Broadband
Revisited

Broadband is not what you think it is. It’s lost its meaning to the aura of speed and
spectrum issues that surround it. You need to understand the technology, the options
available and limitations to make the right choice

Broadband…isn't this an
'always-on' Internet connection
provided by an
ISP? Contrary to popular
belief, this is not the true definition
of broadband. Simply speaking, the
term broadband refers to the ability
of sending multiple channels over a
single link.In other words,you're using
the same connection to pass
multiple signals.A cable TV network
is a perfect example of broadband.
You get a single co-axial cable terminated
to your TV,but the same cable
delivers lots of TV channels for you
to watch.
So despite true broadband having
been there in our lives for so long
in the form of cable TV,we never realized
its true meaning. Instead, the
image that's been created,of broadband,
is completely different—a
24x7 Internet connection.
That's because
the term has largely been promoted
by ISPs for their Internet
connections. The focus has been
more on an always-on Internet connection
than on the actual bandwidth
being offered. If there is
insufficient bandwidth, then multiple
services can't run reliably over
the same connection, which is thevery basis of a broadband connection.
The only advantage of this is
that the connection doesn't drop, so
users can use it for downloading
large software from the Internet.
This has changed recently after
the TRAI (Telecom Regulatory Authority
of India) said that in order for
a connection to qualify as broadband,
its minimum bandwidth must
be 256 Kbps.With so much bandwidth,
users can go beyond Web
browsing, e-mail and downloads.
They can expect more services from
the ISP, which were not possible till
now, due to lower bandwidth that
was being offered.Some of these can
be live audio/video streaming to listen
to songs or watch movies in real
time without compromising on
quality.They can use it for video conferencing,
VPN connections or running
business applications online.
Having more bandwidth also
means opening up a larger pipe for
the world to access your systems,
therefore,security risks increase.So
we've looked at security issues that
arise due to broadband.Lastly,an organization
going for a broadband
connection needs to ensure that it
gets the bandwidth being promised
by the ISP, for which service level
agreements or SLAs are important.
This story examines the current
state of affairs in the world of broadband
Internet and the technologies
that make it possible.
QUALITY OF SERVICE
AND SLAS
The quality of your broadband
connection is affected by two main
factors: the contention rate and the
network congestion. Some of these
issues can be resolved by better
bandwidth management and others
only by upgrading infrastructure to
manage that traffic better. Broadband
service providers offer a SLA
(service-level agreement), that
guarantees you (as a subscriber of
their service) a particular level of
bandwidth and throughput. Bandwidth
refers to the available capacity
and throughput (or speed) to what
you actually experience.
A data capable line has about six
usable stream pipes.Out of this six,
one is reserved and one is used for
internal maintenance purposes by
the ISP. This leaves four pipes available
for subscriber use. The contention
offered to you is the number
of remaining pipes that you can go
ahead and use. A 1:1 contention is
the best,since it guarantees that you
get a pipe for your purposes and you
can burst data all you want on that
pipe. On lower-end connections,
contention levels can be at 1:4 (one
out of four pipes will be available to
you), though 1:2 is also fairly common.
How does this affect your
bandwidth? Let's say that the line
can do 512 Kbps, on this line, a 1:4
contention connection offers you a
guaranteed 128 Kbps (1/4th the
available) at peak usage. The contention
rate depends on both the
availability and demand for bandwidth.
As the number of users for an
ISP grows, they are forced to take
contention levels higher, giving you
a lower actual data rate.Thus,at a 1:2
contention, your effective data
transfer rate at peak usage time effectively
halves from (say) 64 KB/s
(512 Kbps) to 16 KB/s (128 Kbps).
ISPs can only guarantee bandwidth
and throughput from your
terminator to their termination
point. They would not be able to
guarantee service levels beyond
that,since it would depend on traffic
patterns on the Internet itself.While
at the home user level,there may not
be a guaranteed SLA, ISPs do offer
such guarantees for enterprises at an
additional cost. In this SLA, you
should look for guarantees on uptime,
bandwidth and (if applicable)
contention rates. Additional points
would be on how quickly they would
rectify a problem and how (and how
much in advance) they would notify
you before scheduled maintenance.
