Adam Bower wrote:
That's interesting, as the recommended amount has been 1458 for over 3 years now, and this is a BT Wholesale recommendation, not just a random suggestion found on the net. I've never seen any advice that suggested otherwise.
I have no doubt that you're right, but every time I've Googled for "BT MTU MRU MSS" I've been directed to 1500 for BT and 1490 (IIRC) for AOL.
When I Google for 1458 I see where you're coming from, though!
NB: Most of the routers I've tried have had default settings for a BT connection and usually they're 1500/1500/1460 I think, I just noticed that the MSS looks out on this one, probably left over from one of the many tests I've tried recently. Just out of interest, which routers?
Hard to say since I don't usually check default settings, but I've never seen one set to something different when I have checked. As mentioned elsewhere I'm currently playing with a Safecom unit (cheap+cheerful) and an unbranded Conexant chipset box. We've used branded stuff in the past and if I ever checked the MTU it said 1500 (as I'd remember if it said something else) but I don't recall now which ones I have checked.
<edit>I've now seen reference to 1458 as BT's preferred MTU so I'm trying it now.</edit>
Good good, let's see how you get on for now.
On that point: I'm now running with 1458 at home and work. No idea how stable the work connection is since I'm now at home, but my home one is just as bad as before. (This email being sent via VPN to my work PC since my home PC is having problems).
This is where it gets interesting, though: I can now ssh into my router.
From there:
ping -s 1500 www.more-solutions.co.uk gives: --- www.more-solutions.co.uk ping statistics --- 63 packets transmitted, 63 packets received, 0% packet loss round-trip min/avg/max = 40.0/47.1/50.0 ms
However, the same command from my W2k box (now ping -l 1500 www.more-solutions.co.uk) gives: Ping statistics for 212.69.210.250: Packets: Sent = 4, Received = 0, Lost = 4 (100% loss), Approximate round trip times in milli-seconds: Minimum = 0ms, Maximum = 0ms, Average = 0ms
Explain that! Snide comments about W2k vs Linux I can come up with myself! I need to bring a Linux box back home to try, but when I've sent this email I'll reboot this PC with a LiveCD and see whether that's better.
Nope, you shouldn't need to adjust the PC settings at all, the router should do the fragmentation (although, what routers are you using, I find it strange that you've found something with an "odd" default?
I'm sure 1500 is a very common default! Which routers have you found with defaults of 1458?
Of-course I have to be open to the possibility that the problems at home and at work have completely different causes, even if the symptoms are similar.