FRTS - Tc calculation?

[DAVIDE RENDINIELLO]

The document CISCO "Configuring Frame Relay Traffic Shaping" [doc ID. 6151] said:

Tc = BC/CIR

So if I have configured:

CIR= 256000

BC = 32000

Tc = 0.125

Why if I have configured:

CIR= 768000

BC = 96000

Tc = 0.125 .... but the output is : 0.063 ???

See the example below:

DEPOSGMIA1#sh frame-relay pvc interface serial 1/1.1 17

PVC Statistics for interface Serial1/1.1 (Frame Relay DTE)

DLCI = 17, DLCI USAGE = LOCAL, PVC STATUS = ACTIVE, INTERFACE = Serial1/1.1

input pkts 2709191 output pkts 3500453 in bytes 407344171

out bytes 925065916 dropped pkts 0 in FECN pkts 0

in BECN pkts 0 out FECN pkts 0 out BECN pkts 0

in DE pkts 31509 out DE pkts 0

out bcast pkts 123491 out bcast bytes 17259184

5 minute input rate 1000 bits/sec, 3 packets/sec

5 minute output rate 13000 bits/sec, 4 packets/sec

pvc create time 6w1d, last time pvc status changed 4w1d

cir 256000 bc 32000 be 0 byte limit 4000 interval 125

mincir 64000 byte increment 4000 Adaptive Shaping none

pkts 322910 bytes 91004359 pkts delayed 1700 bytes delayed 2070898

shaping inactive

traffic shaping drops 0

Queueing strategy: fifo

Output queue 0/40, 0 drop, 1700 dequeued

DEPOSGMIA1#sh frame-relay pvc interface serial 1/1.1 18

PVC Statistics for interface Serial1/1.1 (Frame Relay DTE)

DLCI = 18, DLCI USAGE = LOCAL, PVC STATUS = ACTIVE, INTERFACE = Serial1/1.1

input pkts 24766760 output pkts 24344877 in bytes 1841649012

out bytes 1300144560 dropped pkts 866 in FECN pkts 0

in BECN pkts 0 out FECN pkts 0 out BECN pkts 0

in DE pkts 86348 out DE pkts 0

out bcast pkts 124526 out bcast bytes 17398936

5 minute input rate 4000 bits/sec, 4 packets/sec

5 minute output rate 41000 bits/sec, 27 packets/sec

pvc create time 6w1d, last time pvc status changed 1w4d

cir 768000 bc 96000 be 0 byte limit 6048 interval 63

mincir 256000 byte increment 6048 Adaptive Shaping none

pkts 2915173 bytes 760239306 pkts delayed 56720 bytes delayed 46797325

shaping inactive

traffic shaping drops 0

Queueing strategy: fifo

Output queue 0/40, 857 drop, 56720 dequeued

[Georg Pauwen]

Hello,

this is because for speeds below 650kbps the Bc value defaults to 1/8 of the configured CIR. For speeds above 650kbps the value defaults to about 1/16 of CIR.

Check out this document for a very good explanation of FRTS:

http://www.internetworkexpert.com/resources/01700368.htm

Regards,

Georg

[DAVIDE RENDINIELLO]

Hello,

I thank you for your wonderful document.

I have verified the parameters indicates and I have verified that with a CIR of 1.5Mbps the TC it is become stabilized to 0.032 second ones.

I have moreover noticed that the router it does not allow to have a byte increment over to 10KByte.

Therefore I have two questions:

1 - Exists a table that indicates the values of default of the Tc based on the configured CIR?

2 - If the configured BC is of 1,280kbps, but BYTE LIMIT is 10KByte, how much is the credit allowed in every timeslot?