jfmezeiPremium
join:2007-01-03
Pointe-Claire, QC
kudos:22 Reviews:
 ·ELECTRONICBOX
| Bell's aggregation overhead I know about the overhead in packets between a person's computer and the BAS. (TCP, IP, PPPoE, ETHERNET, ATM)
What exactly would the overhead be on the link between a BAS and an ISP's LNS ?
Does the PPPoE packet travel naked inside an L2TP packet, or is it inside another Ethernet packet ?
aka: is it PPPoE -> Ethernet -> L2TP -> UDP -> IP -> Ethernet
or PPPoE -> L2TP -> UDP -> IP -> Ethernet
I take it that Bell has implemented jumbo packets on those links, or do single packets arriving from end users to the BAS end up split across multiple L2TP packets on their way to the ISP ? |
| On Legacy, when the packet is travelling from the customer's modem to the BAS, it is PPPoE encapsulated in ATM cells. Once it hits the BAS, the PPPoE headers are stripped, and the packet is converted to PPP over L2TP.
It then continues on to the ISP as either L2TP over an Ethernet or ATM link, depending on what the ISP is connected to Bell with.
On FTTN, the packet travels from the customer modem to the DSLAM on PPPoE encapsulated in ATM cells for ADSL(2+). For VDSL, the packets travel as PPPoE without the ATM encapsulation.
Once the packets hit the DSLAM, they are converted to PPPoE over Ethernet, and sent up to the BAS.
In some cases, ADSL2+ may operate in "Packet Transfer Mode" (PTM), where the ATM layer is eliminated on the wire between the customer's modem and the DSLAM.
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