Configuring Quality Of Service Settings - Cisco 3521 Administrator's Manual

Configuring Gateway Settings
In the For bonded calls, allow downspeeding down to n B channels field, choose the minimum
Step 6
number of B channels that must be available before the gateway attempts to reconnect a video call.

Configuring Quality of Service Settings

You can configure the Cisco IPVC 3500 Series Gateway to add a Quality of Service (QoS) IP
precedence code in the IP header of outbound packets on the IP network. Routers on the network that
support this method can give precedence to such coded packets and facilitate the transmission of the
packets more efficiently. You can set priority levels on the gateway for voice calls, video calls, or both.
The Type of Service (TOS) field in the IP header contains eight bits and indicates the three abstract
quality of service parameters:
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You can use the abstract parameters to choose the actual service parameters when transmitting a
datagram through a particular network. The abstract parameters represent the three-way trade off
between low delay, high throughput, and high reliability. Increasing the performance of one of the
parameters can result in reduced performance of the other two. The TOS field in the IP header is shown
in Figure
Figure 3-1
The function of each bit of the TOS field is as follows:
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The possible precedence settings are:
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Administrator's Guide for Cisco IPVC 3521 BRI Gateway, Cisco IPVC 3526 PRI Gateway, and Cisco IPVC 3540 PRI Gateway
3-14
Delay (D)
Throughput (T)
Reliability (R)
3-1.
TOS Field in the IP Header
0
Precedence
Bits 0-2: Precedence (an independent measure of the importance of the datagram)
Bit 3: 0=normal delay,1=low delay
Bit 4: 0=normal throughput, 1=high throughput
Bit 5: 0=normal reliability, 1=high reliability
Bit 6-7: reserved for future use
111=Network Control
110=Internetwork Control
101=CRITIC/ECP
100=Flash Override
011=Flash
010=Immediate
001=Priority
Chapter 3
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D T
Configuring the Cisco IPVC 3500 Series Gateway
5 6 7
R 0 0
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