Understanding Adsl in SA and Troubleshooting Tools

ichigo

ichigo

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Understanding How Adsl Works
http://www.kitz.co.uk/adsl/equip.htm
contention.gif

Depicting an oversee's model for adsl, which is similar to ours

G.Dmt (G.DMT full-rate ADSL expands the usable bandwidth of existing copper telephone lines, delivering high-speed data communications at rates up to 8 Mbit/s downstream and 1.3 Mbit/s upstream)
http://en.wikipedia.org/wiki/G.992.1

Adsl 2+ (The data rates can be as high as 24 Mbit/s downstream and up to 1.4 Mbit/s upstream depending on the distance from the DSLAM to the customer's premises)
http://en.wikipedia.org/wiki/G.992.5

VSDL 1&2(The data rates can exceed 100 Mbit's downstream and upstream depending on the infrastructure available at the exchanges and dslams and you have to be quite close to them to achieve those speeds and can get quite low speeds)
https://en.wikipedia.org/wiki/Very-high-bit-rate_digital_subscriber_line

Attenuation (is the distance from the exchange/dslam terminal to your house)
http://en.wikipedia.org/wiki/Attenuation

SNR (Signal To Noise Ratio)
The Further you are from the exchange the lower the SNR is by default and decreases/increases depending on your line sync speed, if your line is dropping the first thing you will notice is that your SNR is lower than 12.
http://en.wikipedia.org/wiki/Signal-to-noise_ratio

In Depth Description of what Attenuation/SNR is
http://mybroadband.co.za/vb/showthread.php/186156-Understanding-SNR-and-Attenuation-Rates

Yes Attenuation/SNR is the most important, it can still be improved by building a dslam/exchange near your house or your line can get moved to a closer dslam/exchange.

Attenuation & SNR are not always related to distance, there could be other factors at play.

Also changing to fibre optics will help when they add it to your residential area or business area

CRC Errors (is an error-detecting code commonly used in digital networks and to see if your ISP connection is dropping)
http://en.wikipedia.org/wiki/Cyclic_redundancy_check

Graph to check your adsl potential according to your line attenuation/distance from the exchange, results may vary depending on your SNR
ADSL_Line_Rate_Reach.gif


Tracert (Is a great diagonstic tool used to diagnose your adsl line for common exchange/DNS problems like congestion or slow connections to the DNS, also can be used to check international/local latency problems)

You can also use tracerts to check what latencies you may get to certain gaming servers

How to save a tracert on your drive
Code: 
 tracert [website] > Drive:\filename.txt
http://en.wikipedia.org/wiki/Traceroute

Code: 
[B][U]Local:[/U][/B]

Tracing route to [url]www.telkom.co.za[/url] [196.43.22.222]
over a maximum of 30 hops:
  1    <1 ms    <1 ms    <1 ms  192.168.1.1 
[B]Router[/B]
  2     9 ms     9 ms     9 ms  *.telkomadsl.co.za [*] 
[B]RAS[/B]
  3    24 ms    24 ms    23 ms  196.43.39.166 
[B]DNS[/B]
  4    25 ms    26 ms    25 ms  rrba-ip-bssr-1-ge-2-48.telkom-ipnet.co.za [196.43.23.6] 
[B]DNS[/B]
  5    24 ms    24 ms    24 ms  nbsc-ip-bssr-1-atm-5-0-0-1.telkom-ipnet.co.za [196.43.23.30] 
[B]DNS[/B]
  6    27 ms    27 ms    28 ms  nbsc-ip-rcache-1-vif2.telkom-ipnet.co.za [196.43.22.222] 
[B]Telkoms Website[/B]
Trace complete.

Code: 
[U][B]International:[/B][/U]

Tracing route to google-public-dns-a.google.com [8.8.8.8]
over a maximum of 30 hops:
  1    <1 ms    <1 ms    <1 ms  192.168.1.1 
[B]Router[/B]

  2    10 ms     9 ms     9 ms  *.telkomadsl.co.za [*] 
[B]RAS[/B]

  3     9 ms     9 ms    10 ms  196.43.21.226 
[B]DNS[/B]

  4     *        *        *     Request timed out.

