INTERNET BROADBAND

ITTM, Delhi

Definition of Broadband
An always-on' data connection that is able to support
interactive services including Internet access.
According to Broadband policy 2004,has the capability
of the minimum download speed of 256 kilo bits per
second (kbps) to an individual subscriber from the Point
Of Presence (POP) of the service provider.
According to New Telecom policy 2011, minimum
download speed should be 512 kbps.
It provides Internet, IPTV and VoIP simultaneously
along with basic telephone service.

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What is ADSL ?
Asymmetrical digital subscriber line (ADSL) is emerging as the optimal solution to high-speed
Internet access technology. ADSL matches the asymmetric pattern of Internet traffic with speeds of
up to 8 Mb/s downstream from the network to the end user, and up to 640 kb/s upstream from the
end user to the network. Because ADSL can transmit both voice and data simultaneously over an
existing, single copper pair up to 5.5 KM long, it is the perfect solution for service providers to meet
the increasing customer demand for faster Internet access. With its amazing speed and economical
use of the installed base of copper cable, ADSL keeps the service cost low for both service
providers and end users.
An ADSL system consists of the following components:
ADSL transceiver unit-central office (ATU-C), also referred to as DSLAM
ADSL transceiver unit-remote (ATU-R), also referred to as an ADSL modem
Splitter low pass filter for separating POTS from ADSL
Digital subscriber line access multiplexer (DSLAM) Multiplexes many ADSL copper lines into
one Ethernet uplink fiber and include the splitter in ATU-C Frame.

Splitter- a low pass filter.

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Freq. spectrum used in Broadband

ADSL Bandwidth

UPSTREAM

4 KHz

26 KHz

138 KHz

DOWNSTREAM

1 . 1 MHz

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Modulation Techniques
Traditional plain old telephone service (POTS) uses a narrow 4-kHz baseband
frequency to transmit analog voice signals. This means that even with
sophisticated modulation techniques, current modem technology can only
achieve throughput of up to 56 kb/s. To attain a much higher throughput of up
to 8 Mb/s, ADSL increases the usable frequency range from 4 kHz to 1.1 MHz.
Frequency division multiplexing (FDM) then allows ADSL to create multiple
frequency bands to carry upstream and downstream data simultaneously with
the POTS signal over the same copper pair. The lower 4-kHz frequency range
is reserved for POTS, the middle frequency band is used to transmit upstream
data, and the larger, higher frequency band is used for downstream data.

ITTM, Delhi

XDSL
xDSL,

is a family of technologies that provides digital

data transmission over the wires of a local telephone
network
DSL (Digital Subscriber Line) exploits the unused
analogue bandwidth that is potentially available in the
wires that run from the user premises to the local
exchange
The phone system nominally passes audio between 0.3
KHz and 3.4 KHz, which is regarded as the range required
for human speech to be clearly intelligible. This is known
as voiceband or commercial bandwidth
The local loop connecting the telephone exchange to
most subscribers is capable of carrying frequencies well
beyond the 3.4 kHz upper limit of POTS.

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HOW XDSL WORKS

These technologies provide high rate, bi-directional data
communications by using elaborate modulation and error
correction schemes which send and receive frequencies above 20
kHz - and therefore above the hearing range of humans.
With appropriate filtering at each end of the twisted pair, many
of these approaches also allow an ordinary analogue Plain Old
Telephone System (POTS) telephone service to continue to
operate on the same line.
If this filtering can be achieved without the need for external
power at the customer site, this preserves existing life-line
telephone services, while providing a bi-directional multi-megabitper-second digital communication path to each home or office.

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Advantages of DSL Technology
DSL is more cost-effective because it eliminates the need
for extensive and expensive infrastructure upgrades.
Increased Bandwidth capacity in the existing
infrastructure.
The speed is much higher than a regular voice band
modem.
Voice and data can be transmitted at the same time.
Very Secure and reliable.

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Symmetric Vs Asymmetric

Symmetric bandwidth corresponds to the situation when the maximum rate of

transfer is the same in both directions i.e. upload and download speed.
Asymmetric bandwidth corresponds to the situation when the maximum rate of
transfer is different in each direction. A typical case might be a DSL line with 768
kbps upload and 2 Mbps download.
Asymmetric DSL Standards
======================

ADSL: (Full Rate asymmetrical DSL)

G.lite ADSL (or simply G.lite)
RADSL: (rate adaptive DSL)
VDSL (Very high bit rate DSL)

Symmetric DSL Standards

====================

SDSL: (Symmetric DSL)

SHDSL (Single-pair high-speed DSL)
HDSL: (High bit rate DSL)
HDSL2: (2nd generation HDSL)
IDSL: (Integrated services digital network DSL)

ITTM, Delhi
ASYMMETRIC DIGITAL SUBSCRIBER LINE
ADSL MODEM
Splitter

Splitter

ADSL

LT

Existing

Exchange

Copper Lines

EXCHANGE

Eqpt .

