TFTP protocol port 69 UDP or TCP

TFTP is a very simple file transfer protocol.copy files across a network

TFTP is UDP  based port 69

TFTP server and port 69 UDP or TCP or Both

TFTP is udp based so there is no need for the deny tcp statement.

TFTP is using for PXE boot

Due to its simple design, TFTP could be implemented using a very small amount of memory. It is therefore useful for booting computers such as routers which may not have any data storage devices. It is an element of the Preboot Execution Environment (PXE) network boot protocol, where it is implemented in the firmware ROM / NVRAM of the host’s network card.

 

Abbreviation of Trivial File Transfer Protocol, a simple form of the File Transfer Protocol (FTP). TFTP uses the User Datagram Protocol (UDP)and provides no security features. It is often used by servers to bootdiskless workstations, X-terminals, and routers.

The initiating client host sends either an RRQ (read request) or WRQ (write request) packet, containing the filename and the transfer mode.
The server responds to a received DATA packet with an ACK (acknowledgement) packet if it receives a WRQ message and with a DATA packet if it received an RRQ message (this also indicates the ports in use to the client).
The sending host then sends numbered DATA packets to the destination host after receiving each ACK message. All but the last message contains a full-sized block of data. The destination host replies with numbered ACK packets for each received DATA packet. This forms a simple ARQ protocol, providing retransmission when a packet is lost.
The final DATA packet must contain less than a full-sized block of data (including possibly zero bytes) to indicate that it is the last block of the transfer.

This data transfer is performed in lockstep. Only one packet (either a block of data, or an ‘acknowledgement’) is ever in flight on the network at any time. Due to this lack of windowing, TFTP has a low throughput over high latency (delay) links.