ZyXEL Communications P-791R, User Manual

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Chapter 5 WAN Setup
P-791R v2 User’s Guide
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5.1.1.3 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 (DSL Access Multiplexer). Please
refer to RFC 2364 for more information on PPPoA. Refer to RFC 1661 for more information
on PPP.
5.1.1.4 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 the RFC for more detailed information.
5.1.2 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.
5.1.2.1 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.
5.1.2.2 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 is not practical to have a separate VC for each carried
protocol, for example, if charging heavily depends on the number of simultaneous VCs.
5.1.3 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.
5.1.4 IP Address Assignment
A static IP is a fixed IP that your ISP gives you. A dynamic IP is not fixed; the ISP assigns you
a different one each time. The Single User Account feature can be enabled or disabled if you
have either a dynamic or static IP. However the encapsulation method assigned influences
your choices for IP address and ENET ENCAP gateway.