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Thread: Detecting a congested ADSL exchange - Guide

  1. #1

    Default Detecting a congested ADSL exchange - Guide

    Since questions about exchange congestion keep popping up I thought I'd do a write-up that can be linked to.

    What is exchange congestion

    Exchange congestion occurs when the ADSL users connected to a specific exchange move more data than the exchange can handle. The effect is much the same as a traffic jam on a highway...everything slows down and everyone is late for work. On the ADSL side this shows up as high latency ("ping") and reduced throughput ("download speed"). Gaming, skype and other real-time activities will be hardest hit, though the effect on streaming (youtube) will be noticeable too. The throughput is generally an unreliable indicator for this so we're going to focus on latency.

    How do I test it

    By performing a trace route ("tracert"). This plots a path from your PC to the website you select and reports how long it took to reach each "hop" along the way. This gives us a way to distinguish between a bad ISP and a bad Telkom exchange (Note 1).

    To perform a trace route, you need to open a command prompt window. To do so, hold down the Windows Key (between left CTRL and left ALT) and press R. That opens the Run window. Type in "cmd" (no quotation marks) and hit enter. This opens a black window. Type in "tracert mybroadband.co.za" (no quotation marks).

    What am I looking for?

    I happen to have both a congested and an uncongested trace for my line (Same line, same ISP, different exchange)

    Quote Originally Posted by Congested Exchange
    C:\Users\HX>tracert google.co.za

    Tracing route to google.co.za [74.125.233.55]
    over a maximum of 30 hops:

    1 <1 ms <1 ms <1 ms 10.0.0.2 <<First hop. PC to router. Still inside my house
    2 413 ms 414 ms 435 ms 196-210-142-129.dynamic.isadsl.co.za [196.210.12.129] <<Second hop. Router to exchange. Those 400s are the exchange congestion
    3 384 ms 348 ms 323 ms cdsl1-rba-vl2153.ip.isnet.net [196.38.73.169]
    4 403 ms 438 ms 482 ms cdsl1-rba-vl150.ip.isnet.net [196.38.73.17]
    5 ^C<<Me stopping the trace since I've seen what I need
    Quote Originally Posted by Uncongested exchange
    C:\Users\HX>tracert google.co.za

    Tracing route to google.co.za [74.125.233.63]
    over a maximum of 30 hops:

    1 <1 ms <1 ms <1 ms 10.0.0.2 <<First hop. PC to router. Still inside my house
    2 10 ms 10 ms 10 ms 196-215-178-1.dynamic.isadsl.co.za [196.215.178.1] <<Second hop. Router to exchange
    3 13 ms 14 ms 12 ms cdsl1-rba-vl2360.ip.isnet.net [196.38.73.133]
    4 13 ms 13 ms 13 ms cdsl1-rba-vl150.ip.isnet.net [196.38.73.17]
    5 14 ms 14 ms 14 ms core1a-pkl-te-1-2.ip.isnet.net [168.209.1.139]
    ^C <<Me stopping the trace since I've seen what I need
    C:\Users\ms>
    In the above congested exchange example its taking almost half a second to make it through the first hop. Thats enough to make most fast paced games unplayable simply due to exchange congestion - regardless of how "good" your ISP is. Anything above 25 is suspicious and above 100 is pretty much guaranteed to be a problem. Note...this is for first hop only...seeing 100+ on later hops is normal if its an international site.

    Exchange congestion can also depend on the time of day - a semi-congested exchange will only show symptoms during peak times. Friday afternoons and Saturdays are usually worst. If you've got a semi-congested exchange chances are you'll have a fully congested exchange a couple of months later.

    How do I fix it?

    Sadly, the answer is usually that you don't. Usually Telkom needs to physically upgrade the exchange hardware. You can try reaching out to Telkom support channels, but understand that its a long shot - very very few people have managed to get this fixed without waiting & some have been waiting for years.

    Technical Note 1

    While the above is reasonably reliable (esp if it indicates a good outcome), technically a bad ISP can affect the first hop too since ISP IPC congestion will look the same. The easiest way around this is to re-do the test with a different ISP. So either purchase some cap from a different ISP or use the Telkom guest account (assuming your primary account isn't Telkom already)

    Username: [email protected]
    Password: guest

    NB - the above can only navigate to specific sites. The most interesting being saix.net since it also has a speedtest tool on it. i.e. You'd need to use saix.net instead of google.co.za

    Technical Note 2

    The sharp eyed people will have spotted some differences in the IPs on the tests both in route and end point. Its just Google & IS reshuffling things - the traces were taking almost a year apart. It doesn't affect the overall example though (I checked) so ignore it.

    Technical Note 3

    As per ranger's comment below using the test account is superior from a testing point of view to a standard Telkom Internet account.

