SIN 511 Issue 3.1 - BT Wholesale TV Connect (TVC)

British Telecommunications plc 2020

Registered Office 81 Newgate Street LONDON EC1A 7AJ

Registered in England no.1800000

SIN 511 Issue 3.1

July 2020

Suppliers’ Information Note

For The BT Network

BT Wholesale TV Connect (TVC)

Service & Interface Description

Each SIN is the copyright of British Telecommunications plc. Reproduction of the SIN is permitted only in its

entirety, to disseminate information on the BT Network within your organisation. You must not edit or amend

any SIN or reproduce extracts. You must not remove BT trademarks, notices, headings or copyright markings.

This document does not form a part of any contract with BT customers or suppliers.

Users of this document should not rely solely on the information in this document, but should carry out their

own tests to satisfy themselves that terminal equipment will work with the BT network.

BT reserves the right to amend or replace any or all of the information in this document.

BT shall have no liability in contract, tort or otherwise for any loss or damage, howsoever arising from use of, or

reliance upon, the information in this document by any person.

Due to technological limitations, a very small percentage of customer interfaces may not comply with some of

the individual characteristics, which may be defined in this document.

Publication of this Suppliers’ Information Note does not give or imply any licence to any intellectual property

rights belonging to British Telecommunications plc or others. It is your sole responsibility to obtain any

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the SIN.

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Those BT services marked indicates it is a trade mark of British Telecommunications plc.

This SIN is available in Portable Document Format (pdf) from: https://www.bt.com/about/sinet

Enquiries relating to this document should be directed to: [email protected]

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mailto:[email protected]

SIN 511 Issue 3.1 British Telecommunications plc of 23

CONTENTS

1. INTRODUCTION ....................................................................................................................................... 3

2. SERVICE OUTLINE ................................................................................................................................. 4

2.1 ARCHITECTURE .............................................................................................................................................. 4 2.1.1 Content delivery to TV Connect Headend ........................................................................................... 4 2.1.2 Multicast Content Distribution ............................................................................................................ 6 2.1.3 Home Environment/End User Experience ........................................................................................... 6

2.2 ISP SERVICES ................................................................................................................................................ 7 2.3 TV CONNECT INFRASTRUCTURE DESCRIPTION .............................................................................................. 8

2.3.1 Overview .............................................................................................................................................. 8 2.3.2 End-To-End Service Flow Example (Fibre access, FTTC and FTTP via Openreach GEA) ............... 9 2.3.3 End-To-End Service Flow Example (Copper access from an MSAN) ............................................... 10

3. ISP MULTICAST INGESTION INTO TVC ......................................................................................... 12

3.1 CHANNEL INGRESS TO TV CONNECT HEAD END. ........................................................................................ 12 3.2 MULTICAST STREAM EGRESS ...................................................................................................................... 12 3.3 PHYSICAL ETHERNET PRESENTATION .......................................................................................................... 13

3.3.1 1000Base-T (IEEE 802.3ab) .............................................................................................................. 13 3.3.2 1000Base-X (IEEE 802.3z) ................................................................................................................ 13 3.3.3 10GBase-x (IEEE 802.3ae) ............................................................................................................... 13

4. IP MULTICAST STREAMS ................................................................................................................... 15

4.1 MAXIMUM BANDWIDTH .............................................................................................................................. 15 4.2 CHANNEL AGGREGATION ............................................................................................................................ 15 4.3 MULTICAST SOURCE AND GROUP IP ADDRESSES ......................................................................................... 15 4.4 RETRANSMISSION ........................................................................................................................................ 15 5. TV CONNECT CUSTOMER PREMISES EQUIPMENT (CPE) IGMP REQUIREMENTS .......... 16

5.1 MESSAGE SEQUENCING ............................................................................................................................... 16 5.2 SET TOP BOX (STB) FUNCTIONS ................................................................................................................. 16 5.3 RESIDENTIAL GATEWAY (HOME ROUTER) FUNCTIONS [3] ........................................................................... 16

5.3.1 End user connected via Openreach GEA (FTTC and FTTP) ............................................................ 17 5.3.2 End user connected to an MSAN (WBC copper) ............................................................................... 17 5.3.3 ISP utilising the L2TP handover service option for WBC ................................................................. 18

6. SERVICE AVAILABILITY .................................................................................................................... 19

7. ISP RESPONSIBILITIES ........................................................................................................................ 19

8. REFERENCES .......................................................................................................................................... 20

9. ABBREVIATIONS ................................................................................................................................... 21

10. HISTORY .................................................................................................................................................. 23

