Re: QoS

Thanks for you response

The binary value of 12 is 1100. if you have 8 bits this and the left six vit
are DSCP it would become 10101100 and it needs to be 1011100.

The thing is that there will be a 0 appended and prepended so it becomen
01011100
My question is why is the 0 perpended in front of the bits?
11000 is 24 if the six most significant bits remain DSCP you need to add 24
101 11000

Kind regards,

Maarten Vervoorn
http://ccie.forumotion.com

2010/5/12 Beauty <fordownloadsccie_at_gmail.com>

Hi Marten
>
> the confusion is in the syntax of the command .
>
> the set ip tos commands only allows you to set four bits in the TOS
> byte of the ip header
>
> by choosing a value of 12 you are setting minimum delay and maximum
> throughout
>
> so with the config you have above you will have EF , since IPP(3
> leftmost bits) is set to 5 or 101 in binary and delay and throughput
> bits are set while the remaining bits are clear (11000)
>
> Since dscp bits = 6 most significant bits or leftmost bits
>
> adding this up you have dscp EF(101110)
>
> see command refernce for more info on the set ip tos command
>
> http://www.cisco.com/en/US/docs/ios/qos/command/reference/qos_s1.html#wp1059575
>
> HTH
>
>
> On 5/12/10, Maarten Vervoorn <mr.vervoorn_at_gmail.com> wrote:
> > I have a question about the solution a QoS excersise
> >
> > Requirement - Router originated telnet traffic should have a
> dscp
> > of EF. Give the neccessary config.
> >
> > Restrictions:
> > Do this without using any interface commands
> > Do not use the command -> ip telnet tos xxx
> >
> > The solution to this is:
> > !
> > access-list 101 permit tcp any any eq telnet
> > !
> > route-map telnet permit 10
> > match ip address 101
> > set ip precedence 5
> > set ip tos 12
> > !
> > ip local policy route-map telnet
> >
> > Can you explain the TOS bit numbering for me? If i check the
> configuration
> > you are able to select tos 0-15.
> >
> > What I thought is that TOS is 128 bits (8 caracters). Left 3 are
> Precedence
> > and left 6 are DSCP
> > precedence 5 is 101 00000
> > DSCP ef is 101110 00
> > So if you need to add 00011000 to 1010000 to make 10111000
> > if I calculate 00011000 it is 24
> > What I understood from a previous post is that a 0 is appended and
> prepended
> > so this maken 01011100. But why is in this case the 0 prepended in front
> of
> > the bits. Normaly DSCP are the left six bits. Now for all of a sudden in
> a
> > route-map the DSCP bits are 7,6,5,4,3,2
> > Normaly when you calculate Precedence or DSCP in TOS yoi take bits 8,7,6
> for
> > precedence and 8,7,6,5,4,3 for DSCP
> > Precedence 5 = TOS 160
> >
> >
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> Beauty

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Received on Wed May 12 2010 - 21:24:34 ART