protocol: ByteString,
      host: String,
      port: Int,
      maxAge: Long,
    ) {
      // TODO: register alternate service.
    }
  }

  /** Even, positive numbered streams are pushed streams in HTTP/2. */
  internal fun pushedStream(streamId: Int): Boolean = streamId != 0 && streamId and 1 == 0

  internal fun pushRequestLater(
    streamId: Int,
    requestHeaders: List<Header>,
  ) {