FIGURES

FIGURE 1 BT TV CONNECT SERVICE ARCHITECTURE 4

FIGURE 2 ISP CONNECTIVITY OPTIONS 5

FIGURE 3 OVERVIEW OF NETWORK INFRASTRUCTURE 8

FIGURE 4 END TO END FLOWS FOR AN END USER CONNECTED VIA FIBRE, FTTC AND FTTP VIA OPENREACH

GEA 9

FIGURE 5 END TO END FLOWS FOR AN END USER WITH COPPER ACCESS CONNECTED TO AN MSAN 10

FIGURE 6 TV CONNECT IGMP FLOWS 16


1. Introduction

This Supplier’s Information Note (SIN) 511 provides service description information for

customers of the BT Wholesale TV Connect (TVC) family of products. TVC delivers broadcast

quality TV over BT Wholesale’s dedicated broadband network.

TVC enables ISPs to deliver reliable and cost effective TV services to their end users across

the breadth of the BT 21CN broadband network making TV Connect a viable alternative to

traditional Satellite and DTT signal transmission. This coverage is achieved through our state

of the art, multicast enabled IP based network.

It should be noted that the information contained within this SIN might be subject to change

due to either the results of BT testing or feedback from trial participants. Please check with the

http://www.btplc.com/sinet/ site to ensure you have the latest version of this document.

Numbers in square brackets [ ] denote further references, as listed in Section 8.

Further information about the commercial aspects of TV Connect can be obtained by

contacting your Account Manager or Customer Relationship Manager.


2. Service Outline

2.1 Architecture

Figure 1 BT TV Connect Service Architecture

The TV Connect Service Architecture is indicated in Figure 1. The TV Connect service is built

on top of the underlying Wholesale Broadband Connect (WBC) service.

An ISP planning to purchase the TV Connect (TVC) service will utilise the WBC

PTA or L2TP handover service.

The TV Connect service will multicast live streaming TV Channels from ingress in

the TV Connect Head End at the MIP to end users on the WBC platform.

2.1.1 Content delivery to TV Connect Headend

The ISP will be expected to provide TV content to the Head End, often in

conjunction with a content provider subject to a commercial relationship.

The ISP will be expected to deliver content to the TV Connect Headend as

compressed (encoded IP multicast) content.

The ISP would provide compressed content, encoding, (optionally) encrypting and

conditioning the content themselves, ready for multicast distribution.

The ISP will be entirely responsible for the encryption of their TV channels for

conditional access by end users.

The ISP is expected to provide aggregated multi channel content to the Head End

via the TVC Multicast Ingest Point (MIP) using Ethernet links.

The ISP will be responsible for the provision, management and ownership of the

Ethernet Links up to the agreed handover port in the MIP. This includes utilisation

of bandwidth within these links such that overall bandwidth does not exceed the

overall bandwidth envelope agreed with BT Wholesale.

21C

TVC MIP Headend

ISP Encoding/Encryption

Openreach

MIP Input

21C Interconnect

ISP RET

ISP

Multicast TV channels PathUnicast WBC data pathTV Connect Interface

BRAS/LAC

Residential Gateway

STB

Other Devices


The TVC MIP offers a Geo-Resilient option whereby the ISP may additionally

present their content at the second (Geo-Resilient) site Figure 2 illustrates the three

options available wherein:

o ISP A connects via 2 links to each site (one to each landing point at each

site).

o ISP B connects via 1 link to each site (one to the primary landing point at

each site).

o ISP C connects via 2 links to only the main site, BT Tower (one to each

landing point at BT Tower).

Each of the options clearly offer different levels of physical or geographic

resilience.

Note that the option to connect exclusively at the secondary site is not offered.

The ISP may elect for different resilient options on a per channel basis, however

utilising the same resilient option for all channels provided by the ISP is strongly

recommended.

Figure 2 ISP Connectivity Options

21CDistribution

BT Tower(Main Headend Site)

TVC/MIPSwitch X

TVC/MIPHER X

MAR 1TVC/MIPSwitch Y

TVC/MIPHER Y

BT Colombo House(Secondary Headend Site)

TVC/MIPSwitch X

TVC/MIPHER X

TVC/MIPSwitch Y

TVC/MIPHER Y

MAR 2

ISP B

ISP CISP A

ISP A


2.1.2 Multicast Content Distribution

The TV Connect traffic will be delivered across the end to end network over a

separate logical path from the WBC data traffic. (See Section 2.3.1)

The ISP may choose to provide its own Retransmission (RET) solution for packet

repair. A feed of the full multiplex of their channels may be supplied by BT

Wholesale to support such a solution. Details of handover points will be agreed

during contract negotiation subject to a successful development and test programme

with the ISP. The ISP will be responsible for interconnection to their own

equipment from the agreed handover points. The ISP may forward retransmission

repair and control traffic via the WBC service.