    (Also - in case someone missed it - ranger is considered a trusted source of info on the technical ADSL front).

    Closing Thoughts

    The above is what I do. No doubt others will have different opinions & some like using tools that present the above in a visual format etc. There is also an automated tool available written by a mybb member (I've never used it so can't vouch for it):
    http://mybroadband.co.za/vb/showthre...ot-Report-Tool

    @mods: OP permission hereby granted to edit & improve as necessary
    Last edited by HavocXphere; 13-08-2014 at 09:13 PM.
    Quote Originally Posted by Rouxenator View Post
    I microwaved the socks for a bit and they are fine now.

  2. #2

    Default

    All indications are that more and more people are getting broadband.
    Telkom already have a huge problem with congested exchanges.
    Telkom are simply not fixing the problems, and in cases where they do, it takes ages (years even?).
    This does not bode well for the future of broadband in South Africa.
    But looking at: http://hellopeter.com/telkom/custome...k-and-analysis its clear Telkom simply do not care.

    I've also added a complaint through hellopeter about my congested exchange.
    http://hellopeter.com/telkom/complai...change-1443861

    So, what can be done?
    Smalltalk Advocate.
    MWEB 2 Mbps Uncapped ADSL + Line
    MineThings Free Browser Game

  3. #3

    Default

    Quote Originally Posted by HavocXphere View Post
    So either purchase some cap from a different ISP or use the Telkom guest account (assuming your primary account isn't Telkom already)
    You should only test with a SAIX-based account (which doesn't really use IPC, or at least not the same way), and the easiest way is the guest account.

    Note that Telkom Internet accounts are not SAIX accounts (the statement "assuming your primary account isn't Telkom" is misleading in this aspect), so Telkom Internet customers should also test with the SAIX guest account.
    Nothing I post on this forum represents the views of the company I work for (or used to).
    Note: I no longer work in the telecommunications or ISP sectors.

  4. #4

    Default

    Sorry to nit-pick but isn't the router to exchange the second hop?

    The first hop is from your PC to your home router.

  5. #5

    Default

    Quote Originally Posted by hongkongpom View Post
    Sorry to nit-pick but isn't the router to exchange the second hop?

    The first hop is from your PC to your home router.
    No. It depends on what configuration the user is running within their own walls.

    Generally we'll see two types though:
    1) ADSL router dials out >> Second visible hop is outside
    2) PC dials out via PPPoE >> First visible hop is outside

    This choice affects which "hop" is the first outside hop. i.e. People can theoretically run 20 hops inside their house...the one that is interesting is the first hop that goes outside of the users walls.
    Quote Originally Posted by Rouxenator View Post
    I microwaved the socks for a bit and they are fine now.

  6. #6

    Default

    I have a question, If the 2nd hope is bad, is it most definitely exchange congestion or could it be something else?

  7. #7

    Default

    Quote Originally Posted by 50-saint View Post
    I have a question, If the 2nd hope is bad, is it most definitely exchange congestion or could it be something else?
    Its congested, but if its high late at night (00:00) it could be another factor.
    Intel I5 2500K 1155 | 16GB DDR3 Corsair Dominator | EVGA GTX 970 FTW+ | 7.5TB | Corsair Graphite 600T

  8. #8

    Default

    Quote Originally Posted by Rickster View Post
    Its congested, but if its high late at night (00:00) it could be another factor.
    When doing a tracert, the results give 10 lines. Can someone please explain each line and also give an indication when is it a congested exchange and when is it a bad ISP.

  9. #9
    Super Grandmaster ponder's Avatar
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    Default

    Quote Originally Posted by Tswerie View Post
    When doing a tracert, the results give 10 lines. Can someone please explain each line and also give an indication when is it a congested exchange and when is it a bad ISP.
    How are we suppose to know what your output looks like?
    entia non sunt multiplicanda praeter necessitatem

  10. #10

    Default

    Quote Originally Posted by ponder View Post
    How are we suppose to know what your output looks like?
    I think he wants to know what each hop represents.

  11. #11

  12. #12
    Super Grandmaster ponder's Avatar
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    Quote Originally Posted by AntiGanda View Post
    I think he wants to know what each hop represents.
    How can we inform him without knowing what the output looks like? It differs by location, isp etc etc etc. He asked about the 10 hops, without seeing the output we can't tell him jack...
    entia non sunt multiplicanda praeter necessitatem

  13. #13

    Default

    Bump...

    Since Telkom changed to their "Dynamic Profile Syncing" system I do not get a ping reply from hop 2, it times out, pings thereafter are fine though...

