ICMP Jitter Test

Implementation Principle

An Internet Control Message Protocol (ICMP) jitter test calculates the delay, jitter, and packet loss rate using timestamps carried in ICMP packets. The jitter time is the interval for receiving two consecutive packets minus the interval for sending them. Figure 1 shows the ICMP jitter test process.

Figure 1 Networking diagram of an ICMP jitter test

Source (Device A) adds timestamp t1 to an ICMP packet and sends the packet to Destination (Device B).
Upon receipt of the packet, Destination (Device B) adds timestamp t1' to the packet.
After processing the packet, Destination (Device B) adds timestamp t2' to the packet and forwards it back to Source (Device A).
Upon receipt of the packet, Source (Device A) adds timestamp t2 to the packet. (Timestamps t3/t3' and t4/t4' are similar.)

The NQA source can calculate the following indexes:

Maximum, minimum, and average jitter of the packets from the source to the destination and from the destination to the source.
Maximum one-way delay time of the packets that the source sends to the destination or the destination sends to the source.

The data obtained is used to evaluate the network status.

Related Concepts

An ICMP jitter test can measure jitter either unidirectionally or bidirectionally:

Source-to-destination jitter = (t3' – t1') – (t3 – t1)

A larger absolute jitter value indicates poorer link quality, no matter whether the jitter value is positive or negative.
Destination-to-source jitter = (t4 – t2) – (t4' – t2')

A larger absolute jitter value indicates poorer link quality, no matter whether the jitter value is positive or negative.

RTT = (t2 – t1) – (t2'- t1')

If the RTT is longer than the specified timeout period, the network is congested and ICMP packets will be counted as lost packets.

Packet loss rate = Number of lost ICMP packets/Number of sent ICMP packets (Number of lost ICMP packets = Number of sent ICMP packets – Number of received ICMP packets).

In an ICMP jitter test, you can set the number of packets to be sent consecutively in a single test instance to simulate a certain type of traffic.

Hardware-based ICMP Jitter Test

A hardware-based ICMP jitter test, a supplement to the ICMP jitter test, enables the hardware forwarding engine to transmit packets and add timestamps to packets. The hardware-based ICMP jitter test has the following advantages:

Reduces the interval at which packets are sent. The minimum interval is 10 ms.
Increases the number of concurrent test instances. To increase the number of concurrent test instances, install more interface boards on a device.
Increases the accuracy of the calculated delay and jitter time.

The source can calculate the following indexes:

Maximum, minimum, and average jitter values of the packets exchanged between the source and destination
Maximum one-way delay time of the packets that the source sends to the destination or the destination sends to the source

The obtained jitter value reflects the network status.

**Table 1** Differences between the ICMP jitter test and hardware-based ICMP jitter test
Item	ICMP Jitter	ICMP Jitter (hardware-based)
Minimum interval at which test packets are sent	20 ms	10 ms
Maximum number of concurrent test instances	100 concurrent test instances on each device	The number of concurrent test instances increases with the number of boards.
Jitter calculation	The main control board timestamps packets.	The interface board timestamps packets more precisely.

ICMP Jitter (receive-timestamp-unit)

ICMP jitter (receive-timestamp-unit) is a supplement to the ICMP jitter (hardware-based). It also uses the hardware forwarding engine to send packets and add timestamps for the interconnection with a non-Huawei device that functions as a destination (server).

Compared with ICMP jitter (hardware-based), ICMP jitter (receive-timestamp-unit) has the following differences:

ICMP jitter (receive-timestamp-unit) supports the interconnection with a non-Huawei device that functions as a destination (server). ICMP jitter (hardware-based) supports the interconnection with a Huawei device that functions as a destination (server) only.
To parse the timestamp of the ICMP timestamp packet returned by the destination (server), ICMP jitter (receive-timestamp-unit) uses the user-configured timestamp precision while ICMP Jitter (hardware-based) uses the timestamp precision negotiated between the source (client) and the destination (server).