Question 1: What is adsl?
Answer : Asymmetric Digital Subscriber Line is a high-speed Internet access
service that uses your telephone line to send and receive Internet data at much
faster speeds than a conventional dial-up connection. With ADSL you are
connected to the Internet 24 hours a day (“Always On”). You no longer need to
dial up to open your Internet connection. You can also make and receive
telephone calls while online. This is because the ADSL signal operates on a
digital frequency, while the voice signals (telephone conversation), operate on
an analogue frequency. Voice data and Internet data can, therefore, travel
along the line simultaneously. The "asymmetric" in ADSL refers to the
fact that the data being received by your computer from the Internet (downstream
data / downloading), travels at a faster speed than data travelling from your
computer to the Internet (upstream data / uploading).
Most general users will download more data than they will upload, so
the slower upstream speed is not a problem. For example, when you click on a
hyperlink, your browser sends a few characters upstream to request the page
that the hyperlink points to, and the page then comes downstream (downloads) to
your PC so you can see it.
Question 2 : How Does Adsl works?
Answer : The telephone system was originally designed to carry the voice along
copper telephone wires. The voice is converted into small
electric pulses which travel along the telephone wires. These electric pulses
are then converted back into sound at the other end, so the other person can
hear you. This happens in both directions so you can have a conversation.
ADSL also works through the copper wires of your telephone line. However,
Internet data travels along the wires at a different frequency to the voice
signals. When ADSL is installed a micro-filter is plugged into your phone
connection which separates the frequency of voice signals (telephone line) from
that of your Internet data (broadband connection) and it is this that allows
you to surf the web and talk on the phone at the same time.
Question 3 : What is the speed of ADSL?
Answer : ADSL is fast. Compared to a dial-up modem, which does 56kbits per second downstream, ADSL is up to
ten times faster. That means that a large download that might take ten minutes
on a dial-up modem will happen in around a minute on ADSL.
Question 4 : What are the reasons to get low speed broadband?
Answer :
·
Quality of your phone line - areas with better copper wiring can achieve
somewhat faster DSL speeds.
·
Length of the phone line between the residence and the phone company hub
(exchange hub). DSL technology is "distance sensitive" - its
performance decreases significantly as you get further away from this hub.
· Service glitches.
While normally a constant, DSL speed can suddenly drop if the service provider
has technical difficulty with their network.
Question 5 : What are
the factors that you can control directly to increase your DSL speed
from your end?
Answer :
- Spyware on computer(s). Even when the DSL network may
be functioning at full speed, spyware programs may be consuming the
bandwidth. Anti-spyware programs should be run
regularly on networks to prevent this problem.
- Wireless router. Routers sit between your computers and
the Internet connection. If not functioning properly, a router can greatly
limit the DSL speed. Temporarily connecting a
computer directly to the Internet can help identify this situation.
- Slow wireless network connection. In extreme cases, a
very slow Wi-Fi connection between a computer and a wireless home network
will not keep pace with the speed of the DSL Internet connection.
Improving the quality of the Wi-Fi connection will solve this problem.
- Old computer(s). Very old computers lacking sufficient
processing power or memory cannot keep pace with a high-speed DSL
connection. You can verify this problem by comparing the DSL speed between
computers in your home or buy a new computer.
Question 6 :What is line attenuation?
Answer :
Attenuation is the loss of signal over distance.
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* 20bB. and below = Outstanding
* 20dB-30dB. = Excellent
* 30dB-40dB. = Very Good
* 40dB-50dB. = Good
* 50dB-60dB. = Poor and may experience connectivity issues
* 60dB. and above = Bad and will experience connectivity issues
Line attenuation also affects your speed.
* 75 dB+: Out of range for broadband
* 60-75 dB: max speed up to 512kbps
* 43-60dB: max speed up to 1Mbps
* 0-42dB: speed up to 2Mbps+
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Question 7 : What is SNR?
Answer : Signal-to-noise means
the level of a desired signal to the level of background noise. It is defined
as the ratio of signal power to the noise power, often expressed in (dB).
6dB or below noise margin is bad, it will experience no
synch or intermittent synch problems
7dB-10dB is fair but does not leave much room for variances in conditions
11dB-20dB is good with little or no synch problems (if no large variation)
20dB-28dB is excellent
29dB or above is outstanding
Question 8 : What is SLA?
Answer : Service Level Agreement, a contract between an Provider and the Client
which commits the Provider to a required level of service. An SLA should
contain a specified level of service, support options, penalty provisions for
services not provided, a guaranteed level of system performance as relates to
downtime or uptime, a specified level of customer support and what software or
hardware will be provided and for what fee.
Question 9 : What is the difference between PPPoE and Bridge Mode?
Answer : PPPoE mode
1. User id and password stored
inside the Modem.
2. Multiple PCs can be connected.
For example most of the basic ADSL Modems having at least one ADSL port and one
USB port. In PPPoE mode, can connect one PC to Ethernet port and one PC to USB
port which enable simultaneous internet usage in both the PCs.
3. PPPoE mode is more secured.
4. NAT can be enable in PPPoE mode.
Bridge Mode
1. In bridge mode user id and password to be entered in the dialer of computer.
2. Only single PC can be connected.
3. Less
secured because all the ports are open need good firewall to avoid virus
infection.
