it here

Why is the Internet slow?
Reasons and remedies for a
“slow Internet” experience
WHY IS THE INTERNET SLOW? REASONS AND REMEDIES FOR A “SLOW INTERNET” EXPERIENCE
Why is the Internet slow?
At some stage or other, everyone has heard that plaintive cry from a colleague,
a family member, or indeed you’ve uttered it yourself. It’s also a complaint familiar
to customer support desks at Internet Service Providers (ISPs) across the planet.
Network
ACCESS NETWORK
 SNRM, QLN, Crosstalk,
Interleaving Depth
Device
Home Environment

Hardware capabilities

OS

Browser

Browser caching policy

Security software

DNS configuration

Flash

Background networkusing applications
Figure 1:
Content

Modem/Router

Ethernet, Powerplug
or WiFi connection

Latency to target node


No. of objects per page
WiFi configuration


No. of domains per page
DNS configuration

Site dependencies
Caching policy



HTTP/2 support

CDN
Numbers and types
of devices on WiFi and
their current use

Repetitive Electrical Noise

Dry joints

Intermittent RF noise

Network Latency

Network Contention

Network policies
NETWORK SERVICES
DNS

PARTNER NETWORKS
Peering partners


Network Congestion

Network Routes

TCP/IP scaling
Some potential causes of a “slow Internet” experience
Figure 1 highlights some potential issues that impact the user experience.
We look at the technology, environmental and device choices that impact
the user experience. We examine fundamental technology barriers that limit
throughput and highlight why the user experience on a 100Mbps Internet
connection isn’t 10 times better than a 10Mbps connection and the advent
of 1Gbps connections won’t result in a 10-times better experience again.
Finally, we provide a number of suggested actions for you to determine
why the Internet appears slow to you and, where possible, to resolve same.
Michael Slevin
DIRECTOR, SONALAKE
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WHY IS THE INTERNET SLOW? REASONS AND REMEDIES FOR A “SLOW INTERNET” EXPERIENCE
Let’s look at how it all works and what can
cause a slow user experience
Interactions between browsers (Firefox, Chrome, Safari, Internet Explorer and the like) and
web sites generally use the HTTP protocol to retrieve or send multiple pieces of information,
both text and images from a remote web site. These protocols in turn sit on top of the
TCP/IP protocol. TCP provides reliability and importantly changes its throughput in reaction
to packet loss, packets received out of order, or any similar reason to avoid having to
re-transmit information. Each packet of information sent from A to B is acknowledged.
The time taken for information to get from A to B and for the acknowledgement to get
back to A is referred to as the round trip time (RTT) and is measured in milliseconds (ms).
Today’s web pages can present data from multiple sources, be they advertisements, images
and similar. Good practice for web developers calls for <40 round trips required per page.
However the current average webpage is 2.2MB and only 27% of pages need <50 requests
to correctly render the page1. On average 40 TCP/IP connections have to be established to
load a page (although 30% of webpages need more than 40), with the average webpage
including data from 17 domains (a max of 52 domains being observed)2. A result of this is
that most of us at some stage will encounter web pages that hang … frequently caused by an
advertisement host being down (planned or unplanned). Today’s browsers such as Firefox,
Chrome support 6 simultaneous HTTP connections to a single domain which introduces a
degree of parallelism, but doesn’t help with the multiple domains per web page issue3.
Customer Experience
Distance, Obstacles
& Orientation?
100Mbps or 1Gbps ethernet port?
Machine & drivers capable of
powering 1Gbps
Operating System,
Machine efficiency
WiFi is contended;
Neighbouring WiFi interferes
Browser version?
IE, Chrome, Firefox,
Safari Browser cache
WPA2 better/faster than WPA;
One or multiple Encryption modes supported?
Flash version;
Security/antiVirus
software
DNS config;
Orientation?
Environment interferes;
Distance, walls, insulation a factor
DNS configuration
RF Noise?
Internal house wiring correct?
Figure 2: Summary of in-home/on-device issues impacting throughput
1
http://httparchive.org/interesting.php (March 2016)
2
http://httparchive.org/trends.php (March 2016)
3
HTTP/22 was introduced in 2015 and supports multi-host multiplexing. As this is adopted more, users should
experience an improvement in page load times. ~7% of websites supported HTTP/2 over TLS in February 2016.
