A. DSCP

B. IP precedence

C. TCP window size

D. Interface buffer utilization

E. Interface output queue size Answer: A, B Explanation: WRED calculates the average queue depth just like RED, ignoring precedence, but it decides when to discard packets based on the precedence or DSCP value. Source: Cisco DQOS Exam Certification Guide, Page 438

QUESTION 12 How does per-VC Class-Based Weighted Fair Queuing (CBWFQ) work?

A. A weight is assigned to the entire class, not to an individual flow. Only one class can be assigned to each VC.

B. A weight is assigned to the entire class, not to an individual flow. Multiple classes can be assigned to each VC.

C. Each flow within a class is assigned a separate weight by CBWFQ. Only one class can be assigned to each VC.

D. Each flow within a class is assigned a separate weight by CBWFQ. Multiple classes can be assigned to each VC. Answer: C

QUESTION 13 Place the Random Early Detection (RED) profile parameters in the appropriate boxes.

Answer:

Explanation:

You can set the maximum percentage of packets discarded by WRED by setting the mark probability denominator (MPD) setting in IOS. IOS calculates the maximum percentage using the formula 1/MPD. For instance, an MPD of 10 yields a calculated value of 1/10, meaning the maximum discard rate is 10 percent. Source: Cisco DQOS Exam Certification Guide, Page 436

QUESTION 14 Which statement is true about Frame Relay Fragmentation?

A. Voice packets are never fragmented.

B. FRF.11 Annex-C is used if VoFR is configured on the DLCI.

C. FRF.12 uses separate queues for voice and non-voice traffic.

D. All DLCIs on the same physical interface must use the same fragmentation scheme.

E. An interface uses FRF.11 Annex-C or FRF.12 fragmentation for non-voice traffic and FRF 3.1 encapsulation for voice traffic. Answer: B Explanation: In Frame Relay networks, two fragmentation standards are available on layer-2 (within the Frame Relay encapsulation): When Voice over Frame Relay (FRF.11) and fragmentation are both configured on a PVC, Frame Relay fragments are transmitted in the FRF.11 Annex C format. This fragmentation method is used when FRF.11 voice traffic is transmitted on the PVC and uses the FRF.11 Annex C fragmentation standard. With FRF.11, all data packets contain fragmentation headers regardless of size. This form of fragmentation is not recommended for use with Voice over IP. FRF.12 fragmentation is defined by the FRF.12 Implementation Agreement. The FRF.12 Implementation Agreement was developed to allow long data frames to be fragmented into smaller pieces and interleaved with real-time frames. In this way, real-time voice and non-real-time data frames are carried together on lower-speed Links without causing excessive delay to thereal-time traffic. As a result, FRF.12 is the recommended fragmentation to be used with VoIP.

If a PVC is not configured for VoFR, it uses normal Frame Relay (FRF.3.1) data encapsulation. If fragmentation is turned on for this DLCI, it uses FRF.12 for the fragmentation headers. PVCs carrying VoIP use FRF.12 fragmentation because VoIP is a layer 3 technology that is transparent to layer 2 Frame Relay. VoIP and VoFR can be supported on different PVCs on the same interface, but not on the same PVC. FRF.12 fragments voice packets if the fragmentation size parameter is set to a value smaller than the voice packet size. FRF.11 Annex-C (VoFR) does not fragment voice packets regardless of what fragmentation size is configured. FRF.11 Annex-C needs only to be supported by platforms that support VoFR. Because FRF.12 is predominantly used for VoIP, it is important to use FRF.12 as a general feature on Cisco IOS platforms that transport VoIP over slow speed WAN Links. Sources: IP QoS Link Efficiency Mechanisms 6-53, 6-54

QUESTION 15 What is the default MLP Link Fragmentation and Interleaving (LFI) serialization time?

A. 10 ms

B. 20 ms

C. 30 ms

D. 40 ms

E. 50 ms Answer: C Explanation: The ppp multilink command enables PPP multilink on an interface. This requires either Weighted Fair Queuing (WFQ) or CB-WFQ (Class-Based Weighted Fair Queuing) to be enabled on the same interface. The ppp multilink interleave command enables interleaving of fragments within the multilink connection. The ppp multilink fragment delay command specifies themaximum desired fragment delay for the interleaved multilink connection. The maximum fragment size is calculated from the interface bandwidth and the specified maximum delay. The default is set at 30 milliseconds. If DCEF is configured on a VIP interface, MLP with interleaving runs distributed on the VIP. Source: Cisco IP QoS Link Efficiency Mechanisms, Page 6-49

QUESTION 16 When configuring Compressed Real-time Transport Protocol (RTP), what is the purpose of the passive keyword?

