Q1 : What’s Quality of Service (QoS) pre-classification?
A : QoS pre-classification allows you to match on and classify the first scientific discipline header contents of packets undergoing tunnel encapsulation and/or coding. This feature doesn’t describe the method of repeating the first worth of the sort of Service (ToS) computer memory unit from the first packet header to the tunnel header. For additional data, check with the subsequent documents:
Configuring QoS for Virtual Personal Networks
Quality of Service for Virtual personal Networks, 12.2(2)T Feature Module
Q2 : What’s the MQC?
A : MQC stands for standard Quality of Service (QoS) instruction Interface (CLI). it’s designed to change the configuration of QoS on Cisco routers and switches by process a typical command syntax and ensuing set of QoS behaviours across platforms. This model replaces the previous model of process distinctive syntaxes for every QoS feature and for every platform.
Q3 : What percentage categories will a high quality of Service (QoS) policy support?
A : In Cisco IOS versions ahead of twelve.2 you’ll outline a most of solely two56 categories, and you’ll outline up to 256 categories at intervals every policy if constant categories square measure reused for various policies. If you’ve got 2 policies, the overall variety of categories from each policy mustn’t exceed 256. If a policy includes Class-Based Weighted honest Queening (CBWFQ) (meaning it contains an information measure [or priority] statement at intervals any of the classes), the overall variety of categories supported is sixty-four.
Q4 : How many classes do a Quality of Service (QoS) policy support?
A : In Cisco IOS versions earlier than 12.2 you could define a maximum of only 256 classes, and you could define up to 256 classes within each policy if the same classes are reused for different policies. If you have two policies, the total number of classes from both policies should not exceed 256. If a policy includes Class-Based Weighted Fair Queueing (CBWFQ) (meaning it contains a bandwidth [or priority] statement within any of the classes), the total number of classes supported is 64.
In Cisco IOS versions 12.2(12),12.2(12)T, and 12.2(12)S, this limitation of 256 global class-maps was changed, and it is now possible to configure up to 1024 global class-maps and to use 256 class-maps inside the same policy-map.
Q5 : What commands am I able to use to watch queuing?
A : Use the subsequent commands to watch queuing:
show queue – On Cisco IOS platforms nevertheless the Cisco 7500 Series, this command displays the active queues or conversations. If the interface or Virtual Circuit (VC) isn’t engorged, no queues are going to be listed. On the Cisco 7500 Series, the show queue command isn’t supported.
Q6 : Can I enable fair queueing inside a class?
A : The Cisco 7500 Series with distributed Quality of Service (QoS) supports fair queueing per class. Other platforms, including the Cisco 7200 Series and Cisco 2600/3600 Series, support Weighted Fair Queueing (WFQ) in the class-default class; all bandwidth classes use First In First Out (FIFO).
Q7 : What percentage Virtual Circuits (VCS) will support a service policy simultaneously?
A : the subsequent document provides helpful tips on the amount of Asynchronous Transfer Mode (ATM) VCS which will support. regarding two hundred to three hundred VBR-nrt Permanent Virtual Circuits (PVCs) are safely deployed:
IP to ATM category of Service style Guide
Also, think about the following:
Use a robust processor capable. To Illustrate, a VIP4-80 provides considerably higher performance than a VIP2-50.
Amount of obtainable packed memory. On the NPE-400, up to thirty-two MB (in a system with 256 MB) is ready aside for packet buffer. For Associate in Nursing NPE-200, up to sixteen MB is ready aside for packet buffers on a system with 128 MB.
Q8 : Am I able to modify truthful queuing within a class?
A : The Cisco 7500 Series with distributed Quality of Service (QoS) supports truthful queueing per category. different platforms, as well as the Cisco 7200 Series and Cisco 2600/3600 Series, support Weighted truthful Queuing (WFQ) within the class-default class; all information measure categories use 1st In 1st Out (FIFO).
Q9 : Wherever do I apply a service policy with category based mostly Weighted truthful Queueing (CBWFQ) Associate in Nursing Low Latency Queueing (LLQ) on an Asynchronous Transfer Mode (ATM) interface?
A : As of Cisco IOS twelve.2, ATM interfaces support service policies at 3 levels or logical interfaces: main interface, sub-interface, and Permanent Virtual Circuit (PVC). wherever you apply the policy may be a operate of the standard of Service (QoS) feature that you just are facultative. Queuing policies ought to be applied per Virtual Circuit (VC) since the ATM interface monitors the congestion level per VC, and maintains queues for excess packets per VC. For a lot of info, check with the subsequent documents:
Where Do I Apply a QoS Service Policy on Associate in Nursing ATM Interface?