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WHY IS THE INTERNET SLOW? REASONS AND REMEDIES FOR A “SLOW INTERNET” EXPERIENCE
Don’t forget too, that rendering a single web page will also require a potentially large
number of DNS lookups (to convert the URL to an IP address). So the choice of DNS server
is important. The default servers are usually those provided by your ISP and the default
latency is similar to the RTT for the access network.
There are other DNS providers such as Google and OpenDNS which can be used,
but don’t select servers that have large RTT. DNS servers do give trouble from time
to time with the impact seen as timeouts or “slow” web page rendering for a large
proportion of the ISP’s customers. It is usually possible to select a primary and
secondary DNS – use your ISPs as primary and another as secondary.
Now let’s look at the networks
ADSL2+ access networks seem to have typical RTTs of ~20-30ms. VDSL and Cable networks
seem to be in the 6-10ms range while FTTH networks are in the 3-6ms range. 3G mobile
networks can have latencies >100ms while 4G is >50ms4. For mobile-facing websites, the
number of round trips to render a page should be less than 5 to account for the longer
latency. All of these relate to the latency from the modem to the nearest commercial sites.
If the two end points are 1ms from each other, we can achieve a max throughput for
a single TCP/IP session of 509Mbps with the default TCP/IP window size of 65,5355.
At 10ms, it’s 51Mbps. Yes that’s right, a single TCP/IP session can’t deliver more than
51Mbps when the two end points have a 10ms RTT between them. By the time you get to
30ms, you’re at 17Mbps maximum download for a single TCP/IP session. We can see from
the above that it’s actually RTT that has a greater impact on performance than the available
bandwidth. An individual on a typical VDSL or cable 8ms network offering 100 or 300Mbps
on a default Windows machine can never see more than ~64Mbps for a single connection
to a very local resource.
Incidentally, your uplink path is as important as your downlink path, since in a congested
scenario, your acknowledgement (ACK) of a received packet is what triggers the transmission
of the next. If that gets lost, or a timeout occurs, we see data retransmissions, duplicate
ACKs, and a consequent slowdown in the achieved throughput.
4
Ofcom found an average latency of 53ms for 4G and 63ms for 3G networks in Q4 2014 (http://stakeholders.ofcom.org.
uk/market-data-research/other/telecoms-research/broadband-speeds/mobile-bb-april-15/)
5
Note that for all these examples, the TCP window size is assumed to be 65,535 bytes. This can be increased through
TCP/IP window scaling. This is enabled by default on Mac computers, but, while supported in Windows, its use is
usually restricted when transiting public networks. To enable scaling on a Windows 7 machine, try the command “netsh
interface tcp set heuristics disabled” from a command line with administrative privileges. Note that it will only make a
difference where latency is long and your bandwidth is high. Check your current TCP/IP settings at www.speedguide.net/
analyzer.php
TCP throughput (in bps) = TCP/IP window in (bits) / RTT (seconds)
(but we can also consider that only ~97% of this is payload, the remainder being TCP/IP header)
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WHY IS THE INTERNET SLOW? REASONS AND REMEDIES FOR A “SLOW INTERNET” EXPERIENCE
All Internet access technologies are sold on a contended basis. Unfortunately, the
assumptions underlying the contention ratios may no longer be valid. 300 people attached
to a single DSLAM with an aggregate 2.4Gbps of bandwidth available to them will encounter
problems at peak times getting off that DSLAM which may only have a single 1Gbps interface
into the network. Traffic volumes are growing, leading to pressures on capacity planning and
deployment in the access and backhaul network.
Figure 3 illustrates temporary network congestion6 experienced at two sites connected to
the same DSLAM over the Christmas/New Year break. The graph shows minimum TCP/IP RTT
experienced between test devices and a test location. The normal RTT is 15ms, but during
times of congestion, the minimum (not average) RTT observed during test transactions on
one day exceeded 200ms. The impact to a customer is an experienced throughput as low as
1.5Mbps versus the normal 13Mbps (limited by the ADSL2+ bandwidth).
Figure 3: Indications of network congestion around the Christmas/New
