OSPF and LDP Intricacies

Hi all

I have certain questions on OSPF .

1. Why do we require Link State Request Packet. I mean as per Link State
Routing Protocol, ur entire database has to be synchronised, then you
should not request someone to get something, instead the neighbor should
give you entire LSUs to you

Why they have designed Link State Request packet in OSPF.
Anyhow the neighbor will request for all the LSAs from the DBD, then why do
they have Link State Request Packet in OSPF

In LDP, There is a Loop Detection Mechanism which includes Hop Count TLV
and Path Vector TLV, Can someone throw some light on how these two things
are utilised,
 I have read the RFC and this is wat it says

Loop Detection is a configurable option that provides a mechanism for
finding looping LSPs and for preventing Label Request messages from looping
in the presence of non-merge capable LSRs.

Can someone explain me wat is called as Non-Merged LSRs

-- 
Regards
Routing Freak
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