  5    28 ms    28 ms    27 ms  196.43.10.130 
[B]DNS[/B]

  6    25 ms    25 ms    69 ms  rrba-ip-lir-1-gig-2-0-0-201.telkom-ipnet.co.za [196.43.33.5] 
[B]Telkom Main Exchange[/B]

  7   222 ms   220 ms   220 ms  lon-ip-dir-telecity-gig-1-0-2.telkom-ipnet.co.za [196.43.9.217] 
[B]London International Exchange[/B]

  8   222 ms   223 ms   221 ms  196.25.147.10 

  9   278 ms   253 ms   252 ms  209.85.255.86 

 10   259 ms   259 ms   258 ms  209.85.253.94 

 11   265 ms   262 ms   262 ms  209.85.243.33 

 12   266 ms   280 ms   289 ms  216.239.49.36 

 13   280 ms   269 ms   270 ms  209.85.255.118 

 14   266 ms   265 ms   241 ms  google-public-dns-a.google.com [8.8.8.8] 
[B]Google's Website[/B]
Trace complete.



http://speedtest.mybroadband.co.za/, http://Speedtest.net and http://Speedtest-rba.isdsl.net: are great tools for diagnosing problems like congestion or throughput problems.

You can also use the speedtests to check what latencies you may get to certain gaming servers

Code: 
[B]Speedtest.mybroadband.co.za/[/B]

Your Latest Results [I](Local)[/I]
Test conducted on 26 March 2012 10:33:40 PM
Download Speed: 3463 kbps (432.9 KB/sec transfer rate)
Upload Speed: 418 kbps (52.3 KB/sec transfer rate)
Latency: 61 ms

Your Latest Results [I](International)[/I]
Test conducted on 26 March 2012 10:36:26 PM
Download Speed: 1858 kbps (232.3 KB/sec transfer rate)
Upload Speed: 376 kbps (47 KB/sec transfer rate)
Latency: 429 ms
Local:

International:


Code: 
[B]Speedtest-rba.isdsl.net[/B]

Start Time: 22:22:05
End time: 22:22:06
IP Address: 41.146.11.120
Download Size: 409600 bytes
Time Delta: 1.1366279125214 seconds
Download Speed: 352 KBytes/s
Line Speed: 2816 kbits/s

The best way to report a fault is to go into the Telkom Direct Store

Good info to know so you can improve your latency and adsl experience, so hope you find it useful.

DNS' in the router settings affects your adsl latency/speed so if you in Durban and you have Cape Town as your dns it will affect your adsl latency/speed since any data transfered(uploaded) or downloaded has to go through Cape Town first before going out Internationally or Locally

If you live in Cape Town use these DNS'
Code: 
196.43.46.190(Cape Town)
196.43.50.190(Pretoria)

If you live in Durban/Pietermaritzburg use these DNS'
Code: 
196.43.50.190(Pretoria)
196.43.53.190(Durban)

If you live in JHB/Pretoria use these DNS'
Code: 
196.43.42.190(JHB)
196.43.45.190(Pretoria)

Which ever city you are nearest to you can use the DNS' settings assigned to it and also helps if one of the DNS' is faulty

Although Dialup and ISDN may not be obsolete yet and it's still in use today, ADSL and VDSL will continue to overpower them until both get finally discontinued, but the ADSL/VDSL coverage has a few downfalls in South Africa and also the infrastructure available to them and not to mention cable theft so people's only choice is to use Wireless, Cellphone Networks or the Old School Dialup and ISDN if they are outside of the coverage area for ADSL and VDSL.

Pricing is also quite influencial affecting peoples choices not just the infrastructure and what is available to them.
 
Last edited:
Very nice guide indeed!

I'd replace www.l.google.com with like 8.8.8.8 (Google DNS) or www.bbc.co.uk, because www.l.google.com can also be local!

