QOS vs COS and when it is needed

[david.klein]

I want to understand QOS and COS, and for some reason can not understand how to setup one vs the other, and when one is used vs another, or how they are used together.  If the port that a device is plugged into, never ever uses up all the bandwidth available on a port will it ever need to have QOS vs COS?

One of the problems we are having at the company I work for, is that we use VDI and some of the new PCOIP devices which use Teradici chips and have quad DVI connections, where users are using 4 monitors is having problems.  Mainly our programmers are using these devices, and when you look in our Teradici management for the zero clients you will see disconnects happening all the time.  On the users end at times, and as I said before, most of the users experiencing this have 4 monitors and are programmers, they will see a flickering on their screen, maybe screen go black, maybe a delay when minimizing and maximizing applications, etc

So Teradici has a network checklist which has a lot of COS QOS in it and I am not sure if it will help for one thing and if it does not help, what to do next.

I am attaching the Teradici checklist.  Any of the WAN parts we will not need to do.  All Zero Clients having issues are only on LAN, and also all users having issues are using a Zero client with the 4 DVI's and using 4 monitors.

Thanks in advance

Dave

[Brandon Svec]

QOS and COS are often used interchangeably in discussion.  I consider QOS like the name of the technology where COS is more specific to actually marking Ethernet headers with a 0-7.  So COS is pretty specific and something you turn on and assign.  QOS is not just something you turn on, but a feature with many options and design choices to implement and monitor. So COS is like a subset of QOS. At least that is my general understanding and the meaning and correct use of them.

So what type of Cisco switch are you using?

[david.klein]

cisco 6513 Cores, and Cisco 2960 Stacks

[Brandon Svec]

I would suggest moving or reposting this here: https://supportforums.cisco.com/community/6016/lan-switching-and-routing

This is the small business switch forum and generally not ios switches talked about over here.

I'll just give my opinion that QOS on all switched LAN like you describe is probably not needed.  QOS is normally only used or needed for controlling and monitoring traffic over low bandwidth links (bottlenecks).

[cindy toy]

Hi Brandon,

I moved this discussion to the area that you suggested.

Thanks,
Cindy

[Joseph W. Doherty]

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Posting

"If the port that a device is plugged into, never ever uses up all the bandwidth available on a port will it ever need to have QOS vs COS?"

Well, that depends on how you define using up all a port's bandwidth.  BTW, LANs are not immune to needing QoS.

"So Teradici has a network checklist which has a lot of COS QOS in it and I am not sure if it will help for one thing and if it does not help, what to do next."

Insufficient information to say whether QoS might help or not.  Also insufficient information to say what to do next, with QoS, because QoS is often tailored to meet certain traffic needs given certain conditions.

What you really want to do next, is identify the cause of your performance issues, and depending on what that might be, QoS might be an important part of the solution.