Broadband

TABLE OF CONTENTS

1. BSNL OVERVIEW

A. External/Internal Infrastructure

B. BSNL Service

2. NATIONAL INTERNET BACKBONE (NIB)

A. Architectural principles

B. Infrastructure

C. Economy

3. BROADBAND

A. Digital Subscriber Line (DSL)

B. Asymmetric Digital Subscriber Line (ADSL)

C. Very high Digital Subscriber Line (VDSL)

D. Digital Subscriber Line Access Multiplexer (DSLAM)

E. Routing

F. Broadband Remote Access Server (BRAS)

G. Router

H. Service Control Module

I. Wi-Fi

J. Wi-Max

BHARAT SANCHAR NIGAM LIMITED (BSNL)

OVERVIEW

BSNL is India's oldest and largest communication service provider (CSP). It had a customer base

of 90 million as of June 2008. It has footprints throughout India except for the metropolitan cities

of Mumbai and New Delhi, which are managed by Mahanagar Telephone Nigam Limited

(MTNL). As of June 30, 2010, BSNL had a customer base of 27.45 million wire line and 72.69

million wireless subscribers.

It is India’s largest telecommunication company with 24% market share as on March 31st 2008.Its

headquarters are at Bharat Sanchar Bhawan, Harish Chandra Mathur Lane, New Delhi. It has the

status of MINI RATNA, a status assigned to public sector companies in India.

External/internal infrastructure:

Bharat Sanchar Nigam Limited (abbreviated BSNL) is a state - owned telecommunications company headquartered in New Delhi, India. BSNL is one of the largest Indian cellular service providers, with over 87.1 million subscribers as of April 2011, and the largest land line telephone provider in India. However, in recent years the company's revenue and market share plunged into heavy losses due to intense competition in Indian telecommunications sector.

External infrastructure : Lines and cables ( U/G including OFC )

Internal infrastructure : Battery, Power Plant, E/A, A/C plant, MDF, Switches ( C-DOT, OCB 283, EWSD, AXE etc ), Leased Lines ( MLLN ), Broad Band, MPLS VPN.

Interesting Facts:

There are 2 million BSNL mobile connections in rural

India (a record, no other connection is as famous as bsnl in rural areas)

BSNL supplies phone lines to all other network such as Airtel, Vodafone etc.

Largest pan India coverage-over 11000 towns & 3 lakh Villages.

India’s No. 1 wireless service provider with more than 50 Million customers.

An incredible speed of 2mbps is only offered by BSNL

BSNL Services:

1) BSNL LANDLINE

NEW TELEPHONE CONNECTION

PERMANENT CONNECTION

CONCESSION IN RENTALS

SHIFT OF TELEPHONE

TRANSFER OF TELEPHONE

TELEPHONE TARIFF

2) BSNL MOBILE

POSTPAID

PREPAID

UNIFIED MESSAGING

GPRS/WAP/MMS

DEMOs

TARIFF

SMS & BULK SMS

3) BSNL WLL

4) INTERNET SERVICES

NETWORK

BROADBAND

TYPES OF ACCESS

INTERBET TARIFF

DIAL-UP INTRENET

Wi-Fi

5) BSNL BROADBAND

REGISTER ONLINE

TARIFF

CHECK USAGE

FAQ

6) ISDN

ISDN

TARIFF

7) VIDEO CONFERRENCING

OVERVIEW

TARIFF

FAQ

8) AUDIO CONFERRENCING

OVERVIEW

TARIFF

FAQ

9) TELEX/TELEGRAPH

TELEX/TELEGRAGH

TARIFF

10) INET

OVERVIEW

SERVICES ON I NET

USING ON I NET

11) EPABX

EPABX

CENTREX

TRANSPONDER

RABMN

National Internet Backbone (NIB)

Architectural Principles

The Internet, and consequently its backbone networks, does not rely on central control or

coordinating facilities, nor do they implement any global network policies. The resilience of the

Internet results from its principal architectural features, most notably the idea of placing as few

network state and control functions as possible in the network elements, but instead relying on the

endpoints of communication to handle most of the processing to ensure data integrity, reliability,

and authentication. In addition, the high degree of redundancy of today's network links and

sophisticated real-time routing protocols provide alternate paths of communications for load

balancing and congestion avoidance.