2.1.3 Home Environment/End User Experience

The end user access link may be via WBC fibre or copper as provided by

Openreach.

The ISP will be expected to provide the required equipment (e.g. a Residential

Gateway (home router) and set top box (STB) or other equipment) to an end user

in order to support the live streaming of TV channels.

The ISP will be responsible for end user packages, end user repair and end user

billing.

BT Wholesale will provide interfaces to support provision, repair, service

monitoring and billing.


2.2 ISP Services

The TV Connect product is an optional feature of the WBC service that allows live streamed

content to be multicast delivered to End Users from a Head End within the BT Wholesale

network.

The WBC SIN is available from https://www.bt.com/about/sinet

TVC Service Configuration

An ISP will buy TV Connect from BT Wholesale to deliver channels to its WBC

broadband end users.

BT Wholesale takes on the delivery of TV channels to all the WBC end users as part of

the product.

Only a WBC customer (ISP) can take up the TV Connect service.

The TV Connect service is available to ISPs that take the WBC PTA (PPP termination

and aggregation service) and/or the WBC L2TP (Layer 2 Tunnelling Protocol)

handover service.

The ISP will supply TV channel content to the BT Wholesale TV Connect Head End.

The ISP will be responsible for the Residential Gateway (home router) and set top box

(STB) functionality within the end user’s environment.

It is the responsibility of the ISP to provide any TV Channel restrictions to individual

WBC broadband end users it deems necessary.

For all requests to provide channel capacity within the current network capacity (as agreed and

managed with BT Wholesale) available on the TV Connect network, BT Wholesale will deliver

channel capacity to an ISP’s end users who are on WBC fibre and copper, in line with

forecasted channel demand from the ISP following the process as set out in the TV Connect

Product Handbook.

Where there is a need to provide additional channel capacity beyond the current network

capacity available, the ISP can submit a request by contacting their account team who will raise

a request in to the TV Connect Product Line via the Statement of Requirements (SoR) process.

An assessment of such a request will then be carried out to determine if the demand for

additional capacity can be accommodated in line with the SoR process timelines.

An ISP can check the availability of Multicast at WBC exchanges by using the Broadband

Availability Checker available at http://www.btwholesale.com/ via the Routing and Planning

section under the Applications tab.

When the ISP is ready to raise an order to provide/add channels, all of the channel details -

including whether or not the channel/s are required on both fibre and copper networks - must

be clearly marked in the appropriate fields on the TV Connect CRF.



2.3 TV Connect Infrastructure Description

2.3.1 Overview

An overview of the network infrastructure that supports TV Connect is illustrated in Figure 3.

Figure 3 Overview of Network Infrastructure

The TV Connect service accepts TV channels from a TV content provider into the TV Connect

Head End as compressed streams via the TVC Multicast Ingest Point (MIP) capability.

Compressed (encoded and optionally encrypted) TV channels are checked and policed at the

Multicast Ingest Point (MIP) to ensure that a) the maximum per channel bandwidth, as

contracted by the ISP is not exceeded and b) that the maximum overall bandwidth envelope for

all channels, as contracted by the ISP is not exceeded. Error recovery via Forward Error

Correction (FEC) is not supported, but appropriate Service IP Addressing is provided.

The TV Connect service delivers multicast channels to end users via MSANs and Openreach

GEA. A combination of IP and Ethernet Multicast within BT’s 21C core, at the MSAN (copper

access), and within the Openreach GEA equipment (fibre access, FTTC and FTTP), is then

used to replicate and deliver TV Connect Channels to WBC End Users (EUs). WBC End Users

will then receive the TV channel(s) when requested using the IGMP protocol, as described in

sections 2.3.2 and 2.3.3.

The service is designed for high availability, so TV Connect traffic is delivered over resilient

paths into and across the BT Wholesale 21C infrastructure to MSANs and Openreach GEA

handover points.

BT Wholesale

BT Tower (Main Site)

BT Colombo (Geo-resilient Site)

Residential Gateway

STB

Openreach

Openreach GEA

ISP Encryption/Encoding

Compressed, EncryptedTV Content in

MIP

MIP

MSAN

EES

EEA

L2S

MAR

MAR

PON

DSLAM

21C Core

BRAS/LAC

BEA

LNS

MSIL MSIL

ISP N/WISP N/W

Openreach SMPF

Openreach Cablelink Broadband

ISP

FTTP

FTTC

Residential Gateway

STB

Residential Gateway

STB



MIP

MIP

4x Ethernet

4x Ethernet

Multicast TV channels Path

MIP Channels Path

Unicast WBC data path


2.3.2 End-To-End Service Flow Example (Fibre access, FTTC and FTTP via Openreach

GEA)

An overview of end user end-to-end flows for an end user connected via Openreach GEA is

illustrated in Figure 4.

