Cisco IOS IP SLA Responder is a Cisco IOS Software component whose functionality is to respond to Cisco IOS IP SLA request packets. The IP SLA source sends control packets before the operation starts to establish a connection to the responder. Once the control packet is acknowledged, test packets are sent to the responder. The responder inserts a time-stamp when it receives a packet and factors out the destination processing time and adds time-stamps to the sent packets. This feature allows the calculation of unidirectional packet loss, latency, and jitter measurements with the kind of accuracy that is not possible with ping or other dedicated probe testing.
Reference:
https://www.cisco.com/en/US/technologies/tk869/tk769/technologies_white_paper0900aecd806bf b52.html The IP SLAs responder is a component embedded in the destination Cisco device that allows the system to anticipate and respond to IP SLAs request packets. The responder provides accurate measurements without the need for dedicated probes.
Reference: https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst4500/12-
2/46sg/configuration/guide/Wrapper-46SG/swipsla.html
UDP Jitter measures the delay, delay variation(jitter), corruption, misorderingand packet lossby generating periodic UDP traffic. This operation always requires IP SLA responder.
Reference: https://www.ciscolive.com/c/dam/r/ciscolive/us/docs/2017/pdf/BRKNMS-3043.pdf