Vpi & Vci; Multiplexing; Vc-Based Multiplexing; Llc-Based Multiplexing - ZyXEL Communications Prestige 642 User Manual

Prestige 642 ADSL Internet Access Router
The following terminology may seem a little overwhelming at first to new users of
broadband technology. Relax! This information should be either pre-configured on your
Prestige or supplied by your ISP or telephone company. Think of them as the equivalent of
"telephone numbers" on traditional dial-up PSTN and ISDN modems and routers.
3.9 VPI & VCI
Be sure to use the correct Virtual Path Identifier (VPI) and Virtual Channel Identifier (VCI) numbers
supplied by the Telephone Company. The valid range for the VPI is 1 to 255 and for the VCI is 32 to 65535
(1 to 32 is reserved for local management of ATM traffic). Please see the Appendices for more information.

3.10 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.

3.10.1 VC-based multiplexing

In this case, by prior mutual agreement, each protocol is assigned to a specific virtual circuit, e.g., 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.

3.10.2 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, e.g., if charging heavily depends on the
number of simultaneous VCs.

3.11 Encapsulation

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

3.11.1 ENET ENCAP

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.

3.11.2 PPP over Ethernet

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 PC to an ATM
PVC (Permanent Virtual Circuit) which connects to a xDSL Access Concentrator where the PPP session
3-8 Internet Access