Transaction Ingress (TPU)

TPU is the main protocol to submit new transactions to the Solana network.

Each Firedancer block producer exposes a TPU server accepting transactions via the TPU-UDP and TPU-QUIC APIs.

Incoming transactions enter the "leader pipeline", where they are verified, deduplicated, and ordered for inclusion in blocks produced by the validator.

The TPU APIs are provided by the quic tile.

UDP port numbers

UDP port numbers are configurable by the validator operator. Clients should use gossip to discover the TPU endpoints of a block producer.

The default UDP port numbers are 9001 (TPU-UDP), 9007 (TPU-QUIC).

Connection Table

Firedancer's TPU-QUIC server supports up to one million connections per quic tile.

The network stack automatically load balances connections across multiple QUIC tiles.

Receive limits

Firedancer does not apply receive limits for TPU-QUIC nor TPU-UDP.

API reference

TPU-QUIC uses a connection-oriented transport featuring loss detection, TCP-like retransmission, and acknowledgements. This is the recommended transport protocol.

TPU-UDP is a minimal connection-less ingress protocol. Useful for fire-and-forget clients that optimize for tail latency.

Packet capture

TPU-QUIC connections are encrypted.

By default, the quic tile does not log or otherwise export encryption keys.

To decrypt TPU-QUIC flows in a .pcap file, an external file created by [tiles.quic.ssl_key_log_file] is required.

Due to a limitation in the SSLKEYLOGFILE format, QUIC decryptions can only be decrypted if the full QUIC handshake was captured.

The Wireshark plugin solana_dissector helps view and extract transactions from captured and decrypted QUIC flows.