Understanding Adsl in SA and Troubleshooting Tools

[ichigo]

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

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

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/showthre...enuation-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


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

 tracert [website] > Drive:\filename.txt

http://en.wikipedia.org/wiki/Traceroute

Local:

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

International:

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 
Router

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

  3     9 ms     9 ms    10 ms  196.43.21.226 
DNS

  4     *        *        *     Request timed out.

  5    28 ms    28 ms    27 ms  196.43.10.130 
DNS

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

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

  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] 
Google's Website
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

Speedtest.mybroadband.co.za/

Your Latest Results (Local)
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 (International)
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:

Speedtest-rba.isdsl.net

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.

[Pada]

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:

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]

[ichigo]

sure I will change it tommorow morning and thanks

[ichigo]

Ok changed the tracert to 8.8.8.8 (Google DNS)

I updated with more info and a picture

[Roman4604]

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.

[ichigo]

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.

Oh ok though it looked quite similar to our setup in South Africa

[FNfal]

That picture at the top is not a south African model but its close enough

[ichigo]

That picture at the top is not a south African model but its close enough

Thanks added it to description

[Roman4604]

Oh ok though it looked quite similar to our setup in South Africa

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.

[ichigo]

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.

Thanks changed it

[Roman4604]

Thanks changed it

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).

[ichigo]

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).

So when its a congestion problem is that our exchange or RAS, reason why I though it was the exchange at first

[Roman4604]

So when its a congestion problem is that our exchange or RAS, reason why I though it was the exchange at first

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.

[ichigo]

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.

Thanks for the good explanation

[doublefrangelico]

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 ;-)