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Chapter 6 Broadband
AMG1312-T Series User’s Guide
83
6.5.1.1 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. For instance, it
encapsulates routed Ethernet frames into bridged ATM cells. ENET ENCAP requires that you specify
a gateway IP address in the Gateway IP Address field in the wizard or WAN screen. You can get
this information from your ISP.
6.5.1.2 PPP over Ethernet
The AMG1312-T Series supports PPPoE (Point-to-Point Protocol over Ethernet). PPPoE is an IETF
Draft standard (RFC 2516) specifying how a personal computer (PC) interacts with a broadband
modem (DSL, cable, wireless, etc.) connection. The PPPoE option is for a dial-up connection using
PPPoE.
For the service provider, PPPoE offers an access and authentication method that works with existing
access control systems (for example RADIUS).
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 AMG1312-T Series (rather than individual computers), the
computers on the LAN do not need PPPoE software installed, since the AMG1312-T Series does that
part of the task. Furthermore, with NAT, all of the LANs’ computers will have access.
6.5.1.3 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 AMG1312-T Series 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.
6.5.1.4 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.
6.5.2 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.