See here:
Code: 
Tracing route to www.l.google.com [74.125.233.17]
over a maximum of 30 hops:

  1     6 ms     1 ms     1 ms  mikrotik.tuis.local [192.168.11.1]
  2    12 ms    12 ms    12 ms  41-132-44-1.dsl.mweb.co.za [41.132.44.1]
  3    14 ms    13 ms    12 ms  te1-1-0.511.cpt-ipc-1.mweb.co.za [196.28.178.202]
  4    14 ms    13 ms    13 ms  197-84-2-2.cpt.mweb.co.za [197.84.2.2]
  5    17 ms    19 ms    19 ms  tengige0-2-0-0.11.cpt-up-1.mweb.co.za [196.28.178.97]
  6    19 ms    17 ms    19 ms  197-80-4-137.jhb.mweb.co.za [197.80.4.137]
  7    14 ms    15 ms    14 ms  gi0-2-cpt-cinx.mweb.co.za [196.28.178.133]
  8    15 ms    14 ms    14 ms  google.cinx.net.za [196.223.22.41]
  9    15 ms    15 ms    20 ms  64.233.174.105
 10    15 ms    15 ms    15 ms  cpt01s01-in-f17.1e100.net [74.125.233.17]
 
Ok changed the tracert to 8.8.8.8 (Google DNS)

I updated with more info and a picture
 
Last edited:
Top picture depicts IP Stream, which we don't have here (yet). Still on the older/simpler IP Connect, but we have evolved beyond ATM to metro Ethernet backhaul in most major centres.
 
Roman4604 said:
Top picture depicts IP Stream, which we don't have here (yet). Still on the older/simpler IP Connect, but we have evolved beyond ATM to metro Ethernet backhaul in most major centres.
Click to expand...

Oh ok though it looked quite similar to our setup in South Africa
 
That picture at the top is not a south African model but its close enough
 
ichigo said:
Oh ok though it looked quite similar to our setup in South Africa
Click to expand...
Ya, close enough for the layman.

One other thing though, in your traceroutes you indicate hop 2 is the DSLAM/Exchange. Its actually beyond that (the DSLAMs are not IP devices), the IP resides on the RAS. These are more commonly refered to as an ESR locally, by virtue of the Cisco 10000 Edge Services Routers Telkom uses.
 
Roman4604 said:
Ya, close enough for the layman.

One other thing though, in your traceroutes you indicate hop 2 is the DSLAM/Exchange. Its actually beyond that (the DSLAMs are not IP devices), the IP resides on the RAS. These are more commonly refered to as an ESR locally, by virtue of the Cisco 10000 Edge Services Routers Telkom uses.
Click to expand...

Thanks changed it
 
ichigo said:
Thanks changed it
Click to expand...
Cool, while it may seem trivial, its quite important to understand.

If one has bad 1st (ext) hop latency, one could incorrectly assume the issue must be between yourself and the exchange. Not so, yes a bad line/DSLAM (port) could be the cause, but its also probable the issue is between your local exchange and its upstream parent exchange (where the RAS/ESR resides), in other words nothing to do with your line.

Perfect case in point was the recent botchup on the backhaul between the Fourways exchange (my local) and the upstream Bryanston exchange (housing the area's ESRs).
 
Roman4604 said:
Cool, while it may seem trivial, its quite important to understand.

If one has bad 1st (ext) hop latency, one could incorrectly assume the issue must be between yourself and the exchange. Not so, yes a bad line/DSLAM (port) could be the cause, but its also probable the issue is between your local exchange and its upstream parent exchange (where the RAS/ESR resides), in other words nothing to do with your line.

Perfect case in point was the recent botchup on the backhaul between the Fourways exchange (my local) and the upstream Bryanston exchange (housing the area's ESRs).
Click to expand...

So when its a congestion problem is that our exchange or RAS, reason why I though it was the exchange at first :D
 
ichigo said:
So when its a congestion problem is that our exchange or RAS, reason why I though it was the exchange at first :D
Click to expand...
Either & more, the permutations are many;

- Misconfigured/faulty DSLAM trunk port
- Technical issue on the backhaul, either ATM switch path or metroE ring
- Congestion, oversaturation on the path between your DSLAM and its upstream ESR
- Faulty/misconfigured ESR user-side aggregation port or overload ESR

Its a complex chain of infrastructure, all of which needs to be operating optimally to provide you with satisfactory performance. And this is all way before you even reach your ISP.
 
