1 VDSL | May 2021

VDSL

Product user guide

2 VDSL | May 2021

1.1 Who is VDSL for? ......................................................................... 3

1.2 Key benefits ................................................................................. 3

2 VDSL product description ................................................................ 4

2.1 VDSL components ........................................................................ 5

2.1.1 EXTERNAL TERMINATION POINT (ETP) .................................................... 5

2.1.2 VDSL ACCESS ...................................................................................... 5

2.1.3 COVERAGE AREA .................................................................................. 5

2.1.4 LOCAL AGGREGATION PATH .................................................................. 6

2.1.5 HANDOVER POINT ................................................................................ 6

2.1.6 LOCAL HANDOVER POINT ...................................................................... 6

2.1.7 REMOTE HANDOVER POINT ................................................................... 7

2.1.8 HANDOVER LINKS ................................................................................ 7

2.1.9 BACKHAUL .......................................................................................... 7

2.2 Variants of VDSL .......................................................................... 8

2.2.1 BASEBAND COPPER AND BASEBAND IP ................................................... 9

3 VDSL features ................................................................................. 9

3.1.1 DYNAMIC LINE MANAGEMENT (DLM) ...................................................... 9

3.1.2 SPECTRUM PROFILES .......................................................................... 10

3.1.3 TAIL EXTENSION ................................................................................ 10

3.1.4 SERVICE SPECIFICATION TARGETS ...................................................... 11

3.1.5 EXCEPTIONS TO SERVICE SPECIFICATIONS .......................................... 12

3.1.6 AGGREGATION AND HANDOVER OF TRAFFIC ......................................... 12

3.1.7 GEOGRAPHIC AVAILABILITY ................................................................ 13

3.1.8 CHANGES TO COVERAGE AREAS/HANDOVER POINTS ............................. 14

3.2 Relationship with other products ............................................... 14

3.2.1 POSSIBLE PRODUCT COMBINATIONS .................................................... 15

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1 Overview

1.1 Who is VDSL for?

Our VDSL service enables you to deliver VDSL2 powered, high-speed copper based

internet-grade broadband, where fibre is not an option. services. It’s an

intermediate input service that you can combine with and your own network and

applications and other services to provide high speed broadband services to your

Customers.

VDSL2 uses third generation copper-based DSL technology that is suitable for

people who are on optimal copper lines (typically less than 900-1200m from the

exchange) and is capable of delivering a significantly faster broadband experience

than ADSL2+.

It supports growing demands for bandwidth enabled content, such as Video

Streaming or Remote Working, as well as small business data requirements. VDSL is

suitable for people who require large upstream bandwidth or who regularly

download large files or use their broadband service for multiple applications such as

voice over IP, video streaming and online gaming.

1.2 Key benefits

VDSL has the following key benefits:

• It provides Customers with a high-performing, high quality broadband internet

service in locations where UFB fibre services are not available.

• It improves the capability of older ADSL2+ broadband services, delivering a better

experience for bandwidth hungry content, such as video conferencing, home

networking and automation, video applications, improved remote working and

home security - all over a single broadband access.

• It is an intermediate input product that can be combined with other services and

your own network and applications to provide differentiated solutions to your

customers.

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• It can be combined with Tail Extension to enable you to build up a local, regional or

national presence, without the need to invest or manage dedicated backhaul.

• It seamlessly integrates with handover links, allowing you to utilise the same

handovers for VDSL, Enhanced UBA (EUBA) and High-Speed Network Services

(HSNS) traffic.

VDSL is a high-speed broadband access service, with the following key

characteristics:

• It uses VDSL2 (Very-high bit-rate Digital Subscriber Line 2, G.993.2) protocols to

transmit data over twisted pair copper access lines. VDSL2 is a rate adaptive

technology that adjusts its transmission characteristics to optimise performance for

the individual line characteristics, including noise, attenuation, and error handling.

This rate adaptive nature means that we cannot offer a guarantee as to line speed

or throughput for a particular line.

