Re: Interesting FRTS Behavior Driving Me Mad

From: Iwan Hoogendoorn <iwan_at_ipexpert.com>
Date: Mon, 30 Nov 2009 14:58:13 +0100

Great you found the issue ...

heheh saves me time reading trough your first mail ;-)

-- 
Regards,
Iwan Hoogendoorn
CCIE #13084 (R&S / Security / SP)
Sr. Support Engineer  IPexpert, Inc.
URL: http://www.IPexpert.com
On Mon, Nov 30, 2009 at 10:13 AM, Joe Astorino <jastorino_at_ipexpert.com> wrote:
> Hey Michael, thanks for your reply.  I believe you found the magic ratio I
> was searching for.  I didn't think to look at the byte-count. Excellent!!!
> At least now we know why.  Sort of like how I also found a few months ago
> the highest possible value you can make the Tc is 249ms even though some
> docs say it maxes out at 125ms.
>
> This makes perfect sense now based on the byte count limit of 10000 bytes /
> interval.
>
> 80007 bits / 8 = 10000.875 Bytes = 10000 Bytes rounded down
> 80008 bits / 8 = 10001 Bytes exactly
>
> Nicely done sir!
>
> On Mon, Nov 30, 2009 at 4:00 AM, Michael McFarlin <router.genie_at_gmail.com>wrote:
>
>> Joe
>>
>> That's an interesting observation. I've never noticed this behavior before
>> either. It looks like the maximum byte-limit is 10000. I'm guessing that
>> when you give a Bc value that forces the byte-limit to over 10000 per
>> interval, it recalculates the Bc as well as the Tc. I wonder what purpose
>> this serves.
>>
>> --Here are the values I used in the map class
>>
>> map-class frame-relay FRTS
>>  frame-relay cir 1000000
>>  frame-relay bc 125000
>>
>>
>> R2# sh traffic-shape
>>
>> Interface   Se1/0
>>
>>        Access Target    Byte   Sustain   Excess    Interval  Increment
>> Adapt
>> VC     List   Rate      Limit  bits/int  bits/int  (ms)      (bytes)
>> Active
>>
>> Interface   Se1/0.23
>>
>>        Access Target    Byte   Sustain   Excess    Interval  Increment
>> Adapt
>> VC     List   Rate      Limit  bits/int  bits/int  (ms)      (bytes)
>> Active
>> 203           1000000   7875   125000    0         63        7875      -
>>
>> Notice that 7875*8 = 63000bits
>>
>>
>> -Mike McFarlin
>> router.genie_at_gmail.com
>>
>>
>>
>> On Mon, Nov 30, 2009 at 12:07 AM, Joe Astorino <jastorino_at_ipexpert.com>wrote:
>>
>>> Oh yeah and the essential: two different IOS , two different platforms...
>>>
>>> R2(config-map-class)#do sh ver | i 12.4
>>> Cisco IOS Software, 3800 Software (C3825-ADVENTERPRISEK9-M), Version
>>> 12.4(24)T1, RELEASE SOFTWARE (fc3)
>>>
>>>
>>> R5(config-if)#do sh ver | i 12.4
>>> Cisco IOS Software, 3600 Software (C3640-JK9O3S-M), Version 12.4(13a),
>>> RELEASE SOFTWARE (fc1)
>>>
>>>
>>>
>>>
>>> On Mon, Nov 30, 2009 at 3:02 AM, Joe Astorino <jastorino_at_ipexpert.com
>>> >wrote:
>>>
>>> > Has anybody seen anything like this before?  It seems the formula for
>>> how
>>> > my router is calculating Tc dynamically changes based on the given value
>>> of
>>> > Bc which I have not read about in any book or cisco doc as of yet.
>>> >
>>> >
>>> > R2(config-map-class)#do sh run int s0/1/0 | i frame-relay
>>> >  encapsulation frame-relay
>>> >  frame-relay class foo
>>> >  frame-relay traffic-shaping
>>> >  frame-relay map ip 100.100.100.5 205 broadcast
>>> >  no frame-relay inverse-arp
>>> >
>>> > R2(config-map-class)#do sh run | beg map-class
>>> > map-class frame-relay foo
>>> >  frame-relay cir 768000
