Multiplexing - ZyXEL Communications AMG1312-T10D User Manual

5.5.1.2 PPP over Ethernet
The Device supports PPPoE (Point-to-Point Protocol over Ethernet). PPPoE specifies how a personal
computer (PC) interacts with a broadband modem (DSL, cable, wireless, etc.) connection. The
PPPoE option provides a dial-up connection using PPPoE.
For the service provider, PPPoE offers an access and authentication method that works with existing
access control systems (for example RADIUS).
PPPoE lets you access one of multiple network services, a function known as dynamic service
selection. This enables the service provider to easily create and offer new IP services for
individuals.
Operationally, PPPoE saves significant effort for both you and the ISP or carrier, as it requires no
specific configuration of the broadband modem at the customer site.
By implementing PPPoE directly on the Device (rather than individual computers), the computers on
the LAN do not need PPPoE software installed, since the Device does that part of the task.
Furthermore, with NAT, all of the LANs' computers will have access.
5.5.1.3 PPPoA
PPPoA stands for Point to Point Protocol over ATM Adaptation Layer 5 (AAL5). A PPPoA connection
functions like a dial-up Internet connection. The Device encapsulates the PPP session based on RFC
1483 and sends it through an ATM PVC (Permanent Virtual Circuit) to the Internet Service
Provider's (ISP) DSLAM (Digital Subscriber Line (DSL) Access Multiplexer). Please refer to RFC 2364
for more information on PPPoA. Refer to RFC 1661 for more information on PPP.
5.5.1.4 RFC 1483
RFC 1483 describes two methods for Multiprotocol Encapsulation over ATM Adaptation Layer 5
(AAL5). The first method allows multiplexing of multiple protocols over a single ATM virtual circuit
(LLC-based multiplexing) and the second method assumes a separate ATM virtual circuit (VC-based
multiplexing) carries each protocol. Please refer to RFC 1483 for more detailed information.

5.5.2 Multiplexing

There are two conventions to identify what protocols the virtual circuit (VC) carries. Use the
multiplexing method required by your ISP.
VC-based Multiplexing
In this case, by prior mutual agreement, each protocol uses a specific virtual circuit; for example,
VC1 carries IP, etc. VC-based multiplexing may be dominant in environments where dynamic
creation of large numbers of ATM VCs is fast and economical.
LLC-based Multiplexing
In this case one VC carries multiple protocols with protocol identifying information being contained
in each packet header. Despite the extra bandwidth and processing overhead, this method may be
advantageous if it is not practical to have a separate VC for each carried protocol, for example, if
charging heavily depends on the number of simultaneous VCs.
AMG1312-T10D User's Guide
Chapter 5 WAN Setup
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