• It features dynamic line management (DLM), which is used proactively on every

VDSL port to improve individual line performance by optimising the line for speed

and stability.

• It uses Zero touch Vectoring, which uses line monitoring information to maximise

the data rate by cancelling interference caused by cross talk.

• It includes G.INP, which is an improved mechanism for dealing with impulse noise.

• It uses our Congestion Free Network between the DSLAM and the Handover to

offer a significantly greater best-efforts throughput per connection than our other

copper broadband access products.

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2 VDSL product description

VDSL is an Ethernet-based bitstream product that enables you to offer your

customers delivery of internet-grade, broadband services using VDSL2 technology

(ITU-T Rec.G.993.2). VDSL2 complies with the UBA STD service description.

The following diagram shows the VDSL service:

2.1 VDSL components

2.1.1 EXTERNAL TERMINATION POINT (ETP)

The ETP is the external termination point for telecommunications services at an end-

customer's premises.

Where there is no termination point external to the premises it is either the first jack

on the premises wiring, or the building distribution frame.

2.1.2 VDSL ACCESS

Our VDSL service consists of a VDSL2 data connection operating in packet transfer

mode (PTM) from the ETP at the customer’s premises to the DSLAM at the local

exchange or cabinet.

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VDSL provides a single Ethernet VLAN between the ETP and the handover point.

Your customer must be able to submit or receive 802.1q tagged frames with a CE-

VLAN address of 10 and p-bit settings of 0 (best-efforts) (see technical interfaces for

more information). Non-tagged, or incorrectly tagged frames will be discarded.

Per- End-customer traffic policies are enforced in this section of the network.

2.1.3 LOCAL AGGREGATION PATH

The traffic from numerous DSLAMs in a coverage area is carried to an Ethernet

Aggregation Switch (EAS) located in the nearest Point of Interconnect (POI) over

local aggregation paths. These paths are monitored and proactively dimensioned to

support the VDSL traffic.

2.1.4 COVERAGE AREA

A coverage area is the collection of DSLAMs in a geographic area connected to the

same (closest) handover point, or POI.

Information on VDSL coverage is available from a number of sources:

• The Broadband Checker map on our public website.

• Service Availability API.

• Chorus coverage maps.

• Footprint report - a list of addresses of premises mapped with our ability to deliver

broadband services.

2.1.5 HANDOVER POINT

A handover point or POI is an exchange where you can pick up VDSL2 traffic. You’ll

require a handover link to receive the traffic.

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A POI may have multiple physical Ethernet Aggregation Switches but is treated as a

single handover point.

2.1.6 LOCAL HANDOVER POINT

A local handover point is a POI located in the coverage area in which the VDSL

access tail is provided. A VDSL service handed over in the local handover point does

not incur Tail Extension backhaul charges.

2.1.7 REMOTE HANDOVER POINT

A remote handover point is POI located outside the coverage area that the VDSL

access tail is provided.

If you do not have the ability to hand the traffic over at the local handover point you

can purchase Tail Extension to take the VDSL traffic to your nominated remote

handover point. Tail Extension mapping is generally specified per Coverage Area,

although it can be done per DSLAM, and is shared with ADSL2+ services. Tail

Extension has a separate service description.

2.1.8 HANDOVER CONNECTION AND LINKS

A Handover Link comprises a Handover Connection and an optional Handover Fibre

that connects our network and your network.

The handover connection is an Ethernet interface between our network and your

network, which provides the External Network-to-Network Interface (E-NNI)

function for VDSL.

The handover fibre is a point-to-point fibre that provides connectivity between the

handover connection and your network located outside the POI. Alternatively, the

handover connection can be connected to your equipment installed in the POI co-

location space.

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A minimum of one handover point is required. It is possible to use the same

handover point for all UBA Ethernet services. More information can be found in the

handover links product user guide.

