14 ADSL NETWORK ARCHITECTURE,PROTOCOLS.AND EQUIPMENT NOTE:Since so much of the ADSL network architecture will be reusable by VDSL,it is imperative for ADSL to be successful if VDSL is to leverage off it. This includes DSLAMs,access multiplexers,ATM over ADSL NTs,standard- ized protocol stack and network management,and so on.Hopefully,the ATM access network being developed for ADSL will be fully operational and reliable by the time telcos are able to deploy VDSL in a big way.This will greatly increase VDSL's chances of success. 2.4 MAPPING DIGITAL INFORMATION TO ADSL USER DATA 2.4.1 Premises Architecture and DTE-to-DCE Interface The method to map user data to ADSL PHY will depend on the customer premises configuration.This is likely to be one of the following: Integrated network interface card (NIC):especially for G.992.2 Single user (via bridging):10BaseT,universal serial bus (USB),ATM25 Multiple users (via routing):twisted-pair and wireless home networks,10 Base T.IEEE 1394 In the last two configurations a specific DTE-to-DCE interface (e.g.,PC to ADSL NT)will be required.This interface is currently not standardized. However,there are several candidates for premises architectures.These include: .Broadband media access protocol (BMAP)in ADSL Forum and USB Interoperability Group PPP over Ethernet (PPPOE)in ADSL Forum Frame-based UNI(FUNI)over Ethernet in ATM Forum Layer 2 tunneling protocol (L2TP),which is an IETF draft (note that PPTP is Microsoft's version of this) BMAP and PPPOE extend the PPP session to the client PC,while FUNI is independent of PPP.Both BMAP and FUNI take advantage of an ATM protocol stack in the PC (e.g.,from Microsoft),which effectively enables "ATM to the desktop"without an ATM premises PHY.PPPOE assumes an IEEE 802.3/ Ethernet interface with no ATM stack in the PC. When supporting PPP to the client PC,the ADSL NT must be able to map a PPP session to the associated virtual circuit label (i.e.,VPI/VCD).Each of the premises architectures noted above has a different procedure to do that. NOTE:It is interesting that none of the ATM bridging/routing specifications defined previously(e.g.,LAN Emulation,MPOA,RFC 1577)is being seriously considered for ATM over ADSL.￾                    !  " #   $ #  ￾""% & "  "   "!'  #     "   "  "        "  !      (   ! )*+ ,-../01 2/1/3-4/0567,-3/60 36 -28498:7 2-3- )*+*; .<=>?@=@-<AB?C=ACD<=EFG23:HCIH2J:/FC=<KEA=  "  "L'M "  "      N !      O PQRSTUVRSWQSRXYUZ[QRSU\V]S]VUW^_P`ab  c!dde!e O f[QTgShiSU^j[VkU[WT[QTablmn hQ[jSUiVgiSU[Vgkhiopnq#er O shgR[tgShiSUi^j[VUYhR[QTab "%"    lm n ulvdw u  N  N %%x  o ! !Lx ￾q  y "!    ""& "! '        ""      !   "  O zUYVWkVQW{SW[VV]]SiitUYRY]Ygon#Lq| "pn u  c O LLL   oLLLq| O }UV{S~kViSW_Po|p￾uq   # | O €VSU‚RhQQSg[QTtUYRY]YgoeLq u|"o  LLL# ( q n#L"LLL $ " LLL   Lx |p￾u "  " LLL!nn#L"|p￾u " #    Lxo ! ! # q      ƒƒ#  " ((#   L'M!LLL u„me!v…     #   Lx! †  LLL  Lx ￾     LLL    "   o! !Lu…xuq!        " "   " "! ￾u     # "  …  N  " N " o ! !￾ #L‡|xlrˆˆq    "  "#  ! ;+ ‰Š‹ŒŽ‘’‰’•Ž’Ž™’‘‘‘Œ‹‰ŠŽš™›Ž