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MTU setting on ADSL2+

Community Veteran
Posts: 2,308
Thanks: 228
Fixes: 1
Registered: 04-08-2009

MTU setting on ADSL2+

Can't seem to get to the bottom of this one. BT's Sinet documents state that the ADSL2+ system is optimised for PPPoE and therefore the MTU should be set at 1492. However, most users are using PPPoA to connect. Does this still mean that the MTU should be set at 1458 as before? I assume that the same encapsulation overhead occurs with PPPoA as it always did?
3 REPLIES
Plusnet Help Team
Plusnet Help Team
Posts: 12,776
Thanks: 108
Fixes: 32
Registered: 27-04-2007

Re: MTU setting on ADSL2+

Hi there the encapsulation should work in the same way as far as I'm aware. With regards to MTU a lot of people tend to favour 1500 now so you may want to give that a go.
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 Adam Walker
 Plusnet Help Team
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Registered: 10-06-2010

Re: MTU setting on ADSL2+

Where does it say that it's optimized for PPPoE? SIN 472 (WBC) page 11, and SIN 485 (IPStream Connect) page 13 both say the opposite:
"It should be noted that the use of LLC/SNAP and PPPoE incur a higher protocol overhead and therefore will
provide a lower throughput than the use of PPPoA/VC-mux."
Community Veteran
Posts: 2,308
Thanks: 228
Fixes: 1
Registered: 04-08-2009

Re: MTU setting on ADSL2+

Not sure what the document was, but last year I was shown a SIN by one of the more experienced BT Special Squad (!!!!!!) who fixed a PPPoA/oE fault for me. He pointed out that the backbone of the new ADSL2+ system is oE based. Can't be any more specific the  that, sorry.