How to prioritize the traffic of one Vlan over the other, assigned to the same pair of ports.

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If there are two ports X and Y in which 2 Vlans are assinged. Port X is 10 G and port Y is 1 G. How to prioritize the traffic of VLAN A over VLAN B. 
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Danial Jalil

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Posted 1 year ago

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Patrick Voss, Alum

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Hello Danial,

You can utilize the article below to configure QOS:

https://gtacknowledge.extremenetworks.com/articles/How_To/Configuring-QOS-profiles-and-verify-QOS-is-working

Looks like you just need to create the qosprofile and configure the VLAN to the profile. Please keep in mind that this configuration will only prioritize the traffic on the switch ti is configured on.

Hope this helps!
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Danial Jalil

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Hello Patrick, 
i already have created and assigned qosprofiles to the two VLANS. for exmaple i have assigned qp8 to VLAN A and qp1 to VLAN B still i the traffic of VLAN A drops when both the traffic starts flowing simultaneoiusly. how to make sure i receive every single packet of the VLAN A? 
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Erik Auerswald, Embassador

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You need to ensure that VLAN A never(*) tries to transport data at more than 1Gbps, and strictly prioritize VLAN A over VLAN B.

(Note: For example, Lossless Ethernet and Fibre Channel work by stopping the sender if the network cannot transport the data. This implements admission control for the network. If the sender sends more data than the network can transport, not all the data can reach the destination.)

(*) short bursts may be mitigated by buffers
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Danial Jalil

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Again... how to do it? Port A sends 700Mbps data in VLAN A and 5G Data in VLAN B. Now i want to receive all 700Mbps on Port B irrepective of whether i reiece data of VLAN B or not.. so how to implement that.. i tried qosprofiles but they r not working.
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Patrick Voss, Alum

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Danial,

QOS does not work like this unfortunately. Even though QP8 is a higher priority than QP1 the switch will not empty QP8 fully before it starts passing QP1 traffic. For example, the switch will send 8 packets from qp8 and then 1 from qp1. This example is not exactly how it works nor is it to scale. There is a much more complicated algorithm used to implement the prioritization. I wanted to give you an idea of how it works.

On an over utilized port it is unknown how bursty the traffic is at any given time.
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Danial Jalil

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Thank you patrick
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Patrick Voss, Alum

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Are you over-utilizing that port?
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Danial Jalil

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yep. please see the description i wrote to Erik
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EtherMAN, Embassador

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Just curious as to what your percentages are in your QOS settings when you set up QP8 and QP1... Cant run them both at 100% max bandwidth.

Also the bigger problem you will always have is the switch where the one gig and ten gig are shared.  Very hard to deal with such a huge over subscription like you have said.  You would have to set you QOS up so that neither one could ever use greater than the one gig.  Not sure why you would even consider a 5.7 gig to one gig as a good network design... Sorry to be so blunt but you really need to have all at ten gigs or separate the traffic on two different on gig ports. I would hate to be a user on the one that you are trying to push 5 gigs down a one gig pipe ....  
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Danial Jalil

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Thanks EtherMan
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Danial Jalil

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Thanks for the insight., i was just testing it. Anyway guys I think i have found the solution of my problem let me share it for others as well.. if the traffic is tagged with priority on VLAN A then it will automatically be prioritized over the traffic of VLAN B. So flow control should be enabled on the frames that are being received on any ports. the frames should have the information so that the switch/VLAN recongnizes what to do with it.
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EtherMAN, Embassador

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Good to know this was an exercise and not reality Danial... I think you understand now... I am a big believer in having QOS as the last resort and trying to always over engineer the network where there is no congestion or the need for QOS.  We have very little QOS running in our services even with a very large over subscription model.  We just stay ahead on ten gig and now 100 gig core interfaces.

One other thing I would like to add I have also always felt QP8 should only be used for your internal control and management services and you should never allow customer traffic be configured to use that que.  Keeps your EAPS rings happier.