Download Free Actualtests 642-642 Dumps | Latest Cisco Certification Exams

Actualtests 642-642

642-642 : Quality of Service (QOS) Last Updated Wednesday, September 03, 2008 with 358 Questions

IP Communications Quality of Service (QoS)
Exam Number: 642-642 Exam
Associated Certifications: IP Communications Quality of Service (QoS)
Duration: 182 Q&As
Available Language(s): English
Exam Details
The QOS exam is one of the qualifying exams for the Cisco Certified Internetwork Professional, Cisco Certified Voice Professional, Cisco IP Telephony Design Specialist, Cisco IP Telephony Express Specialist, Cisco IP Telephony Operations Specialist, and Cisco IP Telephony Support Specialist certifications. The QOS 642-642 exam will test materials covered under the Implementing Cisco Quality of Service QOS v2.1 course. The exam will certify that the successful candidate has knowledge and skills necessary to configure and troubleshoot Cisco IOS routers running Quality of Service protocols in Service Provider and Enterprise environments. The exam covers topics on IP QOS, classification and marking Mechanisms, queuing mechanisms, traffic shaping and policing mechanisms, congestion avoidance mechanisms, link efficiency mechanisms, modular QOS command line interface, and QOS Best Practices.

Free 642-642 Exams’s PDF Download
Free Actualtests offers free demo for 642-642 PDF(IP Communications Quality of Service (QoS)). You can check out the interface, question quality and usability of our practice exams . We are the only one site can offer demo for almost all IP Communications Quality of Service (QoS).

Recommended Training about 642-642 exam PDF
The following courses are the recommended training for 642-642 exam PDF.
642-642 Q & A with Explanations
642-642 Audio Exam
642-642 Study Guide
642-642 Preparation Lab
642-642 Exam Preparation from Actualtests with FULL explanations include:
Comprehensive questions with complete details
Detailed explanations of all the questions
Questions accompanied by exhibits
Verified Answers Researched by Industry Experts
Drag and Drop questions as experienced in the Actual Exams
Questions updated on regular basis
These questions and answers are backed by our GUARANTEE.
Like actual certification exams our product is in multiple-choice questions (MCQs).
642-642 Exam: Actualtests’s IP Communications Quality of Service (QoS) PDF
The IP Communications Quality of Service (QoS) PDF for preparing for the 642-642 exam – Actualtests ’s IP Communications Quality of Service (QoS). Actualtests is your premier source for practice tests, and true testing environment. Nothing will prepare you for your next exam like a Actualtests. You find it all here at ciscoexams.org.