Uptime is the amount of time as,
a percentage, that your connection
would remain available for use.During
this period,you should be able to
satisfactorily use your connection
for broadband activities. The normal
quote for uptime is 99.9%.Your
ISP will reserve a certain percentage
for maintenance work,during which
your connection will remain either
completely unavailable or unusable
after a certain level (say,Web browsing
may be possible, but not video
conferencing).Guarantees on bandwidth
and contention would be as
per the plan you subscribe to.
ISPs can notify the corporate/
enterprise customer in advance (if
required) about scheduled maintenance.
The usual process could include
a simple e-mail notifying you
of the proposed maintenance period.
Some ISPs also take it to the
next level, by sending an SMS to a
designated executive in your enterprise
about the downtime.
Further, broadband need not be
purely wired.ISPs such as AirTel and
Sify are providing wireless broadband,
without needing wires at your
end.Satellites and low-interference /high-power transmission towers
are used to propagate your
Internet signal almost the
same way as a TV signal is
propagated. WiFi broadband
complicates quality of service
considerations further, since
obstacles and different types
of materials in between the access
point and the receiver can
severely destroy your connectivity.
Also, the number of
users jumping into the connection
will further degrade
and reduce the available bandwidth.
How do you measure what
you are getting?
This is the biggest problem of
them all.How do you find out what
speed/bandwidth you are getting
and if it is anywhere near what you
are supposed to be getting through
whatever plan you are contracted
under? There are plenty of ways
available that help you clock your
connection.Here are a few.
MRTG
The MRTG (Multi-Router Traffic
Graph) is a tool that shows you
the traffic your connection is seeing
and how fast it is. It is easy to
deploy such a tool and quite a few
ISPs host it themselves and give
you a URL.A sample MRTG application
can be seen on the National
Internet Exchange of India website
at: http://www.nixi.org.
MRTG graphs provide break
ups of your usage by day, week,
month and year. However, it may
not be possible to know if this
bandwidth was seen by their entire
network or if it was specific to your
link. The data used for this representation
is taken live.
Hosted ‘Internet Exchange’
websites like that of
NIXI offer you traffic
patterns of the
network at strategic
points in the country
or world. You
can compare the
MRTG you are seeing
for your connection
with this
pattern to check if
any outages you are
facing are local or
endemic.
Web-based tools
You get good speedchecks
on most download
websites (eg download.com)
where a ‘Clock your speed’
link will find out and tell you
how fast your connection is
and how long it would take
you to download a particular
file at that bandwidth.
SBC Global provides a
speed check at:http://help
.sbcglobal.net/dsl/speedtest.
Although the ‘nearest servers’
list shows only US cities, you
can use it to get a ballpark estimate
of your speed in India as well.Also
ignore the text that reads ‘of your
Yahoo SBC Internet Connection’.
Like the text says, don't use your
Internet connection for a while
from this system while the test is
running,or you will get skewed results.
BandwidthPlace.com also provides
a neat Web-based tool at
http://www.bandwidthplace.com/
speedtest and this is quite reliable.
Interestingly this tool indicates
that almost any speed is ‘below par’
unless you tell it in the beginning
that you're on a 56 Kbps dial-up
connection!
CNet.com has a bandwidth
meter too at http://reviews
.cnet.com/7004-7254_7-0.html.
Though this is classified as a ‘review’,
but it is a bandwidth measurement
tool, alright. It doesn't
matter what you select or type in
on the starting screen. Just enter
some data and click on Go.About a
minute later, you should see a nice
set of comparative graphs telling
you how good or bad your connection
is.
Self help
The easiest way is if you have access
to a server somewhere on the
Internet and preferably on a known
connection.Create a file of any type
and of a known size and upload it to
this server. Use the machine and
connection you want to clock from
and download this file.Time the duration
and divide that file-size with
the time you noted.This will give you
your actual speed for that time. For
example,
File size = 1 MB
Duration to download = 45 secs
Bandwidth =
1 MB 1024 KB
45
=
45
= (22.76x8)KB/s=182Kbps
Third-party tools
Several third-party tools are
available that you can download and
install at strategic stations along
your network that can monitor your
connection and give you nice
reports. A sample list of such tools
are: NetInfo (http://netinfo.tsarfin
.com), OnlineEye Pro (http://www.
pmasoft.net),Traffic Statistics (http:
//www.trafficstatistic.
com). Some of the
above tools are free,others
are shareware.
