A router is connected to an HDLC circuit via a T1 physical interface. The SLA for this link only allows for a sustained rate of 768 kb/s. Bursts are allowed for up to 30 seconds at up to line rate…

Question

Options

• ABe = 46320000 , Bc = 96000
• BBe = ,768000 Bc = 32000
• CBe = ,128000 Bc = 7680
• DBe = ,0 Bc = 96000

• A
  69% (38)
• B
  7% (4)
• C
  18% (10)
• D
  5% (3)

Explanation

Bursts are allowed for 30 seconds Seconds * Bandwidth in bps = Be 30 * 1544000 = Be 30 * 1544000 = 46320000 Traffic Shaping Parameters We can use the following traffic shaping parameters: CIR = committed information rate (= mean time) EIR = excess information rate TB = token bucket (= Bc + Be) Bc = committed burst size (= sustained burst size) Be = excess burst size DE = discard eligibility Tc = measurement interval AR = access rate corresponding to the rate of the physical interface (so if you use a T1, the AR is approximately 1.5 Mbps). Committed Burst Size (Bc) The maximum committed amount of data you can offer to the network is defined as Bc. Bc is a measure for the volume of data for which the network guarantees message delivery under normal conditions. It is measured during the committed rate Tc. Excess Burst Size (Be) The number of non-committed bits (outside of CIR) that are still accepted by the Frame Relay switch but are marked as eligible to be discarded (DE). The token bucket is a 'virtual' buffer. It contains a number of tokens, enabling you to send a limited amount of data per time interval. The token bucket is filled with Bc bits per Tc. The maximum size of the bucket is Bc + Be. If the Be is very big and, if at T0 the bucket is filled with Bc + Be tokens, you can send Bc + Be bits at the access rate. This is not limited by Tc but by the time it takes to send the Be. This is a function of the access rate. Committed Information Rate (CIR) The CIR is the allowed amount of data which the network is committed to transfer under normal conditions. The rate is averaged over a increment of time Tc. The CIR is also referred to as the minimum acceptable throughput. Bc and Be are expressed in bits, Tc in seconds, and the access rate and CIR in bits per second. Bc, Be, Tc and CIR are defined per data-link connection identifier (DLCI). Due to this, the token bucket filter controls the rate per DLCI. The access rate is valid per user-network interface. For Bc, Be and CIR incoming and outgoing values can be distinguished. If the connection is symmetrical, the values in both directions are the same. For permanent virtual circuits, we define incoming and outgoing Bc, Be and CIR at subscription time. Peak = DLCI's maximum speed. The bandwidth for that particular DLCI. Peak = CIR + Be/Tc = CIR (1 + Be/Bc) If the Tc is one second then: Peak = CIR + Be = Bc + Be

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