No `NSTART` parameter in TCP transport

[dvn0]

Latency between client and server appears to negatively impact throughput when using the TCP transport. After some discussion, and testing I think allowing for adjusting the NSTART parameter could improve the situation.

It's implemented in the UDP client, but not TCP.

go-coap/udp/client/conn.go

Line 168 in 51f2671

nStart *atomic.Uint32

[jkralik]

@dvn0 When CoAP is used over TCP, it relies on the congestion control mechanisms provided by the underlying TCP transport layer. TCP itself has well-established congestion control algorithms, and CoAP benefits from these without introducing specific congestion control parameters like "Nstart."

If you employ BlockWise transfer via TCP, it becomes a bottleneck. However, for TCP, BlockWise transfer is unnecessary for large payloads.

[dvn0]

Thank you for the response and info @jkralik. I followed your advice and disabled the blockwise transfer, but this actually incurred a significant throughput penalty.

I think I'm disabling it correctly: https://codeberg.org/eris/eris-go/commit/870f6471c0076dcf820a45bdd897a3cb97198b42

Any ideas?