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    Describing DSL Technology: Teleworker Connectivity

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    rajkumarlodh
    DSL is a technology that delivers high bandwidth internet over existing copper telephone lines. It comes in variants like ADSL, VDSL, and SDSL that differ in maximum speeds and distances supported. ADSL allows voice and data transmission by using splitters to separate the signals. PPPoE and PPPoA are common encapsulation methods, with PPPoE involving Ethernet frames carrying PPP packets and PPPoA routing packets from the customer premises equipment over ATM.

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    Describing DSL Technology: Teleworker Connectivity

    Uploaded by

    rajkumarlodh
    30 views31 pages
    DSL is a technology that delivers high bandwidth internet over existing copper telephone lines. It comes in variants like ADSL, VDSL, and SDSL that differ in maximum speeds and distances supported. ADSL allows voice and data transmission by using splitters to separate the signals. PPPoE and PPPoA are common encapsulation methods, with PPPoE involving Ethernet frames carrying PPP packets and PPPoA routing packets from the customer premises equipment over ATM.

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    ISCW10S02L03

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    DSL is a technology that delivers high bandwidth internet over existing copper telephone lines. It comes in variants like ADSL, VDSL, and SDSL that differ in maximum speeds and distances supported. ADSL allows voice and data transmission by using splitters to separate the signals. PPPoE and PPPoA are common encapsulation methods, with PPPoE involving Ethernet frames carrying PPP packets and PPPoA routing packets from the customer premises equipment over ATM.

    Copyright:

    © All Rights Reserved
    Download as PPT, PDF, TXT or read online from Scribd
    Download as ppt, pdf, or txt
    30 views31 pages

    Describing DSL Technology: Teleworker Connectivity

    Uploaded by

    rajkumarlodh
    DSL is a technology that delivers high bandwidth internet over existing copper telephone lines. It comes in variants like ADSL, VDSL, and SDSL that differ in maximum speeds and distances supported. ADSL allows voice and data transmission by using splitters to separate the signals. PPPoE and PPPoA are common encapsulation methods, with PPPoE involving Ethernet frames carrying PPP packets and PPPoA routing packets from the customer premises equipment over ATM.

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    of 31

    Teleworker Connectivity

    Describing DSL Technology


    DSL Features
    What Is a DSL?

    • Utilizes high transmission frequencies (up to 1 MHz)


    • Technology for delivering high bandwidth over regular
    copper lines
    • Connection between subscriber and CO
    What Is a DSL? (Cont.)

    • Downstream and upstream transmission


    • Symmetrical and asymmetrical services
    • Multiple xDSL variations
    • Can deliver data along with voice (voice over IP)
    • Always-on data connection
    • Bandwidth versus distance
    DSL Types
    DSL Variants

    DSL variants differ in:


    • Nature
    • Maximum data rate
    • Line coding technology
    • Data and voice support
    • Maximum distance
    DSL Variants Examples

    Max. Data Rate


    DSL Technology Nature Data and POTS
    (Down / Up) [bps]

    ADSL Asymmetric 8M/1M Yes

    Symmetric /
    VDSL 52 M / 13 M Yes
    Asymmetric

    IDSL Symmetric 144 k / 144 k No

    SDSL Symmetric 768 k / 768 k No

    HDSL Symmetric 2M/2M No

    G.SHDSL Symmetric 2.3 M / 2.3 M No


    DSL Limitations
    DSL Limitation Factors

    Factors that define maximum distance and speed:


    • Signal attenuation
    • Bridge tap
    • Load coil
    • Wire gauge
    • Impedance mismatch
    • Crosstalk
    • AM radio interference
    DSL Distance Limitations

    Max. Data Rate Max. Distance


    DSL Technology
    (Down / Up) [bps] [feet / km]
    ADSL 8M/1M 18,000 / 5.46

    VDSL 52 M / 13 M 4,500 / 1.37

    IDSL 144 k / 144 k 18,000 / 5.46


    SDSL 768 k / 768 k 22,000 / 6.7

    G.SHDSL 2.3 M / 2.3 M 28,000 / 8.52

    • Maximum data rate and distance assume no impairments.


