RCP is remote copy protocol and it is used to copy files without creating an FTP/TFTP session or logging into a remote system explicitly. To use the RCP command though, you must have every system you intend to use as a source in your .rhosts file.
RCP is a command on the Unix operating systems that is used to remotely copy -- to copy one or more files from one computer system to another. It typically uses the TCP/IP protocol and the .rhosts file for authentication, but has been implemented to alternatively support Kerberos.
Most say that the rcp protocol is not secure for network use, because it sends unencrypted information over the network, among other things. It has largely been replaced by the ssh-based utility scp.
Some details of TFTP:
-It uses UDP port 69 as its transport protocol (unlike FTP which uses TCP port 21).
-It cannot list directory contents.
-It has no authentication or encryption mechanisms.
-It is used to read files from, or write files to, a remote server.
-It supports three different transfer modes, "netascii", "octet" and "mail", with the first two corresponding to the "ASCII" and "image" (binary) modes of the FTP protocol; the third is now obsolete and is rarely used.
-The original protocol has a file size limit of 32 MB, although this was extended when RFC 2347 introduced block-size negotiation in 1998 (allowing a maximum of 4 GB and potentially higher throughput). If the server and client support block number wraparound, file size is essentially unlimited.
Since TFTP utilizes UDP, it has to supply its own transport and session support. Each file transferred via TFTP constitutes an independent exchange. That transfer is performed in lock-step, with only one packet (either a block of data, or an 'acknowledgement') ever in flight on the network at any time. Due to this lack of windowing, TFTP provides low throughput over high latency links.
Due to the lack of security, it is dangerous over the open Internet. Thus, TFTP is generally only used on private, local networks.
