ADSL & Internet Megathread

[chX]

ADSL & Internet Megathread

This thread is designed to help people with common issues relating to ADSL and general Internet usage, and to also act as a learning guide for anyone who is interested in how everything fits together.

The troubleshooting in this guide may save you making a call to your ISP, but there are some troubleshooting steps and details I may miss! They can run further tests / see line statistics that I cannot, so calling your ISP is always a good idea when you're experiencing any issues. Hopefully this guide will help you rule out what might be causing them.

The guide is split up into two main sections. Firstly, an introduction to what ADSL actually is and a quick troubleshooting section. This section outlines various ADSL and Internet issues, and the troubleshooting steps you should take in an attempt to resolve them.

The second section expands on the first, with more detailed information pertaining to why specific issues occur and why the troubleshooting is required.

As a note, this guide isn't fully completed and I will more than likely be editing and adding information in the future. I've decided to post it regardless!


What is ADSL?
ADSL stands for Asymmetric Digital Subscriber Line. It is one of the many varieties of Digital Subscriber Line (DSL). DSL is merely the transmission of digital data via PSTN (Public Switched Telephone Network). It is called Asymmetric because the speeds are asymmetrical – the downstream sync rate is always higher than the upstream rate.

ADSL is mainly deployed in two flavours: ADSL and ADSL2+. The standard of G.DMT (or ADSL1) can reach speeds of up to 12 Mbps (although it is mostly limited at 8 Mbps in Australia) while G.DMT.Bisplus (ADSL2+) can reach speeds of up to (and in some cases over) 24 Mbps downstream. Generally the upstream speeds will not reach higher than around 1.4 Mbps on ADSL2+. An additional standard called Annex M is available which can reach upstream rates of around 3.3 Mbps maximum. However this comes at a cost – the downstream rate is decreased.

One common misconception with ADSL is that it will always reach the maximum theoretical speeds. The speed that a service reaches is dependent on quite a few things.

First and foremost, the length and quality of your phone line. Put simply, the longer your phone line is the slower your service will go. This is purely due to physical limitations. One of the ways we measure signal loss is called attenuation.

Attenuation is the loss of signal in a given medium. As an analogy, if I were to stand 3 meters away from you and spoke, you would hear me fine; however, if I were to stand 700 meters away and spoke at the exact same volume, you wouldn’t be able to hear me anywhere near as well.

In the same way, the further the ADSL signals has to travel down your phone line, the weaker the signal becomes, causing the sync and throughput speeds to decrease. Attenuation is also increased by things like the quality and gauge of the line, line joints and bridge taps -- it takes more energy to turn a signal around corners.

Another factor which varies the sync speeds is interference. RFI (radio frequency interference) can cause certain frequencies to become degraded or completely unusable by your ADSL modem The data that the modem sends from your computer is digital (being binary - 0 or 1); however, in ADSL, this digital data is modulated onto an analog carrier wave and sent down the line.



The ADSL spectrum is divided into a whole lot of frequency ranges (usually called ‘bins’ or ‘sub-carriers’) ADSL has 255 of these while ADSL2+ has 512. Each ‘bin’ has a specific frequency range, and the addition of all of these bins equals your sync speeds. Essentially, the more bins available to be used the higher your sync speed will be.

If something is interfering with the signal on some of those frequencies, those sub-carriers may become unusable, or they may be assigned to carry fewer bits – and your speeds will decrease.

Noise in ADSL is the background noise caused by other electrical devices on the line, such as: phones, fax machines, back-to-base alarm systems, eftpos machines, etc.



Quick Troubleshooting Guide

No sync
There are quite a few things that can prevent a modem from gaining sync. Here’s a quick summary of what you should try if your modem isn’t syncing:

• Turn the modem off for a minute, then turn it back on. It’s cliché, but you’d be surprised how often a powercycle can bring a modem into sync.

• Ensure all cables are plugged in correctly. There should be a phone cable running between the modem and the wall socket / filter or splitter)

• Try a different phone cable. Cables can become faulty or worn out over time!

• Isolate the line down to just the modem (remove all other devices, including filters or splitters) if applicable

• Test the modem on a different phone socket if possible

• Check the phone line for any noise. If you’re supposed to have dial tone, are you getting dial tone? Do you hear any static/crackling/noise on the line? It may be preventing the modem from syncing.

• Try a different modem. You need to try and rule out as much as possible, and sometimes the modem itself is at fault. Don’t necessarily go out and buy one, see if you can borrow one from someone. If not… can you test your modem at another location?