Year period (VisiMetrix dashboard of Visualware generated data)
OK, so those metrics relate to the network between modem and the ISP. However, in the
case of fixed line Internet access, most devices will connect via WiFi. Most readers will know
that WiFi uses unlicensed radio spectrum and thus is subject to interference leading to
packet loss. WiFi comes in many flavours with maximum rated line speeds of 11, 54, 54-600
and 866Mbps (for 801.11b, g, n, ac respectively). However, that 54Mbps for 802.11g refers
to the physical bit rate which translates to a ~22Mbps data rate when error correction
overheads are taken into account. Some WiFi routers permit configuring WiFi in a mode
compatible with multiple variants, e.g. 802.11b/g. Having just one device operating at the
lower/older standard impacts everyone.
Of course, this bandwidth is shared among connected devices. WiFi operates based on
principles of collision avoidance. This works well on lightly loaded networks, but deteriorates
quickly once you get above 10% loading.
6
We can infer congestion with confidence in this instance because we observed the same pattern on a small number of
test lines while the remainder were not impacted.
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WHY IS THE INTERNET SLOW? REASONS AND REMEDIES FOR A “SLOW INTERNET” EXPERIENCE
Radio interference can originate from neighbouring WiFi networks, game controllers,
wireless video cameras, older Bluetooth devices plus the usual set of RF noise sources
including fluorescent lights. The reliability of the connection between your device and the
WiFi router depends on multiple factors including the aforementioned noise, distance
between the devices, radio reflections and movement leading to variable levels of packet
loss as the radio environment changes – a simple change in the orientation of the antenna
on the wireless device can have significant impact. Interference causes WiFi packet loss
which causes WiFi retransmissions which mean greater variability in the arrival rates of the
IP packets carried on the WiFi signal. This variability contributes to increased RTT (2ms to
>60ms) and thus reduced TCP/IP throughput rates. WiFi repeaters/extenders are also bad
news except on lightly loaded networks.
The practical response to this is to ensure you have a new router and give yourself
some breathing space by using channels in the 5Ghz band rather than the crowded
2.4GHz band.
The configuration of the WiFi itself causes issues. There is huge variation in the performance
of wireless routers, with some popular ones having appalling reputations.
Now look at the device itself, be it laptop, smartphone or similar. The obvious things
that impact Internet speed include old versions of browsers or very new versions on old
hardware(!), the local caching policy on the browser, and anti-virus software. Buggy network
drivers can impact. And of course, many users forget that they can have many potentially
bandwidth hungry applications running in the background, examples being Dropbox or
torrent client/servers. The devices themselves can vary hugely in the performance offered
and more expensive does not necessarily mean better.
For Windows users, clean up your machine with CCleaner, get rid of any nasties
with Malwarebytes.
Delivery of popular web content relies on Content Delivery Networks (CDNs). Essentially,
these are local copies of content placed on servers within or close to a particular ISP
(to achieve low latency). Use of an international DNS server can result in content being
delivered from the source or from a CDN in another country rather than the local copy
which is available much faster (larger bandwidth to the server and reduced RTT).
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WHY IS THE INTERNET SLOW? REASONS AND REMEDIES FOR A “SLOW INTERNET” EXPERIENCE
Speed Tests
But what about Internet speed tests? It can be very frustrating to have a poor Internet
experience while a speed test will happily show that your Internet connection is 10, 20,
50, 100Mbps.
Tests run against Ookla’s www.speedtest.net test servers will happily show you speeds
greater than this. Ookla’s Speed tests are multi-threaded. They discard the fastest 10%
(because they can show momentary b/w greater than your connection due to buffering
within the network and device). They also discard the 30% slowest results. So the results
shown are not indicative of what you as a user might expect at all – it really only indicates