Figure 4 End to End flows for an end user connected via

fibre, FTTC and FTTP via Openreach GEA

Channel join request

1. End user issues channel join request via Set Top Box

2. Home router issues proxy request into TV Connect path to Openreach GEA head end

3. Home router replicates proxy request and issues it into PPP path to BRAS

4. Openreach GEA head end receives proxy request from home router and delivers

requested channel to end user

5. BRAS receives proxy request from home router and shapes broadband end user

broadband PPP session to a rate reduced by an amount equal to requested TV channel

bandwidth.

6. In the case of an ISP taking the L2TP handover option for WBC, the home router

replicates the proxy request so that it is forwarded via the PPP session over an L2TP

tunnel from the LAC within the BT platform to the LNS within the ISP’s network.

7. The LNS within the ISP’s network receives the proxy request and is expected to shape

the broadband end user PPP session to a rate reduced by an amount equal to the

requested TV channel bandwidth.

BT Wholesale

TV Headend

Residential Gateway

STB

Openreach

Openreach GEA

MSAN

EES

EEA

L2S

MAR

MAR

PON

DSLAM

21C Core

BRAS/LAC

BEA

LNS

MSIL MSIL

ISP N/WISP N/W

Openreach SMPF


ISP

FTTP

FTTC

Residential Gateway

STB

Residential Gateway

STB



MIP

MIP

7

6

5

4

4

3

31

12

2

4x Ethernet


MIP Channels Path


IGMP Messaging


Channel Leave Request

The channel leave request sequence functions in a similar fashion.

1. End user issues channel leave request via Set Top Box

2. Home router issues proxy request into TV Connect path to Openreach GEA head end

3. Home router replicates proxy request and issues it into PPP path to BRAS

4. Openreach GEA head end receives proxy request from home router and stops

delivering the specified channel to the end user

5. BRAS receives proxy request from home router and removes the shaping on the

broadband end user broadband PPP session by an amount equal to the bandwidth of the

TV channel specified in the leave request.




7. The LNS within the ISP’s network receives the proxy request and is expected to remove

the shaping on the broadband end user PPP session by an amount equal to the

bandwidth of the TV channel specified in the leave request.

2.3.3 End-To-End Service Flow Example (Copper access from an MSAN)

An overview of end user end-to-end flows for an end user connected to an MSAN is illustrated

in Figure 5.

Figure 5 End to End flows for an end user with copper access connected to an MSAN

BT Wholesale

TV Headend

Residential Gateway

STB

Openreach

MSAN

EES

EEA

L2S

MAR

MAR

PON

DSLAM

21C Core

BRAS/LAC

BEA

LNS

MSIL MSIL

ISP N/WISP N/W

Openreach SMPF


ISP

FTTP

FTTC

Residential Gateway

STB

Residential Gateway

STB



MIP

MIP

7

6

5

4

3

12

Openreach GEA

4x Ethernet


MIP Channels Path


IGMP Messaging


Channel Join Request

1. End user issues channel join request via Set Top Box.

2. Home router issues proxy request into TV Connect path to MSAN.

3. Home router replicates proxy request and issues it into PPP path to BRAS.

4. MSAN receives proxy request from home router and delivers requested channel to end

user.

5. BRAS receives proxy request from home router and shapes the broadband end user’s

PPP session to a rate reduced by an amount equal to the requested TV channel

bandwidth.







Channel Leave Request

The channel leave request sequence functions in a similar fashion.

1. End user issues channel leave request via Set Top Box.

2. Home router issues proxy request into TV Connect path to MSAN.

3. Home router replicates proxy request and issues it into PPP path to BRAS.

4. MSAN receives proxy request from home router and stops delivering the channel down

to the end user.

5. BRAS receives proxy request from home router and removes the shaping on the

broadband end user’s PPP session by an amount equal to the bandwidth of the TV

channel specified in the leave request.








3. ISP Multicast Ingestion into TVC

3.1 Channel Ingress to TV Connect Head End.

Presentation of [ISP encoded and encrypted] programme sources from the ISP’s network to the

TVC Head End will be by Ethernet links, as per specification in section 3.3. The number of

links provided will depend on the resilience option selected by the ISP (see Section 2.1.1).

The ISP devices to be connected into the TVC Multicast Ingest Point (MIP) can be located

locally (within range of CAT5e cable, 100 metres maximum or multi-mode fibre optic cable,

550m maximum) or remotely in a location to be agreed with the ISP. For devices that are

remotely located the ISP will be responsible for the provision of interconnecting access circuits

and any associated security arrangements. BT recommends the use of the Openreach Ethernet

Access Direct (EAD) products.

