used worldwide on the PSTN. SS7 uses out-of-band signaling to perform call setup,
maintenance, and teardown tasks. In addition, SS7 is responsible for routing calls through the PSTN andmonitoring call statistics that can be used for billing purposes.
Using an ITSP can reduce costs per line for a business by providing lower-priced services that are similar to
those provided by the PSTN, such as long distance. ITSPs route long-distance calls over the Internet, which
reduces long-distance costs for the customer. VoIP networks can also handle more simultaneous calls to or
from a single location with fewer physical lines.

Packetizer: Understanding VoIP: How Does VoIP Work?
Internet Telephony: The Basics of Internet Telephony
Cisco: Voice Network and Signaling Control: Signaling System 7 U.S. PSTN Features
Cisco: Designing a Long-Distance VoIP Network: Long-Distance VoIP Network Benefits