Skip navigation
Cisco Learning Home > CCNP Wireless Study Group > Discussions
4093 Views 22 Replies Latest reply: Mar 8, 2012 1:59 PM by Adrian Soh RSS 1 2 Previous Next

Currently Being Moderated

wired vs wireless QoS

Mar 4, 2012 5:12 AM

daniel-schmidt 4 posts since
Feb 10, 2009

Hello

 

I got a discussion with a customer abourt wired and wireless QoS.

 

Best practices wired QoS the following cos dscp mapping.

mls qos cos-dscp 0 8 16 24(26) 32 46 48 56

 

i found the following document.

http://www.cisco.com/en/US/partner/tech/tk722/tk809/technologies_configuration_example09186a00807e9717.shtml

 

In the document include a mapping table from the wireless qos-profiles to dscp values.

regarding this mapping, the wired qos have to be

mls qos cos-dscp 0 10 18 26 34 46 48 56

 

Or Nothing have to be change, because the dscp and cos value in the same cos-range like the first mapping?

 

Greetings Daniel

  • Eric A. Nygren 253 posts since
    Aug 11, 2008
    Currently Being Moderated
    1. Mar 5, 2012 9:06 AM (in response to daniel-schmidt)
    Re: wired vs wireless QoS

    I'm using 0 8 16 24 32 46 48 54 tomorrow, so I hope that's right, but it might not be

     

    -Eric N

  • Pete Nugent 275 posts since
    Jan 27, 2012
    Currently Being Moderated
    2. Mar 5, 2012 11:05 AM (in response to Eric A. Nygren)
    Re: wired vs wireless QoS

    Its an area I am still investigating and trying to get my head around all of the QoS mechanisms. Nightmare.

     

    However for Eric lists the default values and Daniel the values discussed in documents, however there is no suggestion as to a need to change these values.

     

    Its definitely an area that I would really like to get to the bottom of.

  • Adrian Soh 228 posts since
    Jan 4, 2009
    Currently Being Moderated
    3. Mar 5, 2012 12:16 PM (in response to daniel-schmidt)
    Re: wired vs wireless QoS

    That's the most common cos-dscp map to use.

     

    The trick with wireless qos is there are upstream (client>AP>WLC>wired) and downstream (wired>WLC>AP>client) to consider.  Note: the WLC QoS 802.1q configuration is based on 802.11 User Priority (UP) values. 

     

    Hope this helps.

  • Pete Nugent 275 posts since
    Jan 27, 2012
    Currently Being Moderated
    4. Mar 5, 2012 12:15 PM (in response to Adrian Soh)
    Re: wired vs wireless QoS

    Adrian

     

    Can you explain further as this is something I really struggle with, perhaps an example?

     

    Any help appreciated.

  • Adrian Soh 228 posts since
    Jan 4, 2009
    Currently Being Moderated
    5. Mar 5, 2012 12:38 PM (in response to Pete Nugent)
    Re: wired vs wireless QoS

    Sorry for the delay.. I was trying to find you some good pdfs..   download the following:

    1. 7925G deployment guide
    2. enterprise mobility guide v4.1.
    3. CWNP CWAP pdf //excellent detail on the packet.

     

    Some useful docs above.

  • Pete Nugent 275 posts since
    Jan 27, 2012
    Currently Being Moderated
    6. Mar 5, 2012 12:42 PM (in response to Adrian Soh)
    Re: wired vs wireless QoS

    Adrian

     

    I am ploughing through all of the above at the moment focusing on the voice side and understanding QoS plus all of the other specific add on parts. Not started to deviate yet from Cisco 7921/5. Think I am getting there though, just sometimes someone might have a real gem of a doc thats as easy as A B C but I dont think thats the case with QoS

     

    Also plan on doing some labs with a QoS generator and packet sniffing so I can see the interactions.

  • Adrian Soh 228 posts since
    Jan 4, 2009
    Currently Being Moderated
    7. Mar 5, 2012 1:18 PM (in response to Pete Nugent)
    Re: wired vs wireless QoS

    Here is my gem.. quick and easy.

     

    http://www.youtube.com/watch?v=44t-0JYEwkA

     

    There are 3 parts to Jerome's videos.

  • Pete Nugent 275 posts since
    Jan 27, 2012
    Currently Being Moderated
    8. Mar 5, 2012 5:53 PM (in response to Adrian Soh)
    Re: wired vs wireless QoS

    Doing my own research on QoS so thought I would look into this as a real world example. Now lets say both are correct 0 8 16 24(26) 32 46 48 56 and 0 10 18 26 34 46 48 56.