At least two Ethernet ports are available on the TVC MIP to accept the programme streams

from the ISP [4], the location and number of ports is dependent on the resilient option chosen

by the ISP as illustrated in Figure 2 and total stream bandwidth requirements.

All signals between the ISP and the Head End will be carried over these physical links.

It is assumed that the programme streams traversing these links will be properly conformed

MPEG2 Single Programme Transport Streams [2].

MIP will monitor and may police ISP ingest bandwidth to ensure that:

The overall bandwidth offered by the ISP into TVC does not exceed the overall

bandwidth envelope agreed with BT Wholesale.

The individual channel bandwidth of each channel offered by the ISP into TVC does

not exceed the individual channel bandwidth agreed with BT Wholesale.

3.2 Multicast Stream Egress

Subject to agreement with BT Wholesale and technical capability, all the channels belonging

to an ISP may be made available to the ISP at a small set of handover points, which are to be

agreed during contract negotiation. The physical interface presentation is as defined in section

3.3. BT Wholesale will only duplicate multicast programme streams the ISP sends into the

TVC MIP as defined in section 3.1 (i.e. another ISP’s programme streams will not be

duplicated back to the ISP).

Where an ISP has multiple interfaces into the MIP at BT Tower and optionally Colombo House

to ingest channels to provide resiliency, BT Wholesale will offer separate copies of each

resilient path back to the ISP at the same location, via an agreed physical presentation as

defined in section 3.3. The ingest and egress interfaces will be separate and may be of different

physical presentation subject to availability and agreement between BT Wholesale and the ISP.

In addition to what is offered in section 4.4, BT Wholesale will offer duplicates of all of the

ISP’s channels at sites beyond BT Tower and Colombo House. Only one copy will be offered

per resilient path at each location, and is subject to suitability of providing this facility at each

location. For example, at the MAR site up to 5 interfaces for duplicate streams are available –

1 off each link from BT Tower and Colombo house (4 total) and 1 off link into the 21CN core

network. The physical presentation of copied streams at the MAR sites and beyond [away from

the BT Tower and Colombo House sites] will be 10GBASE-LR only.


3.3 Physical Ethernet Presentation

3.3.1 1000Base-T (IEEE 802.3ab)

The ISP may provide their programme streams at ingest points using 1000Base-T (IEEE

802.3ab) interfaces, and where capacity requirements dictate provide their multiplex of

multicast channels using multiple physical interfaces per resilient path (e.g. to provide 1.1Gbps

of multicast this can be split over 2 1000Base-T ports, each carrying 550Mbps). Each physical

port can ingest up to 1Gbps of Ethernet traffic, however the volume of multicast programme

traffic will be less than this due to headers and other Ethernet protocol overheads. BT

Wholesale suggest limiting the utilisation of 1Gbps links to 900Mbps to avoid potential high

jitter and packet loss observed in some test scenarios.

The definition of this interface type dictates the use of twisted pair copper CAT5E or higher

grade cable, which will limit the cable distance between the ingest point and ISP equipment to

100 metres.

This interface type is only offered for ingest traffic only.

3.3.2 1000Base-X (IEEE 802.3z)

The ISP may provide their programme streams at ingest points using 1000Base-X (IEEE

802.3z) interfaces, and where capacity requirements dictate provide their multiplex of multicast

channels using multiple physical interfaces per resilient path (e.g. to provide 1.1Gbps of

multicast this can be split over 2 1000Base-X ports, each carrying 550Mbps). Each physical

port can ingest up to 1Gbps of Ethernet traffic, however the volume of multicast programme

traffic will be less than this due to headers and other Ethernet protocol overheads. BT

Wholesale suggest limiting the utilisation of 1Gbps links to 900Mbps to avoid potential high

jitter and packet loss observed in some test scenarios.

The definition of this interface type dictates the use of fibre optic cable, and the MIP product

will only support the use of multi-mode fibre cable. Although the cable length limit of using

OM4 grade fibre at 1Gbps speed is above 550m, the MIP product will restrict the fibre length

to 550 metres between the ISP equipment and the ingest port to provide alignment with the use

of the same fibre cable at 10Gbps speed.

This interface type is only offered for ingest traffic only.

3.3.3 10GBase-x (IEEE 802.3ae)

The MIP product supports the use of 10Gbps Ethernet interfaces for both ingest and egress

multicast traffic. The restrictions of use are indicated below.

At the TV Headend sites (BT Tower and Colombo House) the expectation is that any

connectivity between the TVC MIP and ISP equipment will be in-building, therefore only

10GBase-SR interfaces will be supported for traffic ingest links (ISP sending multicast

programme streams into the MIP) and for traffic egress links (where an ISP requests

programme streams to be duplicated back to their equipment from agreed monitoring points in

the MIP).