QUESTION 1:
Which of the following markers can be set by Committed Access Rate (CAR)? (Choose
all that apply.)
A. DSCP bits
B. QoS Group
C. ATM CLP bit
D. Frame Relay DE bit
E. IP precedence bits
Answer: A, B, E
Explanation:
Source: Cisco IP QoS Introduction, Page 64
QUESTION 2:
What makes the DiffServ model more scalable than the IntServ model? (Choose all that
apply.)
A. DiffServ makes use of per-aggregate QoS instead of per-flow QoS.
B. DiffServ makes use of hop-by-hop signaling which allows DiffServ to scale to a larger
number of application flows.
C. DiffServ is capable of implementing admission control either locally on the routers or be
offloaded to a central policy server using the COPS protocol.
D. DiffServ routers are not compelled to track the state information for each individual
flow.
642-642
Actualtests.com – The Power of Knowing
Answer: A, D
Incorrect:
B. No hop-by-hop signaling uses per-hop behavior
C. This is a feature of both models
Sources: Cisco IP QoS Introduction
http://www.cisco.com/en/US/tech/ CK5 43/ CK7 66/technologies_white_paper09186a00800a3e2f.shtml
QUESTION 3:
The newly appointed Certkiller trainee technician wants to know what the benefits of
using traffic shaping to implement network rate limiting is.What will your reply be?
(Choose all that apply.)
A. Traffic shaping is an effective tool for rate-limiting VoIP traffic.
B. It will not increase packet loss.
C. It will not add to packet transit delays.
D. Traffic shaping can interact with congestion mechanisms embedded in Frame Relay.
E. Traffic shaping can be used on inbound and outbound traffic on a router.
Answer: B, D
Incorrect:
A. Shaping adds variable delay to traffic, possibly causing jitter
C. A shaper typically delays excess traffic using a buffer
E. This is a feature of policing
Explanation:
642-642
Actualtests.com – The Power of Knowing
Source: Cisco IP QoS Traffic Shaping and Policing
QUESTION 4:
Study the Exhibit below carefully:
Router# show interfaces hssi 0/0/0 rate-limit
Hssi0/0/0 45Mbps to R1
Input
matches: all traffic
params: 20000000 bps, 24000 limit, 24000 extended limit
conformed 8 packets, 428 bytes; action: transmit
exceed 0 packets, 0 bytes; action: drop
last packet: 8680ms ago, current burst: 0 bytes
last cleared 00:03:59 ago, conformed 0 bps, exceed 0 bps
Output
matches: all traffic
params: 20000000 bps, 24000 limit, 24000 extended limit
conformed 0 packets, 0 bytes; action: transmit
exceed 0 packets, 0 bytes; action; drop
last packet: 8680ms ago, current burst: 0 bytes
last cleared 00:03:59 ago, conformed 0 bps, exceed 0 bps
According to the exhibit, the router has been configured with Committed Access
Rate (CAR) to rate limit traffic.
What data rate has the traffic been limited to?
A. 192 Kbps
B. 2400 Kbps
C. 4,5 Mbps
642-642
Actualtests.com – The Power of Knowing
D. 20 Mbps
E. 40 Mbps
Answer: D
Explanation:
In the configuration example, CAR is applied on the input and output of a customer
interface on the provider edge router. Traffic is policed to 256 Kbps on input and output,
with some bursting allowed. All exceeding traffic is dropped at the provider edge.
The result of the configuration is that traffic to and from the customer is limited to the
average rate of approximately 256kbps (256000 in the configuration) with sustained
bursts of approximately 32kbps (4kBps or 4000 in the configuration).
Initial bursts at line speed can last up to 3 seconds because the token bucket can hold up
to 96000 tokens (bytes) which equals 768000 bits (3 x 256000 bits).
Source: Cisco IP QoS Traffic Shaping and Policing, Page 4-91
QUESTION 5:
The newly appointed Certkiller trainee technician wants to know which type of software
queuing mechanism is Frame Relay Traffic Shaping implemented with on the physical
interface. What will your reply be?
A. Priority Queuing (PQ)
B. Custom Queuing (CQ)
C. FIFO
D. Weighted Fair Queuing (WFQ)
E. IP Real Time Transport Protocol (RTP) Priority
Answer: D
642-642
Actualtests.com – The Power of Knowing
Explanation:
Works on any (sub) interface type
Shapes traffic on that (sub)interface basis
Can use any physical interface queuing (FIFO, PQ, CQ or WFQ)
Only uses WFQ as the shaping queue (that is, on the input of the shaper)
In contrast, Frame Relay Traffic Shaping:
Works only on Frame Relay (sub) interfaces
Shapes traffic inside individual FR Virtual Circuits
Only permits WFQ as the physical interface queuing method
Can use any queuing method as the shaping queue (that is, on the input of the
shaper)
Source: Cisco IP QoS Traffic Shaping and Policing, Page 4-47
QUESTION 6:
Why is it beneficial to make use of Enhanced LMI (ELMI) on Cisco networks?
