how high the percentage of packet delivery rate of MQTT than CoAP?

27 Views Asked by At

I am willing to know about the comparison of the Packet delivery rate between MQTT and CoAP transmission. I know that TCP is more secure than UDP, so MQTT should have a higher Packet delivery rate. I just want to know, if 2000 packets are sent using both protocols separately what would be the approximate percentage in the two cases? Please help with an example if possible.

1

There are 1 best solutions below

0
Achim Kraus On

If you dig a little, you will find, that both, TCP and UDP, are mainly sending IP messages. And some of these messages may be lost. For TCP, the retransmission is handled by the TCP protocol without your influence. That sure works not too bad (at least in many cases). For CoAP, when you use CON messages, CoAP does the retransmission for you, so also not too much to lose.

When it comes to transmissions with more message loss (eg. bad connectivity), the reliability may also depend on the amount of data. If it fits into one IP message, the probability that this reaches the destination is higher, than 4 messages reaching their destination. In that situation the difference starts: Using TCP requires, that all the messages are reaching the destination without gaps (e.g. 1,2, (drop 3), 4 will not work). CoAP will deliver the messages also with gaps. It depends on your application, if you can benefit from that or not.

I've been testing CoAP over DTLS 1.2 (Connection ID) for mostly a year now using a Android phone and just moving around sending request (about 400 bytes) with wifi and mobile network. It works very reliable. Current statistic: 2000 request, 143 retransmissions, 4 lost. Please note: 4 lost mainly means "no connection", so be sure, using TCP will have results below that, especially when moving around and frequently new TCP/TLS handshakes get required.

So my conclusion: If you have a stable network connection, both should work. If you have a less stable network connection and gaps are not acceptable by your application, both have trouble. If you have a less stable network connection and gaps are acceptable by your application, then CoAP will do a better job.