6–2
MULTINET4 MULTI-PORT SERIAL SERVER & MANAGED SWITCH – INSTRUCTION MANUAL
OPERATIONAL GUIDE
CHAPTER 6: OPERATIONAL GUIDE
FIGURE 6–1: QoS Flow Chart
6.1.2
Priority Queues
The Multinet4 Multi-Port Serial Server & Managed Switch supports 4 distinct priority
queues for each ethernet port.
When a packet is received it is assigned one of four internal priority levels. It is then copied
to some number of output ports (according to the switch's bridging rules) and placed in the
queue that matches its priority level. The queuing discipline is implemented in hardware
and is a fixed weighted fair queuing algorithm that services a certain number of packets
from each queue and then moves on to the next queue. The weighting is 8-4-2-1, meaning
that up to 8 priority-1 packets are sent, followed by up to 4 priority-2 packets, followed by
up to 2 priority-3 packets, followed by a single priority-4 packet. In this way, low priority
packets still have a chance (albeit at a lower rate) to egress the port when there is a heavy
stream of higher priority traffic.
6.1.3
DiffServ Marking
DiffServ markings may be applied to any packet that is generated by Multinet4 (e.g.
terminal server traffic, routed traffic, etc.). This is accomplished through the use of
configurable rules that map DiffServ codepoints to particular packet types or flows. When
an IP packet is sent from the stack (either due to IP forwarding or because the packet was
