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> Difference between PPPOE and PPPOA connections, What is the difference?

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YapChinHoong
post Nov 16 2006, 12:06 AM

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From: Puchong, Selangor, Malaysia.


Here is some notes from my CCNA Complete Guide. laugh.gif

Digital Subscriber Lines (DSL)

- DSL just defines how to transmit data between a customer site and the local CO. Data do not flow through DS0 channels inside the PSTN, but through some ISP IP networks. Hence it does not need to be compatible with the core of PSTN and thus is able to provide high-speed transmissions rate. The speed does not degrade as more users are added to the network.

- The local loop connects to the DSL Access Multiplexer (DSLAM) at the local CO. The DSLAM is responsible for splitting the data and voice signals from the local loop.

- DSL allows concurrent data transmission and voice call.

- DSL is an always-on Internet connection service. It does not require a circuit to be setup before data transmission as with modems and ISDN.

- Its downstream speeds range from 1.5-8Mbps, while upstream speeds range from 64-800kbps.

- ADSL's maximum supported distance to home is 18000 feet (or ~5500 meters).

- Phones generate analog signals at 0-4000Hz, while DSL modems generate analog signals higher than 4000Hz - the interference is minimal. Filters are normally used to prevent interference.

- DSL routers include the DSL modem features, and provide other features, eg: IP routing (allows Internet connection for multiple PCs), DHCP server, NAT, and Port Forwarding.

- DSL is a L1 service. It uses ATM as the L2 protocol for the communication between the DSL router (or modem) and the ISP router. DSL uses PPP over ATM (PPPoA) protocol. PPP and ATM are both L2 protocols, but they provide different functions in DSL connections. PPP provides dynamic address assignment and authentication with CHAP. DSL might require PPP over Ethernet (PPPoE) for transmitting data between a PC and a DSL modem / router.

- DSL transmit ATM cells over DSL lines, instead of SONET. ATM cells are received and processed by the ISP's router.

YapChinHoong
post Nov 16 2006, 12:10 AM

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Group: Senior Member
Posts: 663

Joined: Nov 2004
From: Puchong, Selangor, Malaysia.


As a summary, PPPoA is everywhere (because of Streamyx ADSL), not in enterprise networks only. smile.gif This is because the protocol between the DSL modem and the ISP is ATM, we should be able to find some ATM statistics in the router management page.

PPPoA - Used to transfer data between DSL router and ISP.
PPPoE - Used to transfer data between PC and DSL router.




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