Thanks to BKSlash from #Dubai for this clarification.


  DHCP a nice subject :   Ok here is the deal:
   
  DHCP is used to dynamically allocate IPs.
  In the old days your network manager used to give every machine in the network an IP,
  and if he gives 2 machines the same IP one of them will not work,
  or even both.  

  DHCP is a smart way to solve that problem,
  it automatically assigns IPs to machine on the network.
  It listens for DHCP requests and knows cashes IP so
  most of the time you would get your usual IP 
  (remember the MAC address, which is the address of the Networkcard is
  burned in the card and will always be same ).

  DHCP automates other network setup features too,
  including Default Gateway and DNS so you don't need to put this info for each user.

  If you set your TCP/IP setup options to Automatically get TCP/IP information,
  the network drivers will initiate a DHCP request,
  it's a broadcast request that doesn't go to a particular server
  but goes to all the machines on the network.
  The DHCP server will respond to the request with the IP and other info.
   
  What you are getting is an error saying no DHCP,
  that means the broadcast request for DHCP generated by your PC was not answered.
  Either that DHCP is dead or the line is dead :).  
   
  It seems that ETISALAT has automated the IP 6 hour change using DHCP,
  so everytime you disconnect your PC will initiate another DHCP request
  for IP and routing information.  
   
  BTW : you can force a DHCP request by doing a release then renew in Winipcfg.exe.
  All this applies to a normal network so might be some difference
  with the way you are connected :)
   
  Take care and bye.