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Posts tagged qos
Do You Need the New INE QoS Class?
Jul 23rd
Try these questions on for size! Learn all this and much more in the new QoS class.
1. Based on the following configuration, what traffic will be policed?
class-map C_MUSIC
match protocol kazaa2
match protocol napster
!
class-map match-any C_WEB
match protocol http
match class-map C_MUSIC
!
policy-map P_WEB
class C_WEB
police 64000
!
interface serial 0/0
service-policy output P_WEB More >
Popularity: 5% [?]
New QoS Class : Answers and Explanations
Jul 21st
Try these questions on for size! Learn all this and much more in the new QoS class.
1. Based on the following configuration, what traffic will be policed?
class-map C_MUSIC
match protocol kazaa2
match protocol napster
!
class-map match-any C_WEB
match protocol http
match class-map C_MUSIC
!
policy-map P_WEB
class C_WEB
police 64000
!
interface serial 0/0
service-policy output P_WEB
Popularity: 3% [?]
Cisco 642-642 Quality of Service (QOS)
May 4th
Exam : Cisco 642-642
Title : Quality of Service (QOS)
1. The following commands have been configured under the fa0/1 interface on the 2950 switch:
Voice traffic from the IP phone that is directly connected to the fa0/1 interface is experiencing excessive delays. On the basis of the configuration, what would most likely cause this problem?
A. The default cos-to-dscp map is being used. More >
Popularity: 6% [?]
CCIP Syllabus
Mar 3rd
CCIP Syllabus
CCIP? Certification
Cisco Certified Internetwork Professional (CCIP?) validates advanced knowledge and skills required to manage service provider infrastructures. With a CCIP certification, a network professional working in a service provider organization demonstrates competencies in infrastructure IP networking solutions. The CCIP curriculum includes IP routing, IP QoS, BGP, and MPLS.
Prerequisites:Valid CCNA certification
Exams & Recommended Training More >
Popularity: 2% [?]
642-642 QoS Exam Topics
Nov 12th
Exam Description
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 v2.2 or v2.3 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.
Exam Topics
Popularity: 1% [?]
Done 642-642 QoS today
Sep 14th
As my last project would haven’nt been about qos, i would have not been that good and it would have not been that easy. I’m on my way to the CCVP cert. Currently i just hope i can learn things as quickly as possible. This test has not been that difficult. QoS is a topic that has not changed a lot in the last years. Even cisco’s design guide for campus qos is about 2 years old from 2005. So things you will learn are about standards, that have not changed a lot since.
What i haven’t seen is an RSVP or IntServ implementation. I would like to test it a bit with dynamips, but i have to keep an going.
Just know now how to implement LLQ, CBWFQ, PQ, CQ and WRED for example. Knowing about COS and DSCP values. I have not had anything about thresholds in the test. I had 45 questions and the passing score was 790 points. Thanks to the good vue testcenter. I had quite a lot of problems with prometric. Probably this is the reason why cisco changed to use only vue as a testing center for cisco tests. Everythings was working fine. I did the test at OpenLine, Maastricht in the Netherlands.
Popularity: 1% [?]
QoS campus design / telephony / avaya / diffserv
Sep 14th
I have implemented a QoS design for a customer with about 5000 nodes per campus. The design is relatively straigt through. Once you have decided with classes you want to implement, you have to configure the different devices. There has been an access, distribution and core layer. It’s the best to mark as close to the apllications as possible. So at the access layer we had 3750, 4000/4500. The 3750 supports srr and for the 4000 it’s dependend on the module. But for the 4000/45000 you don’t have input queues. As forexample the 6500 it depends all also on the module. You have to find out what kind of hardware queues there are. It’s probable a notation like 1P3Q8T, what means something like, 1 priority queue, 3 normal queues and 8 thresholds per queue. Sometime you can find also the notation 4Q8T/1P3Q8T, that means the one priority queue is able to be a normal or a prio queue.
If you have measurements about the actual network traffic, you can distribute the traffic on the different queues and thresholds. If not, it’s maybe good enough to have a priority queue and to roughly estimate the other queues, but maybe not go to deep into changing the default thresholds. Later it might be necessary. If you don’t have enough queues left and you want to keep up you queuing schema.
There is a good design guide for enterprise campus QoS implementation and i suggest taking this as a good starting point in you QoS campus design. It coves all the different catalyst types and also gives some suggestions about the ECN/DBL (dynamic buffer limiting) marking espacially for the 4000/4500′er catalyst.
This could be a good feature when both stations (server/client) support the ECN flag. I read about the xp/vista does it not have enabled by default. But it’s only available at the 4000/4500′er.
Make sure you use hardware queueing and not queuing in software. This will save you from having problems with cpu overload. As long queueing is done in hardware, you will be on the safe side.
Avaya does not have recomandations about qos implementations on cisco hardware. Phones can be configures like setting voice bearer traffic to COS 5 and Signaling traffic to COS 3. You can overwrite the data port with the PC connected to COS 0. This would be a relativ straight forwarded setup.
QoS is a quite complex task. It’s necessary to develop and administrate the current needs constantly.
Source:
http://www.cisco.com/univercd/cc/td/doc/solution/esm/qossrnd.pdf
http://de.wikipedia.org/wiki/Network_congestion_avoidance
Popularity: 1% [?]
QoS and what to manage with what
May 11th
There are many different kind of QoS techniques around at Cisco. All of them are like a tollbox for managing traffic. Each technique has it’s preferred operational area. So here are some scenarios in which you would use a certain technique.
- Classification
You want to provide a prefered service to a type of traffic. The packet may be marked or not. Classification don only on one device, without marking the packet is described as a per-hop based classification. PQ (priority queing) and CQ (custom queing) are techniques used for this. Possible methods to identify certain traffic are ACL’s, policy based routing, comiited acces rate (CAR) or network-based application recognistion (NBAR).
