Multitech MultiVOIP MVP100GK Gatekeeper, Руководство пользователя

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Chapter 5 – Gatekeeper Software
Multi-Tech Systems, Inc. MultiVOIP Gatekeeper User Guide 55
IP Parameter Definitions
Field Name Values Description
Diff Serv Parameter
fields
Diff Serv PHB (Per Hop Behavior) values pertain
to a differential prioritizing system for IP packets
as handled by Diff Serv-compatible routers. There
are 64 values, each with an elaborate technical
description. These descriptions are found in
TCP/IP standards RFC2474, RFC2597, and, for
present purposes, in RFC3246, which describes
the value 34 (34 decimal; 22 hex) for Assured
Forwarding behavior (default for Call Control
PHB) and the value 46 (46 decimal; 2E
hexadecimal) for Expedited Forwarding behavior
(default for Voip Media PHB). Before using
values other than these default values of 34 and
46, consult these standards documents and/or a
qualified IP telecommunications engineer.
To disable Diff Serv, configure both fields to 0
decimal.
The next page explains Diff Serv in the context of
the IP datagram.
Call Control PHB 0 – 63
default = 34 Value is used to prioritize call
setup IP packets.
Voip Media PHB 0 – 63
default = 46 Value is used to prioritize the
RTP/RTCP audio IP packets.
Frame Type Type II,
SNAP Must be set to match network’s
frame type. Default is Type II.
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.