    • Maximum data rate is achieved at shortest distance.
    • Maximum distance is achieved at lowest data rate.
    ADSL
    ADSL

    • Coexists with POTS over the same copper wiring


    • Asymmetric data rate:
    – High-speed downstream for intensive applications
    – Slow upstream for undemanding data requests
    ADSL (Cont.)

    • ADSL equipment:
    – ADSL terminal unit-remote (ATU-R)
    – ADSL terminal unit-central office (ATU-C)
    • ADSL features three basic line-coding techniques:
    – Single carrier—CAP modulation
    – Multicarrier with DMT
    – Multicarrier with G.lite
    • ADSL operation and performance is influenced by different
    impairments.
    ADSL and POTS
    Coexistence
    ADSL and POTS Coexistence

    • A key feature of ADSL is coexistence with POTS.


    • Transmission of voice and data signals is performed on the
    same wire pair.
    • Data circuits are offloaded from the voice switch.
    ADSL and POTS Coexistence (Cont.)

    • Splitter versus microfilter


    • How are data and POTS channels separated?
    – POTS splitter at CO
    – Microfilters at customer premises
    ADSL Channels and
    Encoding
    CAP Modulation

    • Single-carrier modulation technique


    DMT Modulation

    • Multiple-carrier modulation technique


    Data over ADSL:
    PPPoE
    Data over ADSL

    • IP packets encapsulated over ATM


    • Three major approaches:
    – RFC 1483/2684 Bridged
    – PPPoE
    – PPPoA
    PPP over Ethernet

    • Ethernet frame carrying PPP frame


    • Service provider end:
    – DSLAM for DSL connection termination
    – Aggregation router for PPP session termination
    • Subscriber end:
    – DSL modem for DSL connection termination
    – PPPoE client for PPP session termination
    • The client device is the PC or the router at the CPE
    PPP over Ethernet (Cont.)

    • IP is assigned to PPPoE client functioning device.


    • A CPE router can connect multiple users via a single ADSL
    connection using NAT/PAT and DHCP.
    PPPoE Session Variables

    DSL and PPPoE deployment types:


    • Router terminating DSL and with PPPoE client
    • Modem terminating DSL and router with PPPoE client
    • Modem terminating DSL and end-user PC with PPPoE client
    PPPoE Session Establishment

    • PPP session is from PPPoE client to the aggregation router.


    • Subscriber IP address is assigned by the aggregation router
    via IPCP.
    Data over ADSL:
    PPPoA
    PPP over ATM

    • Routed solution
    • User packets routed over ATM
    • Service provider end:
    – DSLAM for DSL connection termination
    – Aggregation router for PPP session termination
    • Subscriber end: CPE for DSL connection and PPP session
    termination
    PPP over ATM (Cont.)

    • CPE receives an IP address via IPCP like in the dial model.


    Summary

    • DSL is a family of access technologies for delivering high


    bandwidth over regular copper lines at limited distances.
    • In regards to the downstream and upstream, the DSL can be
    symmetrical or asymmetrical.
    • DSL variants are ADSL, HDSL, RADSL, SDSL, IDSL, VDSL,
    and G.SHDSL.
    • The trade-off among various DSL types is distance versus
    speed.
    • Different impairments influence the achieved operational
    speed.
    Summary (Cont.)

    • ADSL is designed to coexist with POTS because there is a POTS


    splitter at the CO.
    • Splitters and microfilters are used to separate voice from data
    channels.
    • PPPoE and PPPoA are the most frequently used encapsulation
    methods.
    • The PPPoE client software first encapsulates the end-user data into
    a PPP frame, and then the PPP frame is further encapsulated inside
    an Ethernet frame.
    • PPPoA is a routed solution in which the CPE is set up as a router,
    and the CPE routes the packets from the PC of the end user over
    ATM to an aggregation router.

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