Traffic shaping question

Hi,
this TS topic sometimes confuse me so I will ask you, experts, on one task:

"The FR link speed should target a transmission rate of 512 kbps
although the service provider does allow bursting to port speed (1536
Mbps). BECNs shouldn't be processed."

OK. Let say we have FR p2p between two routers. So let see if I get this:
Traffic is always send out of queue at interface speed (clock rate).
So in this task Tc is not mentioned and it should stay 125 ms? If
Tc=125ms, that means in each Tc interval serial interface can send max
192 kbps for sending at full int speed. To achieve CIR=512 kbps, at
each Tc interval, interface should send Bc= 64 kbps, which means that
in takes around 42 msec to send Bc amount of traffic and we have
around 83 msec in every Tc which can be utilized by excess burst.
Right?
Now we come to excess burst. Since the task says "service provider
does allow bursting to port speed", does that mean that at each Tc
interval we can send Bc+Be, where Be=AIR/8 - Bc = 128 kbps?
Theoretically, we can burst non stop to interface speed in this task
and achieve speed of T1 here? What is correlation between this burst
in this task and the Be in tasks where there is only average shaping
put as task? If the task didn't mention "provider allows burst" should
I still need to configure Be? Not for the purpose of bursting till
interface speed, just for burst if there was periods of inactivity
with Bc over interval.
The term "excess bursting". Is it only used for bursts while there was
time of inactivity with Bc traffic so that the average speed over 1
sec at the end should not be more than CIR?

I have two configuration solutions and could you tell me are those
solution doing same thing:

1) map-class frame-relay SHAPE
     frame-relay cir 512000
     frame-relay bc 64000
     frame-relay be 128000
   int s1/0.1
     frame-relay interface-dlci 204
        class SHAPE

2) policy-map SHAPE
      class class-default
      shape average 512000 64000 128000
   int s1/0.1
      service-policy output SHAPE

In solution 1) frame-relay cir ? says:
R4(config-map-class)#frame-relay cir ?
  <1-45000000> Applied to both Incoming/Outgoing CIR, Bits per second
  in Incoming CIR
  out Outgoing CIR

If shaping is only egress process why command frame-relay cir allows
IN and OUT direction?

Thanks.

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Received on Mon Jun 04 2012 - 03:19:46 ART