We tried out Online-
Eye Pro's shareware edition
and it does a lot of
things,including giving
you a monthly traffic report
that you can export
as an Excel spreadsheet
or view as a graph and
print out. The useful
thing about OnlineEye
was its ability to work
with a group of computers
and allow remote management—
very useful on a LAN.It also
bundles some ping, uptime-monitors,
auto dialer and disconnect utilities,
packet sniffers and port
scanners, which make it useful for
network monitoring.
BROADBAND
TECHNOLOGIES
Keeping in mind the official definition
of what broadband is supposed
to be (the ability to use
multiple channels at the same time;
minimum bandwidth of 256 Kbps
according to TRAI), the following
technologies can effectively be used
to set up broadband connects. We
shall examine each one in detail and
classify them according to application
and effectiveness in their deliverables.
Integrated Services Digital
Network (ISDN)
Perhaps the first type of broadband
technology to become popular,
this requires a switched telephone
system. It works by multiplexing
both voice and data signals
digitally over the ordinary copper
wire network,providing high speeds
and quality.ISDN uses two channels
for transmissions, called B (Bearer)
and D (Data). The B channel is for
both voice and data, while D is for
signaling and control information.
The ISDN system also uses two
types of interfaces, each differing in
the number and combination of
channels they carry: the BRI (Basic
Rate Interface) and the PRI (Primary
Rate Interface). BRI supports
two B channels with bandwidths of
64 Kbps each and one D channel at
16 Kbps. PRI has a country dependant
number of B channels and a
single D channel at 64 Kbps.In North
America and Japan,PRI would have
upto 23 B channels, providing
around 1.5 Mbps. In Europe, Australia
and Asia, this goes upto 30 B
channels and 2 Mbps. ISDN supports
multiple simultaneous calls,
and each session on the B channel is
a simple 64 Kbps synchronous bi-directional
flow. Using a technique
called ‘channel bonding’,B channels
can also be multiplexed into a single
channel of higher bandwidth.
All telecom and Internet Service
Providers in India offer ISDN connectivity,
in BRI they use 2 B channels,
offering 64 Kbps and on PRI,we
get 30 B at around 1.5 Mbps. Using
an ISDN connection requires a costly
infrastructure. It requires an ISDN
line from your telephone company
and an ISDN modem or router. Although
the monthly access rates are
comparable or lower than normal
dial-up or DSL charges, the initial
setup fees (mainly for the equipment
you need to install and its related deposit
fee) can cost about Rs 5,000 for
BRI and upto Rs 60,000 for PRI connections.
Applications for ISDN include
Internet access, video conferencing
(most widely used application on
ISDN) and VPN connectivity between
offices. ISDN requires you to
dial out every time you need to connect
and no separate (call) charges
are applicable for your online time
other than your plan rate.
Broadband ISDN (B-ISDN)
B-ISDN was conceived in the
1970s as an extension to ISDN. BISDN
was designed to use ATM
(Asynchronous Transfer Mode) to
use both voice and data on the same
infrastructure.The theoretical maximum
speeds achievable on B-ISDN
stands at 1.5 Mbps over a point-topoint
channel.
This technology stands obsolete
and has been superceded by the DSL
family of technologies.
Digital Subscriber Line
(DSL)
As a concept, DSL is similar to
ISDN and B-ISDN,using ATM channels
to transfer data and voice simultaneously
over the same
telephone-wire. The crux of DSL
technology is the fact that humanaudible
signals lie in the frequency
range 300 to 3,500 Hz, while DSL
transfers data signals in the 10 to 100
KHz range, in 4.3 KHz bands. So, a
telephone cable can be used to carry
voice and data simultaneously. The
maximum frequency is 1.1 MHz for
ADSL (more on ADSL later).As we
write this, even higher frequencies
are emerging, giving rise to more
cousins of DSL such as SHDSL.However,
SHDSL is not currently supported
in India.
Unlike with ISDN where you
would get your own line from your
premises to that of the provider,DSL
uses the same wiring as the normal
telephone. This introduces the concept
of ‘line contention’. Naturally,
the better the contention, the more
the bandwidth available to you.
