Re: QoS verification on the exam

This is classic!

Sent from my iPad

On Apr 10, 2012, at 11:25 AM, Jochen Bartl <jochen.bartl_at_gmail.com> wrote:

> Hi Sud,
>
> I have seen your previous e-mail on GS, but I was a bit lazy and was
> waiting for others to reply ;-)
>
> QoS verification is not very time consuming if you know the tools and
> have the right formulas in mind. I would definetly verify it in the
> lab.
>
> To generate test traffic you can just use telnet, ping or traceroute.
> All those commands allow you to set the value of the ToS field.
> However for telnet you need to set it in global config mode.
>
> "ip telnet tos B8" would mark all outgoing telnet packets with DSCP
> 46/EF. Please be aware that this command requires the number to be in
> hex.
>
> These are the formulas to calculate the ToS value:
>
> IP Precedence to ToS: IP_Precedence_Value * 32
> AF to ToS: FIRST_DIGIT * 8 + SECOND_DIGIT * 2 * 4
> DSCP to ToS: DSCP_VALUE * 4
>
> Here are some examples for calculating the ToS value:
>
> Convert IP Precedence to ToS
> ----------------------------
>
> IP Precedence 4
> ToS = 4 * 32 = 128
> ToS in Hex = 80
>
> Convert AF values to ToS
> ------------------------
>
> AF31
> DSCP = FIRST_DIGIT * 8 + SECOND_DIGIT * 2
> DSCP = 3 * 8 + 1 * 2
> DSCP = 26
> ToS = 26 * 4 = 104
> ToS in Hex = 68
>
>
> Convert a DSCP value to ToS
> ---------------------------
>
> DSCP 46 (EF)
> ToS = 46 * 4 = 184
> ToS in Hex = B8
>
> For verification of the markings you can use "show policy-map
> interface x/y" on routers and "show mls qos interface x/y statistics"
> on switches.
>
> Best regards,
>
> Jochen
>
>
> On Tue, Apr 10, 2012 at 10:25 AM, Sud <mitsuie2_at_gmail.com> wrote:
>> Hello friends,
>>
>> Just wondering whether the group received my mail.
>>
>> Please can you give me some light.
>>
>> Cheers!
>> Sud
>>
>> Sent from my iPad
>>
>> On Apr 6, 2012, at 10:40 PM, Sud Mu <mitsuie2_at_gmail.com> wrote:
>>
>>> Hi all,
>>>
>>> These days I'm going through QoS technologies.
>>>
>>> I'm wondering whether it will be practical to verify the QoS configs in the actual lab based on the time limit we have.
>>>
>>> It's true that the more I verify the more marks I'm sure about. But would like to know whether i should verify that section generating traffic by trying various possibilities.
>>>
>>> I feel like I should be virtually 100% sure about what I configure and leave it not verified.
>>>
>>> Sud
>>>
>>> Sent from my iPad
>>
>>
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Received on Tue Apr 10 2012 - 22:39:08 ART