ZyXEL Communications 645R User Manual

Prestige P645 ADSL Internet Access Router

3-10

Internet Access

In this case, by prior mutual agreement, each protocol is assigned to a specific virtual circuit; for example,
VC1 carries IP, VC2 carries IPX, 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.

The MAC Encapsulated Routing Link Protocol (ENET ENCAP) is only implemented with the IP network
protocol. IP packets are routed between the Ethernet interface and the WAN interface and then formatted so
that they can be understood in a bridged environment i.e., it encapsulates routed Ethernet frames into bridged
ATM cells. ENET ENCAP requires that you specify a gateway IP address in the Ethernet Encapsulation
Gateway field in menu 4 and in the Rem IP Addr field in menu 11.1. You can get this information from
your ISP.

Please refer to RFC 2364 for more information on PPP over ATM Adaptation Layer 5 (AAL5). Refer to RFC
1661 for more information on PPP.

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.