Refer to the exhibit. When applying this policy map on the tunnel1 interface, you see packet loss for the TCP class starting at around 100000 b/s, instead of the configured 150000 b/s.
What is the most likely cause of the discrepancy?
A.
The violate-action command should not be configured.
B.
The current configuration of the load-interval command on the tunnel interface is preventing proper policing calculations.
C.
The burst size is too low.
D.
Policing on tunnel interfaces is not supported.
E.
The CIR keyword is missing in the policer.
Explanation:
Network Jitter and Delay
Real-time voice communications are sensitive to delay and variation in packet arrival times.
Codecs require a steady, dependable stream of packets to provide reasonable playback
quality. Packets arriving too early, too late, or out of sequence result in jerky, jumbled
playback. This phenomenon is called jitter. Increasing jitter buffer size can help, but only to a point.
Because no network can guarantee a perfectly steady stream of packets under real-world
conditions, VoIP phones use jitter buffers to smooth out the kinks. A jitter buffer is simply a
First-In, First Out (FIFO) memory cache that collects the packets as they arrive, forwarding
them to the codec evenly spaced and in proper sequence for accurate playback.
While a jitter buffer can successfully mask mild delay and jitter problems, severe jitter can
overwhelm the jitter buffer, which results in packet loss (see below). Increasing the size of
the jitter buffer can help, but only to a point: A jitter buffer that increases overall round-trip
delay to 300 ms will make normal conversation difficult.
Packet Loss
As mentioned above, packet loss can be the result of the jitter buffer being overwhelmed.
Other reasons include landline media failure and poor wireless signal quality. The latter can
be a big problem with VoFi (Voice over WiFi) service. Regardless of the source, VoIP phones
and gateways attempt to conceal this type of signal degradation by duplicating packets to fill
in the missing data. As with jitter, these techniques can maintain voice quality only to a point.
Packet loss on data networks has long been characterized as a bursty phenomenon,
which is another way of saying it never rains, it pours. Networks tend to either sporadically
drop single packets (these periods are called gaps in packet loss), or large numbers of
contiguous packets in a burst. Packet loss concealment techniques typically have no
problem handling packet loss during gap periods; it is the sustained bursts you must watch
out for.