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PPPoE Settings
01-09-2013, 04:05 PM
Post: #1
PPPoE Settings
I'm not sure how technical everyone is on here or which routers will even tell you, but I was wondering if anyone else on Origin have noticed their PPPoE link is only set with an MTU of 1480 when its usually meant to be 1492?

I was curious if this is an issue of my router configuration or something @Origin have set on their PPPoE head end?

Its not exactly causing any problems but the closer you can get to 1500, the less likelihood of problems and the more efficient the networking is. (and apparently BT supports RFC 4638 so you CAN get 1500, no idea about Digital Region or Origin supporting that but my router OS doesn't support it anyway)

@Origin_Pete

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01-09-2013, 06:10 PM
Post: #2
RE: PPPoE Settings
When I transferred from LBO/Chess I had to manually enter the setting for Origin and was told to set the MTU to 1480.
Guess it must be what they regard as the best setting for their network.

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01-09-2013, 09:37 PM
Post: #3
RE: PPPoE Settings
You'll actually find that Origin have set it to the optimum setting which is what it should be, the 1492 is the maximum setting allowed and quite a few ISP's still use this. BT also use the 1480 setting

Mirdragon
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02-09-2013, 04:21 AM
Post: #4
RE: PPPoE Settings
Really? I have been seeing reports that in fact BT use 1500 on the Home Hub 3 and mini jumbo frames. Although I have been arguing that I don't see how that would be possible as the HG612 only has its MTU set as 1500 so should be limiting PPPoE to 1492 max.

This is why I liked the old Origin method of just routing over Ethernet using VLANs, none of this BS just plain old 1500 MTU.

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08-09-2013, 12:12 PM
Post: #5
RE: PPPoE Settings
I don't really understand the tech hear, but...

When I first went over to DR through Origin I could not get my Vodefone Sure-signal to work which I needed in order to get my mobile calls in my house.

After investigation I understood this to be because of the MTU settings packaging the signal in a way that would not work with the sure signal. However when I bought my own Netgear router and ran it on the 5g setting the router did something to the package size and now the sure-signal works fine.

As I say, don't know the why's but changing to a better quality router sorted my MTU problem.
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18-09-2013, 09:33 AM (This post was last modified: 18-09-2013 09:54 AM by alexatkin.)
Post: #6
RE: PPPoE Settings
Interesting, MTU definitely makes a difference.

My speedtest.net result with the MTU set to 1480 on the test PC:
[Image: 2974355639.png]
Switched MTU to 1500:
[Image: 2974354816.png]
Tested again to be sure it wasn't a fluke:
[Image: 2974360625.png]
Switched MTU back to 1480 to verify result:
[Image: 2974362960.png]


This does appear to be server dependent however as testing to my own VPS with the MTU at 1500 I get:
[Image: 2974377108.png]
MTU 1480:
[Image: 2974382514.png]

For anyone wondering how I got the above I temporarily have my VPS as a speedtest.net private host as we are trying to find out why the Android app is not testing properly.

An upshot of this is they pointed me to the KeepAlive option in Apache that I didn't realise is off by default. Now my ping test mini installation reports upload speed accurately, and all my websites load a TON faster, which piqued my interest to do the MTU test.

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18-09-2013, 06:24 PM
Post: #7
RE: PPPoE Settings
of the course the MTU affects everything - if set correctly it should provide optimum speed - if not you can get defragmentation which requires further transmissions thus reducing speed and increasing overheads

Mirdragon
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ISP: BT|Modem:HG612 (Modded)|Router: Smoothwall|Sync: 68Mbit/18Mbit
Network: HP Procurve|4 x TP-Link AP
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18-09-2013, 06:51 PM (This post was last modified: 18-09-2013 06:53 PM by alexatkin.)
Post: #8
RE: PPPoE Settings
Yeah but its a bit odd as initially I just used the defaults. Its also hard to know when auto detection is working or not, I was surprised to find that the Manchester speedtest.net server was obviously NOT scaling down the MTU properly. (probably has ICMP firewalled)

I also found out something sucky, Android locks the MTU at 1500 and ignores the DHCP flag that sets the MTU. That seems a bit stupid for an OS primarily used with PPP connections. Then again I'm not sure the packet size over mobile data.

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