ISP

IPTV And VOIP (Triple Play Service)

Telephone
Exchange

Internet Gateway
( Broadband)

Telephone
Telephone Line
MTNL Broadband N/W

TV

el
n
n
a
Ch

PC
DSL Modem

VoIP
SOFT SWITCH

HEAD END
EQUIPMENT

Analog
Telephone
Adaptor

Set Top Box

(ENCODERS)
Telephone

DVD

TV

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IPTV : Brief Definition
IPTV (Internet Protocol Television) delivers
television programming to households via a
broadband connection using Internet
protocols. It requires a IPTV set-top box, and
offers key advantages over existing TV cable
and satellite technologies. IPTV is typically
bundled with other services like Video on
Demand (VOD), voice over IP (VOIP) or digital
phone, and Web access, collectively referred
to as Triple Play.

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DSLAM - INTRODUCTION
Digital Subscriber Line Access Multiplexer (DSLAM) is a network device,
located in the telephone exchanges of the service providers, that connects
multiple customer Digital Subscriber Lines (DSLs) to a high-speed Internet
backbone line using multiplexing techniques.
In terms of the OSI 7 Layer Model, the DSLAM acts like a massive network
switch, since its functionality is purely Layer 2.
The aggregated signal then loads onto backbone switching equipment, travelling
through an access network (AN) also known as a Network Service Provider
(NSP) at speeds of up to 10 Gbit/s and connecting to the Internet-backbone.
The DSLAM, functioning as a switch, collects the ADSL modem data (connected
to it via twisted or non-twisted pair copper wire) and multiplexes this data via the
gigabit link that physically plugs into the DSLAM itself, into the Telco's
backbone.

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TYPES OF DSLAMS IN MTNL
A DSLAM delivers exceptionally high-speed data transmission over existing
copper telephone lines. A DSLAM separates the voice-frequency signals from
the high-speed data traffic and controls and routes digital subscriber line (xDSL)
traffic between the subscriber's end-user equipment (CPE) and Broadband
Access Server or BBRAS, but it may not be a direct connection; the BBRAS
can be located anywhere.

DSLAMs of following make are installed in MTNL:

ERICSSON (Ethernet DSL Access)
HUAWEI (SMARTAX MA 5600)
ALCATEL (7302 ISAM)

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DSLAM PORT NAMING

PORT TYPE

ERICSSON

HUAWEI

PORT
NAMING

TYPE OF DSLAM

XYYZTTTT

X: DSLAM TYPE
YY: DSLAM NO. (01, 02 ETC)
Z: SUBRACK NO.(1, 2, 3, 4)
TTTT: PORT NO. (0001 TO 1152)

A 1152 PORTS
B 576 PORTS
C 288 PORTS

XYYZTTTT

X: DSLAM TYPE (I, J, K)

YY: DSLAM NO. (01, 02 ETC)
Z: SUBRACK NO.
TTTT: PORT NO. (0001 TO 0960)

I 960 PORTS
J 480 PORTS
K 240 PORTS

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PHYSICAL CONNECTIONS

DSL OVERVIEW-DSL
CONNECTIVITY

Exchange RSU/MSU

Customer home

MDF

RJ-11

MTNL
Line MDF

DSL Modem
Ethernet
Or USB

Spiltter

MTNL
Exch MDF
2-wire

MTNL Copper
< 5Km

Local
Exchange

2-wire
IP
DSLAM

DSLAM
Exch MDF

2-wire
DSLAM
Line MDF

2x GigE
fiber
Tier 2
Switch

MTNL
Fiber Network
20

ITTM, Delhi
ATM Technology
ATM is a switched, connection-oriented networking
technology that provides dedicated, high-speed
connections to virtually an unlimited number of users. It
operates on a cell-based fast-packet communication
method that supports transfer rates from 1.544 Mbps to
10 Gbps.
Dedicated media connections running in parallel allow
an ATM switch to simultaneously support multiple
conversations.
When Data is transferred in an ATM network, a switched
virtual circuit (SVC) is established between the sender
and receiver. The information is converted into fixedlength cells, which are transmitted through the network
and reassembled into data packets at the destination.

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ATM networks are fundamentally connection oriented. This
means that a virtual connection needs to be established across
the ATM network prior to any data transfer. ATM virtual
connections are of two general types:
Virtual path connections (VPCs), identified by a VPI.
Virtual channel connections (VCCs), identified by the
combination of a VPI and a VCI.
A virtual path is a bundle of virtual channels, all of which are
switched transparently across the ATM network on the basis of
the common VPI. A VPC can be thought of as a bundle of
VCCs with the same VPI value.
VPI identifies the virtual path to be used by the cell during
transmission and VCI identifies the channel to be used. PTI
tells the content of the data portion. It tells the priority of the
cell.