     

    Now bare in mind this is still not crystal clear to me but COS uses a 3 bit field at layer 2 and groups the categories into Class Selector Code Points or CS classes. From CS0 – CS7.

     

    However DSCP works at layer 3 and uses a 6 bit field (technically 8 but the last 2 bits are not really used) creating 64 different QoS values. The first 3 bits to the left of the dscp field can group directly to the CS class the same as COS. Bits 4 and 5 define the drop probability.

     

    When we look at the class map (I have only included a few lines)

     

    DSCP Bits

    DSCP

    802.1p

    802.11e

    WLAN

    Voice Control

    011010

    26 (AF31)

    3

    4 (AC_VI)

    Background (Cisco AVVID Gold Background)

    010010

    18 (AF21)

    2

    2 (AC_BK)

    Silver

    Network management

    010000

    16 (CS2)

    2

    3

    Silver

    Background (Cisco AVVID Silver Background)

    001010

    10 (AF11)

    1

    1 (AC_BK)

    Bronze

    Scavenger

    001000

    8 (CS1)

    0

    1

    Bronze

    Best Effort

    000000

    0 (BE)

    0

    0 (AC_BE)

    Bronze

     

    If there are no drop probability bits it translates to a CS class so 8 is CS1, however 10 is also CS1 but with drop probability. From my understanding 10 will have a higher drop probability than 8.

     

    Again that’s from just a few hours thrashing around and a little background reading over the last few days.

     

    I have not put the whole table in as its something I need to fully understand I am throwing this out there for everyone.

     

    Maybe I could actually pull all the WLAN QoS bits into a unified doc that makes sense? Well makes sense to me.

     

    I await to get flamed!

  • Bryn 4 posts since
    May 6, 2009
    Currently Being Moderated
    9. Mar 6, 2012 12:09 AM (in response to Pete Nugent)
    Re: wired vs wireless QoS

    Hi Pete,

     

    The CS values dont use the drop probability so if it makes sense CS1 is CS1 and thats it, the AF values are the ones which use the drop probability bits from my understanding.

     

    See http://www.rhyshaden.com/qos.htm

     

    See the DSCP to binary/decimal table in this document and it explains that CS values always end with xxx000.

     

    In your example 8 is CS1 and 10 is AF11 you have gone up a class

  • Pete Nugent 1,256 posts since
    Dec 8, 2008
    Currently Being Moderated
    10. Mar 6, 2012 1:50 AM (in response to Bryn)
    Re: wired vs wireless QoS

    Thats what I was trying to say! LOL

     

    If it ends xx000 its a CSx.

     

    Regarding the CS1 to AF11 yes I agree its gone up a class in DSCP terms but if you translate to CoS terms its still 1 as it simply does not understand the drop bits.

     

    Thanks for flaming me! LOL.QoS is probably my worst area.

  • Bryn 4 posts since
    May 6, 2009
    Currently Being Moderated
    11. Mar 6, 2012 2:01 AM (in response to Pete Nugent)
    Re: wired vs wireless QoS

    I will try and dig out the DSCP to COS table map, you will find multiple DSCP values mapped to CoS values just purely becasue there is more of them.

     

    Its probably a weak point because you dont really have to use it generally, QOS only comes into play if there is congestion (wired). Only need it if you feel there is not enough bandwidth available and in most case these days it is 1Gb uplinks to APs etc....

     

    The Jermone stuff is good on QOS however if you can get hold of the old QOS course books or Nuggets for CCVP or CCIP it does a great job of explaining. QOS for wireless is not that in depth really.

  • Pete Nugent 1,256 posts since
    Dec 8, 2008
    Currently Being Moderated
    12. Mar 6, 2012 2:11 AM (in response to Bryn)
    Re: wired vs wireless QoS

    I agree it does not seem to be overly deep but its a critical  to make sure its all glued together properly and maybe knowing me I am going too deep!

  • Adrian Soh 228 posts since
    Jan 4, 2009
    Currently Being Moderated
    13. Mar 6, 2012 1:22 PM (in response to Pete Nugent)
    Re: wired vs wireless QoS

    Hey Pete, sorry its a little crazy here.

     

    Default CAPWAP Control (5246) marking is CS6 .. CAPWAP Data (5247) is dependent on wireless users User Priority (UP) values and WLC QoS profile 802.1q settings.  

     

    Note: cos values exist in 802.1Q header so untagged vlan = cos value 0.

     

    I can't recall who did the CCVP nuggets however if it's Jeremy Cairo it must be good

     

    Bryn, nice link mate.

     

    Hope this helps.

Actions

More Like This

  • Retrieving data ...

Bookmarked By (1)