A. ELMI is responsible for providing virtual provisioning tools at the edge of the Frame
Relay network.
B. ELMI permits routers to dynamically download QoS information from Cisco switches
for use in traffic shaping or for congestion management purposes.
C. ELMI provides the router the ability to use additional QoS tools including rate
limiting with CAR and the Modular QoS Command Line Interface (MQC).
D. ELMI allows the router to deliver packets at the line rate of the Frame Relay interface,
regardless of the condition of the Frame Relay network.
Answer: B
642-642
Actualtests.com – The Power of Knowing
Explanation:
Source: Cisco IP QoS Traffic Shaping and Policing, Page 4-58
QUESTION 7:
Which of the following statements are true when you compare DSCP and IP
Precedence to each other? (Choose all that apply.)
A. DSCP is backwards compatible with IP Precedence.
B.
DSCP cannot be easily mapped into QoS because of its expanded classification options.
C. DSCP is more granular the IP Precedence, since more marking combinations are
available.
D. DSCP appears stubby when compared IP Precedence, since devices make use of
DSCP as defined in RFC exclusively.
E. DSCP is 6 bits long and IP Precedence is 3 bits long.
F. DSCP is more restrictive than IP Precedence, since devices are only allowed to use
DSCP as defined in RFCs.
Answer: A, C, E
Explanation:
A)DSCP is backward compatible with IP Precedence (Class Selector Code point, RFC
1812) but not with the ToS byte definition from RFC 791 (”DTR” bits)
Reference: Introduction to IP QoS (Course) p.45
QUESTION 8:
642-642
Actualtests.com – The Power of Knowing
Which MQC command would you use to perform marking properly?
A. precedence 5
B. ip precedence 5
C. set ip precedence 5
D. set ip mark precedence 5
E. mark ip precedence 5
Answer: C
Explanation:
IP precedence is encoded into the three high-order bits of the ToS field in the IP header.
It supports eight classes of which two are reserved and should not be used for
user-defined classes (IP precedence 6 and 7). IP precedence 0 is the default value and is
usually used for the best-effort class. The set ip precedence command marks packets of a
class with the specified precedence value.
Reference: Introduction to IP QoS (Course) p.9-104
QUESTION 9:
Which of the following statements aptly describes a network well designed for QoS?
A. Packets are classified at each router, based on as many detail as possible, typically
using extended IP ACLs to match the packets for classification.
B. Packets are classified at each router, based on socket address only, typically using
extended IP ACLs to match the packets for classification.
C. Packets are classified and marked, close to the edge of the network. The packets are
treated differently based on this marking at the routers in the middle of the network.
D. Packets are classified based on different parameters, but close to the edge of the
network. The packets are automatically characterized based on flow at the routers.
E. Packets are classified based on socket address, at the router closest to the source of the
traffic. The packets are automatically characterized based on flow at the routers.
Answer: C
Explanation:
To achieve the same level of quality in both directions the packets going to and coming
from the customer network must first be classified and marked.
Classification and marking packets going to the customer network is a more difficult task
because:
1) Classifying and marking must be performed on all edge routers.
2) Classifying and marking requires the identification of the customer network. Using
PBR, CAR, CB-Policing or CB-Marking does not scale because it involves the use of
access lists (this is especially difficult if customer networks are dynamically learned via
642-642
Actualtests.com – The Power of Knowing
BGP).
Reference: Introduction to IP QoS (Course) p.2-35
QUESTION 10:
The newly appointed Certkiller trainee technician wants to know which bit in the
ATM header can be marked by the Class Based Marker to extend IP QoS policy
into an ATM network. What will your reply be?
A. DE
B. PTI
C. FECN
D. CLP
E. BECN
Answer: D
Explanation:
The ATM CLP Setting feature somewhat allows users to extend their IP QoS policies
into an ATM network by setting the ATM CLP bit in ATM cells based on the IP
Precedence value of the packets being sent. As congestion occurs in the ATM network,
cells with the CLP bit set are more likely to be dropped, resulting in improved network
performance for high priority traffic and applications. The set
atm-clp
command marks packets of a class with the ATM CLP bit as a part of an input or output
policy.