In reply to a post by billford:

Yes, and the 'T' stands for 'Transmission'... so you were ignoring the direction of the traffic.

Yes, I had always taken it to mean being in transit; a bidirectional operation.

Now that you made it clear that the MTUs at our end relate only to our uploads, I wonder why when some people have trouble or delay with loading pages or other downloads, that a change of MTU can often fix it.

In reply to a post by XRaySpeX:

In reply to a post by billford:

Yes, and the 'T' stands for 'Transmission'... so you were ignoring the direction of the traffic.

Yes, I had always taken it to mean being in transit; a bidirectional operation.

Ah, getting the TLA wrong... I've done that myself a few times!

Now that you made it clear that the MTUs at our end relate only to our uploads, I wonder why when some people have trouble or delay with loading pages or other downloads, that a change of MTU can often fix it.

It can explain why pages on a specific site won't ever load- the MRU at the far end is (incorrectly) set too low, so your MTU won't fit in it (hence your requests never arrive), but why it sometimes fixes an occasional problem I don't know... my suspicion is that it's not the MTU at fault but something else that clears the problem when the router restarts with the new value.

Can't prove it though

In reply to a post by billford:

It can explain why pages on a specific site won't ever load- the MRU at the far end is (incorrectly) set too low, so your MTU won't fit in it (hence your requests never arrive), but why it sometimes fixes an occasional problem I don't know... my suspicion is that it's not the MTU at fault but something else that clears the problem when the router restarts with the new value.

Or they've screwed up a firewall and blocked fragmented packets (as they think its a security feature). Making your packets smaller so they don't get fragmented can get around this (sometimes).

In reply to a post by jchamier:

Sky FTTC doesn't use PPPoE as they use IPoA (similar to BE) with their proprietory authentication and TalkTalk no idea.

...or slightly more correctly Sky use "1483 MER with DHCP Option 61"

Not the TLA itself, but the meaning of what it abbreviates

I guess it's worth mentioning that BT don't use ATM on VDSL2 so PPPoA doesn't apply. BT use PTM instead.

In reply to a post by simon194:

In reply to a post by jchamier:

Sky FTTC doesn't use PPPoE as they use IPoA (similar to BE) with their proprietory authentication and TalkTalk no idea.

...or slightly more correctly Sky use "1483 MER with DHCP Option 61"

I think 1483 is IPoA - at least in the routers I've used the two are used interchangeably and "MER" is the Sky name for the DHCP Option 61 oddity that I called "proprietory authentication"

In reply to a post by BatBoy:

I guess it's worth mentioning that BT don't use ATM on VDSL2 so PPPoA doesn't apply. BT use PTM instead.

PTM ? I thought BT used PPPoE on WBC FTTC lines?

My Buffalo:-

Method of Acquiring IP Address
Auto Detect Mode - PPPoE

In reply to a post by RobertoS:

My Buffalo is set to its default of 1500.

Where did I get that from? It's rot. (Looks like it's ignored when the easy setup option is used. Which it was).

MTU Size 1454

Oh and re the PMT. That's littered all over the modem GUI.