4A0-107 Sample Questions Answers

af11

af21

af23

af31

Spoke-SDPs bound to an IES

Spoke-SDPs bound to a VPRN interface

SAPs

Network interfaces

All out-of-profile traffic will be dropped before that of any in-profile traffic.

The discard probability slope of an in-profile traffic is steeper than that of an out-of-profile traffic.

When the shared buffer utilization reaches 55%, both in-profile and out-of-profile packets may be dropped.

The maximum probability with which an out-of-profile packet can be dropped is higher than that of an in-profile packet.

When the shared buffer utilization is at 61%, only in-profile packets are currently in the shared buffer pool.

All incoming packets belonging to forwarding class “l2” are stored in the reserved buffer space.

All incoming packets belonging to forwarding class “af” are stored in the reserved buffer space.

All incoming packets belonging to forwarding class “l1” are stored in the reserved buffer space.

In-profile packets in the shared buffer space are being dropped.

The available bandwidth of the port is divided in a strict priority over its children.

Expedited queues must be serviced before best-effort queues.

Orphaned queues are serviced on the 8th scheduling priority.

The configured CIR dictates the maximum port bandwidth that can be allocated during the within-CIR pass for that level.

Set the CIR of queue 3 to a non-zero value corresponding to the customer's expected bandwidth requirements.

Set queue 3 to use priority mode.

Set the traffic classification of packets to in-profile.

Set the high-priority-only value to 0.

Map AF traffic to queue 1

Access ingress, access egress, network egress

Access ingress, network ingress, network egress

Port ingress, port egress, shared bi-directional

Port ingress, port egress, network egress

Port ingress, network ingress, network egress

8

3

4

5

6

64

8

3

16

1

PIR = 4Mbps. CIR = 1Mbps

PIR = 1Mbps, CIR = 1 Mbps

PIR = 10Mbps, CIR = 1Mbps

PIR = 5Mbps, CIR = 1.25Mbps

PIR = 1.25Mbps, CIR = 1.25Mbps

Negative jitter results in a smaller than expected interval between transmitted packets.

Jitter does not have any effect on the quality of video applications.

Serialization delay is not affected by congestion.

Queuing delay is a fixed form of delay in networks.

16

8

32

48

56

SAPs

SDPs

Services

Queues

Schedulers

Forwarding classes

An IES SAP

A VPLS SAP

A network port

AVPRN SAP

An access port

A network policy for every network interface configured on the port.

A slope policy for the port on ingress.

A network queue policy for the corresponding MDA on ingress.

A network queue policy for the port on egress.

level

cir-level

weight

cir-weight

A packet is accepted into a queue based on its priority and forwarding class.

Buffer admission control limits the number of out-of-profile packets that enter the queue.

Both high priority-only buffer space and WRED can be used in a queue.

Priority is used when a packet enters a SAP-ingress queue.

8

3

4

5

6

The CIR has no influence on the forwarding rate of the policer traffic.

The CIR influences whether a packet is considered high-profile or low-profile.

The policer discards all incoming packets when PIR bucket reaches the MBS level.

PIR bucket forwards packets that arrive with rates above PIR as out-of-profile.

ToS

DSCP

PREC

EXP

8

16

6

4

3

The process happens only before the packet goes through the switching fabric.

The process happens only before the packet goes onto the egress port.

Marking/remarking the packets is for future classification.

Marking/remarking the packets will occur right after classification of the packet.

A queue will be serviced as expedited if all of the forwarding classes mapped to it are expedited, regardless of its configured type.

A queue will be serviced as best-effort if all of the forwarding classes mapped to it are best-effort, regardless of its configured type.

A queue will be serviced as expedited if at least one of the forwarding classes mapped to it is expedited, regardless of its configured type.

A queue will be serviced as expedited if its type is configured as expedited, regardless of the forwarding classes mapped to it.

CIR

CIR level

CIR weight

Rate

Level

Weight

16

8

32

48

56

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.