DSL uses a DSL modem or router
connected to the telephone line and
via USB or Ethernet to a computer or
network hub/router/switch. Between
the DSL modem/router and
the telephone line,sits a DSL-splitter
that ensures that the modem and
telephone units receive only those
frequencies the provider has allocated
for each.
The applications for DSL are the
same as for ISDN—high quality
VoIP,video conferencing,high bandwidth
Internet access,VPN,Internet
streaming of audio and video. DSL
requires you to dial out every time
you need to connect and no separate
(call) charges are applicable for your
online time other than your plan
rate.
The following sub-sets of DSL
currently exist.
HDSL (High Bit-rate DSL): Same
as normal DSL
ADSL (Asymmetrical DSL): The
data flows faster in one direction
than in the other.Usually the inward
(download) rates are higher than the
outward (upload) rates.Data speeds
can start at 128 Kbps and can reach
a blistering 1.5 Mbps (downloads).
However,ADSL rates fall off dramatically
as the distance between the
your end and the ISP's terminal
(‘central office’) increases. For example,
the same 256 Kbps line might
show speeds of upto 9 Mbps if the
central office is within 300 meters.
ADSL2 and ADSL2+ are improvements
to ADSL that allow
download rates of upto 25 Mbps at
upto 2.5 Kms from the central office.
Currently,most DSL providers in
India provide ADSL connections by
default. None of them provide
ADSL2 or ADSL2+ yet.
RADSL (Rate Adaptive DSL):
Works just like ADSL,except that the
modem/router can adjust the speed
of your connection as per the quality
and length of your line.Here, the
modem/router uses the unused portions
of the upload bandwidth to
create more download bandwidth.
RADSL is also more tolerant to signal loss and line noise. The lowest
upload speed attainable here is 64
Kbps, the same as a single-channel
ISDN connect.
SDSL (Symmetrical DSL): Transfer
rates start at 72 Kbps and reach
2.3 Mbps over a pair of copper wires
at upto 3 Kms. SDSL is vendor-specific
—both the central office and
the equipment at your premises
should use the same chipset /vendor
equipment, since all communications
are in proprietary formats.
This technology has now been superceded
by G.SHDSL.
VDSL (Very High Bit-rate DSL):
The theoretical maximum speed of
this is 52 Mbps download and 12
Mbps upload,much faster than most
common Ethernet connections (10
Mbps). This is done using two different
frequency bands each,for uploads
and downloads.VDSL can be
further symmetric (26 Mbps, 1.5
Km) or asymmetric (100 Mbps,100
m) also. VDSL is very suitable for
HDTV applications.
Cable Internet
Here,a co-axial Ethernet cable is
used to connect you via a network of
repeaters and routers, to the cable
service provider's office.You would
need a cable modem or router at
your end to receive the connection.
Unlike ISDN and DSL connections,
there is no need to dial anywhere
when using the cable Internet connections.
You just turn on your cable
modem/router and the connection
is available.Typically, cable Internet
is delivered over long distances using
the same line used for you cable
television connection and is provided
by the same company.Hence,
the name ‘cable Internet’. However,
some providers are also known to
draw dedicated Ethernet lines from
the router nearest to you, to give you
better connectivity.
Cable Internet connections can
actually be truly broadband since
the maximum speed attainable over
this cable is anywhere starting from
10 Mbps to 10 Gbps depending on
the terminals the cable provider is
using at their end. Connection
speeds vary drastically here depending
on the number of users online
as well as what they are upto,
since the entire line is shared between
subscribers in the same
neighborhood. Cable providers in
India start connection speeds at a
mere 64 Kbps.
Cable Internet connections and
computers connected over such interfaces
are the most vulnerable to
hacking attempts since they're always
on, and the networks are usually
not switched. Modern cable
modems support DOCSIS 2.0 (Data
Over Cable Service Interface Specification).
DOCSIS 2.0 is a specification
that enhances security and
privacy by encrypting communications
between your end and the
server provider.DOCSIS also allows
the ISP to control your modem from
their end—they use this to monitor
and troubleshoot your connections.
Applications of cable Internet
range from hosting your own private
server to using it for applications
that need a LAN-like connectivity.
The quality is not good enough to
run a call center on low-end connections,
but you can definitely download
large files that are required for
BPO operations. IP-TV and videoon-
demand are also applications
that can use cable Internet.
