How can I configure queues on router 3662 serial interface

Answered Question
Oct 2nd, 2008

Hi,

What is the diference between tx-lmit command and hold queue command?

Actually I have two routers connected through a FR cloud. I make a ping to ROUTER_B's serial interface from ROUTER_A and I have icmp request timout during the day. I noticed from several commands outputs (find them attached) that I have many drop packets and delayed packets.

Could you take a look and help me?

tahnks in advance!

I have this problem too.
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Correct Answer by Istvan_Rabai about 8 years 2 months ago

Hi John,

The tx-ring-limit command sets the size of the hardware transmit queue of the interface which is always a FIFO queue.

The hold-queue command sets the size of the software queue (number of packets).

Based on your description of the problem I have a supposition that your serial interface is continuously overloaded with traffic during the workday.

If this is the situation, playing with the queue size will not bring a fundamental solution.

The reason is that the bandwidth of the interface is probably not enough to handle the traffic that is sent from one router to the other through the frame-relay cloud.

Probably you would need to investigate the possibility of increasing the bandwidth of the frame-relay pvc you are using.

QoS tools are effective only when there are bursts and troughs in the traffic.

Then QoS can buffer certain packets for later service and forward those packets that have higher priority.

In your case the higher buffer space will be filled in very shortly and the packet drops will continue.

Cheers:

Istvan

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aghaznavi Wed, 10/08/2008 - 06:20

To control the number of transmit buffers available to a specified interface on the multiport communications interface (MCI) and serial communications interface (SCI) cards, use the tx-queue-limit command in interface configuration mode.

tx-queue-limit number

frame-relay holdq map-class command was used to configure the size of FIFO traffic shaping queues only.

Configuring Queueing and Fragmentation on the Frame Relay Interface

Router(config)# interface type number

Router(config-if)# encapsulation frame-relay

Router(config-if)# service-policy output policy-map-name

Router(config-if)# frame-relay fragment fragment-size end-to-end

Correct Answer
Istvan_Rabai Wed, 10/08/2008 - 09:58

Hi John,

The tx-ring-limit command sets the size of the hardware transmit queue of the interface which is always a FIFO queue.

The hold-queue command sets the size of the software queue (number of packets).

Based on your description of the problem I have a supposition that your serial interface is continuously overloaded with traffic during the workday.

If this is the situation, playing with the queue size will not bring a fundamental solution.

The reason is that the bandwidth of the interface is probably not enough to handle the traffic that is sent from one router to the other through the frame-relay cloud.

Probably you would need to investigate the possibility of increasing the bandwidth of the frame-relay pvc you are using.

QoS tools are effective only when there are bursts and troughs in the traffic.

Then QoS can buffer certain packets for later service and forward those packets that have higher priority.

In your case the higher buffer space will be filled in very shortly and the packet drops will continue.

Cheers:

Istvan

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