Infrastructure

The Internet backbone refers to the principal data routes between large, strategically interconnected networks and core routers in the Internet. These data routes are hosted by commercial, government, academic and other high-capacity network centers, the Internet exchange points and network that interchange Internet traffic between the countries, continents and across the oceans of the world.

The internet backbone is a conglomeration of multiple, redundant networks owned by

numerous companies. It is typically a fiber optic trunk line. The trunk line consists of many fiber

optic cables bundled together to increase the capacity. The backbone is able to re route traffic in

case of a failure. The data speeds of backbone lines have changed with the times. In 1998, all of

the United States backbone networks had utilized the slowest data rate of 45 Mbps. However the

changing technologies allowed for 41 percent of backbones to have data rates of 2,488 Mbps or

faster by the mid 2000's. The FCC currently defines "high speed" as any connection with data

speeds that exceed 200 kilobits per second. An Azerbaijani based telecommunication company,

Delta Telecom, has recently developed a very efficient trunk line with possible speeds of to 1.6

terabits per second. Internet traffic from this line goes through the countries of Iran, Iraq and

Georgia. Fiber-optic cables are the medium of choice for internet backbone providers for

many reasons. Fiber-optics allow for fast data speeds and large bandwidth; they suffer relatively

little attenuation, allowing them to cover long distances with few repeaters; they are also immune

to crosstalk and other forms of EM interference which plague electrical transmission. 

Modern Backbone

Because of the enormous overlap between long distance telephone networks and the

internet backbone networks, the largest long distance voice carriers such

as AT&T, MCI, Sprint and west also own some of the largest internet backbone networks. These

backbone providers will then sell their service to ISPs. Each ISP has its own contingency

backbone network, and at the very least, is equipped with an outsourced backup. These networks

are intertwined and criss-crossed to create a redundant network. Many companies operate their

own backbones that are all interconnected at various NAPs around the world. In order for data to

navigate through this diverse web that the backbone creates, backbone routers are desperately

needed. These backbone routers are routers that are powerful enough to handle information on the

internet backbone, and they direct data to other routers in order to send it to its final destination.

Without these backbone routers, information would be lost since data would not know how to

locate its end destination. The very largest providers, known as Tier 1 providers, have such

comprehensive networks that they never need to purchase transit agreements from other providers.

As of 2000 there were only five internet backbone providers at the Tier 1 level in the

telecommunications industry.

NIB in India

India's backbone is very extensive due to a very large population. This country alone has

nearly 250 million internet users as of 2009. Four of India's top Internet Service Providers are Tata

Communications, BSNL, MTNL, and Reliance Communications. Tata Communications is a Tier-

1 IP network, with connectivity to more than 200 countries across 400 Pops and nearly 1,000,000

square feet (93,000 m2) of data center and collocation space worldwide. It is India's largest

provider in data center services and also operates India's largest data center in Pune. The backbone

structure keeps on getting stronger because of the huge number of new emerging mobile operators

which leads to decrease in prices due to competition in the market.

Economy of the Backbone

Peering agreements: Backbone providers of roughly equivalent market share regularly

create agreements called peering agreements. These agreements allow the use of another's

network to hand off traffic where is ultimately delivered. They usually do not charge each other for

this use as they all get revenue from their customers regardless.

Transit agreements: Backbone providers of unequal market share usually create agreements

called transit agreements, and usually contain some type of monetary agreement.

Regulation: Antitrust authorities have acted to ensure that no provider grows large enough to

dominate the backbone market. The FCC has also decided not to monitor the competitive aspects

of the Internet Backbone interconnection relationships, as long as the market continues to function

well without regulation.

Broadband

The term broadband refers to a telecommunications signal of greater bandwidth, in some

sense, than another standard or usual signal (and the broader the band, the greater the capacity for

traffic). Different criteria for "broad" have been applied in different contexts and at different times.

