Refer to the exhibit. When applying this hierarchical policy map on the on the tunnel1 interface,
you measure high jitter for traffic going through class 1234. What is the most likely cause of this
jitter?
A.
The configuration of a hierarchical policy map on a tunnel interface is not supported.
B.
Class 5555 and class 5554 are both taking up 100% of the bandwidth, leaving nothing for class
1234.
C.
The burst size for the traffic shaping is wrongly configured to 15000; this would require an
interface capable of sending at 150Mb/s.
D.
The burst size for the traffic shaping has been wrongly configured; it should be set as low as
possible.
E.
The burst size for the traffic shaping has been wrongly configured; it should be set as high as
possible.
Explanation:
Displaying Interleaving Statistics
To display interleaving statistics, use the following command in EXEC mode:
What Is a Token Bucket?
A token bucket is a formal definition of a rate of transfer. It has three components: a burst size, a
mean rate, and a time interval (Tc). Although the mean rate is generally represented as bits per
second, any two values may be derived from the third by the relation shown as follows:
mean rate = burst size / time interval
Here are some definitions of these terms:
Mean rate—Also called the committed information rate (CIR), it specifies how much data can be
sent or forwarded per unit time on average.
Burst size—Also called the Committed Burst (Bc) size, it specifies in bits (or bytes) per burst how
much traffic can be sent within a given unit of time to not create scheduling concerns. (For a
shaper, such as GTS, it specifies bits per burst; for a policer, such as CAR, it specifies bytes per
burst.)
Time interval—Also called the measurement interval, it specifies the time quantum in seconds per
burst.
By definition, over any integral multiple of the interval, the bit rate of the interface will not exceed
the mean rate.
The bit rate, however, may be arbitrarily fast within the interval.
A token bucket is used to manage a device that regulates the data in a flow. For example, the
regulator might be a traffic policer, such as CAR, or a traffic shaper, such as FRTS or GTS. A
token bucket itself has no discard or priority policy. Rather, a token bucket discards tokens and
leaves to the flow the problem of managing its transmission queue if the flow overdrives the
regulator. (Neither CAR nor FRTS and GTS implement either a true token bucket or true leaky
bucket.)
In the token bucket metaphor, tokens are put into the bucket at a certain rate. The bucket itself has
a specified capacity. If the bucket fills to capacity, newly arriving tokens are discarded. Each token
is permission for the source to send a certain number of bits into the network. To send a packet,
the regulator must remove from the bucket a number of tokens equal in representation to the
packet size.
If not enough tokens are in the bucket to send a packet, the packet either waits until the bucket
has enough tokens (in the case of GTS) or the packet is discarded or marked down (in the case of
CAR). If the bucket is already full of tokens, incoming tokens overflow and are not available to
future packets. Thus, at any time, the largest burst a source can send into the network is roughlyproportional to the size of the bucket.
Note that the token bucket mechanism used for traffic shaping has both a token bucket and a data
buffer, orqueue; if it did not have a data buffer, it would be a policer. For traffic shaping, packets
that arrive that cannot be sent immediately are delayed in the data buffer.
For traffic shaping, a token bucket permits burstiness but bounds it. It guarantees that the
burstiness is bounded so that the flow will never send faster than the token bucket’s capacity,
divided by the time interval, plus the established rate at which tokens are placed in the token
bucket. See the following formula: (token bucket capacity in bits / time interval in seconds) +
established rate in bps = maximum flow speed in bps This method of bounding burstiness also
guarantees that the long-term transmission rate will not exceed the established rate at which
tokens are placed in the bucket.
Recommended Burst Values Cisco recommends the following values for the normal and extended
burst parameters: normal burst = configured rate * (1 byte)/(8 bits) * 1.5 seconds
extended burst = 2 * normal bursthttp://www.cisco.com/en/US/docs/ios/12_2/qos/configuration/guide/qcfpolsh.html