ICMP in OpenThread

[Roger]

Hi All,

Can one safely assume when sending a packet to a destination address using the ping command in the CLI, that the payload echoed back is the payload transmitted initially?

[Krzysztof Loska]

Hi Roger,

Yes, this assumption is true. To be even more precise, when you send Echo Request packet using CLI, a timestamp is attached as the payload. Look into cli.cpp file line 1599 - method ProcessPing() calls method HandlePingTimer() to do that. Echo Replay sends the payload back. For reference look into icmp6.cpp file line 185 - HandleEchoRequest() method.

Best regards,

Krzysztof

[Roger]

Hi Krzysztof,

Thank you very much for the detailed answer. I've also noticed the ThreadError otIcmp6SendEchoRequest(otInstance* aInstance,otMessage* aMessage, const otMessageInfo* aMessageInfo,uint16_t aIdentifier) function in the API which I will adapt to my needs.

While I was sending ICMP echo request (10 bytes per second for 1000 iterations) from the CLI, I noticed that some sequence numbers displayed on the CLI was skipped. I'm thinking that these must be packets that got lost during transmission and weren't acknowledged by the sender.

Best regards,

Roger