- Congestion Management
What if an interface is accessed above it’s given bandwidth? Congestion occurs and priority queuing (PQ), custom queuing (CQ), weighted fair queuing (WFQ), and class-based weighted fair queuing (CBWFQ) are tools to mangage congestion.
- Queue Management
If a queue does fill up and buffers are flowing over, packets must be dropped. Which packets to drop, maybe packets with lower priority, to be able to deliver higher priority, this is done with Weighted early random detect (WRED).
- Link Efficiency
Some packets might be to large for efficent transport and it might be neccessary to compress these packets. RTP header compression (Compressed Real-Time Protocol header) can be used for this.
- Traffic shaping and policing
When shaping traffic, you would take care of a certain link not to exceed the configured bandwitdh or maybe another certain bandwith. Traffic is buffered then, with poicing it’s just discarded as other functions are similar for policing.
Queuing techniques, algorithms and when to use them.
- FIFO, First-in, first-out
Is the default queuing algorithm, and delivers packet in the same row it receives them, but could buffer them in between
- PQ, Priority queuing
PQ gives priority to traffic over other traffic, each packet is placed into one of four queues: high, medium, normal, low. There is absolut preferential treatment over low-priority queues.
- CQ, Custom queuing
is used to provide a garantied bandwidth, leaving the remaining bandwidth to other traffic. CQ does this by assigning a specific amount of queue space to each class of packet and then servicing the queues round-robin. PQ and CQ are statically configured. They don’t adapt network changes automatically.
- WFQ, Flow-based weighted fair queuing
provides consistent response time to congested networks, each queue ist serviced on a bye counted base. Each time 1000 bytes are serviced, one stream with 2×500 bytes it qually serviced, like the 1×1000 byte packet. It’s mostly used on serial interfaces. WFQ is IP-precedence aware
- CBWFQ, Class-based weighted fair queuing
CBWFQ is used to provide a minimum of bandwidth to a certain flow. It’s a garanteed amount of bandwidth. If it’s not used by the class other applications can use it.
Tools for congestion avoidance:
- WREDÂ Weighted random early detection is to avoid congestion before it becomes a problem. It’s an algorithm to drop packets if congestion is about to occuring. Senders themself then slows down transmitions speed.
Sources:
http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/qos.htm
Popularity: 1% [?]
QoS and where and what can be marked (MQC)
Feb 22nd
QoS means, to give certain types of traffic in a network priority above other types of traffic or to garanty certain functionallity. And this could be done on many different kind of architectures.
But dependend on the type of traffic QoS can only be used, when certain demands are satisfied. That means, there has to be at least one field in the header of a packet.
Here is a list of Marking Fields
Field Location Length
IP Precedence (IPP) IP header 3 bits
IP DSCP IP header 6 bits
DS field IP header 1 byte
ToS byte IP header 1 byte
Cos ISL and 802.1Q header 3 bits
Discard Eligible (DE) Frame Relay header 1 bit
Cell Loss Priority (CLP) ATM cell header 1 bit
MPLS Experimental MPLS header 3 bits
Cisco has decided to give a more general approach to QoS with the Modular QoS CLI (MQC). This client defines a common set of configuration commands for the definition of for QoS features on a router or switch.
Cisco is in favor of configuring with MQC.
There are three steps that have to be configured within a MQC based setup.
- class-map for matching packets into service classes, the match command can include QoS fields, ACL’s and MAC addresses, the match name is case sensitiv, the match any command matches any packet
- policy-map PHB actions configured under policy-map
- service-policy enabled on an interface
Here is an example:
class-map match-all SMTP-FROM-SERVER1
match access-group name
SMTP-FROM-SERVER1policy-map CBWFQ
class SMTP-FROM-SERVER1
bandwidth 256interface s0/0
bandwidth 512
service-policy output CBWFQip access-list extended SMTP-FROM-SERVER1
permit tcp host 150.1.1.100 eq smtp any
Here the SMTP protocol is serviced with CBWFQ at interface serial0/0.
The class-map command is one of the new MQC based tools for classifying packets.
It possible to match many different kind of options. Including QoS fileds, ACL’s and MAC addresses. Be carefule the map names are case sensitiv.
Multiple match commands can be used in a class-map. The following points need to be considered.
- Four CoS and IPP or eight DSCP values can be listed on a single match cos, match precedence, or match dscp command.
- if a class map matches with multiple match commands, the match-any or match-all parameter on the class-map command defines whether a logical OR or a logical AND is used between the match commands. match-all means AND logic between the parameters, for example: class-map match-all name, match cos 3 4, means to match 3 and 4. With match-any only one match parameter has to be true for the rule to match. So 3 or 4 would suffice.
- The match class name command is nesting the name of another class map logicaly.
Here is a nesting example:
class-map match-all nesting
match access-group 101
match precedence 10class-map match-any morenesting
match class nesting
match cos 10
Source:
http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/qos.htm
http://www.cisco.com/univercd/cc/td/doc/product/software/ios124/124cg/hqos_c/qchintro.htm
Popularity: 1% [?]
642-642 QoS
Jan 3rd
Currently going for the first QoS test for the CCVP. Think this is the most difficult one. I like to take the hard part first. I haven’t seen any RSVP implementations. I wonder if it’s really widely used outside in the network for QoS. I will write some comments to my QoS implementation for a customer with about 5000 access ports per site in the next days.
QoS can be quite a complex task. It seems simple, but implementing it continuously on differnt kinds of hardware queues and different queueing techniques, could be quite callenging.
Popularity: 1% [?]
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