    Also, would the SNR be affected by exchange congestion? Why I ask is that I drop from 18db @6mb on my Incoming SNR to 11db @6mb at the exact time every day (5PM to 7AM).
    BullShyte Baffles Brains...

  14. #14
    Afrihost Representative AfriMan's Avatar
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    Default

    Quote Originally Posted by HavocXphere View Post
    Since questions about exchange congestion keep popping up I thought I'd do a write-up that can be linked to.

    What is exchange congestion

    Exchange congestion occurs when the ADSL users connected to a specific exchange move more data than the exchange can handle. The effect is much the same as a traffic jam on a highway...everything slows down and everyone is late for work. On the ADSL side this shows up as high latency ("ping") and reduced throughput ("download speed"). Gaming, skype and other real-time activities will be hardest hit, though the effect on streaming (youtube) will be noticeable too. The throughput is generally an unreliable indicator for this so we're going to focus on latency.

    How do I test it

    By performing a trace route ("tracert"). This plots a path from your PC to the website you select and reports how long it took to reach each "hop" along the way. This gives us a way to distinguish between a bad ISP and a bad Telkom exchange (Note 1).

    To perform a trace route, you need to open a command prompt window. To do so, hold down the Windows Key (between left CTRL and left ALT) and press R. That opens the Run window. Type in "cmd" (no quotation marks) and hit enter. This opens a black window. Type in "tracert mybroadband.co.za" (no quotation marks).

    What am I looking for?

    I happen to have both a congested and an uncongested trace for my line (Same line, same ISP, different exchange)





    In the above congested exchange example its taking almost half a second to make it through the first hop. Thats enough to make most fast paced games unplayable simply due to exchange congestion - regardless of how "good" your ISP is. Anything above 25 is suspicious and above 100 is pretty much guaranteed to be a problem. Note...this is for first hop only...seeing 100+ on later hops is normal if its an international site.

    Exchange congestion can also depend on the time of day - a semi-congested exchange will only show symptoms during peak times. Friday afternoons and Saturdays are usually worst. If you've got a semi-congested exchange chances are you'll have a fully congested exchange a couple of months later.

    How do I fix it?

    Sadly, the answer is usually that you don't. Usually Telkom needs to physically upgrade the exchange hardware. You can try reaching out to Telkom support channels, but understand that its a long shot - very very few people have managed to get this fixed without waiting & some have been waiting for years.

    Technical Note 1

    While the above is reasonably reliable (esp if it indicates a good outcome), technically a bad ISP can affect the first hop too since ISP IPC congestion will look the same. The easiest way around this is to re-do the test with a different ISP. So either purchase some cap from a different ISP or use the Telkom guest account (assuming your primary account isn't Telkom already)

    Username: [email protected]
    Password: guest

    NB - the above can only navigate to specific sites. The most interesting being saix.net since it also has a speedtest tool on it. i.e. You'd need to use saix.net instead of google.co.za

    Technical Note 2

    The sharp eyed people will have spotted some differences in the IPs on the tests both in route and end point. Its just Google & IS reshuffling things - the traces were taking almost a year apart. It doesn't affect the overall example though (I checked) so ignore it.

    Technical Note 3

    As per ranger's comment below using the test account is superior from a testing point of view to a standard Telkom Internet account.

    (Also - in case someone missed it - ranger is considered a trusted source of info on the technical ADSL front).

    Closing Thoughts

    The above is what I do. No doubt others will have different opinions & some like using tools that present the above in a visual format etc. There is also an automated tool available written by a mybb member (I've never used it so can't vouch for it):
    http://mybroadband.co.za/vb/showthre...ot-Report-Tool

    @mods: OP permission hereby granted to edit & improve as necessary
    Thanks for putting this together. I think it's definitely a good thing to understand congestion and to have as many tools as possible to be able to inform ourselves.

    I have a couple of thoughts here though. I'm pretty sure the second hop on the routing you posted is actually on the ISP network, so I'm not sure how you did that (or if it was for demonstration purposes). That kinda confused me.

    I have a concern around using the Telkom guest account for measuring congestion as (as ranger pointed out) it routes differently to normal ISP accounts and could ultimately misreport. We sometimes see guest accounts authenticate where every ISP account cannot. It would be great to know exactly how these accounts route to be able to determine what is being measured. But it's very possible the the guest account could perform well where every ISP account performs poorly because they don't use the same backhaul, and we're not comparing the same things. I think there is still a lot of value in comparing ISP to ISP to confirm that you get the same or a different experience.
    If AfriMan says it, it is so!

    If you asked an excellent question, please post on Answers!

  15. #15

    Talking ping 155.239.255.250

    ping 155.239.255.250 - it's the right thing to do.
    Last edited by cfilorux; 10-06-2015 at 09:08 AM. Reason: /me likes editing
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