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MTU Size

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MTU Size

The following appears in section 7.3.3 of SIN329 (http://www.sinet.bt.com/):

"The maximum MTU size on the BT Broadband network is 1500 bytes. However, due to the tunnelling overhead and subsequent fragmentation of larger L2TP IP packets, packets not exceeding 1458 bytes are more efficiently carried. BT recommends that the optimum MTU setting is 1458 bytes as this is best suited to the performance of the broadband network. End Users may see an improvement in performance for some applications such as web browsing, FTP and peer-to-peer if they change their network setting to this level. Customers may wish to advise their End User on how to change MTU settings on their particular configurations."

PlusNet have not yet passed this information onto their end users.
4 REPLIES
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RE: MTU Size

Brilliant... it HAS made a difference!! Thanks pal! Smiley
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RE: MTU Size

> PlusNet have not yet passed this information onto their end users.
>

Yep your quite right. Interestingly enough if you have a look at the other ISP forum's on ADSLGUIDE neither have any of them. The only major ISP that doesn't seem to have loads of posts on this slow upload issue is Griffin.

All the problems seems to have started about four weeks ago for each ISP, so it seems to me that BT have changed something.
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RE: MTU Size

> All the problems seems to have started about four weeks ago for each ISP, so it seems to me that BT have changed something.

That sounds plausible, as issue 5.5 of SIN329 was published on 14th October 2002, and one of the major changes listed in Table A. 1 is "Update on MTU size recommendation".
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RE: MTU Size

I think BT started a major system upgrade about 5 weeks ago actually!! And it has caused a few headaches but they say they are getting there!