The Internet Protocol (IP) is a data-oriented protocol used for communicating data across a packet-switched internetwork. IP provides an unreliable service (i.e., best effort delivery). This means that the network makes no guarantees about the packet.
Low-level connectionless protocols such as DDP (under Appletalk) and IP usually provide best-effort delivery of data.
Best-effort delivery means that the protocol attempts to deliver any packets that meet certain requirements, such as containing a valid destination address, but the protocol does not inform the sender when it is unable to deliver the data, nor does it attempt to recover from error conditions and data loss.
Higher-level protocols such as TCP on the other hand, can provide reliable delivery of data. Reliable delivery includes error checking and recovery from error or loss of data.
HTTP is the HyperText Transport Protocol used to establish connections to a web server and thus one of the higher level protocol using TCP to ensure delivery of all bytes between the client and the server. It was not a good choice according to the question presented.
Here is another definition from the TCP/IP guide at: http://www.tcpipguide.com/free/ t_IPOverviewandKeyOperationalCharacteristics.htm
Delivered Unreliably: IP is said to be an “unreliable protocol”. That doesn’t mean that one day your IP software will decide to go fishing rather than run your network. J It does mean that when datagrams are sent from device A to device B, device A just sends each one and then moves on to the next. IP doesn’t keep track of the ones it sent. It does not provide reliability or service quality capabilities such as error protection for the data it sends (though it does on the IP header), flow control or retransmission of lost datagrams.
For this reason, IP is sometimes called a best-effort protocol. It does what it can to get data to where it needs to go, but “makes no guarantees” that the data will actually get there.