test

		std::map<uint64_t, uint64_t> _pending_max_stream_data;

		// ---- Congestion Control (NewReno, RFC 9002) ----

		uint64_t _cwnd = 10 * 1024 * 1024;         // 10MB initial cwnd (aggressive start)

		// RFC 9002 §7.2: kInitialWindow = min(10*max_datagram_size,

		// max(2*max_datagram_size, 14720)). The previous 10MB value

		// bypassed congestion control entirely for any transfer under

		// ~10MB, letting the sender burst far more data than the kernel's

		// UDP receive buffer (already maxed out at this host's

		// net.core.rmem_max of 4MB) can hold — measured 10,502 real

		// kernel-level RcvbufErrors (genuine packet loss, confirmed via

		// /proc/net/snmp) in one benchmark run, which in turn drove

		// spurious PACKET_THRESHOLD retransmissions.

		uint64_t _cwnd = std::min<uint64_t>(10 * _max_udp_payload,

		                                     std::max<uint64_t>(2 * _max_udp_payload, 14720));

		uint64_t _ssthresh = UINT64_MAX;           // slow start threshold

		uint64_t _bytes_in_flight = 0;             // unacknowledged bytes

		static constexpr uint64_t MIN_CWND = 2 * 1472; // minimum cwnd (2 * MTU)