Copyright © 2006 – STM Norway AS
Publication no. 101557, Rev. T, November 3
th
, 2006
Page 50
11. Header compression
The header compression feature has been implemented into the STM SatLink system to reduce the
required bandwidth, specially for VoIP calls. But also other application benefits by the Header
Compression feature. Header compression greatly reduces the amount of overhead associated with each
encapsulated IP packet. It is accomplished by removing, or reducing, redundant information in the packet
headers at one or more layers.
There are two options when using header compression on the STM SatLink system. One is to enable
header compression only for the DSM-CC header. The other option is to enable it for both DSM-CC and
IP/UDP header.
11.1 Enabling Header compression
The terminal will detect if the GW has the Header Compression enabled, and only use the feature if it is
available on the GW. If the Header compression is enabled on the Terminal, but not on the GW, it does
not take effect. The terminal will then continue transmit traffic as usual, without header compression.
To check if the Header Compression is an available feature on the GW, connect to the CLI interface of
the terminal, and enable DSM-CC and UDP Header Compression and check the transmit status.
# dvb hdsmcc
# dvb hudp
# dvb tx show
Satellite (DVB) TX Configuration
--------------------------------
Auto start : Enabled
Population ID : 2
IDU output power : -23 dBm
EIRP : max
Default CW Frequency: 14.488000 GHz
ATM mode : VC-Mux
Header Compression : UDP/IP/DSM-CC
DVB Transmitter Status
--------------------------------
State : On
Header Compression : UDP/IP/DSM-CC
IDU Output Power : -22.9 dBm
Eb/No : 13.5 dB
Timing correction : 2605 us
Frequency correction: 70 Hz
The text in
bold shows the configured values and the status. In this example, Header compression is
enabled on bothe the terminal and the GW. Always remember to save the new configuration, with the
command:
SAVE CONFIG
