Interesting ADSL details...

Just wanted to find out though from any ISP tech:

Is contention at the DSLAM level, or is total network bandwidth dynamically allocated all the time? The reason I ask is that if it is done at DSLAM level (or even groupings of DSLAMs), then those whose lines terminate at residential DSLAMs may get reasonable bandwidth even during office hours while those connected to business district DSLAMs get hardly any bandwidth during business hours.
 
A contention ratio of 128:1 hardly surprises me, and I find it easily believable.
If these figures are true, it tells us that Telkom have allocated about 400Mbit for the entire ADSL user base, approximately 1.6 percent of the SAT3 capacity they have available. In reality is could be lower as not all traffic is international.

Knowing the contention is very useful as it enables us to fairly accurately guess what the international bandwidth is really costing now that we have a rough idea of how much they are using.
 
mebbe thats why the need most to have shaped traffic
 
One should also take the 80/20 rule into account ... that is 20% of the subscribers use 80% of the bandwidth. If Telkom have 100,000 subscribers then 20,000 of them are using most of the bandwidth.

There is probably 75/25 rule on these 20,000 subscribers which would mean 5,000 of them are using 75% of the 80% of total ADSL bandwidth. These 5,000 are probably the members of these forums.

The point is that the average ADSL user is far,far less active then the ppl around here.
 
I think you are all crawling into the hole in which telkom wnat you to believe that bandwidth is a scarce comodity..., which it isnt, broadband is designed to have continuese connectivy even at the maximum speed, there shouldnt even be caps etc, unless you only want to surf etc, but ppl in business cant have caps its just pointless...
 
128:1 ? Sounds a little harsh. 50:1 is already bad on international broadband standards. Its hard to believe even telkom would make it that bad.
 
Ok this is something everyone should realise, without contention, no one would have cheapish internet AT ALL..

Can you imagine japan with 1gigabit fibre 1:1 contention, no way in hell.. They sell 1gigabit fibre connections on a 100-200:1 ratio if not more. 1:1 would mean, if the person doesnt download 24/7, then 1gigabit of internet bandwidth is wasted, since no one else may make use of that bandwidth.. Its yours, and only urs.

The important aspect regarding contention is to plan your contention into 80% of max available bandwidth, 20% of bandwidth should be left atleast for overflow ie. some days users dont follow the trend of the other days, the overflow allocation will "ease" this.
 
Roman4604 said:
One should also take the 80/20 rule into account ... that is 20% of the subscribers use 80% of the bandwidth. If Telkom have 100,000 subscribers then 20,000 of them are using most of the bandwidth.

There is probably 75/25 rule on these 20,000 subscribers which would mean 5,000 of them are using 75% of the 80% of total ADSL bandwidth. These 5,000 are probably the members of these forums.

The point is that the average ADSL user is far,far less active then the ppl around here.
Click to expand...

This would possibly be correct in an uncapped environment but when you're limited (3 gig cap) it throws this calculation out entirely.

128:1 doesn't surprise me, in fact in previous postings I estimated somewhere around 200:1 contention ratio given the fact that users are limited by caps.

At the end of the day contention ratio isn't important. What is important that you get a consistently reasonable service. As people use more bandwidth Telkom will be forced to lower the contention ratio to keep the service reasonable.
 
I love these types of posts, like the totaly unconfirmed leaked prices for November that gets everyone in a huff and a puff about hearsay.
It makes for entertaining reading.

As with the so called prices, all we know is that we are getting ripped off at 'current' prices, nothing more or less than that.
The same applies to the contention ratio's. Telkom hold this very close to their chests even when under pressure at the Icasa hearings. All we know here is that the ratio's must be 'horrible', or else they would of used them as part of their defense.
 
Well best effort, work out total International bandwidth available to Telkom and content it with 100000 users, not all of telkom bandwidth is used for ADSL but you will allready see a scary contention ratio doing this ;-)
 
Perdition said:
This would possibly be correct in an uncapped environment but when you're limited (3 gig cap) it throws this calculation out entirely.
Click to expand...
Not really, it makes it even more valid.

The whole point of a cap is to force subscribers to use their alotted traffic more wisely so that it last them the entire month. This ensures that subscriber base's requirement for bandwidth (rate) is spread as evenly as possible over the month.

The more uniformly the rate is spread across the month, the higher the contention ratio the ISP can run (without serious degredation to the subscribers performance).

So if the vast majority of Telkom's ADSL base dont reach their (3GB) cap, or even come close, then statistically the peak bandwidth rate load on the international links, at any point in time during the month, is less than would be apparent to the power users here.

Therefore the contention ratio of 128:1 on a base of 100,000 is not to bad considering that the average user's rate requirement across the month is relatively light.
 
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