To mitigate against connectivity faults and provide greater reliability only OM4 grade multi-

mode fibre shall be used for connectivity between ISP equipment and the TVC MIP equipment.

This offers a theoretical cable distance limit of 550 metres, however losses caused by splices

and patching of cables should be considered to assess the quality and light levels of the links,

which may result in a shorter usable cable distance.


For the egress interfaces in the MAR sites and beyond in the 21CN network, only 10GBase-

LR interfaces are supported, requiring the use of single-mode fibre cables for a maximum reach

of 10km.


4. IP Multicast Streams

4.1 Maximum Bandwidth

The maximum bandwidth per SPTS Programme Channel shall be 30Mbps in the Wholesale

Network

4.2 Channel Aggregation

The TV Connect product aggregate all the ISP’s channels together to deliver as IP Multicast

for transport across the core of the 21C network. Each channel is identified by unique group

and source IP address and transported together in this group of IP multicast streams.

4.3 Multicast Source and Group IP addresses

The ISP will be expected to complete a Customer Requirements Form (CRF) in conjunction

with BT Wholesale. Multicast group and source addresses will be agreed between BT

Wholesale and the ISP with regards to allocation for each channel during the order process.

The multicast group IP address is used to uniquely identify a particular TV channel.

The multicast source IP address is used to identify the network source equipment of the TV

channel within the TV Connect Head End and is required for multicast routing and geo-resilient

failover.

4.4 Retransmission

In order to facilitate packet repair by retransmission by the ISP, all of the channels belonging

to an ISP may be duplicated and made available to the ISP at a small set of handover points,

which are to be agreed during contract negotiation.

Retransmission repair and control packets may be forwarded via the WBC data service. It is

recommended that an ISP make use of the priority best effort traffic marking for retransmission

repair and control traffic [5] in order to ensure a good experience for end users.


5. TV Connect Customer Premises Equipment (CPE) IGMP Requirements

5.1 Message Sequencing

It is expected that IGMPv3 will be used to signal access to TV Connect channels. An end user

will be joined to a selected channel via

Openreach GEA – fibre to the cabinet (FTTC) or fibre to the home (FTTP).

MSAN – WBC copper

The IGMP messaging sequence is indicated in Figure 6.

Figure 6 TV Connect IGMP flows

5.2 Set Top Box (STB) Functions

The set top box will generate IGMP join and leave messages in response to end user requests

(e.g. channel selection changes) and respond to IGMP query requests (from upstream network

equipment).

The set top box may use the WBC service to communicate with retransmission servers for

packet repair or access other ISP services.

5.3 Residential Gateway (home router) Functions [3]

• The End user Residential Gateway (RG) acts as an IGMP proxy routing agent,

supports IGMP snooping and forks IGMP messages for sending up the TV Connect

and Broadband paths

• Support for IGMPv3 is required on the Residential Gateway

• The TV Connect product will only support IGMPv3 [1]

• The TV Connect product will support IGMPv3 Any Source Multicast (*,G).

EU IGMP Domain Access Network IGMP Domain

TV Connect Multicast PathUnicast WBC Broadband Traffic path

Residential GatewaySTB

OR GEA / MSAN

12 3

2

47

6 5 HierarchicalShaping

BRAS

General & Specific IGMP Queries

Unsolicited IGMP messages, and reports in response to queries

Multicast Group to Bandwidth Table (maintained by OSS)

Residential Gateway Forks IGMP Messages

Key:


• The TV Connect product will not support IGMPv3 Source Specific Multicast (S,G).

• The IGMP protocol has no acknowledgements, in consequence

• Multiple IGMP requests are to be sent by the Residential Gateway. 2 IGMP

requests should be sent initially (IGMPv3 default setting). The “robustness

variable” setting may be adjusted if required in consultation with BT

Wholesale during trials.

• The “Unsolicited report intervals” should be set to 1 second initially (IGMPv3

default setting).

• The Residential Gateway should prioritise IGMP joins and leaves upstream (802.1p

marking of 3 or above)

• Responses to IGMP Queries (keep-alives) by the Residential Gateway shall only be

returned over the interface through which the Queries were received.

5.3.1 End user connected via Openreach GEA (FTTC and FTTP)

For an end user connected via Openreach GEA (FTTC and FTTP)

• The Residential Gateway will support

– IPoE for multicast traffic and PPPoE for BB traffic

– VLAN tag ID of 0 or no VLAN tag ID for multicast and BB traffic

• Fork IGMP requests for sending up multicast and BB paths. More details on the

support of Multicast via Openreach GEA (FTTC and FTTP) including features such

as fast leave are described in SIN 503 [6]

The BRAS will adjust the rate of the PPP session on a receipt of an IGMP join/leave by an

amount equal to the bandwidth of the channel specified in the join/leave.

