Re: One SP Question

Muhammad,

Here, this might help:

* This is the TOS Byte:*

*8th bit*

*7th bit*

*6th bit*

*5th bit*

*4th bit*

*3rd bit*

*2nd bit*

*1st bit*

*D*

*T*

*R*

*ECN*

*ECN*

*IP Precedence bits*

*Using IP Precedence we can only get 8 different traffic classification
groups, binary 000  111, this was not enough for existing and future
networks, therefore, they expanded the IPP section to include the DTR
(Delay, Throughput and Reliability), and as a result of that, we now have
the capability to classify 64 different types of traffic (2 to the power of
6). They called that DSCP, from the 64 different values, they only named 21
of them and set standards based on the 21 of those values.*

*The first 8 values within the standard are called Class Selector (CS),
these are backwards compatible with IPP, and they are as follows:*

*CS*

*Binary*

*DSCP*

*IPP*

*Name of IPP*

*Default*

*000 000*

*0*

*0*

*Routine*

*1*

*001 000*

*8*

*1*

*Priority*

*2*

*010 000*

*16*

*2*

*Immediate*

*3*

*011 000*

*24*

*3*

*Flash*

*4*

*100 000*

*32*

*4*

*Flash-override*

*5*

*101 000*

*40*

*5*

*Critical*

*6*

*110 000*

*48*

*6*

*Routing/P*

*7*

*111 000*

*56*

*7*

*Signalling*

Check how 101 followed with whatever will always map to IPP 5, because the
brown section (The old DTR bits) is zeroed out. Therefore, when you have
a DSCP value of *101110, you should ONLY look at the 3 most significant bits
or as Scott mentioned the left most 3 bits.*

On Fri, Mar 12, 2010 at 1:03 PM, Scott Morris <swm_at_emanon.com> wrote:

> Left-most three bits.
>
> 101 = IP Prec 5
>
> So D.
>
> Scott Morris, CCIEx4 (R&S/ISP-Dial/Security/Service Provider) #4713,
>
> CCDE #2009::D, JNCIE-M #153, JNCIS-ER, CISSP, et al.
>
> CCSI #21903, JNCI-M, JNCI-ER
>
> swm_at_emanon.com
>
> Knowledge is power.
>
> Power corrupts.
>
> Study hard and be Eeeeviiiil......
>
> Muhammad Anser Khan wrote:
>
> Q: DSCP value "101110" looks like which IP Precedence value to
> non-DiffServ compliant devices?
>
> A. IP Precedence 6
> B. IP Precedence 4
> C. IP Precedence 3
> D. IP Precedence 5
> E. IP Precedence 2
> F. IP Precedence 7
>
> What is the correct ans?
>
> Regards,
> Anser
>
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--
Narbik Kocharians
CCSI#30832, CCIE# 12410 (R&S, SP, Security)
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