2.1.9 BACKHAUL

If you do not have a handover link at the local handover point you can purchase Tail

Extension or another backhaul service (for example Chorus Relay Connect), which

will terminate on a remote handover point.

Local traffic and traffic from remote coverage areas may be handed to you at the

same handover point.

More information on backhaul options is available on the Chorus website.

2.2 Variants of VDSL

VDSL allows the delivery of best-efforts traffic only and operates at Full Speed.

VDSL can be provided with or without an active telephone service on the same

copper pair (such as POTS, UCLF Service, Baseband IP, or Baseband Copper voice

services). Voice services do not form part of the VDSL service and separate charges

may apply.

Where:

• Without voice means VDSL is provided without an active telephone service on the

same copper pair.

• With voice means VDSL is provided with an active analogue telephone service on

the same copper pair. The analogue telephone service is not provided as part of the

VDSL2 service and is available separately from us as an agency.

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• With Baseband Copper means VDSL is provided with a Baseband Copper

connection on the same copper pair to the ETP. Baseband Copper is a voice-band

copper pair from the ETP to your handover delivery point in the local exchange.

• With Baseband IP means VDSL is provided with Baseband IP on the same copper

pair to the ETP. Baseband IP provides an analogue voice connection between the

ETP and the DSLAM. At the DSLAM voice frequencies are converted into a

bitstream service and delivered to you at a Handover Connection at the first data

switch.

• Full Speed means the maximum speed that the DSLAM can support on the end-

customers line. Actual speeds may vary, depending on factors such as customer

premises equipment and wiring, the length and characteristics of the copper path

between the customer and the DSLAM, and network congestion.

2.2.1 BASEBAND COPPER AND BASEBAND IP

The Baseband Copper and Baseband IP services are not provided as part of the

VDSL service and are as defined in the Baseband Service Description and product

user guide.

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3 VDSL features

VDSL has the following features:

3.1.1 DYNAMIC LINE MANAGEMENT (DLM)

DLM is an inherent feature of the VDSL product. We proactively use DLM on every

VDSL port to improve individual line performance by optimising the line for speed

and stability.

DLM enables an iterative process that monitors and optimises the VDSL port and

associated line over the lifetime of the connection as follows:

• DLM collects performance data from all VDSL ports on a daily basis.

• DLM analyses the performance data and determines whether the active VDSL line

profile is optimal or not. If not, a new line profile is chosen based on the collected

data and activated for that particular customer's connection.

• DLM is a self-learning technology: it’s not a one-off implementation, it continues to

adapt and improve as the conditions of the line change (such as noise profiles,

house wiring changes or copper plant enhancements).

3.1.2 ZERO TOUCH VECTORING

VDSL Vectoring configures broadband VDSL lines dynamically to cancel interference

due to ADSL2+/VDSL2 crosstalk, significantly increasing performance as shown

below.

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In concept, vectoring is comparable to the noise-cancelling technology used in

headphones. It produces a clean signal for each line by measuring the crosstalk

from all other lines in the same cable bundle and generating anti-phase signals to

cancel the crosstalk signals out, resulting in almost zero noise.

Vectoring is only effective if all lines in a cable bundle are fed by the same DSLAM.

This makes vectoring unsuitable for some locations, such as where cable pairs are

spread across multiple DSLAMs.

There are three levels of VDSL modem vectoring capability:

• Full vector-capable CPE: VDSL modems that fully comply with G.993.5 get full

vectoring gain in both downstream and upstream direction.

• Vector-friendly CPE: VDSL modems that comply with G.993.2 Annex X and Y

standards will get a reduction in crosstalk. This enables full vectoring capable lines

to benefit from noise reduction.

• Legacy VDSL2 CPE: Legacy VDSL modems will not receive any benefits from

vectoring.

For vectoring to provide the full benefit on connections, CPE needs to support all of

the following requirements:

• G.993.5 and its corrigenda

• G.vector (G.993.5) minimises crosstalk impact;

• G.993.2 and G .998.4 Amd 1 - Seamless Rate Adaption - adapts a steady line rate

to the signal to noise ratio (SNR) without the line needing to be re-synched.

