Ken.McAllister wrote: > Both problems (not sending email with more than a few words, and not > receiving secure web pages) are apparently solved by taking mtu in > stages down to 250. The original setting (from ifconfig) was > apparently MTU:1500.
250???? This is an unfeasibly small MTU - you will be sending up to 6 times more packets during your connection - that's a lot of overhead, that's a lot of extra data. If this were on a pay-per-data connection, the ISP would now be charging you more money for the same connection. Plus it will push your latency up. I said that "1200" was insanely low - 250 is embarassing! > I wonder what made the change necessary? Switching from Mandrake to > Ubuntu? Does Mandrake continue to work with the old MTU default of 1500? You cannot alter the IP state of Telstra's machines by switching OS ... > I wonder why Telstra Clear didn't suggest MTU to me? Perhaps they would > have if they'd known. I have a current ADSL problem with a customer, involving Telstra and MTU. The router engineer spoke to them, at great length, and they said "lower the MTU". He said, "what value should I use?". They said, "oh, we don't know - just try a few things until it works". To be fair, there are good reasons to do with PPPoE encapsulation of PPPoA connections, combined with IPsec ESP/AH headers being added by the router that could trigger all this. But *we* know what they are. Telstra, the ISP who have chosen to set up their network in this state, *don't* know what they are. I suspect that there are some technicians in there who know what they're doing, but they're not the ones that are allowed/made to talk to customers. And I'm sure that there is nothing unique about Telstra, either ... Sorry, this is turning in to a rant. But lowering MTU to 250 isn't a fix, it's proof that your ISP have a problem that must be fixed. -jim
