Multiplexing; Vpi And Vci - ZyXEL Communications P-660HN User Manual

One of the benefits of PPPoE is the ability to let 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 ZyXEL Device (rather than individual computers),
the computers on the LAN do not need PPPoE software installed, since the ZyXEL 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 ZyXEL Device 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 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 that each
protocol is carried over a separate ATM virtual circuit (VC-based multiplexing). 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) is carrying. Be
sure to use the multiplexing method required by your ISP.
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.
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.

5.5.3 VPI and VCI

Be sure to use the correct Virtual Path Identifier (VPI) and Virtual Channel Identifier (VCI)
numbers assigned to you. The valid range for the VPI is 0 to 255 and for the VCI is 32 to
65535 (0 to 31 is reserved for local management of ATM traffic). Please see the appendix for
more information.
P-660HN-Fx User's Guide
Chapter 5 WAN Setup
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