![]() TFTP is a cut-down version of FTP, designed so that a TFTP server can be hosted within a device such as a router without requiring excessive processing and memory resources. TFTP was designed as a lightweight file transfer mechanism primarily used for transferring short configuration files to routers and other devices, typically over a short dedicated link or at least within a LAN environment. ![]() ![]() 3.5.4.1 Higher-Layer Protocols That Use UDP as a Transport Protocol UDP is a low-latency protocol as it does not require that a connection be set up and does not wait for acknowledgments. UDP does not send any handshaking messages, further reducing bandwidth usage when compared with TCP. UDP uses less network bandwidth because it has a smaller header (8 bytes compared with TCP's 20 bytes) as it does not have to carry the additional control information that TCP needs. UDP incurs significantly lower overheads than its transport layer counterpart TCP does. The concept of idempotent commands is discussed in Chapter 6, but to give a simple example, the command “add ten pounds to account number 123” is not idempotent, while the command “set the balance of account number 123 to thirty pounds” is. If UDP datagrams carry commands in the application information flow, then it is highly recommended that the commands are designed to be idempotent that is, they are designed to be repeatable without having side effects. Thus, if an application is sensitive to the receipt of duplicate data, then additional support to detect this must be designed in to the application itself. Without sequence numbers, it is also not possible for the receiver to know if a datagram has been duplicated during transmission across the network and thus received twice or more as far as UDP is concerned, these are all different datagrams. The order in which UDP datagrams are received is not guaranteed to be the same as the order in which they were sent because of the lack of sequence numbers. ![]() For this reason, UDP is often described as having “send and prey” reliability. However, the big difference is that while TCP has mechanisms to discover the loss and automatically retransmit the segment, UDP does not have such mechanisms, so a lost segment stays lost unless this is resolved by a higher-layer protocol or at the level of the application. In fact, the chances of any single UDP segment being lost in isolation are basically the same as the chances of an isolated loss of a TCP segment. As a result, UDP is said to be unreliable. There is also no congestion control or flow control. There are no sequence numbers, acknowledgments, or automatic retransmission. UDP is a simple protocol, lacking the reliability and quality mechanisms provided by TCP. Users can only PUT (drop) files where they have remote WRITE access. TFTP ignores the rest of the security string. That is, the files must be secured “Nxxx”. Users can GET (retrieve) only files that grant all users remote READ access. The TFTP server on the remote system sets the restrictions on which files users can retrieve, as well as restrictions on storing files. The files remote users are allowed to retrieve from a remote system are typically secured for public access that is, anyone on the network can read the files. TFTP does not provide any mechanism for users to logon to the remote system with a userid and password and verify which files they can access. The HP TFTP client is used to transfer public files to and from a remote system.įiles can be transferred to or from any system on a network that has a TFTP server that accepts requests from the TFTP client. Remote TFTP clients are used to transfer public files to and from an HP Nonstop Server host system's TFTP server (TFTPSRV).
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