Re: QoS

---------- Forwarded message ----------
From: Maarten Vervoorn <mr.vervoorn_at_gmail.com>
Date: 2010/5/12
Subject: Re: QoS
To: Kambiz Agahian <kagahian_at_ccbootcamp.com>

Hi Kambiz,

So the reason why is because it is devided in two hex bit. Because normaly
101 would be 1010 0000 (160) if you converd it into TOS bits. The last hex
bit is the tos bits you can configure in you r route-map. and the first
represents the precedence.

I see how this is done. I only find this confusing

Thanks for you response.

Maarten Vervoorn

2010/5/12 Kambiz Agahian <kagahian_at_ccbootcamp.com>

Maarten,
>
> This is one of the grandfather questions; I guess the last time it was
> seen on the GS was back in 7-8 year ago :)
>
> You're after EF so you'll come up with 101110
>
> Padding with Zero's: 0101 1100
>
> 0101 ->HEX 5 -> IPP (Prec)
> 1100 ->HEX 12 -> TOS
>
> That's why you see:
> set ip precedence 5
> set ip tos 12
>
>
> Please see RFC-1349 for more details.
>
> HTH
>
> --------------------------
> Kambiz Agahian
> CCIE (R&S), CCSI, WAASSE, RSSSE
> Technical Instructor
> CCBOOTCAMP - Cisco Learning Solutions Partner (CLSP)
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>
>
> -----Original Message-----
> From: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] On Behalf Of
> Maarten Vervoorn
> Sent: Wednesday, May 12, 2010 12:25 PM
> To: Cisco certification
> Subject: 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#wp
> 1059575
> >
> > 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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> > >
> > >
> >
> >
> > --
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> > Beauty
>
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Received on Wed May 12 2010 - 21:41:53 ART