SAP-ingress policy

SAP-egress policy

IP-criteria policy

Network-queue policy

Slope policy

Network policy

In order to mark Layer 2 traffic, sgt-qos will set various ToS bits.

DSCP bits can be set per application, per routing instance.

The DSCP marking stays nc1 for all applications. Only the internal FC is manipulated across different applications.

In order to mark Layer 2 self-generated traffic, network interfaces must be set to dot1Q.

The internal forwarding class for self-generated traffic is set once and applied to the base router and all VPRN instances.

Packets marked with dscp = af33

Packets marked with dot1p = 4

All packets mapped to queue 2 have the same priority to enter this queue.

There are no packets mapped to queue 2.

It defines a premium service that effectively creates a dedicated link between peers.

It defines four different AF traffic classes.

Every AF class in each differentiated services node is allocated a certain amount of forwarding resources.

Within each AF class, IP packets are marked with one of three possible drop precedence values.

The egress port scheduler takes the ratio of requested bandwidth to total bandwidth request from all children. It allocates bandwidth fairly, using these percentages and not exceeding the egress interface speed.

The egress port scheduler allocates bandwidth based on a WRR distribution method that takes into account the CIR and PIR requested at each level and the max speed, either default or configured, on egress.

The egress port scheduler allocates bandwidth on a first come, first served distribution method that takes into account the total CIR and PIR requested at each level and the max PIR requested from a single level.

The egress port scheduler will limit the bandwidth offered to the egress port based on the over-subscription factor, provisioned under the router interface, while using a WRR scheduler for the remaining bandwidth.

The egress port scheduler will use the Russian Dolls Method to allocate bandwidth to each level of requested bandwidth. HPO-Only is automatically set to 100%, allowing only high priority traffic to be buffered during congestion.

It maps customer traffic to forwarding classes on ingress.

It can use customer QoS markings to do the mapping.

The default SAP-ingress policy classifies all traffic into FC “be” with low priority.

It serves the classification, queuing, and marking functions of QoS but does not serve scheduling

It enables fine-tuned SLA control that is not possible when using a common set of queues for all L2/L3 services.

It enables CFHP and hierarchy scheduling (egress) for each network interface.

It improves scalability by allowing the use of queues instead of the default set of policers used on network egress.

It allows for enforcing bandwidth reservations of the LSPs that are used by the SDPs configured on the network interfaces.

True

False

It sets both the forwarding class and the packet’s dot1p, lsp-exp, precedence, or dscp field to the same value.

It groups all packets together into a single aggregate stream, and gives all packets the same treatment.

It copies the three most significant bits in the packet’s dscp field into the forwarding class.

It assigns a forwarding class based on the packet’s dot1p, lsp-exp, precedence, or dscp value.

8

16

32

48

The first 3 bits of the DSCP value are copied directly into the EXP field on the first network egress.

The EXP bits are set on the first network egress, based on a combination of the SAP-ingress classification and the network policy applied.

The 3 priority bits are copied directly from the dot1p header into the EXP field of the first MPLS header.

The EXP bits are set based on a default map that translates DSCP codes into internal forwarding classes on SAP-ingress.

The priority (low/high) to be assigned to the packets.

The profile (in/out) to be assigned to the packets.

The queues to be assigned to the forwarding classes.

The markings to be marked on the packets.

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.

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.

Microflow reservations using RSVP

DSCP to EXP translation

Traffic classification

Automatic profiling and policy configuration

Buffer memory management

Traffic scheduling

TRUE

FALSE

0

min

max D. 50000

PIR = 5 Mbps, CIR = 0 Mbps

PIR= 4 Mbps, CIR = 1 Mbps

PIR= 6 Mbps, CIR = 4 Mbps

PIR= 6 Mbps, CIR = 1 Mbps

When queues use shared buffer space, buffers are more efficiently utilized.

Queues that use reserved buffer space will have memory available for their reserved portion.

