Tài liệu Chapter6_dsl

DSL Chapter 6 Digital Subscriber Line (DSL) Korea-Vietnam Friendship IT College DSL Overview • • • • Introduction DSL Technology and standards Asymmetric DSL Symmetric DSL 2 Korea-Vietnam Friendship IT College DSL Introduction • xDSL is the term for the Broadband Access technologies based on Digital Subscriber Line (DSL) technology – “x” signifies that there are various flavors of DSL • Provides always-on, high-speed data services over existing copper wires to residences & businesses – POTS service and DSL coexist on same copper line • Lower rate xDSL (up to 1.5 Mbps) is gaining popularity in the residential market; will get faster and cheaper • High performance xDSL (up to 52 Mbps) targets business and high-end users 3 Korea-Vietnam Friendship IT College DSL Introduction Benefits • High-speed data service Application • High speed Internet access • SOHO • Multimedia, Long distance learning, gaming • Video on Demand • VPN • VoDSL - DSL typically >10x faster than 56-kbps analog modem • Always on connection – No need to “dial-up” • Uses existing copper wires – Co-exists w/ POTS service • Reasonably priced today and getting cheaper 4 Korea-Vietnam Friendship IT College DSL DSL Technology • Convert traditional telephone twisted-pair copper wires to broadband communication media • Utilize the spectrum unused by voice transmissions. 5 Korea-Vietnam Friendship IT College DSL DSL technology • Digital data are sent in packets composed of digital bitstreams in the spectrum above the 3.4 kHz (Kilohertz) RF (Radio Frequency) band. Voice conversations occupy the spectrum between the 300 Hz and the 3.4 kHz RF frequencies. 6 Korea-Vietnam Friendship IT College DSL DSL network configuration 7 Korea-Vietnam Friendship IT College DSL DSL Standards • ANSI • ETSI • ITU: • ITU-T G.992.1 Recommendation supports utilization of a filter for splitting data from voiceband signals. • ITU-T G.996 Recommendation defines methods and procedures for benchmarking performance and interoperability of DSL transceivers. • The ITU-T G.997.1 Recommendation describes DSL functions in using SNMP (Simple Network Management Protocol) and DSL Physical Layer or Layer 1 operations. • DSL FORUM • DLNA • UPnP 8 Korea-Vietnam Friendship IT College DSL Asymmetric DSL (ADSL) • “Asymmetric” => faster downstream rate vs. upstream – Suitable for applications such as web-browsing, MP3 downloading, Video on demand (VoD) 9 Korea-Vietnam Friendship IT College DSL Asymmetric DSL (ADSL) • Types of asymmetric DSL – Asymmetric DSL (ADSL) • The original and most popular • Other asymmetric DSL technologies derived from ADSL – Universal ADSL (UDSL), a.k.a. G.Lite or DSL Lite • Expedites and reduces cost of deployment process by moving the splitting process from the CP to the CO • Splitter-less nature slows the bit rate considerably 10 Korea-Vietnam Friendship IT College DSL Asymmetric DSL (ADSL) – Rate-Adaptive DSL (RADSL) • Detects highest possible line rate & adjusts accordingly – Very High Bit-rate DSL (VDSL) • Used to get high speed over short local loops • Typically used in conjunction with Fiber to the Curb (FTTC) • Still in development phase 11 Korea-Vietnam Friendship IT College DSL Symmetric DSL (SDSL) • “Symmetric” => downstream & upstream rates are equal – Suitable for office type apps like Video conferencing • Types of symmetric xDSL – Symmetric DSL (SDSL) • Based on HDSL but single pair • Spectral compatibility an issue (crosstalk & interference) – High bit-rate DSL (HDSL) • The first of the symmetric DSL technologies • Uses multiple wire pairs (2 or 3) to achieve high bit rates 12 Korea-Vietnam Friendship IT College DSL Symmetric DSL (SDSL) – HDSL 2 • Single-pair version of HDSL • More standards driven to improve interoperability and spectrally compatible with other loop services (ISDN, T1, HDSL) • Takes into consideration diminishing amount of copper pairs – Single-pair HDSL (SHDSL) • Similar to HDSL 2, but more generalized • Business class DSL for transporting T1/E1, ISDN, ATM, and IP – ISDN DSL (ISDL) • DSL over ISDN; okay to pass through repeaters & DLCs • Always-on, flat rate billing, and transmit data over data network 13 Korea-Vietnam Friendship IT College DSL DSL Technologies 14 Korea-Vietnam Friendship IT College DSL DSL Equipments Two groups of equipment • Central Office - DSL Access Multiplexer (DSLAM), Repeaters • Customer Premise - DSL Modems, Gateways, Network Interface Card (NIC), splitters and filters 15 Korea-Vietnam Friendship IT College DSL DSLAM • DSLAM is usually found in a Central Office • xDSL line cards are installed in a DSLAM to terminate incoming xDSL signals • The DSLAM then combines multiple xDSL access lines into one high speed line • The muxed traffic is converted into ATM cells which gets sent over an ATM backbone 16 Korea-Vietnam Friendship IT College DSL DSL Modem/Gateway • A xDSL modem is the device found at the customer’s premise which is used to transmit & receive xDSL signals • Could be an external “box” or a network interface card placed inside a computer • An xDSL Gateway combines the functionality of a modem and router 17 Korea-Vietnam Friendship IT College DSL ADSL Modem Structure Mbit/s kbit/s Mbit/s ADSL Modem ADSL Modem Line POTS Filter POTS Linecard kbit/s POTS Filter Exchange End Customer End 18 Korea-Vietnam Friendship IT College DSL Summary 19 Korea-Vietnam Friendship IT College