TSAT 3000 - 3.8.1 LCC_TX_QUE_SIZE; 3.8.2 LCC_RETRANS_QUE_SIZE

TSAT 3000 - Telemetry and data transfer via SATellite
TSAT 3000 Configuration Parameter Description, January 2013 Page 57 of 124
3.8.1 LCC_TX_QUE_SIZE
Default 40, Range 10…250
Set the maximum number of packets that may be stored in the satellite link Transmission-Queue
before transmission.
Note: The flow control of STREAM COM ports (PORT_FLOW_CTRL [n]), and User-Data from the
NMS and IP-STACK, are controlled by the number of packets in the Transmission-Queue. See
also
PORT_PRIORITY [n] and LCC_MANAGEMENT_PRIORITY.
Priority Mnemonic Flow Control ON Flow Control OFF
0 VERY_LOW_PRIORITY Size > 39 % Size <= 30 %
1 Size > 48 % Size <= 39 %
2 Size > 56 % Size <= 48 %
3 LOW_PRIORITY Size > 65 % Size <= 56 %
4 Size > 74 % Size <= 65 %
5 HIGH_PRIORITY Size > 83 % Size <= 74 %
6 Size > 91 % Size <= 83 %
7 VERY_HIGH_PRIORITY never n/a
If any packets are queued for transmission when the Transmission-Queue is full, the oldest
packets with lowest priority will be discarded, and the new packets inserted in Queue. By this
way, the Transmission-Queue will never grow larger than the specified maximum.
3.8.2 LCC_RETRANS_QUE_SIZE
Default 32, Range 1…250
Set the maximum number of packets that may be stored in the satellite link Retransmission-
Queue. I.e. Secure-Link packets that have been transmitted, but not acknowledged yet.
Note the difference:
•
LCC_RETRANS_QUE_SIZE: Total max outstanding packets – All Links.
•
LCC_WINDOW_SIZE: Max outstanding packets – Single Link.
HUB: To utilise full Window-Size towards all
RTs, LCC_RETRANS_QUE_SIZE should be set equal
(
LCC_WINDOW_SIZE x NET_NO_OF_RTS ). This could cause a lot of packets to be temporary
stored in Retransmission-Queue, and possible empty Packet-Pool. See
PKT_POOL_SIZE.
Therefore, you’ll normally limit the maximum number of packets to be stored in
Retransmission-Queue: Using value
LCC_WINDOW_SIZE x [some times, f.ex. 4].
RT: Effective Window-Size is MINIMUM( LCC_RETRANS_QUE_SIZE, LCC_WINDOW_SIZE ).
Therefore, you’ll normally set
LCC_RETRANS_QUE_SIZE equal LCC_WINDOW_SIZE.