Understanding Per-VC Transmit Queuing on the PA-A3 and NM-1A ATM Interfaces
Q10 : However do Weighted truthful Queueing (WFQ) and sophistication based mostly Weighted truthful Queueing (CBWFQ) operate?
A : truthful queueing seeks to portion a good share of associated interface’s information measure among active conversations or informatics flows. It classifies packets into subqueues, known by a speech communication positive identification, employing a hashing algorithmic rule supported many fields of the informatics header and therefore the length of the packet. the subsequent is, however, the load is calculated:
W=K/(precedence +1)
Q11 : Am I able to rate traffic supported the URL?
A : Yes. Network-based mostly Application Recognition (NBAR) permits you to classify packets by matching on fields at the applying layer. before the introduction of NBAR, the foremost granular classification was layer four Transmission management Protocol (TCP) and User Datagram Protocol (UDP) port numbers. For additional data, check with the subsequent documents:
Network-Based Application Recognition Q&A
NBAR Application Networking
Using Network-Based Application Recognition and Access management Lists for block the Code wiggler
How to Defend Your Network Against the Nimda Virus
Q12 : However square measure routing updates and Point-to-Point Protocol (PPP) / High-Level circuit management (HDLC) keepalives processed once a service policy is applied?
A : Cisco IOS routers use the subsequent 2 mechanisms to grade management packets:
IP precedence
pak_priority
Q13 : Is Quality of Service (QoS) supported on interfaces designed with Integrated Routing and Bridging (IRB)?
A : No. you can’t assemble QoS features once the interface is designed for IRB.
Q14 : Is category based mostly weighted truthful Queuing (CBWFQ) supported on subinterfaces?A : Cisco IOS logical interfaces don’t inherently support a state of congestion and don’t support the direct application of a service policy that applies a queueing methodology. Instead, you initially have to be compelled to apply to shape to the sub-interface victimization either Generic Traffic Shaping (GTS) or class-based shaping. For additional info, discuss with Applying QoS options to local area network Subinterfaces.
Q15 : What tools am I able to use to watch vocalization information science performance?
A : Cisco presently offers many choices for observation Quality of Service (QoS) in networks exploitation Cisco’s vocalization information science solutions. These solutions don’t live voice quality exploitation sensory activity Speech Quality menstruation (PSQM) or a number of the new projected algorithms for voice quality menstruation. Tools from Agilent (HP) and NetIQ square measure on the market for this purpose. However, Cisco will supply tools that give some plan of the voice quality you’re experiencing by activity delay, noise, and packet loss. For additional data, see exploitation Cisco Service Assurance Agent and Internet work Performance Monitor to Manage Quality of Service in vocalization information science Networks.
Q16 : What bytes are counted by informatics to Asynchronous Transfer Mode (ATM) category of Service (COs) queueing?
A : The information measure and priority command organized in a very service policy to change class-based weighted truthful queueing (CBWFQ) and low latency queuing (LLQ), severally, use a Kbps price that counts equivalent overhead bytes as are counted by the show interface command output. Specifically, the layer three queuing system counts Logical Link management / Sub-network Access Protocol (LLC/SNAP). It doesn’t count the following:
ATM Adaptation Layer five (AAL5) Trailer
Padding to form the last cell a fair multiple of forty-eight bytes
Five-byte cell header
Q17 : RSVP is often employed in conjunction with category based mostly Weighted truthful Queueing (CBWFQ). once each Resource Reservation Protocol (RSVP) associate degreed CBWFQ are organized for an interface, do RSVP and CBWFQ act severally, exhibiting identical behavior that they’d if everyone were running alone?
A : RSVP looks to behave as if CBWFQ isn’t organized relating to information measure handiness, assessment, and allocation.
once exploitation RSVP and CB-WFQ in Cisco IOS code unharness twelve.1(5)T and later, the router will operate specified RSVP flows associate degreed CBWFQ categories share the obtainable information measure on an interface or PVC, while not over-subscription.
Q18 : If a category at school-based mostly Weighted truthful Queueing (CBWFQ) isn’t victimization its information measure, will alternative categories use the bandwidth?
A : Yes. Though the information measure guarantees provided by supply the information measure and priority commands are represented with words like “reserved” and “bandwidth to be set aside”, neither command implements a real reservation. Meaning, if a traffic category isn’t victimization its organized information measure, any unused information measure is shared among the opposite categories.