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• G.inp Amd 1 and 2 (G.998.4) - minimises impact noise impact.

• TR-249, Section 8.9 - Protection against connection on one wire and disorderly

leaving from the user.

3.1.3 G.INP

G.INP provides an improved mechanism for dealing with impulse noise. Impulse

noise consists of short or long pulses of interference and comes in two types.

• Single High Impulse Noise Event (SHINE), as generally the result of on/off

switching of appliances in the home; and

• Repetitive Electrical Impulse Noise (REIN), as generally the result of motor

controllers, electrical fences, or older dimmers.

G.INP (G.998.4) specifies the use of physical layer retransmission to provide

enhanced protection against impulse noise.

The approach is similar to the retransmission method used in TCP/IP. Instead of IP

packets, however, data transfer units (DTU) are sent between transmitter and

receiver. When packets get corrupted during transmission, the transmitting peer is

informed and the DTU is resent. As the DTU error detection and retransmission

occurs at the physical layer, G.INP only takes a few milliseconds.

The result is that G.INP achieves enhanced impulse noise protection with good

efficiency at shorter delays compared to traditional interleaving forward error

correction (I-FEC). G.INP only transmits when required, i.e. noise is detected on the

line, minimising latency impacts when there is no impulse noise, but it also means

the bit rates are not fixed anymore, depending on the number of retransmissions.

If CPE is not G.INP compatible, then VDSL2 will fall back to standard INP.

3.1.4 SPECTRUM PROFILES

The spectrum profiles to be used for VDSL2 are based on use of the ITU-T G.993.2

998E and 998ADE17 VDSL2 profiles.

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The VDSL2 998E spectrum profile forms the default profile for all end-customers.

The 998ADE17 spectrum profile will only be used for end-customers on short loops

(an attenuation level corresponding to about 200 m or less) and will be activated by

us only where this will optimise the customer experience.

Note that DLM will optimise the line based on the selected spectrum profile.

3.1.5 SERVICE SPECIFICATION TARGETS

VDSL has the following minimum service specification targets. Actual Customer

experience is expected to be much higher than this.

Metric Internet Class of Service (1500-byte packet)

Throughput 99.9% probability of providing to any provisioned end-

customer a minimum uplink and downlink average throughput of 96kbps during any 15-minute period on demand.

Mean one-way packet

delay

<1s

One-way packet

delay variation

Unspecified

One-way packet

loss ration

Unspecified

Notes:

• VDSL will likely only form a small part of any such end-to-end application. Actual

performance is not guaranteed as it is subject to external influences.

• These service specifications are the minimum design targets. Actual experience

should be substantially better than this.

• The service specifications relate to the performance of VDSL from the ETP to the

handover point and exclude delays such as serialisation or transcoding.

• Packet loss ratio and delay variation will be evaluated over an interval of 15

minutes.

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• Traffic may be policed at both an aggregate level and at an end- customer level to

ensure compliance with the service specification.

• To achieve the specifications of VDSL service your customer’s line speed must

meet the minimum thresholds.

3.1.6 EXCEPTIONS TO SERVICE SPECIFICATIONS

VDSL will not be available where the line quality does not meet the required line

speed threshold to deliver the service, usually due to distance of the premises from

the equipment.

VDSL2 performance will be affected by:

• Protocol overheads, such as TCP/IP.

• Network load or other user traffic demand.

• Constraints within either you, or your customer’s domains.

• The presence of any real time traffic on the same DSLAM.

• The actual loading of the local aggregation path.

• Any constraints external to VDSL2 technology (e.g. line distance, external noise, or

interference).

3.1.7 AGGREGATION AND HANDOVER OF TRAFFIC

Each end-customer is located in a coverage area. The traffic from numerous DSLAMs

in a coverage area is carried to the local handover point over local aggregation

paths, dimensioned to support the throughput rate for VDSL2 traffic.