• The BRAS will respond to IGMP joins/leaves after a configurable delay with a

default setting of 1s.

The BRAS will send IGMP queries independently of the Openreach GEA equipment

• The BRAS will send periodic IGMP queries over the PPPoE session

– General queries will be sent at a default interval of 125s with a default

maximum response time of 10s

– The BRAS will use a “robustness variable” setting of 3 as default.

Settings for timer values and “robustness variables” may be adjusted in consultation with BT


5.3.2 End user connected to an MSAN (WBC copper)

For an end user connected to an MSAN (WBC copper)

• The Residential Gateway will support a dual VC architecture

– Accept TV Connect multicast traffic on ATM VP/VC 0/35 with IPoA and

broadband traffic on ATM VP/VC 0/38 with PPPoA

– Fork IGMP requests for sending up multicast and broadband paths

• The MSAN will send periodic IGMP queries



maximum response time of 100s.

– Specific queries will be sent at a default interval of 10s with a default

maximum response time of 8s.

The MSAN will use a “robustness variable” setting of 2 as default.

The MSAN will support the fast leave mode of IGMP.

5.3.3 ISP utilising the L2TP handover service option for WBC

For an ISP utilising the L2TP handover service option for WBC, the ISP will be expected to

provide similar IGMP aware line shaping functionality to that of the BT BRAS.

The ISP LNS will adjust the rate of the PPP session on a receipt of an IGMP join/leave by an

amount equal to the bandwidth of the channel specified in the join/leave.

• The ISP LNS will respond to IGMP joins/leaves after a configurable delay with a

default setting of 1s.

The ISP LNS will send IGMP queries independently of the MSAN

• The ISP LNS will send periodic IGMP queries over the PPPoA session


maximum response time of 10s

– The LNS will use a “robustness variable” setting of 3 as default.

Settings for timer values and “robustness variables” may be adjusted in consultation with BT



6. Service Availability

Only a WBC customer (ISP) can take up the TV Connect service. The TV Connect service is

available to ISPs that take the WBC PTA (PPP termination and aggregation service) or L2TP

(Layer 2 tunnelling protocol) handover service.

An ISP can check the availability of Multicast at WBC exchanges by using the Broadband

Availability Checker available at http://www.btwholesale.com/ via the Routing and Planning

section under the Applications tab.

7. ISP Responsibilities

The ISP will be responsible for End User engagement, including client management (e.g. client

streaming, updates, and problem resolution)

The ISP specified Set Top Box will need to be capable of receiving TV Connect Streams,

decryption, and error recovery via retransmission.

The ISP will be responsible for the encoding and Conditional Access for their TV Channel

content.

The ISP will be responsible for connectivity to the TVC Head End up to the agreed handover

port in the MIP.

The ISP will be responsible for live streaming the TV Channel content into the TVC Head End.

The ISP will be responsible for the Residential Gateway (home router) and set top box

functionality within the end user’s environment. The Residential Gateway (home router) will

proxy IGMP requests upstream onto the TV Connect path and into the Broadband PPP path

towards the BRAS.

The ISP will participate in collaborative testing to support BT Wholesale with provision and

repair of the TVC service.

The ISP will ensure that all technical details required to complete the CRF are provided.

The ISP will be responsible for packet repair via Retransmission.

For an ISP that takes the L2TP handover service the ISP will be responsible for IGMP aware

PPP session shaping functionality.

http://www.btwholesale.com/


8. References

Protocol Standards:

[1] IGMPv3 IETF RFC 3376 Internet Group Management Protocol Version3

http://datatracker.ietf.org/doc/rfc3376/

[2] MPEG2 – TS ETSI TS 102 034 (V1.4.1): “Digital Video Broadcasting (DVB);

Transport of MPEG-2 TS Based DVB Services over IP Based

Networks”.

[3] TR101 Technical Report DSL Forum TR101 Migration to Ethernet based

DSL Aggregation April 2006– section 6 Multicast

[4] Gigabit Ethernet IEEE http://www.ieee802.org

IEEE 802.3ab – 1000BASE-T

IEEE 802.3z – 1000BASE-X

IEEE 802.3ae – 10GBASE-x

[5] SIN 472 BT Wholesale Broadband Connect (WBC) Products Service

Description

http://www.btplc.com/sinet/ https://www.bt.com/about/sinet

[6] SIN 503 Generic Ethernet Access Multicast, Service and Interface

Description


http://datatracker.ietf.org/doc/rfc3376/

http://www.ieee802.org/

http://www.btplc.com/sinet/




9. Abbreviations

21CN 21st Century Network

ATM Asynchronous Transfer Mode

AVC Advanced Video Coding

BB Broadband

BEA Broadband Edge Aggregator

BRAS Broadband Remote Access Server

BT British Telecommunications plc

BTW BT Wholesale

CA Conditional Access

CAT5 Category 5 cable

CPE Customer Premises Equipment

CRF Customer Requirements Form

DSL Digital Subscriber Line

DSLAM Digital Subscriber Line Access Multiplexer

DTT Digital Terrestrial TV

DVB Digital Video Broadcast

EAD Ethernet Access Direct [Openreach]

