QOS on 4948

Unanswered Question
Jan 9th, 2009
User Badges:
  • Silver, 250 points or more

I would like an explanation on how the TX queue work on that peice of equipement.


If I do a sh qos int ten1/49, I get this:


QoS is enabled globally

Port QoS is enabled

Administrative Port Trust State: 'cos'

Operational Port Trust State: 'cos'

Trust device: none

Default DSCP: 0 Default CoS: 0

Appliance trust: none

Tx-Queue Bandwidth ShapeRate Priority QueueSize

(bps) (bps) (packets)

1 2500000000 disabled N/A 2080

2 2500000000 disabled N/A 2080

3 2500000000 disabled high 2080

4 2500000000 disabled N/A 2080



What`s the purpose of the bandwidth field?

  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 5 (1 ratings)
Loading.
Jon Marshall Fri, 01/09/2009 - 09:14
User Badges:
  • Super Blue, 32500 points or more
  • Hall of Fame,

    Founding Member

  • Cisco Designated VIP,

    2017 LAN, WAN

Dominic


There are 4 queues on egress and each queue is allocted 1/4 of the bandwidth ie. 2.5Gbps in this case. You can change the allocation between the queues, or at least you can on some ports but i have never used a 4948-10G model.


You then map DSCP/Cos values to queues.


I suspect you may after something more specific. Attached is a link to Egress configuration on 4900 -


http://www.cisco.com/en/US/docs/switches/lan/catalyst4500/12.2/44sg/configuration/guide/qos.html#wp1463276


If i have not answered your question please come back.


Jon


dominic.caron Fri, 01/09/2009 - 12:11
User Badges:
  • Silver, 250 points or more

So, the high priority queue will be service first. The 3 other queue will share 1/3 each of the remaining transmit time. If I resume this,


1-If there is a packet in the high queue, put it on the tx-ring

2-take one packet from each other normal priority queue and place it on the tx-ring.

3-Start over


There is probably a check to see if the high priority queue is empty between each lower priority packet been put on the tx-ring.


Am I on the right track ?

dominic.caron Fri, 01/09/2009 - 12:15
User Badges:
  • Silver, 250 points or more

I've just read the link, got my answer, thanks.

Actions

This Discussion