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xDSL Basics

xDSL Basics. “Digital Subscriber Line”. Central Office. Regional POP. Customer Premises. 2. Backend Systems. IAD. DSLAM. xDSL Basics. ADSL Asymmetric DSL e.g. 2Mbps down/384kbps up Speed dependent on loop length - 512kbps => 6Mbps SDSL Symmetric DSL e.g. 384kps down/384kbps up

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xDSL Basics

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  1. xDSL Basics “Digital Subscriber Line” Central Office Regional POP Customer Premises 2 Backend Systems IAD DSLAM

  2. xDSL Basics • ADSL • Asymmetric DSL • e.g. 2Mbps down/384kbps up • Speed dependent on loop length - 512kbps => 6Mbps • SDSL • Symmetric DSL • e.g. 384kps down/384kbps up • Others • IDSL, HDSL, VDSL, etc, etc

  3. IAD Example • IAD (Integrated Access Device) • Customer Premises Device • LAN Network Interface /Router • Phone/Fax/Modem Interfaces • e.g. 8-24 x RJ11 Customer Premises • DSL Modem • ADSL, SDSL, IDSL • ATM or Frame Relay Transport

  4. DSLAM Example • DSLAM (DSL Access Multiplexor) • Central Office/Local Exchange System • Typically located in a CLEC/ILEC colocation cage • Line cards support various flavours of xDSL • Aggregation of users onto PVCs • Connectivity to backbone • OC-3/DS-3/T1 • ATM/Frame Relay/IP Central Office

  5. DSLAM Example

  6. VoDSL Economics • DSL Flat Rate Per Minute • Internet Access $40 n/a • Voice over DSL $32 $100 • Total $72 $100 • Modest 4 lines + 1M/256k • Voice can increase DSL revenue 4-10 times!

  7. Central Office Central Office Customer Premises Customer Premises Customer Premises Customer Premises Customer Premises Access Network VoDSL Network Topology Regional POP Customer Premises xDSL Internet Data DS-3/T1 Intranets DSLAM IAD Subscriber Management System Voice xDSL DS-3/T1 PSTN Voice Gateway DSLAM IAD

  8. Access Network QoS: Dual Aggregation Realtime VC (#22) rtVBR (ATM) CIR Set (FR) Non-Realtime VC (#16) nrtVBR (ATM) CIR Not Set (FR)

  9. AAL2 Loop Emulation Source 1 #1 #2 Source 2 #3 #4 Source 3 #5 Header STF H #1 H #3 H #5 Header STF #5 H #2 H #4 • Used with G.711/G.726 w/ silence suppression

  10. Voice Gateway IAD Voice Gateway Voice Voice IAD AAL2 AAL2 DSLAM DSLAM Voice Voice ATM ATM ATM AAL2 FRF-8 Frame to Cell AAL2 xDSL xDSL DS-3 DS-3 FR FR AAL5 AAL5* ATM ATM xDSL xDSL DS-3 DS-3 Packet/Cell Protocols

  11. Central Office Collocation Cage Central Office Collocation Cage Customer Premises Customer Premises Customer Premises Customer Premises Customer Premises Customer Premises Access Network GR303/CAS Signalling CLEC Regional POP xDSL Internet DS-3/T1 Intranets Data DSLAM IAD Subscriber Management System Voice Gateway Voice xDSL DS-3/T1 Class 5 Switch DSLAM IAD PSTN GR-303

  12. VoDSL Orthodoxy Layer 2 Technology.... • Dual Aggregation for Toll QoS • AAL2 for Efficient Bandwidth • ABCD/CAS Signalling Delivers... • Toll Quality Voice & Basic CLASS telephony Requires... • Costly IAD with Ethernet and phone jacks • IAD DSP for echo cancellation/silence/codec

  13. VoATM/DSL Limitations • Regulatory Environment may prevent Broadband Internet Service Providers from provisioning voice services over Layer 2 network • Unbundling local loop & collocation is not yet a reality in most worldwide markets - early DSL deployments are data only

  14. Multimedia over DSL:The Upside! Leased Line 1.5Mbps nx ISDN Bandwidth 768kbps DSL 384kbps 1970 1980 1990 2000

  15. Multimedia over DSL:The Upside! Increased Bandwidth drives Video Quality 128k 384k 1M T1 $$$ Increased Video Usage drives Bandwidth Demand

  16. Orthodox VoDSL Roadmap Video VoATM VoIP High Speed Packet Data 2000 2001 2002

  17. Multimedia over DSL:Accelerated Benefits Add value earlier Video PSTN VoATM VoIP High Speed Packet Data Add more value 2000 2001 2002

  18. VoIP/DSL Realities • Dual Aggregation for Toll QoS • Voice over IP over ATM works well • Use dual aggregation to manage VoIP QoS • Real issue is QoS per service provider (PPTP/SVCs) • AAL2 for Efficient Bandwidth • CRTP and Link Level Fragmentation resolve IP issues • 2/4 bytes replaces 40 bytes IP/UDP/RTP cost • VoIP Signalling • MGCP & H.323 offer a full set of signalling features • Signalling gateways to SS7 widely available

  19. DSL Access NetworkPacket/Cell Protocols Voice/Video IAD Voice/Video Voice Gateway RTP RTP DSLAM UDP UDP FRF-8 Frame to Cell IP IP FR FR AAL5 AAL5 ATM ATM xDSL xDSL DS-3 DS-3

  20. Central Office Collocation Cage Central Office Collocation Cage Customer Premises Customer Premises Customer Premises Customer Premises Customer Premises Customer Premises Access Network Next Gen. over DSL Next Gen. Telco Regional POP xDSL Internet DS-3/T1 Intranets Data DSLAM IAD Subscriber Management System IP Phones Voice xDSL DS-3/T1 VoIP PSTN Packet Class 5 Switch DSLAM IAD

  21. VoIP/DSL: The Advantages! • Web Data and Video Media Integration NOW! • Choice of Voice Service Provider • Unified Voice & Data Network Management • VPN/Security Integration • Connectivity to • IP PBXs (e.g. Nortel) • Next Gen. Network (e.g. Sonus) • IP Telephones (e.g. Cisco) • Video Appliances (e.g. Polycom) • PCs!

  22. VoIP/DSL: The Bottom Line! • Is it wiser to invest in rail or air? • Is it wiser to invest in copper or fiber? • Is it wiser to invest in AAL2 or RTP/IP? Why invest in dedicated voice technology at all...leverage the Layer 3 data network!!!

  23. More Information Steve Roe sroe@www.ridgeway-sys.com Phone: +44 118 938 1111 http://www.ridgeway-sys.com

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