User's Manual Part 2

Chapter 9 The VoIP General Screens
BM2022w User’s Guide
158
• G.729 is an Analysis-by-Synthesis (AbS) hybrid waveform codec. It uses a filter based on
information about how the human vocal tract produces sounds. The codec analyzes the incoming
voice signal and attempts to synthesize it using its list of voice elements. It tests the synthesized
signal against the original and, if it is acceptable, transmits details of the voice elements it used
to make the synthesis. Because the codec at the receiving end has the same list, it can exactly
recreate the synthesized audio signal.G.729 provides good sound quality and reduces the
required bandwidth to 8kbps.
Quality of Service (QoS)
Quality of Service (QoS) refers to both a network's ability to deliver data with minimum delay and
the networking methods used to provide bandwidth for real-time multimedia applications.
Type Of Service (ToS)
Network traffic can be classified by setting the ToS (Type Of Service) values at the data source (for
example, at the BM2022w) so a server can decide the best method of delivery, that is the least
cost, fastest route and so on. The ToS field is consist of 8 bits. The first 3 bits indicate the priority of
the packet.
DiffServ
DiffServ is a class of service (CoS) model that marks packets so that they receive specific per-hop
treatment at DiffServ-compliant network devices along the route based on the application types
and traffic flow. Packets are marked with DiffServ Code Points (DSCPs) indicating the level of
service desired. This allows the intermediary DiffServ-compliant network devices to handle the
packets differently depending on the code points without the need to negotiate paths or remember
state information for every flow. In addition, applications do not have to request a particular service
or give advanced notice of where the traffic is going.
DiffServ uses the first 6 bits of the 8-bit ToS value so that it can be backward compatible with non-
DiffServ compliant but ToS-enabled network device. See
Section 9.6.1 on page 162 for more
information.
SIP
The Session Initiation Protocol (SIP) is an application-layer control (signaling) protocol that handles
the setting up, altering and tearing down of voice and multimedia sessions over the Internet. SIP
signaling is separate from the media for which it handles sessions. The media that is exchanged
during the session can use a different path from that of the signaling. SIP handles telephone calls
and can interface with traditional circuit-switched telephone networks.
RTP
When you make a VoIP call using SIP, the RTP (Real time Transport Protocol) is used to handle voice
data transfer. See RFC 1889 for details on RTP.
Speed Dial
Speed dial provides shortcuts for dialing frequently used phone numbers. You can map a phone
number to a self-defined key(s) and then use that key(s) to call the phone number. For example,
you can map 123456 to #01. When you press #01 it means that you press 123456.