>>> >  frame-relay bc 80007
>>> >
>>> > With this setup, I expect the long standing formula Tc = Bc / CIR to
>>> hold
>>> > true.  Therefore Tc should be equal to 80007 / 768000 = 0.10417578125
>>> > seconds = 104ms rounded down and indeed it is
>>> >
>>> > R2(config-map-class)#do sh traffic
>>> >
>>> > Interface   Se0/1/0
>>> >        Access Target    Byte   Sustain   Excess    Interval  Increment
>>> > Adapt
>>> > VC     List   Rate      Limit  bits/int  bits/int  (ms)      (bytes)
>>> > Active
>>> > 205           768000    10000  80007     0         104       9984      -
>>> >
>>> >
>>> > However, as soon as I cross the Bc boundary of 80007 and set it to 80008
>>> my
>>> > Tc is changed to what appears to be (Bc / CIR) / 2 !!!  WTF?
>>> >
>>> > R2(config-map-class)#do sh traffic
>>> >
>>> > Interface   Se0/1/0
>>> >        Access Target    Byte   Sustain   Excess    Interval  Increment
>>> > Adapt
>>> > VC     List   Rate      Limit  bits/int  bits/int  (ms)      (bytes)
>>> > Active
>>> > 205           768000    5000   80008     0         52        4992      -
>>> >
>>> > As you can see the Tc has been set to 52 ms which just so happens to be
>>> 1/2
>>> > of the previous value of 104ms.  Any clues?
>>> >
>>> >
>>> >
>>> >
>>> >
>>> > --
>>> > Regards,
>>> >
>>> > Joe Astorino CCIE #24347 (R&S)
>>> > Sr. Technical Instructor - IPexpert
>>> > Mailto: jastorino_at_ipexpert.com
>>> > Telephone: +1.810.326.1444
>>> > Live Assistance, Please visit: www.ipexpert.com/chat
>>> > eFax: +1.810.454.0130
>>> >
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>>> (R&S,
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>>>
>>>
>>> --
>>> Regards,
>>>
>>> Joe Astorino CCIE #24347 (R&S)
>>> Sr. Technical Instructor - IPexpert
>>> Mailto: jastorino_at_ipexpert.com
>>> Telephone: +1.810.326.1444
>>> Live Assistance, Please visit: www.ipexpert.com/chat
>>> eFax: +1.810.454.0130
>>>
>>> IPexpert is a premier provider of Classroom and Self-Study Cisco CCNA
>>> (R&S,
>>> Voice & Security), CCNP, CCVP, CCSP and CCIE (R&S, Voice, Security &
>>> Service
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>>
>>
>> --
>> Mike McFarlin
>> router.genie_at_gmail.com
>>
>
>
>
> --
> Regards,
>
> Joe Astorino CCIE #24347 (R&S)
> Sr. Technical Instructor - IPexpert
> Mailto: jastorino_at_ipexpert.com
> Telephone: +1.810.326.1444
> Live Assistance, Please visit: www.ipexpert.com/chat
> eFax: +1.810.454.0130
>
> IPexpert is a premier provider of Classroom and Self-Study Cisco CCNA (R&S,
> Voice & Security), CCNP, CCVP, CCSP and CCIE (R&S, Voice, Security & Service
> Provider) Certification Training with locations throughout the United
> States, Europe and Australia. Be sure to check out our online communities at
> www.ipexpert.com/communities and our public website at www.ipexpert.com
>
>
> Blogs and organic groups at http://www.ccie.net
>
> _______________________________________________________________________
> Subscription information may be found at:
> http://www.groupstudy.com/list/CCIELab.html
>
>
>
>
>
>
>
>
-- 
Regards,
Iwan Hoogendoorn
CCIE #13084 (R&S / Security / SP)
Sr. Support Engineer  IPexpert, Inc.
URL: http://www.IPexpert.com
Blogs and organic groups at http://www.ccie.net
Received on Mon Nov 30 2009 - 14:58:13 ART

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