# Net4sat wiki

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openbach:exploitation:reference_scenarios:network:jitter:index

## Jitter Metrology

### Context

The jitter is a metric derived from the delay (more specifically from the one-way delay). The term “jitter” is a bit equivocal in the studies and may be confusing depending on the definition chosen by the author of the paper. That's why the term “packet delay variation” should be preferred even if, in practice, “jitter” remains the most commonly used term.

Despite being widely used to assess the performance of a deployed network, this metric is most of the time not formalized. What does this metric clearly return?

RFC 3393 provides a general formalization of the metric. However, according to RFC 5481 (supported by the definition suggested by ITU-T Y.1540), two jitter metrics can be retained: packet delay variation (PDV) and inter-packet delay variation (IPDV).

• IPDV is the one-way delay difference of two consecutive packets.
• PDV is the one-way delay difference of two packets in a chosen interval considering the packet with the minimum delay in the stream as the reference. However, it may be possible to use the packet with the mean delay as reference. This definition of the jitter remains a bit hazy: most of the time, the measured jitter by a tool is IPDV.

### Objective

Several OpenBACH jobs can be compared:

• iperf3 may be a well-known tool allowing the jitter measurement. The job must be run in UDP mode to assess the jitter (IPDV). See “Rate metrology” for more information about the tool.
• owamp-server and owamp-client are two jobs returning one-way delay. A new feature has been added to the OpenBACH jobs (not the original tool) to compute IPDV and PDV. See “Delay metrology" for more information about the jobs.
• D-ITG composed of the OpenBACH jobs d-itg_send and d-itg_received is a tool generating several types of flow (UDP, TCP, ICMP or simulating VoIP flow for example). It is based on a client/server architecture and return several interesting metrics such as the one-way delay, the jitter (IPDV), the throughput and the packet loss rate.
All the proposed jobs measure the jitter using active method (meaning generating their own test flow).