A. All RTP packets are compressed, regardless of other parameters.

B. Outgoing RTP packets are compressed; incoming RTP packets do not need to be.

C. Outgoing RTP packets are compressed only if incoming RTP packets are compressed.

D. Incoming RTP packets may be compressed; all outgoing RTP packets are not compressed. Answer: C Explanation:

RTP header compression is configured with the ip rtp header-compression command. The passive option instructs the peer to use RTP header compression only if the remote peer initiates RTP header compression. On frame relay, the frame-relay ip rtp header-compression configures header compression with interfaces using pure frame relay encapsulation. In Cisco IOS, RTP header compression is now fast and CEF-switched. If distributed CEF (DCEF) is configured, CRTP also runs in distributed mode. Up to 256 connections, which is also the default value, can be compressed over a point-to- point link. Source: Cisco IP QoS Link Efficiency Mechanisms, Page 6-36

QUESTION 17 Which two Cisco IOS-supported payload compression algorithms search the byte stream forredundant strings, replacing them with shorter dictionary tokens? (Choose two)

A. Predictor

B. STAC (Stacker)

C. Diffie-Helman (DH)

D. Microsoft Point-to-Point Compression (MPPC) Answers: B, D Explanation:

The STAC (or Stacker) algorithm is based on the well-known LZ (Lempel-Ziv) compression algorithm. The LZ (sometimes also called LZW) algorithm searches the byte stream for redundant strings, and replaces them with shorter dictionary tokens. The dictionary is built in real time, and there is no need to exchange the dictionary between the compression peers, because the dictionary is reconstructed from the data received by the remote peer. The MPPC method also uses the same LZ algorithm. The STAC and MPPC algorithms yield very goodcompression results, but are CPU-intensive. Source: Cisco IP QoS Link Efficiency Mechanisms, Page 6-7

QUESTION 18 RTP header compression can be used to reduce which three headers? (Choose three)

A. IP

B. UDP

C. RTP
D. TCP

E. PPP Answer: A, B, C Explanation: All compression methods are based on eliminating redundancy when sending the same or similar data over a transmission medium. One piece of data, which is often repeated, is the protocol header. In a flow, the header information of packets in the same flow does not change much over the lifetime of that flow. Therefore, most of header information could be sent only at the beginning of the session, stored in a dictionary, and then referenced in later packets by a short dictionary index. Two methods were standardized by the IETF (Internet Engineering Task Force) for use with IP protocols: TCP header compression (also known as the Van Jacobson or VJ header compression) is used to compress the packet TCP headers over slow Links, thus considerably improving the interactive application performance. RTP header compression is used to compress UDP and RTP headers, thus lowering the delay for transporting real-time data, such as voice and video over slower Links. Source: Cisco IP QoS Link Efficiency Mechanisms, Page 6-21

QUESTION 19 When using Modular QoS Command Line Interface (MQC), traffic that does not have a match is ______.

A. Ignored by the MQC

B. Dropped (implicit deny all)
C. Placed in the default class

D. Process switched through the router Answer: C Explanation: Modular Quality of Service Command-Line Interface (MQC) The MQC is a command-line interface (CLI) structure that allows you to create traffic policies and attach these policies to interfaces. In the MQC, the class-map command is used to define a traffic class (which is then associated with a traffic policy). The purpose of a traffic class is to classify traffic. The Modular quality of service (QoS) CLI structure consists of the following three processes:

• Defining a traffic class with the class-map command.
• Creating a traffic policy by associating the traffic class with one or more QoS features (using the policy-map command).
• Attaching the traffic policy to the interface with the service-policy command. A traffic class contains three major elements: a name, a series of match commands, and, if more than one match command exists in the traffic class, an instruction on how to evaluate these match commands. The traffic class is named in the class-map command line; that is, if you enter the class map cisco command while configuring the traffic class in the CLI, the traffic class would be named "cisco". The match commands are used to specify various criteria for classifying packets. Packets are checked to determine whether they match the criteria specified in the match commands. If a packet matches the specified criteria, that packet is considered a member of the class and is forwarded according to the QoS specifications set in the traffic policy. Packets that fail to meet any of the matching criteria are classified as members of the default traffic class. Source: http://www.cisco.com/en/US/products/sw/iosswrel/ps1839/products_feature_guide09186a0080110bcd. html
  
  QUESTION 20 What purpose do polices in the Modular QoS Command Line Interface (MQC) serve?

A. They are used to bind polices to the interfaces.

B. They are used to define the polices for classifying data.

C. They are used to bind traffic classifications to QoS polices.

D. They are used to apply end-to-end polices in network devices. Answer: C Explanation:

The Quality of Service mechanisms that have been added to the Cisco IOS all had their own set of classification options. For example: Committed Access Rate (CAR) can classify packets by using:

-Access lists

-QoS group

-

DSCP

-

Rate limit access list Traffic Shaping (GTS) can classify packets by using access lists Priority Queuing (PQ) and Custom Queuing (CQ) can classify packets by using:

-

Access lists

-

Packets size -

Fragment

-

TCP or UDP port number The Modular Quality of Service Command Line Interface (MQC) was introduced to allow any supported classification to be used with any QoS mechanism. The separation of classification from the QoS mechanism allows new IOS versions to introduce new QoS mechanisms and reuse all available classification options. On the other hand, old QoS mechanisms can benefit from new classification options. Another important benefit of the MQC is the reusability of configuration. MQC allows the same QoS policy to be applied to multiple interfaces. CAR, for example, required entire configurations to be copy-pasted between interfaces and modifying configurations was tiresome. The Modular QoS CLI,therefore, is a consolidation of all the QoS mechanisms that have so far only been available as standalone mechanisms. This module focuses on the classification element of the Modular QoS CLI. Source: Cisco IP QoS-Modular QoS CLI Classification, Pages 8-3, 8-4