• Call your ISP and see if they know of any outages in the area. They might be able to check other services on your exchange and find that there is an outage they didn’t know about, and your call alone revealed it to them.

• Your ISP should also be able to run through further troubleshooting and possibly perform line tests.

No Auth
Auth failures are mostly caused by incorrect modem details, account suspension or outages.

First, make sure your modem is actually getting sync. Without sync, it definitely won’t auth.

• Confirm your username and password in the modem is correct.

• Try switching the encapsulation mode. The two main encapsulations are PPPoE with LLC multiplexing and PPPoA with VC-Mux. Try the other one. If the RADIUS is getting hammered with incorrect details (which you then fix) it may apply a temporary block on the service. Changing the encapsulation may remove this block, and allow you to auth.

• Ensure the VPI in the modem is set to 8 and the VCI is set to 35. This is standard across Australia.

• Make sure that your account isn’t suspended!

• Call your ISP and see if there are any known outages.

• Firmware upgrade / factory reset and reconfigure your modem.

• Create a bridged connection. In a setup consisting of a modem going straight to a PC, creating a bridged connection essentially gets the modem to handle sync, while the PC itself handles the authentication. Your modem should be able to be set to bridge mode, and you can create a PPPoE dialer on a computer connected to it. Doing this will show whether or not the modem is having an issue in authing, or there is a greater issue present. This also prevents you from having to test another modem in most cases!

Dropouts

First of all, confirm what type of dropouts you're having. Is the modem losing sync, losing auth or is your PC losing connectivity?

You can usually figure this out by checking the LEDs on the modem. Which ones turn off when a dropout occurs? Does your PC say "A network cable is unplugged", or that the wireless network has been disconnected? Are you still able to ping the modem when the dropout occurs?

For sync/auth dropouts:

• Ensure the entire setup is correct. If you have Naked ADSL, you should only have a modem plugged directly into a phone socket. If you have ADSL running parallel to a standard phone service, you will need to have every device using that line (bar the modem itself) filtered. This means either the use of in-line filters or a central splitter (discussed in more detail later in this thread)

• If you have other devices on the phone line (phones, fax machine, EFTPOS, alarm system, foxtel, etc) try an isolation test. This means that you'll need to unplug everything except for the modem (which should be plugged directly into a wall socket). Does this resolve the dropouts? Leave it overnight and call your ISP so they can check connection logs.
  
  If the modem doesn't drop out while under isolation, it indicates that either one of the devices on the line is faulty, or a filter isn't doing it's job correctly.
  
  If it continues to drop out, keep going with the troubleshooting!
• Try a different phone cable between the modem and the wall socket, while the modem is under isolation. Phone cables can become faulty!
• Try the modem out on a different phone socket (if you have more than one in the house). If you haven't already, try testing it on the socket closest to the front of the house. This is usually the first socket in regards to wiring, and can rule out any internal wiring issues.
• Remove the modem from the line, and plug a phone directly into a socket (even on Naked ADSL!) Do you hear any noise? Static? Crackling? Buzzing? If so and you have a telephony service, call your voice service provider and get them to test it out. Noise on the line itself can cause dropouts! If you're on naked ADSL (you don't have a phone service), let your ISP know.
• Try a different modem on the line, or test your modem at another location. Modems (like everything else) can become faulty with time.
• If you're able to (your ISP allows it), try changing your ADSL profile to increase stability. This is explained in more detail later on.

Speed/Packetloss/Latency issues

Speed, packetloss and latency issues can sometimes be tricky to troubleshoot. Sometimes the issue can come down to congestion, internal wiring, modem issues, DSLAM issues, and all sorts of other things.

In regards to speeds, something needs to be cleared up. There's sync speed and then there's throughput speed.

Sync speed is the speed that the modem is connecting at between it and the DSLAM. It's reported by the modem itself. Throughput speed would be the speed you're downloading a file at, for example.

Throughput is always lower than the sync speed, as there are overheads in the PPP / ATM / TCP / UDP / etc etc packets which take up some of this bandwidth.

For low sync speeds:

• Powercycle the modem (turn it off for 1-2 minutes, turn it back on). Does the sync speeds increase?

