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What is a low-latency, low-bandwidth algorithm for synchronizing, say, a text file between a client and a server?

Is there a design where the client send a delta of it's current state and it's last ACK'd state from the server? I am thinking Quake3 networking..

EDIT 1:

More specifically, how would a diff/delta algorithm behave in a client/server environment.

e.g. Is it more expensive to calculate a diff on the client side, send to server, server interprets and updates its store, sends ACK to client? Or is it cheaper to have a replication model where client sends its full state and server stores it..?

EDIT 2:

100 KB text file. Something small, not too large.

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You mean like a diff?

Store the server-side's version of the file in the client. Whenever you need to synchronize, run a diff (you can either write your own or use a library). Then send the difference over to the server and have the server patch it's local version.

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I guess a diff/delta algorithm is part of it. I updated the original question to elaborate on what I'm trying to ask
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If a client also edits text, and has an undo/redo feature then undo stack can be used for delta. For large texts and small changes using undo stack should be more efficient than running a diff.

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For text you can use delta algorithm, take a look, for example, on how rsync works.

Google uses a different approach to update chrome, you can "google" it to see.

Edit: If it was a server generating one change and replicating in lots of clients, it should be done in server. From the question's changes, I understood that a client (or many clients) will produce the changes and want them to be replicated on server.

Well... I'd take in account 4 things:

  • network performance
  • number of clients
  • number of changes expected
  • performance of the server and of the client

Too many clients sending and doing that on server: it's almost a DoS I'd only do that on server if there were few clients, high server performance and low client performance. Otherwise, I'd only do that on clients.

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Is that efficient in a client/server environment?

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