Broadband in telecommunications refers to a signaling method that includes or handles a

relatively wide range (or band) of frequencies, which may be divided into channels or frequency

bins. Broadband is always a relative term, understood according to its context. The wider (or

broader) the bandwidth of a channel, the greater the information-carrying capacity. In radio, for

example, a very narrow-band signal will carry Morse code; a broader band will carry speech; a still

broader band is required to carry music without losing the high audio frequencies required for

realistic sound reproduction. A television antenna described as "broadband" may be capable of

receiving a wide range of channels; while a single-frequency or Lo-VHF antenna is "narrowband"

since it only receives 1 to 5 channels. In data communications a digital modem will transmit a data

rate of 56 kilobits per seconds (kbit/s) over a 4 kilohertz wide telephone line (narrowband or voice

band). However when that same line is converted to an non-loaded twisted-pair wire (no telephone

filters), it becomes hundreds of kilohertz wide (broadband) and can carry several megabits per

second (ADSL).

Technology

The standard broadband technologies in most areas are ADSL and cable internet. Newer

technologies in use include VDSL and pushing optical fiber connections closer to the subscriber in

both telephone and cable plants. Fiber-optic communication, while only recently being used

in fiber to the premises and fiber to the curb schemes, has played a crucial role in enabling

Broadband Internet access by making transmission of information over larger distances much

more cost-effective than copper wire technology.

In a few areas not served by cable or ADSL, community organizations have begun to

install Wi-Fi networks, and in some cities and towns local governments are installing municipal

Wi-Fi networks. The newest technology being deployed for mobile and stationary broadband

access is WiMAX.

Broadband in DSL

The various forms of digital subscriber line (DSL) services are broadband in the sense that

digital information is sent over a high-bandwidth channel. This channel is located above (i.e., at

higher frequency than) the baseband voice channel on a single pair of wires.

Digital Subscriber Line

Digital Subscriber Line (DSL) is a family of technologies that provides digital data

transmission over the wires of a local telephone network. DSL originally stood for digital

subscriber loop. In telecommunications marketing, the term Digital Subscriber Line is widely

understood to mean Asymmetric Digital Subscriber Line (ADSL), the most commonly installed

technical variety of DSL. DSL service is delivered simultaneously with regular telephone on the

same telephone line. This is possible because DSL uses a higher frequency. These frequency bands

are subsequently separated by filtering.

The data throughput of consumer DSL services typically ranges from 256 Kb/s to 40

Mbit/s in the direction to the customer (downstream), depending on DSL technology, line

conditions, and service-level implementation. In ADSL, the data throughput in the upstream

direction, (i.e. in the direction to the service provider) is lower, hence the designation

of asymmetric service. In Symmetric Digital Subscriber Line (SDSL) service, the downstream and

upstream data rates are equal.

Basic technology

Telephones are connected to the telephone exchange via a local loop, which is a physical

pair of wires. Prior to the digital age, the use of the local loop for anything other than the

transmission of speech, encompassing an audio frequency range of 300 to 3400 Hertz

(voiceband or commercial bandwidth) was not considered. However, as long distance trunks were

gradually converted from analog to digital operation, the idea of being able to pass data through

the local loop took hold, ultimately leading to DSL.

In current practice, speech is digitized by using an analog-to-digital converter sampling at a

rate of 8000 samples per second, capturing eight-bit values and producing a 64 kilobit per

second data stream. According to the Nyquist–Shannon sampling theorem, if an input audio signal

injected into such an analog-to-digital converter contains frequency components higher than half

of the sampling frequency, then such high frequency components will be aliased by the system,

and so must be blocked at the input by an appropriate low-pass filter in order to prevent such

effects. Due to the presence of the low-pass filter, input frequencies above four kilohertz (KHz)

will be blocked, preventing the passage of arbitrarily high frequencies through the normal

telephone voice path.

The local loop connecting the telephone exchange to most subscribers has the capability of

carrying frequencies well beyond the 3.4 kHz upper limit of POTS. Depending on the length and

quality of the loop, the upper limit can be tens of megahertz. DSL takes advantage of this

unused bandwidth of the local loop by creating 4312.5 Hz wide channels starting between 10 and

100 kHz, depending on how the system is configured. Allocation of channels continues at higher

and higher frequencies (up to 1.1 MHz for ADSL) until new channels are deemed unusable. Each

channel is evaluated for usability in much the same way an analog modem would on a POTS

connection. More usable channels equates to more available bandwidth, which is why distance and

line quality are a factor (the higher frequencies used by DSL travel only short distances). The pool

of usable channels is then split into two different frequency bands for

upstream and downstream traffic, based on a preconfigured ratio. This segregation reduces

interference. Once the channel groups have been established, the

individual channels are bonded into a pair of virtual circuits, one in each direction. Like analog

modems, DSL transceivers constantly monitor the quality of each channel and will add or remove

them from service depending on whether they are usable.

