Ericsson EFN324, User Manual, Page: 48 / 176

IndexIndex
established. There are four ‘out’ queues, reflecting different priority
levels, for each port. Because there is only one common physical
memory area, all ‘queues’ in this context are logical queues.
 Queuing and scheduling
Depending on the priority setting determined during the ingress flow
processing, the packet is placed in one of the four out­queues
associated with each port.
If there is more than one packet waiting to be sent, the order of the
outgoing packets is determined by the scheduling method configured
for the switching domain. The next packet to be sent is selected
according to the scheduling mechanism. In general, the higher the
priority, the shorter the waiting time.
The following scheduling mechanisms may be configured for each
port:

None – that is, first in, first out.
 Strict priority
– the waiting packet with the highest priority
is sent first, using first in, first out, within each priority group.

Weighted fair queuing (Deficit Round Robin) – packets
with lower priorities are not completely held back by packets with
higher priorities. Each priority class gets a certain share of the
total sending time. The lower the priority, the lower the share of
sending time.
 Combined strict priority and weighted fair queuing
(Modified Deficit Round Robin)
– the highest prioritized packets
are strictly sent first. When no highest prioritized packets are in
the queue, the others are sent according to weighted fair queuing.
5.6 Marking Priority
The p­bit marking or remarking takes effect in several ways, depending on
how it is defined.
In case a marking is defined at node level flow, with the value transparent,
frames will maintain the incoming p­bit value. In case a tag is added, the p­bit
added will assume the same value as the incoming p­bit.