Dear Bardia Safaei,

the ETX Metric - as well as PDR - can serve as a measure of link reliability.

According to RFC 6687:

Expected Transmission Count (ETX Metric): The expected number of

transmissions to reach the next hop is determined as the inverse

of the link PDR (Packet Delivery Ratio). Consequently, in every hop, if the link quality (PDR) is high, the expected number of transmissions to reach the

next hop may be as low as 1. However, if the PDR for the

particular link is low, multiple transmissions may be needed.

See also Fig. 008364 at the address:

https://www.researchgate.net/publication/320244798_RPL_-_IPv6_Routing_Protocol_for_LLNs

Best regards

Anatol Badach

Thank you dear Anatol

Actually, the ETX is based on the PDR. The goal of my question is to get familiar with independent types of metrics.

Dear Bardia,

maybe this address can help:

https://www.researchgate.net/publication/326960652_RPL_Routing_Metrics_and_Constraints

Best regards

Anatol Badach

Thank you