• Isolate everything (bar the modem) from the line (if applicable). Make sure it's plugged directly into a socket. Does the sync speeds increase again? If so, something you disconnected is causing interference.
• Ensure the phone cable between the modem and socket/filter/etc is below 3 meters. Anything that exceeds it by a lot (ie 5-10+) can cause issues as the cable is unshielded and thus more susceptible to attenuation / interference.
• Try the modem on a different phone socket (if possible) while the line is isolated. This once again rules out internal wiring issues.
• If you're able to, try fiddling with your ADSL profiles/modem modulation. If you're on ADSL2+ but getting speeds below 8 Mbps, you may actually sync at a higher rate on an ADSL1 profile / modulation!
• Try a different modem on the line.

For low throughput speeds:

Check your sync speed as above. If it's low, you'll need to troubleshoot that. If the sync speed is fine but you're downloading at significantly lower rates:

• Where are you testing it? Download a test file from your ISP's website (Internode's mirror, BigPond's unmetered downloads, etc). Sometimes specific websites hosted on servers in different locations will only provide lower download rates. If you're downloading from a server in Germany, it probably won't go as fast as a local server.
• Try downloading multiple files at the same time. Sometimes, it will limit the speed of one download. If you're syncing at 8 Mbps but downloading a file at 300 Kb/s -- try a second file. Do you get another 200-300 Kb/s?
• If you're downloading at very low rates from multiple different sources, isolate your network down. How many computers are using your internet at the same time? Make sure you only have one computer, connected via ethernet, not wireless!
  
  
• If possible, test different computer's (while only using one at a time). Is the computer itself running slow? Perform virus / malware / adware scans. Try another browser (internet explorer, firefox, safari, google chrome, etc)
• Make sure there's nothing using the bandwidth (ie P2P programs, games, etc) Use Netlimiter to help diagnose this.
• Test for packetloss. If there is packetloss, it may give the illusion of slow throughput speeds. You can test for packetloss with a simple ping test.
  
  Assuming you're using a Windows operating system, bring up command prompt:
  • Start -> Run -> cmd
  • Type ping <host> -n 100
  Where <host> can be a website or IP. It's best to use a local site, such as your ISP's DNS servers or website.
  
  -n 100 forces it to ping 100 times.
  
  
  
  So an example would be
  ping 192.231.203.132 -n 100 (pings Internode's primary DNS server 100 times)
  
  If you're seeing lots of "Reply from" then that's indicating that packets are getting through. If you see an occasional "Request timed out", that's a lost packet. At the end of 100, it will give you a small summary of sent/received and lost packets. If you have a percentage of packets lost above ~5%, it very well may be causing throughput issues.
  
  The standard troubleshooting for packetloss is practically the same as above. Try pinging your modem to make sure you're not getting packet loss between your PC and modem (which would in turn cause packet loss everywhere else)
  
  And if nothing else appears to be working, try another modem!
  
  Also call your ISP. There may be backhaul / RIM / line congestion that you are unaware of.

A closer look

This section aims to provide more detailed information and expand on the above.

Sync and Auth
In order to successfully troubleshoot ADSL issues, it’s good to know exactly what everything means and how to identify what may be happening. You may have heard the terms sync and auth thrown around, but what exactly does it all mean?

Sync (synchronization) occurs when the modem successfully trains (negotiates) with the DSLAM. This training establishes parameters such as which modulation type to connect with (ADSL, ADSL2+, Annex A or Annex M?), and quite a few other things.

Having sync means that your modem is “talking” to the DSLAM. This doesn’t necessarily mean you’re connected to the internet, yet!

Auth (authorization) occurs when your modem has successfully sent your username and password details, they have hit your ISP’s RADIUS (Remote Authentication Dial In User Service) server, and the details have been confirmed as correct.

You then have an active internet connection which you can use to troll and rep farm!

Sync is usually shown on your modem by an ADSL or DSL or LINK light. Generally (and it differs between modems), a solid sync light indicates sync and a flashing sync light indicates that the modem is actively training.

Auth is usually represented by an INTERNET or PPP light. Each modem has different LEDs, so it may be wise to consult the modem’s manual if you’re unsure on anything.


Dropouts

Dropouts are one of the most common issues with ADSL. There’s a whole lot of factors which can cause them, ranging from modem issues to even bad weather.

Filtering
One of the main causes of dropouts is filtering issues. On any non-NakedDSL connection, you are required to filter any device apart from your modem. This means: phones, fax machines, dialup modems, security systems, foxtel (that connects to the phone line), eftpos machines – pretty much anything else plugged into your phone line.

