Multi-Tech Systems MVP210-SS User Manual download pdf (Page 108)

Technical Configuration MultiVOIP User Guide

108

The IP Datagram with Header, Its Type-of-Service field, & DiffServ

bits =>

0 4 8 16 19 24 31

VERS HLEN

TYPE OF

SERVICE

TOTAL LENGTH

IDENTIFICATION

FLAGS

FRAGMENT OFFSET

TIME TO LIVE PROTOCOL HEADER CHECKSUM

SOURCE IP ADDRESS

DESTINATION IP ADDRESS

IP OPTIONS (if any) PADDING …

end of header

DATA

…

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, 0-7, ranging from “normal” precedence (value of

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 non-audio packets (packets concerning call set-up and tear-down,

gatekeeper registration, etc.).

The MultiVOIP Call Control PHB parameter defaults to 34 decimal (22 hex; 100010

binary – consider vis-à-vis TOS field above) for Assured Forwarding behavior. The

MultiVOIP Voip Media PHB parameter defaults to the value 46 decimal (2E hex;

101110 binary – consider vis-à-vis TOS field above). To disable DiffServ, configure

both fields to 0 decimal.

1 2 ... 103 104 105 106 107 108 109 110 111 112 113 ... 414 415

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Multi-Tech Systems MVP210-SS User Manual Page 108