User's Manual

Chapter 15 VoIP
B222s User’s Guide
136
15.8 Technical Reference
This sect ion cont ains background m aterial relevant t o the VoI P screens.
15.8.1 VoIP
VoI P is t he sending of voice signals over I nt ernet Protocol. This allows you t o m ake phone calls and
send faxes over the I nt ernet at a fraction of the cost of using t he t radit ional circuit- switched
telephone network. You can also use servers to run t elephone service applicat ions like PBX services
and voice m ail. I nt ernet Telephony Service Provider ( I TSP) com panies provide VoI P service.
Circuit- swit ched t elephone net works require 64 kilobit s per second (Kbps) in each direct ion to
handle a t elephone call. VoI P can use advanced voice coding t echniques wit h com pression to reduce
the required bandwidt h.
15.8.2 SIP
The Session I nit iation Prot ocol ( SI P) is an application- layer control ( signaling) prot ocol t hat handles
the set ting up, altering and t ear ing down of voice and m ultim edia sessions over t he I nt ernet .
SI P signaling is separat e from t he m edia for which it handles sessions. The m edia t hat is exchanged
during t he session can use a different path from t hat of the signaling. SI P handles t elephone calls
and can interface wit h t radit ional circuit- switched t elephone net works.
SIP Identities
A SI P account uses an ident it y (som et im es referred to as a SI P address). A com plet e SI P ident it y is
called a SI P URI ( Uniform Resour ce I dent ifier) . A SI P account 's URI ident ifies t he SI P account in a
way sim ilar t o t he way an e-m ail addr ess identifies an e-m ail account . The form at of a SI P identit y
is SI P- Num ber@SI P-Service-Dom ain.
SIP Number
The SI P num ber is t he part of t he SI P URI t hat com es before t he “ @” sym bol. A SI P num ber can
use let ters like in an e-m ail address ( j ohndoe@your-I TSP.com for exam ple) or num bers like a
telephone num ber (1122334455@VoI P- provider.com for exam ple) .
SIP Service Domain
The SI P ser vice dom ain of t he VoI P service provider is t he dom ain nam e in a SI P URI . For exam ple,
if the SI P address is
1122334455@VoI P- provider.com , t hen “ VoI P- provider.com ” is t he SI P ser vice
dom ain.
SIP Registration
Each LTE Device is an individual SI P User Agent ( UA). To provide voice ser vice, it has a public I P
address for SI P and RTP prot ocols to com m unicat e wit h ot her ser vers.
A SI P user agent has t o register wit h t he SI P registrar and m ust provide inform at ion about t he
users it represent s, as well as it s current I P address (for the rout ing of incom ing SI P request s) .