Re: FRTS Default Bc value

Hello Brian,
Thank you very much for your quick response. The cosmetic bug does bring my
sanity back :)

So just so I'm clear. The "show frame-relay pvc xxx" command will display
the incorrect values in the Bc field, but will show it correctly in the
byte increment field? Is that the field I can rely on using that command?
The same cosmetic bug will be displayed with the "show traffic-shape" when
looking under the Sustained bits/int field, correct?

In terms of the Be, if you don't configure the Bc value (only CIR), the IOS
it will always default to Be = CIR/8, but that's not the ideal value when
configuring shaping for high speed interface especially with voip. Is that
a correct statement?

Basically, my other question relates to the default value that IOS sets.
This default value does not change with higher interface speed, but should
be configured manually differently. Is that also a correct statement?

Thank you

Tom

On Sun, Apr 1, 2012 at 10:07 PM, Brian McGahan <bmcgahan_at_ine.com> wrote:

> Hi Tom,
>
> This is a cosmetic bug in legacy FRTS. If you apply the same policy in
> MQC you'll see the correct Bc value reflected. Also the Bc isn't always
> the CIR/8. As the CIR goes up the router needs more intervals per second
> in order for the shaper to achieve the desired rate. For low speed CIR
> values you will see that Bc = CIR/8, but as CIR goes up this is not true.
> What would be more accurate would be to say that the CIR in Bits / Second
> = Bc in Bits / Tc milliseconds, or in other words that Bc = CIR/1000 * Tc,
> since Bc is expressed in milliseconds as opposed to seconds. This formula
> always stays true as the CIR goes up or down, or if you manually change the
> Bc.
>
>
> HTH,
>
> Brian McGahan, CCIE #8593 (R&S/SP/Security)
> bmcgahan_at_INE.com
>
> Internetwork Expert, Inc.
> http://www.INE.com
>
>
> -----Original Message-----
> From: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] On Behalf Of
> Tom Kacprzynski
> Sent: Sunday, April 01, 2012 9:51 PM
> To: Cisco certification
> Subject: FRTS Default Bc value
>
> Hello,
> I ran into an output of a FRTS show command that contradicts what I know
> so far and figure ask the experts to see where is the disconnect.
>
> Based on what I know and the Enterprise QoS SRND, the Bc value by default
> should be set to Bc= CIR/8.
> If I configure traffic shaping on an FR interface I see that bc on my DCLI
> 205 is set to 7000 bits (which is correct) :
>
> Rack1R2#sh frame-relay pvc 205
>
> PVC Statistics for interface Serial0/0/0 (Frame Relay DTE)
>
> DLCI = 205, DLCI USAGE = LOCAL, PVC STATUS = ACTIVE, INTERFACE =
> Serial0/0/0
>
> input pkts 275289 output pkts 125138 in bytes 20715768
> out bytes 12816805 dropped pkts 0 in pkts dropped 0
> out pkts dropped 0 out bytes dropped 0
> in FECN pkts 0 in BECN pkts 0 out FECN pkts 0
> out BECN pkts 0 in DE pkts 0 out DE pkts 0
> out bcast pkts 13544 out bcast bytes 1013448
> 5 minute input rate 1000 bits/sec, 1 packets/sec
> 5 minute output rate 1000 bits/sec, 1 packets/sec
> pvc create time 2d10h, last time pvc status changed 00:01:48
> cir 56000 * bc 7000 * be 0 byte limit 875 interval 125
> <-------------------bc 7000
> mincir 28000 byte increment 875 Adaptive Shaping none
> pkts 135 bytes 15363 pkts delayed 0 bytes delayed 0
> shaping inactive
> traffic shaping drops 0
> Queueing strategy: fifo
> Output queue 0/40, 0 drop, 0 dequeued
>
>
> Now if I apply a map-class with cir of 256,000 I don't see what I would
> expect, which is the Bc to be set to 32,000 but rather the Bc is set to
> 256,000. This does not make much sense to me especially that when I look at
> show traffic-shape the Tc is still set to .125sec.
>
> map-class frame-relay FRTS
> frame-relay cir 256000
>
>
> interface Serial0/0/0
> ip address 136.1.245.2 255.255.255.0
> encapsulation frame-relay
> no fair-queue
> frame-relay class FRTS
> frame-relay traffic-shaping
> frame-relay map ip 136.1.245.5 205 broadcast no frame-relay inverse-arp
> end
>
>
> Rack1R2#sh frame-relay pvc 205
>
> PVC Statistics for interface Serial0/0/0 (Frame Relay DTE)
>
> DLCI = 205, DLCI USAGE = LOCAL, PVC STATUS = ACTIVE, INTERFACE =
> Serial0/0/0
>
> input pkts 107 output pkts 0 in bytes 9918
> out bytes 0 dropped pkts 0 in pkts dropped 0
> out pkts dropped 0 out bytes dropped 0
> in FECN pkts 0 in BECN pkts 0 out FECN pkts 0
> out BECN pkts 0 in DE pkts 0 out DE pkts 0
> out bcast pkts 0 out bcast bytes 0
> 5 minute input rate 1000 bits/sec, 1 packets/sec
> 5 minute output rate 0 bits/sec, 0 packets/sec
> pvc create time 00:01:04, last time pvc status changed 00:01:04
> cir 256000 *bc 256000* be 0 byte limit 4000 interval 125
> <<--------------bc 256,000
> mincir 128000 byte increment 4000 Adaptive Shaping none
> pkts 0 bytes 0 pkts delayed 0 bytes delayed 0
> shaping inactive
> traffic shaping drops 0
> Queueing strategy: fifo
> Output queue 0/40, 0 drop, 0 dequeued
>
> Does anyone have any idea where the disconnect is?
>
> Thank you,
>
> Tom
>
>
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Received on Sun Apr 01 2012 - 22:56:10 ART