ZyXEL Communications Prestige 792H, User Manual

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Prestige 792H User’s Guide
Wizard Setup 3-3
ATM PVC (Permanent Virtual Circuit), which connects to ADSL Access Concentrator where the PPP
session terminates. One PVC can support any number of PPP sessions from your LAN. For more
information on PPPoE, see the appendix.
3.3.3 PPPoA
PPPoA stands for Point to Point Protocol over ATM Adaptation Layer 5 (AAL5). It provides access control
and billing functionality in a manner similar to dial-up services using PPP. The Prestige encapsulates the
PPP session based on RFC1483 and sends it through an ATM PVC (Permanent Virtual Circuit) to the
Internet Service Provider's (ISP) DSLAM (digital access multiplexer). Please refer to RFC 2364 for more
information on PPPoA. Refer to RFC 1661 for more information on PPP.
3.3.4 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 that each protocol is carried over a separate ATM virtual
circuit (VC-based multiplexing). Please refer to the RFC for more detailed information.
3.4 Multiplexing
There are two conventions to identify what protocols the virtual circuit (VC) is carrying. Be sure to use the
multiplexing method required by your ISP.
3.4.1 VC-based Multiplexing
In this case, by prior mutual agreement, each protocol is assigned to 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.
3.4.2 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