Significance Of Jitter; Solution Components - HP Aruba JL253A Management And Configuration Manual

The above diagram shows a typical deployment, where voice & video traffic are exchanged between branch
offices of an enterprise over the backbone network. Assessment of the network readiness is always helpful for
hosting such services. Parameters like RTT, Jitter and one way delay are a good indicator of network health which
assist a network administrator to diagnose latency related issues in the network. VoIP traffic is generally sensitive
to delays in the network.
Jitter stands for inter-packet delay variance. If the inter-packet delay increases between successive probe
packets, jitter is said to be positive. If the inter-packet delay decreases, jitter is said to be negative. Positive jitter
values are undesirable for a network as they indicate increased latencies. A value of 0 jitter is desirable.

Significance of jitter

Consider a media player which plays video streams from a server. Assume that packets take 1 second in flight to
reach the media player. This means the moment a user requests a video from the server, the very first packet will
arrive after one second and successive packets will be sent immediately (ideally). In real world scenarios,
intermediate node latencies, different return paths for different packets and network congestion can contribute to
varying delays. To counter such effects, packets are buffered at the media player. The amount of packet buffering
needed can be derived from the jitter values.
NOTE: The above analogy is applicable for other voice & video services and can be a good measure
to assess the possibility for hosting a service on a network.

Solution components

IP SLA responder
This device receives IP SLA probe packets from a configured initiator, timestamps the frame at a pre-defined
location in the packet upon receipt and sends the same frame back to the initiator.
IP SLA initiator
This device initiates IP SLA probe packets to multiple destinations each with a certain user configurable packet
content and periodicity.
The initiator timestamps the frame at a pre-defined location before sending the frame out to the configured
destinations and re-timestamps the frame at a different location once it receives the same back from the
responder.
Chapter 17 IP Service Level Agreement 605