what your line is capable of in total. They are not measuring the quality of the connection
(in terms of packet loss, or capability to sustain a high throughput).
However, knowing the capacity of a link is important, particularly for people on the first
generation ADSL technology. All of the copper-based fixed line access technologies rely on
RF signals carried on the wire (coax or twisted pair) which makes them subject to electrical/
RF noise events. While ADSL2+ and VDSL lines will generally recover after an intermittent
noise event, the original ADSL technology will not and requires you to restart your modem
to regain your normal connection bandwidth. Very occasionally, an ADSL2+ line will revert
to ADSL in reaction to a noise event, requiring a modem restart to get it back to ADSL2+.
We have also seen VDSL lines train themselves down from the 40Mbps range to 3Mbps
due to line impairments.
So keeping an eye on your modem sync rate is worthwhile, either directly or by
proxy using a capacity speed test.
A single-threaded TCP/IP test enables us to look at the real user experience in a lot
more detail. Figure 4 on the following page is a single threaded test showing TCP/IP
throughput over an 8-second timespan on an ADSL line from a test server. You can see
that a throughput of ~7.5Mbps to 8Mbps is achieved for most of the time. However,
you can also see that there were three large pauses (1400ms, 500ms, 500ms) when no
data was transferred. You can also see a single burst to near 10Mbps, all of this on a line
synchronised at 7.4Mbps. www.speedtest.net would show this as a perfect line, but
the detailed graph of a single session below shows significant problems. The packet loss
highlighted in red, results in retransmissions of data, so the useful data transmitted in
the 8-second window is much less than expected which impacts the performance of the
application or user’s browsing experience.
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WHY IS THE INTERNET SLOW? REASONS AND REMEDIES FOR A “SLOW INTERNET” EXPERIENCE
Figure 4: A single TCP/IP download over 8 seconds
(Visualware public test)
By contrast Figure 5 shows the millisecond-by-millisecond behaviour of a perfect session
(VDSL line delivering 40Mbps over 7ms RTT).
Figure 5: A near perfect single TCP/IP download over 8 seconds
(Visualware non-public test)
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WHY IS THE INTERNET SLOW? REASONS AND REMEDIES FOR A “SLOW INTERNET” EXPERIENCE
The graph in Figure 6 illustrates a bad congestion scenario – lots of gaps where no data is
transmitted resulting in an average throughput of 1.2Mbps instead of a normal 7Mbps.
Figure 6: TCP/IP throughput over an 8-second period (congested)
(Visualware non-public test)
Incidentally, in a scenario like this, you will find that the minimum RTT for a set of packets
will be impacted, so the congestion will manifest itself in a the minimum RTT for a PING
response moving from say 12ms to 23ms in the scenario illustrated above. While not
100% reliable, PING response times can act as an indicator of congestion and packet loss
in the network.
As we’ve said above, Ookla’s www.speedtest.net will return the overall capacity of a line.
It doesn’t tell you what you can usefully get out of that line in terms of sustainable
downloads or in terms of reliable connectivity.
www.speedof.me has a nice intuitive animated results screen shown below (but can cause
Firefox and Chrome to crash).
Figure 7: A sample www.speedof.me test result
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WHY IS THE INTERNET SLOW? REASONS AND REMEDIES FOR A “SLOW INTERNET” EXPERIENCE
Testing from Ireland against a UK-based server gave us ~35Mbps which is respectable
given the 25ms RTT to the server. Ookla’s www.speedtest.net returned ~51 Mbps to
a server with 7ms RTT 7.
www.testmy.net is interesting (46Mbps from UK-based server but no RTT given).
It supports both single and multithreaded tests. The www.testmy.net test also responds
correctly if you override windows settings and permit TCP/IP windows scaling on public
networks. With TCP windows scaling enabled, a 5.9Mbps download throughput from
Hong Kong to Ireland becomes 16.4Mbps.
So use www.speedtest.net to see what the Internet connection is capable of and
www.speedof.me & www.testmy.net to see what the connection can achieve with
a degree of reliability.
Visualware (www.myspeed.visualware.com) gives the most detail including jitter/packet
loss for VoIP simulation, capacity tests and single threaded TCP/IP Quality tests. This latter
