Multiplexing; Vc-Based Multiplexing; Llc-Based Multiplexing; Encapsulation - ZyXEL Communications Prestige 650ME User Manual

Adsl bridge

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Prestige 650ME ADSL Bridge

3.9

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.

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.

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.

Be sure to use the encapsulation method required by your ISP. The Prestige supports the following

methods.

PPPoE provides access control and billing functionality in a manner similar to dial-up services using PPP.

The Prestige bridges a PPP session over Ethernet (PPP over Ethernet, RFC 2516) from your computer to an

ATM PVC (Permanent Virtual Circuit) which connects to a xDSL 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 Appendices.

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.

Internet Access

3-11

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