T.E.S - TransWorld Ent. Services [Karachi ISP]


Asad Wrote:
Why does it goes down during peak hours? It is fiber and should be able to consistently deliver full bandwidth 24/7. Is there congestion in their own network resulting in them hitting their network’s limits?

I see. So unlike DSL on copper, fiber optic is not a shared connection, and should maintain bandwidth 24/7 ?. Well, that’s certainly interesting.

I will look into it.

Sheikh ‘AngashT-e-Badanda’ Chilli


Even DSL is not shared connection per se. The medium (copper) and line parameters effect the maximum speed attainable.

On fiber, the same is valid. However, as a medium, fiber can offer far higher speeds. There should be no degradation in the speed unless there is:

  • Some issue in your installation - negated since you do get your assigned speed in certain timeslots.
  • Issue in ISP’s fiber network. The network capacity in your neighborhood could be a limiting factor.
  • Configuration issues by your ISP with regards to the bandwidth assigned to you.


All of them are shared one way or the other. A dedicated line costs in a range (10-100x) that only huge commercial entities can afford.

Normally there is a pool of bandwidth with a lot of users, a limit of users is fixed upon it which is normally termed as the contention ratio. There are other controls which modify this limit with respect to usage. Also controls which will shift high traffic users to other pools with less of the same.

PTCL has a minimum ratio of 5-10 connections per connection type. Don’t know about these fiber networks.

So there is a possibility that many/most of the users are high traffic ones. They will bog down the system by filling in all the pools and force the load balancers to operate on the minimum quality levels configured. Thus essentially removing the balancing effect and resulting in network congestion.

The more active high traffic users, the lower the speed in peak times.


Speeds offered by all residential ISPs are maximum caps and not guaranteed speeds AFAIK. Sometimes (or generally if you are very lucky) you will get that advertised speed for downloads and anywhere from 1/2 MBPS onwards to full speed for uploads. This is ADSL or asynchronous DSL. Bandwidth is shared across several users, so if many customers are watching HD videos then speed for all of thwm will drop, but if it is mixed type of usage (e.g. FB, web browsing, etc.) then you may get advertised speed.