Network Connectivity Diagram

Typical setup and connection procedures

Physical connection must come first. On the customer side, the DSL Transceiver, or ATU-

R, or more commonly known as a DSL modem, is hooked up to a phone line. The telephone

company (telco) connects the other end of the line to a DSLAM, which concentrates a large

number of individual DSL connections into a single box. The location of the DSLAM depends on

the telco, but it cannot be located too far from the user because of attenuation, the loss of data due

to the large amount of electrical resistance encountered as the data moves between the DSLAM

and the user's DSL modem. It is common for a few residential blocks to be connected to one

DSLAM.

Tier 2 LAN Switch

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Tier1 GigE

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When the DSL modem powers up it goes through a sync procedure. The actual process varies

from modem to modem but generally involves the following steps:

1. The DSL transceiver performs a self-test.

2. The DSL transceiver checks the connection between the DSL transceiver and the computer.

For residential variations of DSL, this is usually the Ethernet (RJ-45) port or a USB port;

in rare models, a FireWire port is used. Older DSL modems sported a native ATM

interface (usually, a 25 Mbit serial interface). Also, some variations of DSL (such as

SDSL) use synchronous serial connections.

3. The DSL transceiver then attempts to synchronize with the DSLAM. Data can only come

into the computer when the DSLAM and the modem are synchronized. The

synchronization process is relatively quick (in the range of seconds) but is very complex,

involving extensive tests that allow both sides of the connection to optimize the

performance according to the characteristics of the line in use. External or stand-alone

modem units have an indicator labeled "CD", "DSL", or "LINK", which can be used to tell

if the modem is synchronized. During synchronization the light flashes; when

synchronized, the light stays lit, usually with a green color.

The accompanying figure is a schematic of a simple DSL connection (in blue). The right side

the shows a DSLAM residing in the telephone company's central office. The left side shows the

customer premises equipment with an optional router. This router manages a local area network

(LAN) off of which are connected some number of PCs. With many service providers, the

customer may opt for a modem which contains a wireless router. This option (within the dashed

bubble) often simplifies the connection.

Equipment

The customer end of the connection consists of a terminal adaptor or in layman's terms

"DSL modem". This converts data between the digital signals used by computers and

the voltage signal of a suitable frequency range which is then applied to the phone line.

In some DSL variations (for example, HDSL), the terminal adapter connects directly to the

computer via a serial interface, using protocols such as ethernet or V.35. In other cases

(particularly ADSL), it is common for the customer equipment to be integrated with higher level

functionality, such as routing, firewalling, or other application-specific hardware and software. In

this case, the equipment is referred to as a gateway.

DSL Connection schematic

Some kinds of DSL technology require installation of appropriate filters to separate, or

"split", the DSL signal from the low frequency voice signal. The separation can take place either at

the demarcation point, or with filters installed at the telephone outlets inside the customer

premises. Either way has its practical and economical limitations. See ADSL for more information

about this.

At the exchange, a digital subscriber line access multiplexer (DSLAM) terminates the DSL

circuits and aggregates them, where they are handed off onto other networking transports. In the

case of ADSL, the voice component is also separated at this step, either by a filter integrated in the

DSLAM or by specialized filtering equipment installed before it. The DSLAM terminates all

connections and recovers the original digital information.

Brief Functions of DSL Components

• DSL CPEs : At customer premises. On end it connects telephone cable coming from

exchange. At the other end, it connects to PC through Ethernet and Telephone through RJ-

45 connector

• DSLAM : called as DSL Access Multiplexer. It has a built in splitter which splits voice and

data. While voice follows the normal conventional path through exchange, data is

aggregated and up linked through Ethernet Port (Gigabit Ethernet for 480 port and Fast

Ethernet for lower DSLAM)

• LAN Switch : For aggregating multiple DSLAM and providing a common uplink

• BRAS : called as Broadband Remote Access Server. First intelligent device in the whole

chain. It terminates the customer session, authenticates, allott IP addresses and keeps track

of user session for billing along with RADIUS

• SSSS: Called as Subscriber Service Selection System. When customer logs in he will be

welcome with this customized screen from where he can select various range of service.

