Question : IP general understanding

Hi there,
I have a question in regards of IP in general, is said to be unreliable but why if is working fine? I know that has the limits of grow and some other buts here and there but whats unreliable about it? i was doing a search on it and i found that the errors that was not getting capture in their previous version IPv4 are been fix in IPv6 but what are those types of errors? and if the errors ara not been detected how are they been handle?
Probably is a broad question but what i'm trying to get here is a more understandable way in plain english rather than the book definition or explanation that is just confussing. If any one can halp me to have a better understanding i will realy appreciate.
Thanks
JSCTECHY  

Answer : IP general understanding

IP is connectionless meaning that it sends data without making sure the computer its sending data to even exists.  It also is unreliable because at the Network layer (which IP operates in) there is no guaranteed delivery of packets, if it makes it great, if it doesnt then oh well.  Reliable delivery can be assured using TCP, but this is done in the Transport layer.  Even though upper layers can assure reliability, IP in and of itself cannot therefore the protocol is unreliable.  IPv6 addresses some security concerns of IPv4 which include IPSec.  IPSec is optional in IPv4, but required in IPv6.  Also, Layer 2 MAC addresses are not statically bound to IP addresses as they are in IPv6 (no need for ARP).  This makes spoofing more difficult.  It uses a hierarchical addressing scheme and ICMP discovery protocol to aid routers in creating lookup tables that are not so complex and time consuming to perform lookups.  As far as errors, one consideration is duplicate IP addresses, but this issue is still not resolved in IPv6.  There are other issues of course, but this should give you a general idea.