4A0-107 Nokia Quality of Service Question and Answers

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.

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.

Profile mode queues

Priority mode queues

1 queue

3 queues

3 forwarding classes

1 forwarding class, with 2 subclasses

1 forwarding class, with 3 subclasses

8

3

4

5

6

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.

True

False

Policing, expedited

Metering, marked discard eligible

Marking, marked discard eligible

Policing, discarded

Shaping, discarded

It may exceed PIR of the queue.

It may be exceeded by the average servicing rate of the queue.

It varies depending on the traffic characteristics.

It is the rate at which packets are forwarded out of the queue.

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.

When using priority-mode queues, traffic marked as low-priority on ingress and scheduled in the above-CIR loop will be considered as in-profile at egress.

When using priority-mode queues, traffic marked as high-priority on ingress and scheduled in the above-CIR loop will be considered as out-of-profile at egress.

When using profile-mode queues, traffic marked as low-priority on ingress and scheduled in the above-CIR loop will be considered as out-of-profile at egress.

When using profile-mode queues, traffic marked as in-profile on ingress and scheduled in the above-CIR loop will still be considered as in-profile at egress.

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.

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.

On the network egress port.

On the SDP.

On the access ingress port.

On the egress MDA.

On the SAP.

On the ingress MDA.

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.

ToS

DSCP

PREC

EXP

3

4

6

8

AF

EF

H2

H1

BE

802.1p adds 16 bits to the Layer 2 header,

802.1p adds 16 bits to the Layer 3 header.

802.1p specifies 64 different priority levels.

802.1p uses a field in the 802.1Q header.

802.1p uses a field in the Layer 3 IP header

802.1p defines a 3-bit Class of Service field.

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.

prec

lsp-exp

src-ip

do1p

TRUE

FALSE

To have control over the amount of the low priority packets that enter the queue.

To control any traffic flowing through the shared buffer space of the queue.

To limit the number of the TCP sessions that go into slow start during congestion.

To force the TCP algorithm to increase its transmission window upon detecting a 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

NC, low

NC, high

BE, low

BE, high

Access ingress ports

Access egress ports

Network ingress ports

Network egress ports

PIR = 4Mbps. CIR = 1Mbps

PIR = 1Mbps, CIR = 1 Mbps

PIR = 10Mbps, CIR = 1Mbps

PIR = 5Mbps, CIR = 1.25Mbps

PIR = 1.25Mbps, CIR = 1.25Mbps

H2

NC

L2

EF

H1

BE

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.

Closest

Average

Min

Max

SAP-ingress policy

SAP-egress policy

IP-criteria policy

Network-queue policy

Slope policy

Network policy

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