This provides on demand service without manual intervention

• RADIUS : This in conjunction with BRAS authenticates customer, upload customer profile

in the SSSS and keeps track of billing

• LDAP : It stores customer database viz username, password and the default services that it

can subscribe to.

• Provisioning: This is the most critical components for ensuring quick delivery of service.

It ensures end-to-end provisioning of service right from DSL CPEs to DSLAM to Switch

to BRAS to LDAP

Asymmetric Digital Subscriber line (ADSL)

The distinguishing characteristic of ADSL over other forms of DSL is that the bandwidth is

greater in the direction to the customer premises than the reverse, giving rise to is asymmetric

characteristic. Providers usually market ADSL as a service for consumers to connect to the

Internet in a relatively passive mode: able to use the higher speed direction for the download from

the Internet but not needing to run servers that would require high speed in the other direction

With standard ADSL the band from 26.000 kHz to 137.825 kHz is used for upstream

communication, while 138 kHz – 1104 kHz is used for downstream communication. Each of these

is further divided into smaller frequency channels of 4.3125 kHz. These frequency channels are

sometimes termed bins.

Very high bit rate digital subscriber line (VDSL)

It is a DSL technology providing faster data transmission (up to 52 Mbps downstream and

16 Mbps upstream) Second-generation VDSL2 systems (ITU-T G.993.2 Approved in February

2006) utilize bandwidth of up to 30 MHz to provide data rates exceeding 100 Mbit/s

simultaneously in both the upstream and downstream directions. The maximum available bit rate

is achieved at a range of about 300 meters; performance degrades as the loop attenuation increases.

Currently, the standard VDSL uses up to 7 different frequency bands

Digital Subscriber Line Access Multiplexer

A Digital Subscriber Line Access Multiplexer (DSLAM, often pronounced dee-slam)

allows telephone lines to make faster connections to the Internet. It is a network device, located in

the telephone exchanges of the internet service providers, that connects multiple customer Digital

Subscriber Lines (DSLs) to a high-speed Internet backbone line using multiplexing techniques. By

placing additional remote DSLAMs at locations remote to the telephone exchange, telephone

companies provide DSL service to locations previously beyond effective range.

Path taken by data to DSLAM

1. Customer premises: DSL modem terminating the ADSL, SHDSL or VDSL circuit and

providing LAN interface to single computer or LAN segment

2. Local loop: the telephone company wires from a customer to the telephone company's

central office or to a Serving area interface, often called the "last mile" (LM).

3. Central Office (CO):

Main Distribution Frame (MDF): a wiring rack that connects outside subscriber lines

with internal lines. It is used to connect public or private lines coming into the building

to internal networks. At the telco, the MDF is generally in proximity to the cable

vault and not far from the telephone switch.

xDSL filters: DSL filters are used in the Central Office (CO) to split voice from data

signals. The voice signal can be routed to a POTS provider or left unused whilst the

data signal is routed to the ISP DSLAM via the HDF (see next entry).

Handover Distribution Frame (HDF): a distribution frame that connects the last mile

provider with the service provider's DSLAM

DSLAM: a device for DSL service. The DSLAM port where the subscriber local

loop is connected converts analog electrical signals to data traffic (upstream traffic for

data upload) and data traffic to analog electrical signals (downstream for data

download).

xDSL Connectivity diagram

Role of DSLAM

The DSLAM equipment at the telephone company (telco) collects the data from its many

modem ports and aggregates their voice and data traffic into one complex composite "signal"

via multiplexing. 

The aggregated traffic is then directed to a telco's backbone switch, via an access

network (AN) also called a Network Service Provider (NSP) at up to 10 Gbit/s data rates.

The DSLAM acts like a network switch since its functionality is at Layer 2 of the OSI

model. Therefore it cannot re-route traffic between multiple IP networks, only

between ISP devices and end-user connection points. The DSLAM traffic is switched to

a Broadband Remote Access Server where the end user traffic is then routed across the ISP

network to the Internet. Customer Premises Equipment that interfaces well with the DSLAM to

which it is connected may take advantage of enhanced telephone voice and data line signaling

features and the bandwidth monitoring and compensation capabilities it supports.