test can be quite revealing but its efficacy is limited by the low number of test servers
available. Visualware returned ~48Mbps capacity to a server with 13ms RTT. Single threaded
TCP/IP quality tests to the UK reveal a rate of 14Mbps from a server with 28ms RTT (18Mbps
is the theoretical max) and highlighting a lot of packet reordering and packet loss. We can
get a sustained 3.7Mbps to a server in the USA with RTT of 121ms (which is close to the
theoretical best we can get of 4.2Mbps2). As you can see, latency matters a lot – shaving
5 milliseconds from the London-New York route was the sole driver for the Hibernia Express
sub-sea cable completed in 2015.
Google’s Network Diagnostic Test (www.measurementlab.net/tools/ndt/) gives similar
results and detail to Visualware.
Use Visualware or NDT for deeper diagnosis if the results of the first tests above
are poor – the tests are also useful to highlight issues with specific devices.
7
Speedtest tells me I have ~240Mbps download capability on my home network, even when run from a 10 year old
laptop. This is primarily because the test is run against the ISPs own test servers only 7ms away. Speedof.me tells
me I can get 14Mbps to London, but importantly tells me that I’m 47ms away from London on my home network.
The 240Mbps capability is almost irrelevant in the face of such latency, and it is that higher latency that normal
Internet usage is subjected to. In this instance, a lower bandwidth access technology with a headline 50Mbps
download capability will in fact achieve much better results than the 240Mbps line due to lower latency.
Your ISPs connectivity to the domains you’re interested in matters.
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WHY IS THE INTERNET SLOW? REASONS AND REMEDIES FOR A “SLOW INTERNET” EXPERIENCE
Netalyzr (www.netalyzr.icsi.berkeley.edu) takes a while to run, but is superb, and available
as a smartphone app for normal people or as a command line tool for readers of this paper8.
It includes bandwidth tests, but a lot more besides, checking DNS settings, firewall. Note that
the 18Mbps recorded in the test below (Figure 8) from a server 96ms away implies a degree
of multithreading is occurring – 4 parallel sessions could drive 21Mbps throughput at 96ms.
No packet loss occurred, so we might hypothesise that Netalyzer uses 4 parallel sessions.
Figure 8: An extract from the Netalyzer test results
We’ve seen that there are potentially many answers to the question “why is the Internet slow
for me”?
On the following page is a partial checklist to help diagnose your issues. Of course,
determining the root cause of a perceived slow connection is always much easier if it impacts
everyone at a particular site.
It also helps if you’ve prepared a little bit and have collected some baseline measurements.
From your modem, collect and store the current xDSL metrics, downstream and upstream
sync rates for xDSL, SNR metrics and interleaving depth – just take a snapshot and store it
– see Figure 9, Figure 10 and Figure 11 (for DOCSIS cable modems). Metrics that reflect the
stability of your line include the number of spontaneous resynchronisations since the modem
was powered up, the time since the last resynchronisation, the Errored Second (ES) and
Severe Errored Second (SES) count. Not all modems report this information.
8
A sample test result is found at http://netalyzr.icsi.berkeley.edu/restore/id=example-session
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WHY IS THE INTERNET SLOW? REASONS AND REMEDIES FOR A “SLOW INTERNET” EXPERIENCE
Figure 9: Principal ADSL metrics (from modem)
Figure 10:DOCSIS metrics (from modem)
11
WHY IS THE INTERNET SLOW? REASONS AND REMEDIES FOR A “SLOW INTERNET” EXPERIENCE
Figure 11:DOCSIS SNR (from modem)
Ping a couple of reference sites, local and international and store the results – better still
use traceroute. Traceroute will tell you the RTT to the target site and also the route (and
number of hops) taken to get there9. It will help to have these for comparison with the
results you get the next time you feel that “the Internet is slow”. If the results are similar,
don’t blame the ISP. The “MTR” application combines both ping and traceroute and may
be a handier solution for you.
We’ve seen that slow throughput is potentially due to a number of causes.
9
We have observed on a few occasions that throughput was being impacted every time we routed via a particular LNS
(the first hop in the ISP’s network). You’ll only find that out by doing a traceroute at regular intervals so that you have
