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PPoE or PPoA?

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sjrinfroyle
Grafter
Posts: 895
Registered: ‎08-05-2011

PPoE or PPoA?

Is one faster than the other? Does one have less overheads?
6 REPLIES
CX
Grafter
Posts: 745
Thanks: 2
Registered: ‎16-09-2010

Re: PPoE or PPoA?

I believe PPPoA is optimal. PPPoE does work on 21CN though.
Not sure about FTTC.
sjrinfroyle
Grafter
Posts: 895
Registered: ‎08-05-2011

Re: PPoE or PPoA?

Thanks for the response. Does anybody else have any experience?
coolbr33ze
Grafter
Posts: 68
Registered: ‎05-08-2011

Re: PPoE or PPoA?

Here's the difference....
Don't know about any of that, but found this :-

Quote
All ADSL lines use 'ATM' as the encapsulation between your modem and the exchange. The ATM protocol chops all data into 48 byte chunks called 'cells'. To send an Ethernet packet over ATM, you need to chop the Ethernet frame into a string of up to 32 cells. If you send a PPP frame over ATM, the Ethernet framing is removed and only the PPP is sent but it still ends up being 32 cells max per frame.
PPPoE overheads are a little more than PPPoA. I think that the PPPoE requires about 20 - 30 bytes or so more. Because ATM cells are fixed lengths, the difference between PPPoE and PPPoA only matters if the frame that is being sent plus the overhead requires one more cell. For example, if the PPPoA frame is 720 bytes long, it can be sent in 15 cells. But the PPPoE frame would require 16 cells because the extra overhead wouldn't fit into 15.
The PPPoE method ends up requiring perhaps 1-2% extra overhead. If you think you might notice this, change to PPPoA. But unless you peg your line to 100% utilisation for long periods, you really won't notice any difference. The extra PPPoE overhead will just fill up the cells that were empty anyway.
More recently, Telstra has been setting up DSL lines so that the modems always train to 1500 and the shaping is done in the BRAS instead of on the DSL line. I think (and I stand to be corrected here), that this practice eliminates all difference between PPPoE and PPPoA if you've got a 512k or 256k service. (A 1500 service still sees the 1% benefit from PPPoA - if you can sustain 100% load on your 1500 line).
whelpton
Grafter
Posts: 104
Registered: ‎06-06-2011

Re: PPoE or PPoA?

As far as I am aware, PPPoA also allows for multiplexing whilst oE doesn't. Could be mistaken.
Community Veteran
Posts: 4,887
Thanks: 128
Fixes: 24
Registered: ‎14-07-2009

Re: PPoE or PPoA?

Historically (20CN), all UK ISPs used PPPoA except for AOL who used PPPoE. 
Community Veteran
Posts: 1,412
Thanks: 4
Registered: ‎29-01-2009

Re: PPoE or PPoA?

Quote from: CX23882
Not sure about FTTC.

That only works with PPPoE - No ATM layer in the FTTC architecture.
Plusnet Customer
Using FTTC since 2011. Currently on 80/20 Unlimited Fibre Extra.