DSLAMs are also used by hotels, lodges, residential neighborhoods, and other businesses

operating their own private telephone exchange.

In addition to being a data switch and multiplexer, a DSLAM is also a large collection of

modems. Each modem on the aggregation card communicates with a single subscriber's DSL

modem. This modem functionality is integrated into the DSLAM itself instead of being done via

an external device like a traditional computer modem. Like traditional voice-band modems, a

DSLAM's integrated DSL modems usually have the ability to probe the line and to adjust

themselves to electronically or digitally compensate for forward echoes and other bandwidth-

limiting factors in order to move data at the maximum connection rate capability of the

subscriber's physical line. This compensation capability also takes advantage of the better

performance of "balanced line" DSL connections, providing capabilities for LAN segments longer

than physically similar unshielded twisted pair (UTP) Ethernet connections, since the balanced line

type is generally required for its hardware to function correctly. This is due to the nominal line

impedance (measured in Ohms but comprising both resistance and inductance) of balanced lines

being somewhat lower than that of UTP, thus supporting 'weaker' signals (however the solid-state

electronics required to construct such digital interfaces is more costly).

Tier 2 Network

A Tier 2 Network is an Internet service provider who engages in the practice

of peering with other networks, but who still purchases IP transit to reach some portion of the

Internet.

Tier 2 providers are the most common providers on the Internet as it is much easier to

purchase transit from a Tier 1 network than it is to peer with them and then attempt to push into

becoming a Tier 1 carrier.

Tier 1 Network

Although there is no authority that defines tiers of networks participating in the Internet,

the most common definition of a tier 1 network is one that can reach every other network on

the Internet without purchasing IP transit or paying settlements.

By this definition, a tier 1 network is a transit-free network that peers with every other tier-

1 network. But not all transit-free networks are tier 1 networks. It is possible to become transit-free

by paying for peering or agreeing to settlements. It is difficult to determine whether a network is

paying settlements if the business agreements are not public information, or covered under a non-

disclosure agreement. The Internet "peering community" is roughly the set of peering coordinators

present at Internet exchanges on more than one continent. The subset representing "tier 1"

networks is collectively understood, but not published as such.

Strictly observing this definition of "tier 1" would exclude every network. For instance,

many large telephone companies are tier 1 networks, but they buy, sell, or swap fiber amongst

themselves. Payments between companies are not all known, nor whether they cover peering

connections.

As a result, the term "tier 1 network" is used in the industry to mean a network with no

overt settlements. An overt settlement would be a monetary charge for the amount, direction, or

type of traffic sent between networks.

Routing

Internet traffic between any two tier 1 networks is critically dependent on the peering

relationship of the partners, because a tier 1 network does not have any alternate transit paths. If

two tier 1 networks arrive at an impasse and discontinue peering with each other (usually in a

unilateral decision), single-homed customers of each network will not be able to reach the

customers of other networks. This effectively partitions the Internet and traffic between certain

parts of the Internet is interrupted. This has happened several times during the history of the

Internet. Those portions of the Internet typically remain partitioned until one side purchases transit,

or until the collective pain of the outage or threat of litigation motivates the two networks to

resume voluntary peering.

Lower tier ISPs and their customers may be unaffected by these partitions because they

may have redundant interconnections with more than one tier-1 provider.

Frequent misconceptions of the tier hierarchy include:

Tier 1 networks are closer to the backbone of the Internet.

In reality, tier 1 networks usually have only a small number of peers (typically only other

tier 1 networks and very large tier 2 networks), while tier 2 networks are motivated to peer

with many other tier 2 and end-user networks. Thus a tier 2 network with good peering is

frequently much closer to most end users than a tier 1.

Tier 1 networks by definition offer better quality Internet connectivity.

By definition, there are networks which tier 1 networks have only one path to, and if they

lose that path, they have no backup transit which preserves their continuous connectivity.

Some tier 2 networks are significantly larger than some tier 1 networks, and are often able

to provide more or better connectivity.

Broadband Remote Access Server (BRAS)

A broadband remote access server (BRAS, B-RAS or BBRAS) routes traffic to and

from broadband remote access devices such as digital subscriber line access

multiplexers (DSLAM) on an Internet service provider's (ISP) network.