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ATM Virtual Path And Virtual Channel Connections

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DSLAM (DSL Access Multiplexer)
D

S
LOCAL
LOOP

B
OF

INTER
NET

Within the block identified as 'Service provider', there are three important
components:
DSLAM
- DSL Access Multiplexer
A Digital Subscriber Line Access Multiplexer (DSLAM) is a network device,
usually at a telephone company central office, that receives signals from
multiple customer Digital Subscriber Line (DSL) connections and puts the
signals on a high-speed backbone line using multiplexing techniques.
BBRAS
- Broadband Remote Access Server
The BBRAS is the piece of equipment that sits between the DSLAM at the
telephone exchange and the ISP that connects to the Internet.
ISP
- Internet Service Provider
The Broadband Access Servers are connected to an Internet Service Provider
or ISP. This is the place where the connection to the Internet is made.

Ericsson network

BBRAS 6
Element
T1

7
T2 42 (Working as on
date)
DSLAM 445
Radius 1 (From M/s Oracle
Product name Portal)

Connectivity

Gateways

to

All the internet traffic iscomingfrom

DSLAM to T2, the from T2 to T1, from T1
to BBRAS as layer 2 traffic.Allthe
BBRAS'sare connected to Two switches
(known asAggregationA and Aggregation
B)using fiber cable. And these switches
are connected to two gateways
routers(4th floor and 9th floor)withsix
pairsof fibers. That is from Agg-A Three
pairs of fibers are going to gateway 1
andThree pairs of fibers are going to

Network Elements in
Huawei system
Network Elements in Huawei system

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Network Overview

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Ericsson Broadband
Network

RADIUS
Remote

Authentication Dial In
User Service
Concept of AAA
Authentication
Authorization
Accounting

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How Broadband Service Works?

55
Billing
Billing
server
server start
start
accounting
accounting
R

Radius
Server

Core

11
PPP
PPP
oE
oE is
is
initiated
initiated
by
by
subscrib
subscrib
er
er

22
PPPoE
PPPoE
session
session
ends
ends here
here
and
and session
session
ID
ID is
is
allocated
allocated

Authentication
Authentication
system
system checks
checks
account
account &password
&password

BRAS
BRAS allocates
allocates
valid
valid IP
IP
33

BBRAS

Lan
44
Subscrib
Subscrib switch
er
er gets
gets IP
IP
and
and visit
visit
Internet
Internet

ITTM, Delhi
BB Service Flow
PC CPE DSLAM T2 T1 BRAS

1.
2.
3.
4.
5.
6.

Service flow begins from Client BRAS which terminated

PPP sessions.
The process for user connection to internet is:
Client starts pppoe session by using pppoe software.
ADSL modem translates IP packets into ATM cell.
DSLAM recovers ATM cells to IP packets.
DSLAM uses Q-in-Q protocol/VMAC, which adds a new vlan
/vmac tag to the recovered IP packets. Each user has a
respective vlan/vmac.
T2 forwards IP packet to T1 & T1 transfers the IP packets to
BRAS.
BRAS also supports Q-in-Q protocol /vmac according to
different outer vlan and inner vlan to identify Different
users.

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LAN Switches

Important features of LAN Switch:

Supports multiple service VLANs
Aggregates links towards T1 switch or BRAS
Supports multicasting
Controls flow of Ethernet frames
Ensures QoS for different types of traffic
Allows management through CLI, Console, Telnet,
SNMP and System log

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T1/T2/Aggregation/NOC Switches
Definition: They are LAN switches
used for aggregating and crossconnecting clients, servers and
other network devices.
Devices used in MTNL: 3COM
7700 LAN Switches
(ERICSSON) and NE80E T-1
Switch, S6506 T-2 Switch
(HUAWEI)

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Broadband Remote Access Server (BRAS)
Definition: BRAS is a network
device used to route traffic to
and from broadband remote
access devices such as DSLAM
on an ISP network. It aggregates
users sessions from access
network and plays major role
policy management and QoS.
Devices used in MTNL: Juniper
ERX 1440 (ERICSSON) &
MA5200G-8 (HUAWEI)

ITTM, Delhi
BRAS
Important Features:
Aggregates the circuits from access devices such as DSLAMs
Provides layer 2 connectivity through either transparent bridging or PPP sessions
over Ethernet
Enforces quality of service (QoS) policies
Provides layer 3 connectivity and routes IP traffic through Internet service
providers backbone network to the Internet

Thanks

..Broadband

Faculty, ITTM