Comtech EF Data DMD1050 - Manual (Page 37)

DMD1050 Satellite Modem Board Theory of Operation
MN-DMD1050 3–11
Revision 9
The interface sends out another pause frame with the pause time set to zero as soon as free buffer
space becomes available.
3.7.1.5 Ethernet Daisy Chain
When disabled, Port 2 on the Ethernet Data Interface operates normally. Data received on Port 2
that is not addressed to other equipment on the LAN side, is transmitted over the satellite.
When Port 2 is selected for Daisy Chain, any data received on Port 2 is forwarded to of the other
LAN side ports (Ports 1) and is not transmitted over the satellite. This is extremely useful in a
point-to -multipoint configuration as illustrated in Figure 3-5.
3.7.1.6 Ethernet QOS Type
When Normal QOS is selected, the interface determines a packets priority based on the
following:
 IEEE 803.3ac Tag when present
 IPv4 Type of Service / Differentiated Services Field
 Ipv6 Traffic Class
When Port Based QOS is selected, the interface determines the priority of a packed based upon
the port on which it arrived.
 Port 1 (JS1) has the highest priority
 Port 2 (JS2) has the second highest priority
3.7.1.7 Ethernet QOS Queue
When Fair Weighted queuing is selected, the interface transmits packets at a rate of 8, 4, 2, and 1
from the highest priority queue to the lowest respectively. With fair weighted queuing, all queues
with data in them are guaranteed to receive some bandwidth.
When Strict Priority is selected, the interface transmits packets from the highest priority queue
until it is empty. It then begins transmitting data from the next highest priority queue. If higher
priority data arrives, the interface finishes the current packet and then goes back to transmitting
packets from the higher priority queue until it is again empty. Care must be taken when selecting
Strict Priority, as it is entirely possible for the lower priority queues to be stalled indefinitely.