Wait, retransmit the same block, then acknowledge
02TFTP sends one data block and waits for its acknowledgment. The negotiated interval bounds this wait before retransmission, not the whole application transfer.
The server sends ACK 1, which the client receives. The successful short-file exchange completes; the outstanding DATA 1 wait ends.
Source for this drawing: RFC 2349 · Read RFC source: Timeout Interval · p.2 ↗
New to this? Start hereA quick picture + helpful background
A message needs an address.
Think of a packet as a small addressed envelope. Devices pass it onward; transport protocols decide what delivery promises an application gets.
Helpful first, if these ideas are unfamiliar
These pictures are analogies to help you learn. The linked RFC explains the actual rules.
Terms in this drawing
Related RFCs and changes
“Updates” changes part of an earlier RFC. “Obsoletes” replaces it. This list shows selected related documents.
A timeout interval is measured in seconds before retransmitting; it is not a whole-file completion deadline.
- A timeout interval is measured in seconds before retransmitting; it is not a whole-file completion deadline.
- On timeout, retransmit the last packet rather than advancing the data block number (RFC1350 §2).
- This chosen successful octet-mode write uses DATA 1 with 300 bytes, below the ordinary 512-byte data limit. ACK 1 acknowledges that final short block.
The axis and selected times are teaching values, not a real timer, congestion-control implementation or UDP test. Packet loss, ACK loss, duplicate handling and retry policies are simplified; no eventual-delivery guarantee.
Read the RFC section ↗