Telkom DSL Key Performance Indicators
Telkom released its ADSL performance indicators for July to September 2009
Telkom released its ADSL performance indicators for July to September 2009
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Telkom ADSL KPIs
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InTheCube
Expert Member
Don't contetion ratios only apply to the ISP, who is actually selling bandwdith? If so, then this figure should be TelkomInternet's contention ratio?
Each ISP (especialy Tier 1 ISPs) set their own contention ratios and manage it on their own networks, right? Smaller ISPs who just resell services from the bigger ISPs don't have any say in contention ratios, right?
Hectic
Executive Member
Noted, but without knowing what the seemingly somewhat useless ADSL regulations are saying, I'm not sure how to interpret this info? Is the the reporter saying that the other ISP's are not adhering to the regulations?
The contention ratio seems ok and the good news, I suppose is that the figures on the rest of the KPI are falling, but I'm not sure what those percentage figures actually really represent i.t.o actual figures.
The contention ratio seems ok and the good news, I suppose is that the figures on the rest of the KPI are falling, but I'm not sure what those percentage figures actually really represent i.t.o actual figures.
All that Telkom says in its website is:
Contention ratios are an international norm and all ISP's make use of it. The contention ratio does not remain constant as it fluctuates as the service grows and more customers and infrastructure are added.
But they said previously (http://mybroadband.co.za/nephp/5304.html)
According to Telkom the 20:1 contention ratio given on the website is for the ‘local access network only’. Telkom further said that the international ADSL contention ratio can not be released since “this is business sensitive information and cannot be released.”
retromodcoza
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I really wish ICASA did a better job with their ADSL Regulations. Published contention ratios can be of great value, especially with so many new ISPs starting to launch services...
Sting
Ghost in the Machine
Yes
saffakanera
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Very true, we are up for a terribly rough ride if more of these fly-by-night ISP's start popping up with unacceptable contention ratios.
Given the fact that, for them, the costs vs profit margin is huge when bs'ing people into accepting almost criminal levels of service, which seems to be the general business vibe in SA, start small, grab as MUCH as you can, get out.
gregmcc
Honorary Master
How exactly do they get to this figure? Do they ping their own news servers?
Lets concentrate on the DSLAM. Say a DSLAM has 100 users connected to it, all at 4Mb/s for a total of 400Mb/s. Now the DSLAM needs a backhaul to the ATM network at 400Mb/s not so? No, they do not provision 400Mb/s backhaul to the DSLAM, they provision at the 20:1 ratio which means that for every 20 users they will provision 4Mb/s of bandwidth/pipe. So for 100 users they provision 5x4Mb/s which equals 20Mb/s.
The principals that apply to ISP bandwidth provisioning also apply to DSLAMs. The same also goes for normal telephone subscribers, there is a contention ratio involved. If all the fixed line subscribers tried to use they're phones at the same time many of then would get a route busy tone as the network was simply not designed to cater for everyone at the exact same time. Same goes for cellular networks btw.
Hope my explanation makes sense.
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InTheCube
Expert Member
This makes sense. So the reason for my ADSL being slow, could also be a problem at the DSLAM (snyc issues aside), and not just with my ISP. Too many ADSL subscribers connected to an exchange/DSLAM, all sucking down on their 4mbps lines at full speed, is seriously gonna affect the rest of the users connected to the same exchange/DSLAM, right?
So if Telkom is publishing a 20:1 contention ratio for its local public access network (ADSL backhaul + exchanges, etc), then if I were an ADSL ISP, there's no way I could guarantee a client of mine a contention ratio better than 20:1, right? So I would provision my own network to cater for users at a contention ratio of 20:1? It's no use catering less than this, while the bottleneck is at the exchange/DSLAM...
This I disagree with. Aren't telephone subscribers provisioned on an ATM network, and not an IP network. IIRC, ATM networks establish dedicated end-to-end circuits, while IP is a best-effort, packet delivery system. There is a big difference between a dedicated circuit, and a best-effort packet delivery system. So with regards to contention ratios for telephone subscribers, there is a fixed number of circuits that can be accommodated, so once all the ciruits are used up, no further users can be accommodated, and so just get a route busy tone until another call ends and the circuit is freed up. It doesn't degrade all other users slightly to accommodate another user. However, with ADSL, if the exchange/DSLAM is maxed out, and you add another user, the new user will still have service, as well as all other users, but at a more degraded level.
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The contention ratio is not and issue and 20:1 is not really high. You have to understand that not everyone uses it at the same time. Then you get the nature of TCP/IP traffic on the net, it's mostly of a bursty nature if I could call it that which creates usable overlaying gaps. Correct, no point in a ISP having a contention ratio lower than 20:1 for it's users via ADSL, different scenario for leased circuits. Most ISP's contention ratios higher than the dslam ratio anyway.
It's hard for me to explain this but let's just say the contention ratio on the dslam is not really something you should worry about as the chances of it affecting you are slim. It was design for optimal performance vs cost. All telco's around the world have contention ratios, no one has a 1:1 ratio.
Last time I checked it did not use ATM (or IP) but was still using the SDH transmission network as multiple E1 circuits etc, Telkom's ATM network was almost dormant for many years and still does not carry that much data. This might have changed with NGN. Either way, at the end of the day everything goes across the SDH transport network be it ATM, IP, Voice etc., it's the last port of call for all traffic.
Agreed, maybe I should have made it clearer and been specific that I'm not relating my comment to adsl/ip/data. Yes, existing callers won't have a degraded service but once fully uitilised the other users will have NO service at all, hence the route busy tone=no service. There is still a contention ratio here. 1000 phones, circuits for only 300 for example, cannot remember the provisioning ratio but if need be I can call a ewsd switching guru quickly.
Apologies, should have been clearer and more specific about this.
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Leftfoot
Expert Member
Ponder is correct there with telephone lines. Sure, to the exchange each telephone has is own circuit, whether on its own copper, or multiplexed. But beyond the SLMA (first switching equipment for Siemens EWSD exchanges) calls are mulipexed in 2Mb/s highways. Only a certain percentage of connected clients would be able to call if they all picked up at the same time (based on profile priority,ie police, businesss , residential etc), the rest would get route busy tone until a route became free.
You may have noticed at big stadium events not being able to phone out. Cell networks also work on a contention ratio.
This is the first time I've ever seen anyone intelligent post on these forums.
Good job chap.
Sting
Ghost in the Machine
I'll join you!
InTheCube
Expert Member
@Ponder, Leftwood: Thanks for the detailed technical explanations... very interesting.
So where does the IPC link come into play? Is IPC just a connection to get access to Telkom's ADSL cloud? If so, then I suppose there is contention at this level as well? E.g. an ISP gets a 155mbps IPC link into Telkom's ADSL cloud, but could oversell this to its subscribers to make up for a better return, right?
Then we also have the ISPs network which needs to be have access to local and international bandwith, another 2 areas where contention ratios come into play. For e.g. - buying a 155mbps pipe on Seacom, and another 155mbps pipe on national routes?
Right?
So where does the IPC link come into play? Is IPC just a connection to get access to Telkom's ADSL cloud? If so, then I suppose there is contention at this level as well? E.g. an ISP gets a 155mbps IPC link into Telkom's ADSL cloud, but could oversell this to its subscribers to make up for a better return, right?
Then we also have the ISPs network which needs to be have access to local and international bandwith, another 2 areas where contention ratios come into play. For e.g. - buying a 155mbps pipe on Seacom, and another 155mbps pipe on national routes?
Right?