Roman4604 said:
Either & more, the permutations are many;

- Misconfigured/faulty DSLAM trunk port
- Technical issue on the backhaul, either ATM switch path or metroE ring
- Congestion, oversaturation on the path between your DSLAM and its upstream ESR
- Faulty/misconfigured ESR user-side aggregation port or overload ESR

Its a complex chain of infrastructure, all of which needs to be operating optimally to provide you with satisfactory performance. And this is all way before you even reach your ISP.
Click to expand...

Thanks for the good explanation :D
 
Last edited:
Hi Guys and thanks for making things much clearer.

In troubleshooting my current situation, I need a bit of specific info.

Now that I know a critical factor is the length of the cabling from my modem/router to the DSLAM or Exchange, I'd like to know how to figure out where my DSLAM is. Is it in one of those small blue and white boxes (approx 1.2mx30cmx60cm) on the street corners or is it a housed in a small building? (etc etc) I don't trust Telkom to provide this info.

This site shows the location my of my "exchange". (could this be the DSLAM and not the exchange?)
http://www.broadbandstats.co.za/exchange/RNHL05


The reason I'm asking is because Telkom told me that I was more than 5KM from the exchange and that this was the reason I was limited to 384Kbps and thus the reason my latency and speed are so bad (<120KBps). I do realise after reading this excellent guide that even though I am 4.4Km as the crow files from the abovementioned exchange, the cables might be more than 5km. This is why I'm hoping that there is a DSLAM inbetween, and thus the reason for trying to find a way to identify it so that I can ask to be connected via it, if I am not.

I am desperate.... No Line of Sight for cellular/wireless providers, no more than 34KB/s download speed on cellular provider even with professionally-installed YAGI antenna directly connected to router, >5km from ADSL exchange .... FML ;-)
 
doublefrangelico said:
"Now that I know a critical factor is the length of the cabling from my modem/router to the DSLAM or Exchange, I'd like to know how to figure out where my DSLAM is. Is it in one of those small blue and white boxes (approx 1.2mx30cmx60cm) on the street corners or is it a housed in a small building? (etc etc) I don't trust Telkom to provide this info."

No this is not a DSLAM that is a street box ( cable from the exchange meets the local cabling that feeds the poles )
Click to expand...
 
Last edited:
doublefrangelico said:
Hi Guys and thanks for making things much clearer.

In troubleshooting my current situation, I need a bit of specific info.

Now that I know a critical factor is the length of the cabling from my modem/router to the DSLAM or Exchange, I'd like to know how to figure out where my DSLAM is. Is it in one of those small blue and white boxes (approx 1.2mx30cmx60cm) on the street corners or is it a housed in a small building? (etc etc) I don't trust Telkom to provide this info.

This site shows the location my of my "exchange". (could this be the DSLAM and not the exchange?)
http://www.broadbandstats.co.za/exchange/RNHL05


The reason I'm asking is because Telkom told me that I was more than 5KM from the exchange and that this was the reason I was limited to 384Kbps and thus the reason my latency and speed are so bad (<120KBps). I do realise after reading this excellent guide that even though I am 4.4Km as the crow files from the abovementioned exchange, the cables might be more than 5km. This is why I'm hoping that there is a DSLAM inbetween, and thus the reason for trying to find a way to identify it so that I can ask to be connected via it, if I am not.

I am desperate.... No Line of Sight for cellular/wireless providers, no more than 34KB/s download speed on cellular provider even with professionally-installed YAGI antenna directly connected to router, >5km from ADSL exchange .... FML ;-)
Click to expand...

What you need to find is a big white cabinet then you can work how far you actually are from it, its the mini exchange/dslam apparently. If you close to it your cable is either faulty or it goes wacko around the whole neigbourhood before it reaches it :D.

Exchange on broadbandstats is in a brick building it isnt the mini-exchange/dslam
 
Updated with helpful DNS' settings when you faced with a faulty DNS causing you to download/upload slowly and to have high latency and with VDSL 1&2.
 
Last edited:
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