My 2cents.
 
You can  never (ok. You can 'probably' never) get more than 80% payload throughput simply because of overheads. Hence if you are actually using 80% of your link, that is a commonly accepted norm. You could argue that the ISP's then need to sell it as 80% and not as 100% but that is a different debate all together.
 
Even STM links which have dedicated Overhead bytes offer a payload 140 Mbits/sec as opposed to 155 Mbits which is what is sold.

On Tue, Sep 29, 2009 at 4:29 PM, aki <aki275@googlemail.com> wrote:
In a simple nutshell. :-)
 
A simple Dedicated scenario:
 
!  SEACOM    !                          10Mbit
! 155Mbits      !-------------------------------------------Client A
!  Internet       !
! Water Tank  !                           1Mbit
!                    !--------------------------------------------Client B
!                    !
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
 
Consider Seacom above as a Water tower with capacity of 155Mbits. Out of which there are 2 clients, A and B.
 
Client A takes 10Mbit
Client B takes 1 Mbit
 
Seacom water tower has enough capacity to sustain dedicated services. Remove 11Mbits for its tank to clients, remaining 144Mbits. Therefore, there is ample supply.
 
A simple Shared Scenario
 
!  SEACOM    !                          10Mbit
! 155Mbits      !-------------------------------------------Client 1
!  Water Tank !                           1Mbit
!                    !--------------------------------------------Client 2
!                    !--------------  ------- -------------------- Client 200 ( each on 1Mbit/s )
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
 
Total clients = 202
Total capacity used = 200 + 10 +1 = 211 Mbits
 
Services are now cheaper. 155Mbit water tank can sustain "211Mbits" demand by sharing resources and usage patterns. BUT, when they all need the services then the problems begin.
 
Hope you can visualize the issues. SPs should not call shared services as dedicated services. Call them Corporate or Business packages.
 
Rgds.
 
 
 
 
 
 
 

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