Le mardi 21 août 2007, Charles Connell a écrit : > Hi all, > > I've asked this before, but got no answers: > > Could the people who really know (protocol authors/maintainers) please let > me know what the message size constraints are for each protocol? With this > knowledge the Cryptography plugin can warn the user about using a bad > protocol.
Hi First, thanks for giving some love the the crypto plugin. :-) There is afaik no way to get the maximum size of message for different protocols. Maybe we need to add that to a protocol capabilities API. I could anyway give you the answer for the MSN protocol and the Jabber protocol. For MSN: the maximum size of message is 1664bytes, including message header. Since the text is encoded in utf8, some char might be longer than one byte. The header contains the information about colors and fonts and few others small stuff that we can't calculate easily. This restriction is empiric. i calculated it few years ago, the server might now allow bigger message, I don't know. However, in Kopete I split message that are longer than this number message in several chunks that are reassembled by Kopete in one message for reception. Not all client can reassemble message. (The official client do for few years) Anyway, as far crypto plugin is concerned, i think you can send message as long as you want. For Jabber: The protocol itself doesn't impose any limit on message size. Anyway, server implementation to prevent DOS. The maximum length of packets depends of the server implementation. Both the user's server, but also the receiver's server. So this is not really possible to give the maximum length. But in practice, the maximum length is bigger than one MB, which should be more than enough for most encrypted message. If we send a longer message, we get disconnected. I don't know for others protocols.
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