Multiplexing; Vpi And Vci; Ip Address Assignment - ZyXEL Communications AMG1202-T10A User Manual

Chapter 6 WAN Setup
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.
6.4.1.3 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.
6.4.1.4 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.

6.4.2 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.

6.4.3 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.

6.4.4 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.
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AMG1202-T10A User's Guide