4A0-107 Nokia Quality of Service Questions and Answers

SAP-ingress only

SAP-egress only

SAP-ingress and SAP-egress

Network ingress

Network egress

Closest

Average

Min

Max

Set the queue’s CBS to 0

Set the queue’s MBS equal to the CBS

Set the queue’s high-priority-only equal to the MBS

Set the queue’s MBS to 0

Set the queue’s high-priority-only to 0

Packets can be classified into 16 different FCs when using priority mode queuing.

This feature is available on egress SAPs within any service.

MPLS EXP bits can be changed based on multi-field classification.

If a Behavior Aggregate (BA) and Multi-field (MF) match occurs, only the MF override parameters will take effect.

If a Behavior Aggregate (BA) and Multi-field (MF) match occurs, the BA classification can override the forwarding class while the MF classification can override the profile.

WRED

shapers

schedulers

markers

weighted fair queues (WFQ)

IOM3

FP3 based IMM

IOM1

IOM2

An arbiter can adjust the CIR of its child policers.

An arbiter rate-limits the collective output of several policers towards each egress FFPC.

An arbiter can adjust the bandwidth assigned to its child arbiters and child policers.

An arbiter does not need to honor the configurations of its child policers.

Ensure that traffic flows conform to their traffic profile.

Log violations of metered traffic flows exceeding the CIR value set on the entity across which the traffic is moving.

Provide fairness between traffic flows, so that conforming (in-profile) traffic flows are not starved of bandwidth and/or buffer space by non-conforming (out-of-profile) flows.

Minimize packet loss and reduce end to end latency.

Ensure that variable latencies do not cluster short bursts of originally conforming packets and render them nonconforming.

The primary contributors to latency are distance, scheduling, and congestion.

The weighted round robin scheduling algorithm will result in more delay for high priority traffic than the regular round robin algorithm.

The round robin scheduling algorithm will result in less jitter for low priority traffic than a strict priority scheduler.

Packet loss can be reduced by decreasing the amount of buffer space available to a queue.

Latency can be reduced by increasing the amount of buffer space available to a queue.

It will be discarded because the high-priority-only threshold is exceeded.

It will be stored in the queue’s reserved buffer space and become out-of-profile.

It will be stored in the queue’s reserved buffer space and remain in-profile.

It will contend for shared buffer space with packets from other queues.

All AF traffic will be marked "in-profile" at the SAP-ingress.

All TCP traffic will be mapped to forwarding class EF.

UDP traffic is placed in queue 3 while ICMP traffic is placed in queue 5.

EF traffic will receive higher scheduling priority than H2 traffic.

Traffic that does not match any of the IP criteria will be placed in queue 3.

2

3

5

6

Defining the slope of the TCP slow-start mechanism for self generated traffic.

Defining the slope of the scheduling rate per forwarding class when using HQoS.

Defining the high and low slope values when deploying buffer admission control for UDP traffic in the committed buffer pool.

Defining the high and low slope values when deploying buffer admission control for TCP traffic in the shared buffer pool.

Defining the high and low slope values when deploying buffer admission control for TCP traffic in the committed buffer pool.

Shapeless policing at SAP-ingress only.

Shapeless policing at SAP-ingress and egress.

Biased round robin queuing at ingress only.

Soft shaping at all network interfaces.

Soft shaping at network ingress only.

H-QoS capabilities must be enabled globally on the router

A scheduler-policy must be configured.

The queues in the SAP-ingress and SAP-egress policies do not require additional configuration attributes to make use of the hierarchical schedulers.

The network queue policy must be configured to make use of the scheduler-policy.

The scheduler-policy must be referenced in the SAP-ingress and SAP-egress policies.

The scheduler-policy must be applied on the service SAP.

WRED monitors the shared buffer space utilization over a period of time.

WRED disables the TCP slow-start congestion control mechanism.

WRED uses two configurable slopes for each buffer pool: a high slope and a low slope.

WRED uses the shared buffer utilization, instead of the individual queue depth, to get a better picture of the average resource utilization of the shared buffer space.

WRED polices the shared buffer pool and marks all packets above a certain rate as "discard eligible."

ToS

DSCP

PREC

EXP

EF

H1

L1

H2

L2

512 MB ingress, 512 MB egress

256 MB ingress, 256 MB egress

1 GB dynamically allocated between ingress and egress.

768 MB dynamically allocated between ingress and egress.

768 MB, with a minimum of 256 MB ingress and egress, and an additional 256 MB dynamically allocated.

DSCP

PREC

Dot1p

ToS

Q-in-Q

NC, low

NC, high

BE, low

BE, high

Scheduler policies cannot be children of an egress port-scheduler.

HQoS provides a static method of allocating scheduling resources to each queue and/or child.

Scheduler policies can be applied to the MDA to schedule network ingress traffic.

Every time a scheduler-policy is assigned to a SAP, a new hardware scheduler is created to service the SAP.

A scheduler applied to multiple SAPs within the same service will result in a single hardware scheduler operating across all SAPs within the service.

The process of delaying packets within a traffic stream to have them conform to a defined traffic profile.

The overall treatment of a defined subset of a customer's traffic within a DiffServ domain.

The process of discarding packets within a traffic stream in accordance with the state of a meter to enforce a defined traffic profile.

The action of setting the DiffServ codepoint of a packet prior to its entry into a downstream DiffServ domain.

A specified algorithm or operation that is implemented in a node in order to realize one or more per-hop behaviors.

Packet drops in the local queue resulting from traffic congestion.

Packet drops on the downstream nodes resulting from traffic congestion.

Packet drops in the local queue resulting from traffic bursts.

Packet drops on the downstream nodes resulting from traffic bursts.

Its rate fluctuates rapidly with time.

Its bandwidth requirements are high.

Time between packets remains unchanged and end-to-end delay is kept to a minimum.

All packets received are guaranteed to be delivered to the destination.

It will be discarded because the high-priority-only threshold is exceeded.

It will be queued but re-marked as "out-of-profile."

It will be queued in the reserved portion of the buffer pool and remain "in-profile."

It will be queued in the shared portion of the buffer pool but contend for shared buffer space with packets from other queues.

It will be queued in the shared portion of the buffer pool but may be dropped if the buffer utilization exceeds the start-average value of the low slope.

If CIR = PIR, then all packets will be considered as in-profile.

CIR can be set to 0.

CIR can be larger than PIR.

CIR can be set to ‘max’.

IntServ uses a protocol like RSVP to provide QoS guarantees on a per-flow basis.

DiffServ groups multiple microflows into bigger streams called macro flows.

Intserv requires that network routers allocate resources for thousands of individual flows.

Diffserv classifies packets into forwarding classes only at the first network hop.

Packets corresponding to a layer-2 service can be pre-marked on SAP-ingress.

Packets corresponding to a layer-2 service can be pre-marked on network-ingress.

Packets corresponding to a layer-3 service can be pre-marked on SAP-ingress.

Packets corresponding to a layer-3 service can be pre-marked on network-ingress.

Classification

Marking

Buffer admission control

Scheduling

The weight specifies the priority of the queue during scheduling up to its CIR.

The weight specifies the priority of the queue during scheduling above-CIR, up to its PIR.

The weight is used to determine how this queue and other queues or schedulers at the same CIR-level share available CIR bandwidth at that level.

The weight is used to determine how this queue and other queues or schedulers at the same level share available above CIR bandwidth at that level.