The BRAS sits at the core of an ISP's network, and aggregates user sessions from

the access network. It is at the BRAS that an ISP can inject policy management and IP Quality of

Service (QoS).

The specific tasks include:

Aggregates the circuits from one or more link access devices such as DSLAMs

Provides layer 2 connectivity through either transparent bridging or PPP sessions

over Ethernet or ATM sessions

Enforces quality of service (QoS) policies

Provides layer 3 connectivity and routes IP traffic through an Internet service provider’s

backbone network to the Internet

A DSLAM collects data traffic from multiple subscribers into a centralized point so that it can

be transported to a switch or router over a Frame Relay, ATM, or Ethernet connection. The router

provides the logical network termination. The BRAS is also the interface to authentication,

authorization and accounting systems.

Internet Router

A router is a device that forwards data packets across computer networks. Routers perform

the data "traffic directing" functions on the Internet. A router is connected to two or more data

lines from different networks. When data comes in on one of the lines, the router reads the address

information in the packet to determine its ultimate destination. Then, using information in

its routing table, it directs the packet to the next network on its journey or drops the packet. A data

packet is typically passed from router to router through the networks of the Internet until it gets to

its destination computer unless the source IP is on a private network.

The most familiar type of routers are home and small office routers that simply pass data,

such as web pages and email, between the home computers and the owner's cable or DSL modem,

which connects to the Internet (ISP).

In enterprises, a core router may provide a "collapsed backbone" interconnecting the

distribution tier routers from multiple buildings of a campus, or large enterprise locations. They

tend to be optimized for high bandwidth.

Forwarding

The main purpose of a router is to connect multiple networks and forward packets destined

either for its own networks or other networks. A router is considered a Layer 3 device because its

primary forwarding decision is based on the information in the Layer 3 IP packet, specifically the

destination IP address. This process is known as routing. When each router receives a packet, it

searches its routing table to find the best match between the destination IP address of the packet

and one of the network addresses in the routing table. Once a match is found, the packet is

encapsulated in the Layer 2 data link frame for that outgoing interface. A router does not look into

the actual data contents that the packet carries, but only at the layer 3 addresses to make a

forwarding decision, plus optionally other information in the header for hint on, for example, QoS.

Once a packet is forwarded, the router does not retain any historical information about the packet,

but the forwarding action can be collected into the statistical data, if so configured.

Forwarding decisions can involve decisions at layers other than layer 3. A function that

forwards based on layer 2 information, is properly called a bridge. This function is referred to as

layer 2 bridging, as the addresses it uses to forward the traffic are layer 2 addresses (e.g.  MAC

addresses on Ethernet).

Besides making decision as which interface a packet is forwarded to, which is handled

primarily via the routing table, a router also has to manage congestion, when packets arrive at a

rate higher than the router can process. Three policies commonly used in the Internet are tail

drop, random early detection (RED), and weighted random early detection (WRED). Tail drop is

the simplest and most easily implemented; the router simply drops packets once the length of the

queue exceeds the size of the buffers in the router. RED probabilistically drops datagrams early

when the queue exceeds a pre-configured portion of the buffer, until a pre-determined max, when

A typical home or small office router showing the ADSL telephone line and ETHERNET network cable connections.

it becomes tail drop. WRED requires a weight on the average queue size to act upon when the

traffic is about to exceed the pre-configured size, so that short bursts will not trigger random drops.

Another function a router performs is to decide which packet should be processed first

when multiple queues exist. This is managed through quality of service (QoS), which is critical

when Voice over IP is deployed, so that delays between packets do not exceed 150ms to maintain

the quality of voice conversations.

Yet another function a router performs is called policy-based routing where special rules

are constructed to override the rules derived from the routing table when a packet forwarding

decision is made.

These functions may be performed through the same internal paths that the packets travel

inside the router. Some of the functions may be performed through an application-specific

integrated circuit (ASIC) to avoid overhead caused by multiple CPU cycles, and others may have

to be performed through the CPU as these packets need special attention that cannot be handled by

an ASIC.

Service control module:

It is responsible for authentication and management of user access requests. It identifies

legal users. It can extract and record the statistics of user data packets and online duration for

implementing the traffic based or duration based accounting function.

