Quality Of Service - Samsung Officeserv 7100 Technical Manual

OfficeServ 7100
TECHNICAL MANUAL
MMC 830 and MMC 831: IP type to "Private with Public" set up private and
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public IP addresses.
MMC 840: For each remote ITP, set IP type to "Public with Firewall".
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Quality of Service

Quality of Service when deploying VoIP is always a consideration. In the IP network
environment there are several tools to assist in providing a voice quality that can
sometimes be comparable to circuit switched voice. When working via an IP network
there are issues that are beyond the control of the communications system.
The main concerns for QoS are Lost Packets, Delay (fixed or variable) and Jitter. To
use these terms it must be understood that the quality of voice via IP is based or
measured by a Mean Opinion Score (MOS). MOS is a numerical measure of the quality
of human speech when using VoIP. Subjective test (opinionated) provide a numerical
score to determine voice quality. These scores are based on compression methods
and provide a mathematical equivalent to speech quality where 5 is the best and 1 is
the worst.
Table 3. MOS Guidelines
Compression MOS Score
G.711 4.5
G.729 3.9
G.729A 3.65
G.723 3.8
Table 4. MOS Quality Assessments
Score Listening
Quality
5 Excellent
4 Good
3 Fair
2 Poor
1 Bad
Before applying QoS sufficient bandwidth must be available. A G.711 call over a
64Kbps link will result in a 20% loss of data and provide poor quality. IE. G.711 = 64
kbps payload +16 kbps header = 80 kbps. So, then an 80 kbps packet on a 64 kbps
circuit results in 20% loss. Provisioning of bandwidth is an important factor in all VoIP
applications.
Network congestion is another source for packet loss and delay. There are tools
available in many router operating systems that provide for equal queuing to voice and
Byte/ms
80/5
10/10
10/10
24/30
Listening Effort
Complete relaxation possible, no effort required
Attention necessary, no appreciable effort required
Moderate effort required
Considerable effort required
No meaning understood with any feasible effort
2.6.23
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SPECIAL APPLICATIONS
PART 2 JANUARY 2009
Bit Rate (Kbps)
64
8
8
5.5~6.5
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