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dscp / qos / queue depths

Ruby Brownell
Occasional Visitor

dscp / qos / queue depths


My understanding for Provision switches, the default mappings do not need to be defined; true?

Also, when set to a a 4 buffer queue, the

.1p pri TO
qos queue and depth TO
dscp priority map

goes something like this:

802.1p Pri 2
qos queue 1 - depth 8%
qos dscp-map 001110 priority 2

802.1p Pri 1
qos queue 1 - depth 8%
qos dscp-map 001010 priority 2

802.1p Pri 1
qos queue 1 - depth 8%
qos dscp-map 001100 priority 2

802.1p Pri 0
qos queue 2 - depth 17%
qos dscp-map 010010 priority 0

802.1p Pri 0
qos queue 2 - depth 17%
qos dscp-map 010100 priority 0

802.1p Pri 3
qos queue 2 - depth 17%
qos dscp-map 010110 priority 0

802.1p Pri 4
qos queue 3 - depth 30%
qos dscp-map 011010 priority 3

802.1p Pri 4
qos queue 3 - depth 30%
qos dscp-map 011100 priority 3

802.1p Pri 5
qos queue 3 - depth 30%
qos dscp-map 011110 priority 3

802.1p Pri 6
qos queue 4 - depth 45%
qos dscp-map 100010 priority 4

802.1p Pri 6
qos queue 4 - depth 45%
qos dscp-map 100100 priority 4

802.1p Pri 7
qos queue 4 - depth 45%
qos dscp-map 100110 priority 4

802.1p Pri 7
qos queue 4 - depth 45%
qos dscp-map 101110 priority 5

Is this corect?

So all i need to do to set the dscp map to a vlan is this:

vlan
qos dscp 110100

True?

So if I am trying to get my voice into the highest percentage queue, is there any difernce between a dscp map of 100010 100100 100110 110100 regarding switch cpu time? If so, what?

3 REPLIES
Pieter 't Hart
Honored Contributor

Re: dscp / qos / queue depths

Depending on type of switch you can designate a vlan as "voice" vlan.

[no] interface vlan VLAN-ID voice
Usage: [no] voice
Description: Labels this VLAN as a Voice VLAN, allowing you to separate, prioritize, and authenticate voice traffic moving through
your network.
This is a VLAN context command. It can be called directly from the VLAN context or follow the 'vlan VLAN-ID' command.

No need to manually create queues, qos values etc.....

- can't answer the question about cpu usage, but my guess would be that the impact on cpu is not different between dscp values.
Ruby Brownell
Occasional Visitor

Re: dscp / qos / queue depths

it is my understanding that the vlan voice parameter allows lldp-med interaction with the link device and the switch port. if the device doesnt understand lldp-med, then the voice parameter doesnt do much. the L2 and L3 qos settings can be established via lldp-med, but the L3 settings would require enabling diffserv on the switch. if it isnt enaled, then setting dscp isnt buying anything. The default vlan voice param's are L2=6 L3=46(EF).

Anyhow, I belive you are corerct in that I am splitting hairs with regard to cpu useage differences between code point 46 to 63. I am just curious to know why someone might want to set dscp to 46 from one vlan and 63 in another.

ideas?
ryderse
Occasional Advisor

Re: dscp / qos / queue depths

I have a somewhat similar question but I started a new thread since it's not exactly the same. However some of the points made here seem to answer my questions.

 

http://h30499.www3.hp.com/t5/ProCurve-ProVision-Based/QoS-options-on-HP2910-and-2620-for-voice-traffic/td-p/5817465#.UGXq35h6u3Y

 

If I use the 'voice' option I do not need to use the QoS options?