MA5200G sends the user’s accounting information to the RADIUS server. BRAS allocates

IP address through DHCP. It supports 4k to 96k IP addresses.MA5200G adopts packet binding

technology. After user passes authentication It checks the binding relation of the IP address, MAC

address, logical port and PPPoE session ID in each packet of this user and the packets that do not

match will be discarded.

Wi-Fi

Wireless Technology is an alternative to wired Technology for connecting the devices in

wireless mode. Wi-Fi refers to the IEEE 802.11 communication standard for wireless LAN. Wi-Fi

network connect computers to each other to the internet and to the other wired networks.

Wi-Fi networks use Radio Technologies to transmit & receive date at high speeds.

WiMAX

WiMAX (Worldwide Interoperability for Microwave Access) is a telecommunications

protocol that provides fixed and mobile Internet access. The current WiMAX revision provides up

to 40 Mbit/s with the IEEE 802.16m update expected to offer up to 1 Gbit/s fixed speeds.

The name "WiMAX" was created by the WiMAX Forum, which was formed in June 2001

to promote conformity and interoperability of the standard.

The forum describes WiMAX as "a standards-based technology enabling the delivery of

last mile wireless broadband access as an alternative to cable.

Comparison between Wi-Fi and Wi-MAX

Comparisons and confusion between WiMAX and Wi-Fi are frequent because both are

related to wireless connectivity and Internet access.

WiMAX is a long range system, covering many kilometres that uses licensed or unlicensed

spectrum to deliver connection to a network, in most cases the Internet whereas Wi-Fi uses

unlicensed spectrum to provide access to a local network.

Wi-Fi runs on the Media Access Control's CSMA/CA protocol, which is connectionless and

contention based, whereas WiMAX runs a connection-oriented MAC.

WiMAX and Wi-Fi have quite different quality of service (QoS) mechanisms. WiMAX uses

a QoS mechanism based on connections between the base station and the user device. Each

connection is based on specific scheduling algorithms.

Advantages of Broadband

Connection speed is up to 100 times faster than dialup connection. You can download

pictures files, software in seconds or minutes instead of hours. Online gaming is only

possible using a broadband internet access. It does not affect the phone line. For DSL

internet access, you can use the same phone line for both voice/fax and data transmission.

For cable internet access, you are connected to the internet via the cable network. In either

case, your phone line is not occupied while you are connected to the internet.

It is convenient because the internet connection is always on.

You don't need to dial an access number and risk getting a busy signal.

Broadband internet offers unlimited access and you won't be charged based on the

connection duration.

Broadband internet not only gives you high speed internet access, it can also provide cheap

phone services via VoIP technology.

Disadvantages of Broadband

High monthly fee compared to dialup internet access.

Higher security risk than dialup connection. A personal firewall is needed to protect your

computer.

Not all phone wires are equipped for DSL service.

Not all cable TV networks are equipped for cable internet access.

May not be available in rural or remote areas.

Applications

In telecommunication: Broadband in telecommunications refers to a signaling method

that includes or handles a relatively wide range (or band) of frequencies, which may be

divided into channels or frequency bins. The wider the bandwidth of a channel, the greater

the information-carrying capacity.

Telemedicine enables health care professionals and patients to take advantage of digital

communications to save money, time, and travel and most importantly, improve the quality

of care.

Teleworking or telecommuting is working from home or outside the traditional office or

workplace using a digital device and an Internet connection. Telework benefits employers

who see savings in o Information Gathering: More and more people are using the

Internet to gather information for anything from medical information to job searching and

news and information and shopping.

Tourism: Broadband and community content allow people to find out what is available in

tourist destinations and also helps people to see events or exhibits they might otherwise

never be able to visit in person.

Entertainment: Many people use the Internet for fun, to play games, gamble, download

movies, music, TV shows, books or information and services. As technology advances the

applications and opportunities for e-commerce and entertainment expand exponentially

Office overhead costs as well as increased productivity and motivation of their employees.

E-Government refers to the increasing push for government at all levels to make more

services available online. Local governments use e-Government to deliver services and

information to their residents and customers 24 hours a day, seven days a week.

Public Safety: Broadband networks can assist police, fire and other law enforcement

personnel in many crisis situations.

National Security: Broadband can be used by national, state and local authorities for

surveillance, videoconferencing, data mining, pattern matching and other applications to

assist law enforcement and medical services.