a set of good and bad results.
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WHY IS THE INTERNET SLOW? REASONS AND REMEDIES FOR A “SLOW INTERNET” EXPERIENCE
The table below is a guide to help you determine whether the cause is the remote site
you’re interacting with, the latency between your device and the remote website, your
ISP’s peering links and network (including DNS servers), your access to the ISP, your home
network or your device(s). While some remedies are offered, we haven’t the bandwidth
here to cover all issues for all device types, nor for all modem and network types.
Symptom
What to do
A few sites are slow
– eBay, Amazon,
some popular
content you’ve
seen on Facebook,
Twitter
It might simply be that a site is particularly busy, can’t cope
with the traffic or is having problems. We seem to expect/
accept this for Ticketmaster but for very few other sites.
Sadly, we’re also seeing more denial-of-service attacks which
drastically impact targeted websites.
It’s only one device
on the network
affected? – nobody
else is complaining
Check with other devices.
Run a speed test from more than one device.
Use Visualware, Netalyzer or NDT.
Is everyone on site
similarly impacted?
For ADSL and ADSL2 users, the WAN bandwidth is likely to be
the limiting factor – for VDSL, Cable and FTTH networks, either
WiFi, or the two ends of the communication are likely to be
the limiting factors.
It might also be that some of your ISP’s (or another provider’s)
peering links are saturated towards those sites. This is where
it helps if you have pre-recorded some traceroute responses
to compare the good times with the bad.
If its just one device, focus on getting it back to “normal”.
Possible issues could be anti-virus software, bad drivers,
use of a different (bad) DNS server, stale or corrupt caches,
browser add-ons or plugins, OS thrashing, duplicate LAN IP
address allocation, etc. For Windows folk, use CCleaner as a
first port of call.
Run a speed test – www.speedtest.net to see what the
“pipe” is capable of and www.speedof.me, www.testmy.net
to see what a line can achieve with a degree of reliability.
Check via your modem that you are still synced at your
expected data rate e.g. 34Mbps. For xDSL, it’s the
downstream and upstream line rate (typically given in kbps)
so 34000 represents 34Mbps. Depending on the diagnostics,
you might see how many times a modem has resynchronised
(re-connected) since it was booted. This figure should be low,
less than once a week. A very high figure (once or more per
day) indicates some impairment on your line – a topic for
another day.
If your downstream/upstream attenutation has changed,
there’s been a change in the physical copper line. Were you
playing with the phones at the weekend? If not, then get your
ISP to investigate. Is it an unusually dry or wet spell?
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WHY IS THE INTERNET SLOW? REASONS AND REMEDIES FOR A “SLOW INTERNET” EXPERIENCE
Is everyone on site
similarly impacted?
(continued)
High numbers of Errored Seconds (ES) or Severe Errored
Seconds (SES) point to problems with the DSL line or your
environment in terms of noise. A high interleaving depth
introduces latency but with the benefit of a more stable
connection. If your SNR is well above 6dB, consider asking
your ISP to reduce the interleaving Depth. Kitz (www.kitz.
co.uk) is a good source of information for those of you
interested in learning more about DSL lines. If your SNR
is poorer than before, your RF conditions on the line have
changed – it might be intermittent or permanent (e.g. a
neighbour has subscribed and your line is suffering from
increased crosstalk). On some modems, you can see the
Quiet Line Noise (QLN).
Power cycle the modem and check that you return to your
previous “normal” link speeds. Make sure your modem is
correctly wired and DSL microfilters are in use where needed.
Another problem which likely impacts all attached devices is
the default DNS server for your home network. Try manually
configuring a DNS server to Google’s (8.8.8.8) and check again.
If your ISP’s DNS server is in trouble, try reconfiguring the DNS
server on the modem. Compare your current DNS response
times to others10. Another reason you might want to change
DNS provider (other than speed) is related to restricting
access to particular sites. For example Norton has specific
free DNS servers which restrict access to adult themed sites
and OpenDNS allows you to restrict specific sites.
Still got problems?
Connect a device to the modem by ethernet cable and run
