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Technical Configuration | MultiVOIP User Guide |
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The IP Datagram with Header, Its
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0 | 4 | 8 | 16 | 19 | 24 | 31 | ||
VERS | HLEN | TYPE OF |
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| SERVICE |
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| IDENTIFICATION |
| FLAGS | FRAGMENT OFFSET |
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TIME TO LIVE | PROTOCOL |
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| HEADER CHECKSUM |
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| SOURCE IP | ADDRESS |
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| DESTINATION IP ADDRESS |
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| IP OPTIONS (if any) |
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| PADDING … |
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| end of header |
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| DATA |
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| … |
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The TOS field consists of eight bits, of which only the first six are used. These six bits are called the “Differentiated Service Codepoint” or DSCP bits.
The Type of Service or “TOS” field
0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 |
PRECEDENCE
D
T
R
unused
three precedence have eight values,
0)to “network control” (value of 7). When set, the D bit requests low delay, the T bit requests high throughput, and the R bit requests high reliability.
Routers that support DiffServ can examine the six DSCP bits and prioritize the packet based on the DSCP value. The DiffServ Parameters fields in the MultiVOIP IP Parameters screen allow you to configure the DSCP bits to values supported by the router. Specifically, the Voip Media PHB field relates to the prioritizing of audio packets (RTP and RTCP packets) and the Call Control PHB field relates to the prioritzing of
The MultiVOIP Call Control PHB parameter defaults to 34 decimal (22 hex; 100010 binary – consider