SatLink VSAT User Guide
Publication no. 101557
Copyright © 2009 – STM Group, Inc.
Page 64 (160)
• 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.
11.1 Configuring QoS for the Return Link
In order to determine the QoS group an IP packet belongs to, the STM SatLink VSAT uses a multi-field
classifier. This multi-field classifier is used to perform a look-up in a classification table for all IP packets
that shall be transmitted on the return link. 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 MFC classification:
• IP source address
• IP destination address
• DSCP / TOS
• Protocol type
• TCP/UDP source port number
• TCP/UDP destination port number
Additionally the Ethernet User Priority as per IEEE 802.1Q can be used for QoS classification. Refer to
section 18.7 for more details on mapping the Ethernet User Priority to a return link QoS class.
The MFC in the STM SatLink VSAT can also be used to set the DSCP field in the IP header.
The format of the QoS module of the MFC table is:
SubIdx Idx Grp Classification Parms HitCount
0-255 0-6 1-65535
The index parameter is used to uniquely identify an entry in the classification table and decides the order
in which the classification table is searched. When an IP packet is to be classified, the classification table
is searched from index 0 and upward. 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 classification table. If a match is not found for
an IP packet it will be treated as best effort traffic.
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