ADSL

ADSL uses an adaptive bit rate, so the data rates depend on line quality typically depending on the loop length.

ADSL is deployed with POTS typically. ADSL uses frequencies higher than POTS, so the POTS (analogue) signals are transmitted along with the ADSL signals on the same pair. (ADSL would start at 20-40KHz). It would also seem possible to run ISDN in parallel with ADSL by starting the ADSL starting frequency above the ISDN spectrum. (ADSL would start at 170KHz). High end of the used frequency range is 2.2MHz.

When used as delivery mechanism for ISPs, IP address allocation is handled with DHCP.

ADSL Technologies

DMT, on the other hand, is a multicarrier modulation technique that breaks the data transmission channels into 256 subchannels and divides up the data among them. The advantage is that data is directed away from channels with too much interference, a not uncommon problem with decades-old copper wire, and sent down clear transmission paths.

CAP speeds currently are 1.5Mbps downstream and 64Kbps upstream. (Westell Technologies plans to deliver a 2Mbps upstream, 900Kbps downstream modem in the first quarter of next year.) DMT transmits at 6Mbps downstream and 640Kbps upstream.

IP with ATM and ADSL

Classical ethernet ARP

ARP

Node wishes to contact an IP address in same subnet, broadcasts an ARP request on subnet/segment and that station respondes.

RARP

Reverse ARP. A (diskless) station broadcasts a reverse ARP request on a segment (the driver can find the hardware MAC address) and a RARP server responds with an IP address corresponding. (Can it get multiple replies for multiple subnets? (DHCP comes in here somewhere too, since the IP address allocation is its business)

Classical IP/ATM

ATMARP

Node wishes to contact an IP address in same subnet, sends an ATMARP request to the ATMARP server which respondes.

InvATMARP

Given a PVC/SVC in existence node sends InvARP to find IP address of station at other end of VC.

Functions Required

Management

Things missing include

• DMT/CAP channel views
• Accounting
• Delivered data service, e.g. I/F to IP or ATM or bit stream or bridged etherent... specifically
  Bit synchronous mode (STM)
  Packet mode
  ATM mode

• Transmission convergence (digital interface)
  • Rates/multiplexing
  • Forward Error Control (FEC)
  • Framing/mapping
  • Protocol Processing
  • OAM processing
  • Alternatives
    • Bit synchronous mode (STM)
    • Packet mode
    • ATM mode
• Physical Media Dependent (line interface)
  • Line code (modulation)
  • Initialisation
  • POTS splitter/interface
  • Scrambler/descrambler
  • Base EOC functions
  • Alternatives
    • DMT
    • QAM
    • CAP
    • Baseband

Random notes

• In future SDH/SONET networks may be at core with ADSL at an SDH-ADM
• TCP/IP needs to have an upstream data rate of 1/14th of the downstream rate for video. (Presumably for the ACKs)
• DSLAM may have to support Peak Cell Rate policing
• If the deployment is ATM/ADSL, and there is only ATM multiplexing (not full switching) in the CPE, then until all (core) switches support Q.2931 (and the PC also will support Q.2931 signalling which uses PC processor cycles), then nailed-up PVCs will be necessary. (Though could tunnel signalling traffic through to a UNI at the network side ATM switch).
• ISDN unlike ADSL has its POTS service directly linked into the PSTN.

Acronyms

USB

UNiversal Serial BUS Interface

AAL

ATM Adaptation Layer

ABR

Available Bit Rate

ADM

SDH/Sonet Add Drop Multiplexor

ADSL

Asymmetric Digital Subscriber Line

ADT

ATM Digital Terminal

AINI

ATM Inter-Network Interface

AIU

ATM Interworking Unit

AMI

Alternate Mark Inversion

AN

Access node. Concentration point for broadband and narrowband data.

ANI

Access Network Interface

ANSI

American National Standards Institute

ANT

ADSL Network Termination

ARP

Address Resolution Protocol

ATE

ATM Terminating Equipment

ATM

Asynchronous Transfer Mode

ATPARP

ATM Address Resolution Protocol

ATU-C

ADSL Transmission Unit at the network end (central office)

ATU-R

ADSL Transmission Unit at customer premises (remote)

ATU

ADSL Transceiver Unit

AWG

American wire Gauge

B

Auxiliary data input to Service Module (set top box)

B-ISUP

Broadband Integrated Services User Part

BCCP

Bearer Connection Control protocol

BER

Bit Error Ratio

Broadcast

broadcast data input in simplex mode (typically broadcast video).

CAP

carrierless amplitude and phase modulation (c.f. DMT)

CATV

Cable Television

CBR

Constant Bit Rate

CDV

Cell Delay Variation

CEBus

Consumer Electronics Bus

CLEC

Competitive Local Exchange Carrier

ILEC

Incumbent Local Exchange Carrier

CPE

Customer Premises Equipment

CSMA/CD

Carrier Sense Multiple Access Collision Detect

CTD

Cell Transfer Delay

DAML

Digital Added Main Line

DAVIC

Digital Audio Visual Council

DCS

Digital Cross-connect System (SDH/Sonet)

DMT

Discreet multitone (c.f. CAP)

DSLAM

DSL Access multiplexer

ES

Errored Second.