Other technologies not
prevalent in India
The above technologies are available
in India. But there are lots of
other ways you can have a broadband
connection and these are used
in some parts of other countries.
Let's briefly look at them.
Satellite Internet
Internet connectivity through
satellite. The equipment costs Rs
30,000 upwards and monthly bills
can be upto Rs 3,000. Connections
experience severe delays (upto 0.9
seconds) making it unsuitable for
anything other than casual browsing
or very slow e-mail access.Useful
if you're stuck in a desert or a
similar remote area,like deep inside
a forest,with a satellite phone capable
ofWeb browsing.
Power-line Internet
Transmission of broadband dataover high-voltage power lines. This
is a very noisy way of being online,
since the electric power-line is inherently
noisy. Any power-saving
device on the route would introduce
distortions into the signals and this
would need to be cleaned out. Any
implementation should have a builtin
error correction and noise-filtering
system to keep out these
disruptions. This technology is still
in its infancy stage.
Another major issue with PLI is
the plan to use the 10-30 MHz frequency
range for data streams. This
is used by shortwave and Ham radio,
and these services would be affected
by PLI,since high voltage power-cables
are unshielded.
Wireless broadband
This is slowly catching on in India,
with the rise of so many
hotspots. But this is not yet enough
to create a completely wireless ISP,
since all hotspots currently are locally
created and controlled.
SECURITY ISSUES
"With great power come great responsibilities",
said Ben Parker (Spiderman
fame).If this lies at the back
of your mind just like that of Peter
Parker (Spiderman himself), you
have understood the crux of this
write-up. In our context, we could
very well say that with better bandwidth
come great responsibilities.
Is broadband prone to more
security threats?
Well, for this question you don't
have a straightforward answer in
'Yes' or 'No'.But the amount of threat
on a given network from the outside
world (Internet) is directly proportional
to the time for which you are
connected with the outside world.
And technically, broadband should
be a 24-hour on connection. That
means logically you are always potentially
crackable.
And of course as you are on a
faster network (at least 256 kbps),
running hacking tools like a
portscan or maybe getting data out
of your systems using some key logger
is also technically faster. And it
won't make your network significantly
slow and as a result nobody
will notice that some malicious activity
is happening on the network.
When you opt for any corporate
broadband plan,in most of the cases
you get a static IP address.And if you
are not using that IP address for any
specific reason like providing VPN
access to you mobile and users,then
the only good these IP addresses do
is to make yourself very easily identifiable
to those with the wrong intentions.
So the greater power of broadband
can lead to greater security
threats if we do not secure and treat
the connection and the medium
wisely.
Best practices
Now let's talk about how you can
use your broadband connection
wisely to reap the benefits while
keeping the threats away.
The first and the most important
thing when you are using a 24Hr on
connection is a firewall.If you have a
very small network and you are getting
the connection terminated in a
PC then activate the operating system's
firewall (and keep it properly
patched). But this is not the preferable
mechanism for even a mediumsized
network, where the best practice
would be to have a dedicated
network firewall server or appliance
installed.And terminate your broadband
connection on it.For smaller or
branch networks, you can build a
firewall using customized live Linux
CDs such as SmoothWall,which can
act as full fledged firewalls.
After implementing the firewall,
make sure that all the ports which
you don't require to provide some
service are closed. You can check
whether after implementing the firewall
the ports are properly blocked
or not.This is done by running some
port scanning software such as
NMAP from outside your network.
You can even run a full-fledged network
assessment tool like Nessus on
you public IP address.
For hosting your own Web or
FTP server, it is a must that you install
them in a DMZ (de-militarized
zone).A DMZ is a sort of buffer zone
that separates the Internet and LAN.
It's considered a separate network
that is more trusted than the Internet
but less trusted than the internal
LAN. Generally any public Internet
services, which an enterprise provides,
are installed in this zone.
Even if you are using appliances,
your firewall equipment needs to be
continuously patched,to ensure that
it can override the latest vulnerabilities.
Finally, ensure that you continuously
play the devil's advocate,if not
the devil himself, and try to compromise
your own security measures
from outside so that you can
find out what is wrong with your security
setups and make the necessary
corrections.