EEA Ethernet Edge Aggregator

EES Ethernet Edge Switch

EMM Entitlement Management Messages

EU End User

FEC Forward Error Correction

FTTC Fibre To The Cabinet

FTTH Fibre To The Home

GE Gigabit Ethernet

GEA Generic Ethernet Access (Openreach product)

HD High Definition

HE Head End

IEA Inner Ethernet Aggregator

IEEE Institute of Electronic and Electrical Engineers

IETF Internet Engineering Task Force

IGMP Internet Group Management Protocol

IP Internet Protocol

IPoA IP over ATM

IPoE IP over Ethernet

ISP Internet Service Provider

ITU International Telecommunications Union


L2S Layer 2 switch

L2TP Layer 2 Tunnelling Protocol

LFE Low Frequency Effects (Channel used in surround sound)

LAC L2TP Access Concentrator

LNS Layer Two Network Server

MIP Multicast Ingest Point

MPEG2 Motion Picture Experts Group compression algorithm

MSAN Multi-Service Access Node

MSIL Multi-Service Interconnect Link

OSS Operational Support System

PON Passive Optical Network

PPP Point-to-Point Protocol

PPPoA Point-to-Point Protocol over ATM

PPPoE Point-to-Point Protocol over Ethernet

PTA Point to Point Termination and Aggregation

RET Retransmission (packet repair)

RFC Request For Comment

RG Residential Gateway

s Seconds

SD Standard Definition

SIN Supplier Information Note

SMPF Shared Metallic Path Facility

SMPTE Society of Motion Picture and Television Engineers

SPTS Single Programme Transport Stream

STB Set Top Box

STIN Supplier Trial Information Note

TV Television

TVC TV Connect

UDP User Datagram Protocol

UHD Ultra High Definition

VC Virtual Circuit

VLAN Virtual Local Area Network

VP Virtual Path

WBC Wholesale Broadband Connect


10. History

Issue Date Changes

STIN 1.0 13th January 2012 First Issue for Publication on http://www.sinet.bt.com

STIN 1.1 14th September 2012 STIN updated to reflect learning from Product Trials

SIN 1.0 18th December 2012 STIN raised to SIN

SIN 1.1 25th January 2013 SIN updated to clarify availability of TV Connect over WBC

Copper

SIN 1.2 26th March 2013 SIN updated to include L2TP handover option

SIN 1.3 25th July 2013 SIN updated to include alternative Head End trial and

clarification to audio description options

SIN 1.4 10th October 2013 SIN updated to include channel resilience via alternative

Head End as firm option

SIN 1.5 7th November 2013 SIN updated to include additional information on channel

capacity management and service availability

SIN 1.6 9th May 2014 SIN updated to include option for SDI egress connection

from Head End

Change of SINet site references from

http://www.sinet.bt.com to http://www.btplc.com/sinet/

SIN 1.7 23th July 2015 SIN updated to include UHD channel Specifications

SIN 1.8 SIN Updated to extend TVC offering to incorporate options

to ingest pre-encoded (ISP encoded) content. 16/10/2015.

Reviewed and updated 29/10/2015.

SIN 1.9 November 2016 SIN updated to extend TVC offering to support the ingest of

Audio Description Broadcaster Mix for encoding to delivery

an alternative Audio Description format to Receiver Mix.

Minor editorial updates for clarity on specification.

SIN 1.10 October 2017 TV Connect Protect option withdrawn.

Minor editorial updates to clarify diagrams.

Removed invalid example of product option from section 5.

SIN 2.0 December 2017 Withdrawal of the encoding capability of TV Connect.

Documentation correction to requirements of End User

connectivity to MSAN WBC Copper (section 5.3.2)

SIN 3.0 December 2019 Added support for 10Gbps interfaces and duplication of

multicast traffic back to ISP

SIN 3.1 July 2020 Change SINet site references from

http://www.btplc.com/sinet/ to


-END-

http://www.sinet.bt.com/

http://www.btplc.com/sinet/


SIN 511 Issue 3.1 - BT Wholesale TV Connect (TVC)

Documents

Transcript of SIN 511 Issue 3.1 - BT Wholesale TV Connect (TVC)