ETSI

European Telecommunications Standards Institute

FEC

Forward Error Correction

FTTC

Fiber-to-the-curb

FTTH

Fiber-to-the-home

G.703

ITU Physical/electrical characteristics of Hierarchical Digital Interfaces

G.704

ITU Synchronous frame structures used at Primary and Secondary Hierarchy Levels

G.992.1

ADSL Transceivers (previously G.dmt)

G.992.2

Splitterless ADSL Transceivers (previously G.lite)

G.994.1

Handshake Procedures for DSL Transceivers, (previously G.hs or G.handshake)

G.995.1

Overview of DSL Recommendations, (previously G.ref)

G.996.1

Test Procedures for DSL Transceivers, (previously G.test)

G.997.1

Physical Layer Management for DSL Transceivers, (previously G.ploam)

HAN

Home ATM Network

HDN

Home Distribution Network

HDSL2

High-bit-rate DSL (version 2)

HDT

Host Digital Terminal

HFC

Hybrid Fiber Coax

HPF

High Pass Filter

ILMI

Integrated Local Management Interface

ISA

Industry Standard Architecture (A PC bus standard)

ISDL

ISDN-like DSL

ISDN

Integrated Services Digital Network (called DSL in ANSI T1.413)

ISP

Internet Service Provider

InARP

Inverse Address Resolution Protocol

L2TP

Layer Two Tunnelling Protocol (draft-ietf-pppext-l2tp-*)

LCS

Line Code Specific

LOF

Loss of Frame

LOL

Loss of Link

LOS

Loss of Signal

LPR

Loss of Power

Loop

twisted pair copper telephone line.

MAC

Media Access Controller

MCR

Minimum Cell Rate

MGN

Margin

MSDSL

Moderate speed Digital Subscriber line

MSDSL

Multi-rate Symmetric DSL

NEXT

Near end crosstalk

NGDLC

Next Generation Digital Loop Carrier

NHRP

Next Hop Resolution Protocol

NID

Network Interface Device

NNI

Network Node Interface

NT

Network Termination

NAP

Network Access Provider

NSP

Network Service Provider

NTP

Network Transport Provider

OAM

Operations and Management

OAN

Optical Access Network

OLT

Optical Line Termination

ONU

Optical Network Unit

OSS

Operation Support System

PC

Personal Computer

PCI

Peripheral Component Interconnect

PCMCIA

Personal Computer Memory Card International Association

PCR

Peak Cell Rate

PDN

Premises distribution network (ATU-R <-> SM) active/passive

PHY

Physical (layer)

PMD

Physical Media Dependent (sub-layer)

PNNI

Private Network Node Interface

POF

Plastic Optical Fiber

PON

Passive Optical Network

POP

Point of Presence

POTS

Plain Old Telephone Service

POTS-C

I/F between PSTN and POTS splitter at network end

POTS-R

I/F between PSTN and POTS splitter at premises end

PSD

Power Spectral Density

PSTN

Public Switched Telephone Network

PVC

Permanent Virtual Circuit

PVC

Permanent Virtual Connection

QAM

Quadrate Amplitude Modulation (c.f. DMT, CAP)

QoS

Quality of Service

RADIUS

Remote Authentication Dial In User Service (RFC2138)

RADSL

Rate Adaptive DSL

RAM

Remote Access multiplexer

RARP

Reverse Address Resolution Protocol

RBB

Residential Broadband

RJ45

10BASE-T Connector standard for UTP cabling

RSVP

(IETF) Resource Reservation Protocol

RT

Remote terminal

RTP

Real Time Protocol

SDH

Synchronous Digital Hierarchy

SDSL

Symmetric DSL

SM

Service Module (e.g. set top box)

SNR

Signal to Noise Ratio

SONET

Synchronous Optical Network

STB

Set Top Box

STM

Synchronous transfer Mode

SVC

Switched Virtual Circuit

Splitter

Filter to separate low frequency POTS from high (ADSL)

T-SM

I/F ATU-R <-> PDN

T1.403

Carrier to customer installation DS1 Metallic

T1.413-1995

ANSI Standard for ADSL Modems

T1

A Telecommunications Standard Committee

T1E1.4

ANSI Committee for interfaces, network power & Protection digital subscriber loop access

T

I/F PDN <-> SM

TC

Transmission Convergence (sub-layer)

TDR

Time domain reflectometry

TIA422

Medium range (300m)serial data data transmission standard

TL1

Transaction Language 1

TX

Transmit

U-C

I/F loop <-> POTS splitter on network side

U-C₂

I/F ATU-C <-> POTS splitter on network side

U-R

I/F loop <-> POTS splitter on premises side

U-R₂

I/F ATU-R <-> POTS splitter on network side

UBR

Unspecified Bit Rate

UNI

User Network Interface

UPI

User Premises Interface

V_A

(logical) I/F ATU-C <-> Access Node

V_C

(logical) I/F Network <-> Access Node

VBR

Variable Bit Rate

VDSL

Very High Speed Digital Subscriber Line

nrt-VBR

Non-Real-Time Variable bit Rate

rt-VBR

Real-Time Variable bit Rate

References