A filter is essentially a device which prevents the ADSL signals from reaching your phones / other devices. The modem itself does not need to be directly filtered, as it contains an internal filter which removes the lower frequency voice signal.

There are a few types of filters, but the main two are in-line and central. An in-line filter is a small device you plug between your wall socket and device. Usually they have 3 ports – one to connect to the wall socket, one for the modem (if you need the modem to share the same socket as a phone) and one for a phone.

A central splitter/filter is usually installed by a tech. They pretty much create a ‘dedicated’ ADSL socket, which receives the voice and ADSL signals, while any other socket will have the ADSL signals filtered out. They usually work a lot better, but are more expensive and harder to replace.



This is an example of an in-line filter.



This is a central splitter.

Phones (especially if faulty) can send noise down the line. If these slightly higher frequency signals aren’t filtered out, it can interfere with some of the lower frequency ADSL signals (usually used for modem training and negotiation) and cause dropouts. It can also cause noise issues on the phone itself, when those lower ADSL frequencies interfere with the phone’s higher frequencies.

Cabling & Equipment
Cables are often overlooked in basic troubleshooting, but they are quite important to test.

Standard phone cables are unshielded and are more likely to be affected by attenuation and EMI (Electromagnetic Interference) than what the copper lines are. Generally, it is recommended that the phone cable between your modem and wall or filter is under 3 meters in length. Cables greater than 3m can start to lose some signal (resulting in slower speeds) and can also cause drop out issues.

If you are having dropouts, it is also recommended that you try changing the cable your modem uses. Cables, like most other things in the world, do become faulty / worn out.

It is also recommended that you test the modem on any other active phone sockets (if applicable) in the premises. Preferably you would want to test it on the first socket in the premises, which is usually towards the front of the house.

By testing the first socket in the house, you are effectively ruling out any internal wiring issues that may be causing dropouts and possibly other issues.

Another important troubleshooting step is an isolation test. Basically, you unplug everything from your phone line and have only your modem plugged directly into the socket (no filter/splitter.) Obviously, you are only required to do this if you actually have a telephony service and are not on NakedDSL.

If this solves the issue, then it’s quite possible some of the equipment (phones, filters, cabling) is faulty and causing dropouts.

Perform an overnight isolation test (as sometimes dropouts are intermittent and it might not drop out for hours at a time) and then give your ISP a call, as they can generally check your connection logs.

Of course, there is one other piece of hardware which you need to rule out in a dropout fault – the modem itself.

Modems do sometimes become faulty, and it’s not uncommon for all sorts of issues to occur when this happens.

The two best ways of ensuring your modem is working correctly and isn’t the cause of a dropouts issue:
- Test another modem; or
- Test your modem in another location

Some ISPs may offer to send you a test modem after most of the initial troubleshooting is completed. If not, ask a friend / relative / neighbour who has a modem if you can borrow it.


Line profiles and SNR Margin
If your ISP allows you to change line profiles, it is worth trying a more stable profile. Generally, the profiles which provide more stability also sacrifice some speed.

SNR stands for Signal-to-Noise Ratio, and is just that – how much signal there is compared to how much background noise (interference) there is on the line.

The ISP sets a minimum, target and maximum SNR, which is further determined by the profile you are using. The higher the SNR, the clearer the signal is which is being sent up and down the line.

When the modem is initially training, it will inspect each sub-carrier and find the SNR of each one. ADSL uses QAM (Quadrature Amplitude Modulation) in order to send data down the line. Essentially, an analog carrier signal has shifts made in its amplitude and phase to represent a digital signal.

If there is noise or some other interference affecting this signal, then it may be unclear what the amplitude or phase actually was. The less noise a sub-carrier has, the more bits can be allocated to that sub-carrier. The more bits that are assigned to an amplitude/phase change = a higher number of possible amplitude/phase combinations

For example:

If you are assigning 2 bits per symbol (change in amplitude/phase), it would look like this:
00
01
10
11

So a bit stream can be broken up:
01-11-10-00-11-00-01

If you are assigning 3 bits per symbol, it would look like this:
000
001
010
011
100
101
110
111

So a bit stream may look like this:
000-010-110-111-011-001-000

During training, the modem will decide which sub-carriers can transmit the most bits and which ones need to transmit less. Extremely noisy sub-carriers are not used at all.

If the SNR drops below the minimum value (an example could be noise suddenly occurring on the line), the modem will attempt to increase its transmitting power to raise the SNR again. If it cannot do this, there will more than likely be bit errors (as the noise levels will distort the modulation and make it unclear what the intended symbol was.) The modem will then need to drop the connection and re negotiate, which causes a dropout.

