Copyright Nokia Networks OyC33906001SE_00 2-11Figure 2-5 Choosing the VCC2 for tunneling example2.2.8 Point-to-Point Protocol over Ethernet (PPPoE)Standard PPPoE mode is used when M1122 is operating as a bridge.PPPoE protocol defines how PPP sessions are mapped into Ethernetpackets. When M1122 operates as a bridge, this protocol is transparentto M1122.2.2.9 Payload encapsulationsBoth routed and bridged protocols are encapsulated in the ATM link byusing either RFC 2684 LLC/SNAP encapsulation or VC multiplexing.M1122 also supports PPP over AAL5 encapsulation, in which routedprotocols are first encapsulated in PPP (RFC 1661). PPP is thenencapsulated in ATM according to the IETF PPP over AAL5 usingRFC 2364 VC multiplexing or LLC/NLPID encapsulation.2.2.10 Weighted Fair Queueing (Class of Service)As a Class of Service (CoS) function, M1122 supports Weighted FairQueueing (WFQ) for each ATM VCC. The CoS function ensures thatdifferent IP traffic flows are treated fairly in the upstream (towards theInternet) direction. This may be necessary, in some cases, because theupstream capacity of the ADSL line is somewhat limited compared tothe Ethernet bandwidth on the office or home LAN. The WFQ CoS
