Copyright © 2006 – STM Norway AS
Publication no. 101557, Rev. T, November 3
th
, 2006
Page 42
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Real-time traffic packets are dropped at the head of the transmission queue if the queue
overflows, while best effort traffic packets are dropped at the tail of the queue.
-
The transmission queue length are tailored for each QoS class
•
Precedence
-
Real-time traffic is given precedence over best effort traffic.
Typing CLI command
# ip qos show
will output, among other, the QoS Policy Table:
QOS Policy Table
Grp Cls CrM Pri QLength Drop Timeout Description
0 0 0 0 400000 0 120 Best Effort
1 1 1 1 15000 1 120 VoIP Audio
2 1 1 2 4000 1 120 VoIP Signalling
3 2 1 5 500000 1 120 VIC Video
4 2 1 4 50000 1 120 VIC Audio
5 2 1 3 10000 1 120 VIC Signalling
6 3 0 6 400000 0 120 Critical Data
The parameters in the QoS policy Table are not user configurable.
8.1
Configuring QoS for the return link
In order to determine the QoS group an IP packet belongs to, the STM SatLink terminal uses a multi-field
classifier. This multi-field classifier is used to perform a look-up in a QoS classification table. This table
can store up to 15 different masks that the IP packets will be matched to.
The following parameters in the IP header can be used for doing the QoS classification:
•
IP source address
•
IP destination address
•
DSCP / TOS
•
Protocol type
•
TCP/UDP source port number
•
TCP/UDP destination port number
Additionally the QoS classificator in the STM SatLink Terminal can set the DSCP field in the IP header
based on the multi-field classifier.
The format of the QoS classification table is:
Index
QoS
Group
Dest. IP
Address
Mask
Source IP
Address
Mask
DSCP
Range
(Start-Stop
values)
Protocol
Type
(up to 3
values)
TCP/UDP
Source Port
Range (Start-
Stop values)
TCP/UDP
Dest. Port
Range (Start-
Stop values)
0-255
0-6
0-63
0-255
0-65535
0-65535
The index parameter is used to uniquely identify an entry in the QoS classification table and decides the
order in which the QoS classification table is searched. When an IP packet is to be QoS classified, the
QoS classification table is searched from index 0 and upwards. If a match is found, the search is stopped,
and the IP packet is thereafter handled with the QoS Group for this entry in the QoS classification table. If
a match is not found for an IP packet it will be treated as best effort traffic.