speed tests. Connect the same device via WiFi and retest compare your ethernet and WiFi experience.
Ethernet results
are bad?
What else is running on your home network? Disable WiFi
temporarily and remove other ethernet-attached devices.
If you get a good result, bring back Wifi and try again on
ethernet. A bad result would indicate that one or more
devices on your network is hogging your bandwidth.
Check - use the modem or download the “Fing app”.
Don’t forget that your uplink is as important as the downlink.
A congested or busy uplink will severely impact the
throughput achievable on the downlink.
Maybe its time to prioritise your traffic or a specific traffic
type or traffic from a set of devices. Consult your router
manual and configure & enable QoS.
10
GRC’s DNS Benchmark (www.grc.com/dns/benchmark.htm) or Namebench (https://code.google.com/archive/p/
namebench/downloads) will point you in the right direction. NOTE of course, that value added services such as VoIP
and TV will likely preclude you from changing the DNS server settings on the modem. You can of course still change
the DNS configuration for specific devices.
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WHY IS THE INTERNET SLOW? REASONS AND REMEDIES FOR A “SLOW INTERNET” EXPERIENCE
If you suspect
that its WiFi
performance
Download a WiFi monitoring app and check signal strength
at various locations. We like “WiFi Analyser” and “Netgear
WiFi Analytics”. The latter can record strength in different
rooms and also look at channel interference. A neighbour’s
WiFi may be killing your WiFi in part of your house – the app
will show you less utilised channels.
If you want to be more thorough, download a WiFi mapping
app which, with a bit of patience, can generate a WiFi signal
strength heat map overlayed on a floor plan of your house.
Caveat – no app will show you RF interference from sources
other than other WiFi signals.
Strengths
look good?
Check what devices are on WiFi – use the modem or
download the “Fing app”.
Again look at the WiFi configuration – see if you can find
a simpler configuration. Teenagers tend to share WiFi
passwords – it’s quite possible that the gang of teenagers
hanging about outside your house are on your WiFi.
Momentarily change the SSID of your WiFi, link to that and
check speeds again. Good speeds now will point to WiFi
congestion within the home.
At this stage,
we’re beginning to
suspect congestion
in the network,
but is it the access
network or selected
peering links?
All Internet access technologies are sold on a contended
basis. Unfortunately, the assumptions underlying the
contention ratios may no longer be valid. 300 people
attached to a single DSLAM with an aggregate 3Gbps of
bandwidth available to them will encounter problems at
peak times getting off that DSLAM which may only have a
single 1Gbps interface into the network. Traffic volumes
are growing leading to pressures on capacity planning and
deployment in the backhaul network.
To “prove” congestion outside your home, take reference
readings (minimum and average RTT times to and from
a number of sites). Do this from both WiFi and Ethernet
connected devices. MTR (or WinMTR) is a handy tool for this.
Now run the same set of tests when you suspect a problem.
The Minimum RTT should be never change by more one or
two milliseconds (a route may have changed). The average
can fluctuate depending on the busyness of the network.
A change in the Minimum RTT or of course significant packet
loss (for both WiFi and Ethernet connected devices) is a sign
of congestion outside your control.
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WHY IS THE INTERNET SLOW? REASONS AND REMEDIES FOR A “SLOW INTERNET” EXPERIENCE
Sidebar
Of course, having a regular history of line conditions enables you to identify changes
in line condition and their impact, when they happen. Figure 12 shows the impact of
an increase in Quiet Line Noise on the carrying capacity of an ADSL line - the increase
in Quiet Line Noise (3rd graph) reduces the carrying capacity of the line (2nd graph).
The carrying capacity is represented by the area under the lines in the 2nd graph –
the area under the red line is ~15% of the area under the blue line, meaning that
throughput is reduced to 15% of normal when the noise on the line increased.
The root cause was a misbehaving modem power supply.
Figure 12:Detailed snapshots of line conditions showing the “good” state
in blue and the “bad” state in red.
16
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