If you do not wish to (or are unable to) collect VDSL traffic from the local handover

point and would like to transport the traffic to a remote handover point where you

have an already established a handover link, you may do so using:

• Tail Extension feature, or

• Chorus Relay Connect, or

• Third party transport.

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You may, via handover links and/or any of the options above, connect your network

to any number of handover points throughout the country. However, in order to

consume VDSL you must connect to a minimum of one handover point.

Please note that it’s not possible to deliver all unbundled services over a single

handover link. VDSL traffic can be delivered over the same handover link with other

Ethernet based access tails like Enhanced UBA or HSNS. However, VDSL traffic

cannot be shared with other non-Ethernet services such as UFB. Please refer to the

handover link product user guide for more comprehensive information on service

options.

3.1.8 TAIL EXTENSION

Tail Extension is a backhaul service that extends a VDSL access tail from the local

handover point to the remote handover point that you’ve nominated.

Tail Extension is a commercial, optional feature provided in accordance with the Tail

Extension Service Description.

3.1.9 CONGESTION FREE NETWORK

VDSL is delivered over a Congestion Free Network, which means that we

continuously monitor the network internodal link capacity between the DSLAM and

each handover point and proactively augment capacity before any part fills up.

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It is important to note that a congestion free network does not guarantee zero

frame loss, as some frame loss can occur at even a low utilisation, as show below:

The net effect of the congestion free policy, however, is that the VDSL2 line rate is

the main limiting factor in the Chorus network. However, your Customer’s actual

throughput may depend on external factors such as Wi-Fi performance, handover

and upstream network congestion, and the location performance of applications and

content servers.

3.1.10 GEOGRAPHIC AVAILABILITY

VDSL is available where we have coverage and your customer’s line speed meets

the minimum thresholds.

Our prequalification tool will analyse the exchange or cabinet capability and physical

characteristics of the copper line serving your customer’s premises and determine if

that copper line is VDSL capable. We will accept any order if the line prequalification

returns a maximum of 15dB.

We also recommend that you prequalify the circuit to determine if your customer is

a suitable candidate for VDSL.

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3.1.11 CHANGES TO COVERAGE AREAS/HANDOVER POINTS

The location of handover points and related coverage areas may change in the

future. We’ll give you at least one month’s notice if a new coverage area is going to

be introduced. We’ll give you 12 months’ notice if the existing coverage areas and

associated handover points change and those changes will have any impact on you

(i.e. requiring you to install new handover points or pay backhaul charges because

of the change).

Coverage area mapping for Tail Extension will need to be updated if coverage areas

are added or changed.

3.2 Relationship with other products

Our VDSL service can be combined with a number of other input products, as shown

in the figure below

VDSL

EUBA

HSNS

Tail Extension

Tail Extension

Tail Extension

Ha

nd

ove

r Li

nk

Exchange Co-location

Chorus Relay Connection

Point-to-Point Fibre

VDSL2 Modem

Service ProviderBNG

You need at least one Ethernet handover link to be able to consume VDSL, but you

can optionally add a number of additional components to create an end to end

solution that fits your needs:

• Tail Extension allows you to extend a VDSL connection from a local handover point

to a Remote handover point. This allows you to provide VDSL nationally with just

one handover link and scale up as demand requires.

• Exchange Co-location allows you install you network equipment in our secure and

robust exchange space, providing a convenient way to integrate your network with

ours. This also includes tie cables that allow you to connect to third party fibre or

backhaul.

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• Chorus Relay Connection allows you to extend a handover link from one Chorus

handover point to a remote location. This would allow you to serve multiple

handover points from a single location.

• Point-to-Point fibre allows you to combine ICABS and DFAS services to connect a

handover connection to a remote location, either within another handover point, or

to a separate premises within range of the Chorus fibre network.

This flexibility allows you to customise your customer’s end to end service.