When a queue is not using its reserved portion, other queues can use it.

Using reserved buffer space prevents a queue from being starved of buffer resources by other queues.

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 EXP bits in the MPLS header.

The packet's source and destination IP addresses.

The service ID of the service to which the SAP belongs.

The dot1p bits in the frame header.

The packet's Ethertype.

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.

8, 6, 3

8, 8, 6

16, 8, 4

8, 6, 4

24, 16, 8

IOM3

FP3 based IMM

IOM1

IOM2

Has the ability to distinguish traffic in 32 different ways.

Uses the RSVP protocol to create microflows through a network.

Has the ability to manually configure foiwarding classes through a network.

Uses the RSVP protocol to create macroflows through a network.

2

3

5

6

None of the above.

When applied at the port level for access ingress.

When applied at the FP (Forwarding Pass) level for access ingress.

When applied at the FP (Forwarding Pass) level for network ingress.

When applied at the port level for network egress.

The administrative PIR values are ignored and both operational rates are set to the minimum residual rate allowed by the hardware.

The administrative PIR value is ignored and both operational rates are set to the administrative CIR value.

They are chosen as the largest multiple of the hardware rate step that is less than or equal to the corresponding CIR/PIR administrative value.

They are chosen as the smallest multiple of the hardware rate step that is greater than or equal to the corresponding CIR/PIR administrative value.

All out-of-profile traffic will be dropped before any in-profile is dropped.

The time average factor of 0 will discard all packets arriving in the shared buffer pool.

When the shared buffer utilization reaches 51%, in-profile packets might be dropped.

The highest probability with which an out-of-profile packet can be dropped is 20%.

When an in-profile packet arrives and the shared buffer utilization is at 69%, the packet will have approximately a 60% likelihood of being discarded.

When applied at the FP (Forwarding Path) level for access egress

When applied at an access port for ingress or egress

When applied at the FP (Forwarding Pass) level for access ingress

When applied at the port level for network egress

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.

The DSCP value will be set to af21.

The DSCP value will be set to be.

TheDSCPvaluewillbesettoaf23.

The DSCP value will be set to af 12.

Thedot1pvaluewillbesetto5.

Thedot1pvaluewillbesetto2.

The dot1p value will be set to 3.

Multi-field classification can use both MAC criteria and IP criteria in the same SAP-ingress QoS policy.

Behavior aggregate classification can use both lsp-exp and dscp in the same SAP-ingress QoS policy.

Multi-field classification cannot use both IP criteria and IPv6 criteria in the same SAP-ingress QoS policy.

Behavior aggregate classification cannot use both dot1p and lsp-exp in the same SAP-ingress QoS policy.

There are a maximum of 8 levels of priority serviced using a round-robin algorithm.

The default scheduler will spend an equal amount of time in each queue, as long as there is traffic present

The H1 internal forwarding class will receive its CIR before AF traffic.

Orphaned queues will be scheduled out of the BE queue.

A queue servicing EF and AF traffic will require explicit configuration to set the queue to expedited.

It will be stored in the reserved buffer space and remain out-of-profile.

It will be stored in the reserved buffer space and become in-profile.

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

It will be discarded because the high-priority-only threshold has been reached.

Burst-limit sets a limit on the maximum burst of packets transmitted during each scheduler visitation time.

Proper configuration of the burst-limit can prevent packet drops on the downstream nodes resulting from traffic bursts.

The lower the configured burst limit value, the lower the burst allowed to enter the queue.

If the burst-limit is not configured, a default burst-limit value will be used by the queue.

Classification

Marking

Queuing

Congestion management

Scheduling

Dot1p

DEI

EXP

DSCP/PREC

Change the CIR-level value for the best-effort queue to 8.

Do not change anything; it is already guaranteed to receive its CIR

Change the CIR-level value for the best-effort queue to 1.

Change the CIR-weight value of the AF queue to 0.

Gold

Assured

High Priority

Best Effort