sub10EthMgmtQoSQSchedulingType

The scheduling discipline applied to the
queue.
              
qosSPQ - Strict Priority Queueing
              
Queues are serviced in strict priority
order. Packets on the queue are servicedd
and transmitted until either the queue is empty
or a packet is found in a higher queue,
in the latter case the higher priority queue
take precedence.
              
Individual PCP (CoS) bits or DSCP markings in each
packet are not observed within the
queue and are not therefore transmitted first
according to their relative priority. Instead
it is possible to map certain VLANs, PCP bits
and DSCP marking to certain queues to achieve
priority transmission.
              
The mapping of VLAN, PCP bits or DSCP markings
to a specific queue are managed using
tables :
              
sub10EthMgmtQoSVlanTable
sub10EthMgmtQoSPCPTable
sub10EthMgmtQoSDSCPTable
              
qosDWRR - Deficit Weighted Round Robin
              
A weighting is allocated to each queue
which defines the number of bytes
that can be transmitted from that
queue in a single visit of the
scheduler. This is used to calculate
a quantum which is the number of bytes
that can always be transmitted in each visit
of the scheduler.
              
A deficit counter is also maintained across
visits from the scheduler, at each visit
the quantum is added to the deficit. This
ensures that on average a queue that is not
loaded to its intended capacity will utilise
the calculated deficit at times when the queue
is busy. At startup Deficit counter is initialised
to zero.
              
On each visit of the scheduler packets are
transmitted according to the following
rules...
              
Deficit = Quantum + Deficit.
              
while (Queue not empty and PktLength <= Deficit)
Transmit Pkt
Deficit = Deficit - PktLength
              
Remaining Deficit is carried forward to the
next visit of the scheduler.
              
Effective behaviour of DWRR is as follows:
              
1. Available bandwidth is shared fairly when queues
are not saturated
2. Lower priority saturated queues will transmit
at their allocated service rate.
3. Any remaining bandwidth is shared amongst
unsaturated queues.
              
NB. In a mixed configuration where some queues are
configured as Strict Priority (SP) and some configured
as Deficit Weighted Round Robin (DWRR), then queues configured
as SP should all be higher in scheduling priority than those
configured as DWRR. This is to avoid the lower priority queues
having transmission precedence over higher priority queues.

MIB

SUB10SYSTEMS-MIB

OID

.1.3.6.1.4.1.39003.4.2.3.4.1.2

Type

column

Access

readwrite

Status

current

Parent

sub10EthMgmtQoSQEntry

Table

sub10EthMgmtQoSQTable

Siblings

5