Talkswitch 24-CA User Manual page 134

25Kbps bandwidth downstream for each call. G.729 provides very good
call quality while minimizing bandwidth usage.
The G.726 (32Kbps) CODEC is a better quality solution compared to the
G.729 CODEC. However, it requires more bandwidth per call. A G.726 call
typically requires 50 Kbps bandwidth upstream and 50Kbps bandwidth
downstream for each call.
The G.711 CODEC provides the best voice quality. The trade-off is the
bandwidth requirement. G.711 calls typically requires up to 100 Kbps
bandwidth upstream and 100 Kbps bandwidth downstream.
If the power goes out, does the VoIP network stay up?
To ensure a reliable network connection, all elements of the VoIP network
should be connected to back-up power supplies (UPS). These elements might
include LAN switches, routers, firewalls, broadband connection devices (i.e.
cable modems, DSL modems), and VoIP devices. If the power goes out at the
Internet Service Provider, then no VoIP calls can be made. Calls can still be
placed over the regular phone lines.
What happens to VoIP if the IP network fails?
If the connection to the IP network is lost, it will not be possible to make
VoIP calls. Calls can still be placed over the regular phone lines.
Can a firewall prevent VoIP calls from passing through?
The purpose of a firewall is to control what kinds of traffic enter and leave
your network. The TalkSwitch 48-CVA is designed with embedded applications
to help traverse firewalls properly. To allow VoIP calls to pass through your
firewall, you may need to use the port forwarding feature on your firewall.
TalkSwitch 48-CVA default uses the following ports for VoIP:
Format Type
RTP (voice): UDP
SIP
(signaling): UDP
What is SIP?
The Session Initiation Protocol (SIP) is a signalling protocol used for
establishing sessions in an IP network. A session could be a simple two-way
telephone call or it could be a collaborative multi-media conference session.
Over the last couple of years, the Voice over IP community has adopted SIP as
its protocol of choice for signalling. SIP is an RFC standard (RFC 3261) from
1 2 6
Unit 1 Unit 2
6000-6006 6010-6016
5060 (This port is mapped to only one unit)
T A L K S W I T C H U S E R G U I D E • N O R TH A ME R ICA
Unit 3 Unit 4
6020-6026 6030-6036