In the following illustration, the transmit ring has been configured to hold four packets. If three packets already are on the ring, then at best we can queue to the fourth position and then wait for the other three to empty. Use the tx-ring-limit command to tune the size of the transmit ring to a non-default value.
Cisco recommends tuning the transmit ring when transmitting voice traffic. Traffic prioritization is especially important for delay-sensitive, interactive transaction-based applications. To minimize delay and jitter, the network devices must be able to service voice packets as soon as they arrive, or in other words, in strict priority fashion. Nothing short of strict priority works well for voice. Unless the voice packets are immediately de-queued, each hop will introduce more delay.
Without immediate de-queueing at the router interface, a single router hop can account for most of this delay budget. For more information, refer to the Voice Quality Technical Tips. Note: With both commands, the kbps value should take the Layer 2 overhead into account. In other words, if a guarantee is made to a class, that guarantee is with respect to Layer 2 throughput. Although the bandwidth guarantees provided by the bandwidth and priority commands have been described with words like "reserved" and "bandwidth to be set aside", neither command implements a true reservation.
In other words, if a traffic class is not using its configured bandwidth, any unused bandwidth is shared among the other classes. The queueing system imposes an important exception to this rule with a priority class. As noted above, the offered load of a priority class is metered by a traffic policer. During congestion conditions, a priority class cannot use any excess bandwidth. The original implementation of LLQ over Frame Relay on these platforms did not allow the priority classes to exceed the configured rate during periods of non-congestion.
In addition, packets smaller than an FRF. From the above discussion, it is important to understand that since the priority classes are policed during congestion conditions, they are not allocated any remaining bandwidth from the bandwidth classes. Thus, remaining bandwidth is shared by all bandwidth classes and class-default. This section explains how the queueing system distributes any remaining bandwidth.
Here is how the Class-Based Weighted Fair Queueing Feature Overview describes the allocation mechanism: "If excess bandwidth is available, the excess bandwidth is divided amongst the traffic classes in proportion to their configured bandwidths.
If not all of the bandwidth is allocated, the remaining bandwidth is proportionally allocated among the classes, based on their configured bandwidth. In the following illustration, the transmit ring has been configured to hold four packets. If three packets already are on the ring, then at best we can queue to the fourth position and then wait for the other three to empty. Use the tx-ring-limit command to tune the size of the transmit ring to a non-default value.
Cisco recommends tuning the transmit ring when transmitting voice traffic. Traffic prioritization is especially important fornetwork delay-sensitive, interactive applications. To minimize delay and jitter, the devices must be abletransaction-based to service voice packets as soon as they arrive, or in other words, in strict priority fashion.
Nothing short of strict priority works well for voice. Unless the voice packets are immediately de-queued, de-queued, each hop will introdu introduce ce more delay. The International Telecommunications Union ITU recommends a maximum millisecon millisecondd one-way end-to-end delay.
Without Without immediate de-queueing at the router interface, a single router hop hop can account for most of this delay budget. For more information, refer to the Voice Quality Technical Tips. Note: With both commands, the kbps value should take the Layer 2 overhead into account. In other words, if a guarantee is made to a class, that guarantee is with respect to Layer 2 throughput.
For more Queueing? Although the bandwidth guarantees provided by the bandwidth and priority commands have been described with words like "reserved" and "bandwidth to be set aside", neither command implements a true reservation. In other words, if a traffic class is not using its configured bandwidth, any unused bandwidth is shared shared among the oth other er classes. The queueing system imposes an important exception to this rule with a priority class.
As noted above, the offered load of a priority class is metered by a traffic policer. During congestion conditions, a riority class cannot use any excess bandwidth. This table describes when a bandwidth class and a priority class can use excess bandwidth: Command Congestion NonCongestion bandwidth Allowed to exceed the Command priority Command allocated rate. Cisco IOS meters the packets and applies a traffic measurement system via a token bucket. Matching packets are policed to the configured bps rate, and any excess packets are discarded.
Allowed to exceed the allocated rate. The class can exceed its configured bandwidth. The original implementation implementation of LLQ over Frame Relay on these platforms did not allow the priority classes to exceed the configured rate during periods of noncongestion.
In add addition, ition, packets small smaller er than an FRF. Inhaltsverzeichnis ausblenden Inhaltsverzeichnis anzeigen. Inhaltsverzeichnis anzeigen.
Druck PDF. Die Daten werden geladen. Bitte haben Sie einen Moment Geduld. Use the priority-pgid command to create the priority groups in a DCB map. Also, if any class doesn't use its full bandwidth allocation, the leftover will automatically be distributed to the other classes proportionally, based upon the configured percentages. View All Articles. View All Delivery Formats. My GK. Checkout Cart Loading
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