This is where the SNR Margin comes into play. It’s best to think of the SNR margin as a “buffer zone.” For example, if a specific sub-carrier has an SNR of 40dB, and the SNR margin is set to 6dB, only 34dB of signal will be used (which in turn decreases the amount of bits allocated and thus also decreases the sync speed) A higher SNR margin does increase the stability of the service.

You basically want to find a good balance; an SNR which provides decent sync speeds while keeping the SNR margin high enough to prevent dropouts.

----
Please don't hesitate to ask any questions or provide feedback (good or bad) on the guide. I hope that some people can find it useful.

[Swordfish]

awesome work chX !

[chX]

Cheers Swordy. Thread is now stickied as well.

[fury]

Huge effort, nice work. Now to make ppl read it before making threads ;p

[Jam0864]

Really well done here, sticky the shit.

[RETN]

wow nice, good read
will hopefully help many people out
nice effort bud

[ja$on]

big read will read later
hopefully can find something to fix my netpacket error warning messages ffs so annoying

[chX]

Originally Posted by ja$on

big read will read later
hopefully can find something to fix my netpacket error warning messages ffs so annoying

I had a quick read of that thread.

Are you using wireless or ethernet?

Try doing some of the packetloss testing which I outlined in the guide, and see if it's your actual connection or CSS doing some funky shit.

[xr6_turbo]

You do reliase no one reads these, whilst it is an awesome idea...pretty pointless using big words like CPE when 10% know what it means hahaha

Nice work though Chx, excellent detail.

I fit central splitters

[chX]

Originally Posted by xr6_turbo

You do reliase no one reads these, whilst it is an awesome idea...pretty pointless using big words like CPE when 10% know what it means hahaha

Nice work though Chx, excellent detail.

I fit central splitters

Yeah, I realise. But it's like that with a lot of things. If people are really in need, they might read it and might pick up something which helps them out.

Wanna fly over and fit one for me, for free?

[ja$on]

Originally Posted by chX

I had a quick read of that thread.

Are you using wireless or ethernet?

Try doing some of the packetloss testing which I outlined in the guide, and see if it's your actual connection or CSS doing some funky shit.

im on wireless man
i have dsl ?? i think its called dsl power bundle from optus (its a really old plan but its 50x better than the new plans)
anyway
i have my socket thingy connected to a firewall which is thne connected to my wireless router then i use wireless on my pc
>< its soooo annoying

[chX]

From what I read on various other threads that issue mainly occurs on wireless. Try connecting an ethernet cable between your router / PC if possible and see if it still happens.

[ja$on]

its too far its on the other side of the house and upstairs haha
man my comp just died it shutdown itself had a bsod but i couldnt read the message in time it just shut down must be the heat its like 41degrees outside and probs friggen 80degrees in my room

[Jam0864]

I used to have that dsl power plan, fucking awesome plan.

[chX]

Originally Posted by ja$on

its too far its on the other side of the house and upstairs haha
man my comp just died it shutdown itself had a bsod but i couldnt read the message in time it just shut down must be the heat its like 41degrees outside and probs friggen 80degrees in my room

Got a phone socket closer to where your PC is? Either move the modem/router closer to you, or move your PC closer to it so you can test it out with an ethernet cable.

You may even be getting packet loss / speed reduction in general if it's that far away.

[xr6_turbo]

I'd be saying lots of loss...

Run a cable or POE

[WOlfy]

Great work mate chx.
Will help alot of people
+1

[chX]

Originally Posted by WOlfy

Great work mate chx.
Will help alot of people
+1

Cheers man. I hope it does help people. :P

[Cloudstrike]

You are all now qualified to work on helpdesk!

[chX]

Originally Posted by Cloudstrike

You are all now qualified to work on helpdesk!

Go look at some rocks, faggot. <3

[fury]

you both sux and cloudstrike ur not 14

[chX]

Nah, he actually is 14. I'm inviting him over for cordial and ice cweam later this week.

[Cloudstrike]

Originally Posted by chX

Go look at some rocks, faggot. <3

Geology is the bomb diggity!

Originally Posted by fury

you both sux and cloudstrike ur not 14

I am 14, seriously.

[xr6_turbo]

Cloud is 14

[h0rdy]

Wow good read. nicely done, hope this helps alot of people.