ZyXEL Communications VMG1312-B Series User Manual page 101

Chapter 6 Broadband
Encapsulation
Be sure t o use t he encapsulat ion m et hod required by your I SP . The Device can work in bridge m ode
or rout ing m ode. When t he Device is in rout ing m ode, it support s t he following m et hods.
IP over Ethernet
I P over Et hernet ( I PoE) is an alt ernat ive t o PPPoE. I P packet s are being delivered across an
Et hernet net work, wit hout using PPP encapsulat ion. They are rout ed bet ween t he Et hernet int erface
and t he WAN int erface and t hen form at t ed so t hat t hey can be underst ood in a bridged
environm ent . For inst ance, it encapsulat es rout ed Et hernet fram es int o bridged Et hernet cells.
PPP over ATM (PPPoA)
PPPoA st ands for Point t o Point Prot ocol over ATM Adapt at ion Layer 5 ( AAL5) . A PPPoA connect ion
funct ions like a dial- up I nt ernet connect ion. The Device encapsulat es t he PPP session based on
RFC1483 and sends it t hrough an ATM PVC ( Perm anent Virt ual Circuit ) t o t he I nt ernet Service
Provider 's ( I SP) DSLAM ( digit al access m ult iplexer) . Please refer t o RFC 2364 for m ore inform at ion
on PPPoA. Refer t o RFC 1661 for m ore inform at ion on PPP .
PPP over Ethernet (PPPoE)
Point- t o- Point Prot ocol over Et hernet ( PPPoE) provides access cont rol and billing funct ionalit y in a
m anner sim ilar t o dial- up services using PPP . PPPoE is an I ETF st andard ( RFC 2516) specifying how
a personal com put er ( PC) int eract s wit h a broadband m odem ( DSL, cable, wireless, et c.)
connect ion.
For t he service provider, PPPoE offers an access and aut hent icat ion m et hod t hat works wit h exist ing
access cont rol syst em s ( for exam ple RADI US) .
One of t he benefit s of PPPoE is t he abilit y t o let you access one of m ult iple net work services, a
funct ion known as dynam ic service select ion. This enables t he service provider t o easily creat e and
offer new I P services for individuals.
Operat ionally, PPPoE saves significant effort for bot h you and t he I SP or carrier, as it requires no
specific configurat ion of t he broadband m odem at t he cust om er sit e.
By im plem ent ing PPPoE direct ly on t he Device ( rat her t han individual com put ers) , t he com put ers on
t he LAN do not need PPPoE soft ware inst alled, since t he Device does t hat part of t he t ask.
Furt herm ore, wit h NAT, all of t he LANs' com put ers will have access.
RFC 1483
RFC 1483 describes t wo m et hods for Mult iprot ocol Encapsulat ion over ATM Adapt at ion Layer 5
( AAL5) . The first m et hod allows m ult iplexing of m ult iple prot ocols over a single ATM virt ual circuit
( LLC- based m ult iplexing) and t he second m et hod assum es t hat each prot ocol is carried over a
separat e ATM virt ual circuit ( VC- based m ult iplexing) . Please refer t o RFC 1483 for m ore det ailed
inform at ion.
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VMG1312-B Series User's Guide