Question 10 : What is Last Mile?
Answer : In telecommunications technology, connectivity between the customer's home to the telephone company via Copper cable called last
mile.
Question 11 : What is leased Line?
Answer : A permanent telephone connection between two points set up
by a telecommunications common carrier. Typically, leased lines are used by
businesses to connect long distant offices. Unlike normal dial-up connections,
a leased line is always active. The fee for the connection is high. Because the
connection doesn't carry anybody else's communications, the carrier can assure
a given level of quality.
What is the Function of BRAS or BNG
- Aggregates the circuits from one or more link access
devices such as DSLAM
- 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
- Release Public ip to the subscriber
Question 12 : What it the Function of DSLAM?
Answer : The DSLAM equipment collects the
data from its many modem ports and aggregates their voice and data traffic into
one complex composite "signal" via multiplexing.
Depending on its device architecture and setup, a DSLAM aggregates the DSL
lines over its Asynchronous Transfer Mode (ATM), frame relay,
and/or Internet Protocol network (i.e., an IP-DSLAM
using PTM-TC [Packet Transfer Mode - Transmission Convergence]) protocol(s)
stack.
The DSLAM acts like a 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 BRAS where
the end user traffic is then routed across the ISP network to the Internet.
Question 13 : Explain Broadband Call Flow?
Answer :
- When the PPPoE client is dialed, the PPPoE client
broadcasts a PPPoE Active Discovery Initiation (PADI) message to BNG.
- The BNG that receive the PADI message respond
with a PPPoE Active Discovery Offer (PADO) message advertising the domains
and contexts they support if configured to advertise.
- The PPPoE Client sends a PPPoE Active Discovery
Request (PADR) message to the BNG.
- The BNG receives the PADR message and prepares to
bring up the PPP session. Then
responds with PPPoE Active Discovery Session-Confirmation (PADS) message
advertising PPPoE session ID.
- The PPPoE Client sends PPP LCP Configuration
Request message advertising to BNG.
- The BNG responds with PPP LCP Configuration Ack
if PPP parameters are acceptable.
- The BNG then sends PPP CHAP Challenge to PPPoE
Client.
- The PPPoE Client responds with PPP CHAP Response.
- The BNG sends Access-Request packet to AAA Server with the
session’s PPP username and CHAP password.
- AAA sever reply Access-Accept to BNG and BNG will
release public ip to the subscriber.
Question : 14 What is the difference between PPPoE
and PPPoA?
Answer : Point to Point Protocol over Ethernet (PPPoE) and Point to
Point Protocol over ATM (PPPoA) are both technologies that offer a provider the
opportunity to roll out broadband services. This document will show why PPPoE
should be chosen over PPPoA.
Advantages of a both PPPoE & PPPoA based broadband service
• End user authentication to the network, forces the end user to authenticate
to AAA server before being allowed access to the network
• Billing options, gives the provider the ability to offer different billing
options, by time, by data, unlimited or by services purchased
• IP address conservation, a provider can limit the number of IPs a specific
user can receive or can force a user off the connection at will
• Trouble shooting, a provider can easily tell what users are on or off on a
per user basis
• Scalable, all authentication, authorization, and accounting can be handled
for every user using existing AAA server
• Invisible to end user, both can be integrated in the Customer Premise
Equipment CPE making the connection process invisible to the end user – though
we do recommend they stay off the CPE but it is easily done and PPPoA is
traditionally only on the CPE
• Service Selection, both can be used to offer multiple services and service
selection
Negatives of PPPoA
• Only a single session per CPE can be established. In PPPoE we offer the
ability to log in to multiple services or create multiple sessions all at the
same time over the same line
• CPE setup and access, in general PPPoA must be configured on the CPE itself,
PPPoA software is not available on platforms. Either the CPE must support PPPoE
or an ATM network interface must be installed in the PC. ATM network interface
cards are expensive and both can be difficult for an end user to configure.
Once an end user has the ability to configure the CPE it opens up the problem
for incorrect configurations making trouble shooting by the provider very
difficult resulting in increased support costs
Positives of PPPoE
• Brand management, by having the customer use software to log on and off they
force the user to see the providers brand, logo or company name. Word of mouth
is the strongest form of advertising
• Increased revenue opportunities, with PPPoE we can offer the ability to log
in to multiple services or create multiple sessions all at the same time over
the same line. What do we mean by multiple services? How about a special
account for a child that gives them G rated access only? How about a dedicated
movie or music server?
• Ease of support, PPPoE
software has troubleshooting and help files built in to the
application. If an error occurs the error message can be present to the end
user with a possible resolution preventing the customer from ever having to
call the provider for help. In PPPoA everything is done in the CPE meaning when
a problem occurs the only notification is lights on the CPE which tell a user
nothing
• End User Familiarity, client side software present users with the familiar
look and feel of dial-up which if purchasing a broadband service means they are
almost 100% familiar with the dial-up look and fee reducing their learning
curve to use the new service
• Works in existing environment, if a provider already offers an Ethernet based
service PPPoE can be implements without changing the existing CPE, as mentioned
above PPPoA needs an ATM interface
