Re: Af Clasess

Nice chart. The link offered the same information more or less. What was
your answer?

On Fri, Oct 23, 2009 at 12:02 AM, Narbik Kocharians <narbikk_at_gmail.com>wrote:

> Some times it helps to understand the bits and see the chart. I am sorry if
> this is very basic for some and i know that we all know it, but it *MAY*help
some people.
>
> *QOS:*
>
>
>
> *8*
>
> *7*
>
> *6*
>
> *5*
>
> *4*
>
> *3*
>
> *2*
>
> *1*
>
>
>
>
>
>
>
> *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 current 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*
>
>
>
> Note in the above chart the *DTR bits* are not used and you are basically
> left with the *IPP bits,* and this is why they are backwards compatible to
> IPP.
>
> The remaining 12 standards are called Assured Forwarding and they are as
> follows:
>
>
>
>
>
> They divided the 8 bits as follows:
>
>
>
> *8*
>
> *7*
>
> *6*
>
> *5*
>
> *4*
>
> *3*
>
> *2*
>
> *1*
>
> *I*
>
> *P*
>
> *P*
>
> *D*
>
> *T*
>
> *R*
>
> *ECN*
>
> *ECN*
>
> *CLASS*
>
> *CLASS*
>
> *CLASS*
>
> *DP*
>
> *DP*
>
> *DP always zero*
>
>
>
>
>
> *4*
>
> *2*
>
> *1*
>
> *2*
>
> *1*
>
> *0*
>
>
>
>
>
> *32*
>
> *16*
>
> *8*
>
> *4*
>
> *2*
>
> *1*
>
>
>
>
>
>
>
> The first line identifies the bits 1  8.
>
> The second line identifies the IPP (IP Precedence) bits (6, 7, and 8), the
> DTR bits (3, 4 and 5) and the ECN bits (bits 1 and 2).
>
> The third line reveals the Class and Drop probability sections.
>
> The forth line identifies the decimal value of the corresponding bit in
> each section, note how the bits value in the Class section start from 1,
> whereas, in the DP section it starts from 0.
>
> The fifth line identifies the DSCP section and the decimal value of the 6
> bits.
>
>
>
> These are the classes and their corresponding values, both AF values and
> the DSCP values. Within each class the higher DP values are more likely to
> be dropped.
>
>
>
> Class
>
> *Drop Probability 1*
>
> *Drop Probability 2*
>
> *Drop Probability 3*
>
> * *
>
> *Class 1*
>
> **
> **
> **
> *AF11*
>
> *001 01 0*
>
> *DSCP = 10*
>
> * *
>
> *AF12*
>
> *001 10 0*
>
> *DSCP = 12*
>
> * *
>
> *AF13*
>
> *001 11 0*
>
> *DSCP = 14*
>
> * *
>
> *Class 2*
>
> * *
>
> *AF21*
>
> *010 01 0*
>
> *DSCP = 18*
>
> * *
>
> *AF22*
>
> *010 10 0*
>
> *DSCP = 20*
>
> * *
>
> *AF23*
>
> *010 11 0*
>
> *DSCP = 22*
>
> * *
>
> *Class 3*
>
> * *
>
> *AF31 *
>
> *011 01 0*
>
> *DSCP = 26*
>
> * *
>
> *AF32*
>
> *011 10 0*
>
> *DSCP = 28*
>
> * *
>
> *AF33*
>
> *011 11 0*
>
> *DSCP = 30*
>
> * *
>
> *Class 4*
>
> * *
>
> *AF41*
>
> *100 01 0*
>
> *DSCP = 34*
>
> * *
>
> *AF42*
>
> *100 10 0*
>
> *DSCP = 36*
>
> * *
>
> *AF43*
>
> *100 11 0*
>
> *DSCP = 38*
>
> * *
>
>
>
> The 21st standard was assigned to Voice traffic and its called *Expedited
> Forwarding* or (*EF*). The Binary value of this is: *101* *110 *or *DSCP
> value of 46*
>
> Please ignore the typos, this was done in 10 minutes.
>
> On Thu, Oct 22, 2009 at 5:03 PM, Johnny B CCIE <jbccie_at_gmail.com> wrote:
>
>> AF32 may have a "higher drop probability" however AF21 will get
>> dropped first due to lower class. Reference EF = 5 and then AF41 being
>> video, and in that order. Also take into account some providers don't
>> even take into account AF21 and lower anyway and so this traffic might
>> even be treated as best effort or 0.
>>
>>
>>
>> On Thu, Oct 22, 2009 at 6:13 PM, Divin Mathew John <divinjohn_at_gmail.com>
>> wrote:
>> > Which class has a Higher Drop Probability?
>> >
>> > AF21 or AF32?
>> >
>> > AF21 = 010 010
>> > AF32= 011 100
>> >
>> >
>> > --
>> >
>> >
>> > Jules Renard - "Literature is an occupation in which you have to keep
>> > proving your talent to people who have... -
>> > http://www.quotationspage.com/quote/38638.html
>> >
>> >
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>>
>>
>>
>>
>>
>
>
> --
> Narbik Kocharians
> CCSI#30832, CCIE# 12410 (R&S, SP, Security)
> www.MicronicsTraining.com <http://www.micronicstraining.com/>
> Sr. Technical Instructor
> YES! We take Cisco Learning Credits!
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Received on Fri Oct 23 2009 - 00:52:37 ART