Which transport-layer protocol provides reliable delivery of data?

A.
IPX

B.
TCP

C.
IP

D.
HTTP

Explanation:
TCP (Transmission Control Protocol) is a transport layer (Layer 4) protocol. It is connection
oriented, and thus provides reliable delivery of data.
Incorrect Answers:
A: IPX is a network layer protocol (Layer 3) and does not provide reliable delivery of data. Reliable
delivery is the responsibility of upper layer protocols. The network layer is only responsible for
routing of the data, and is not concerned with actual delivery of that data, which at this level we
call packets. The network layer runs essentially connection-less protocols.
C: IP is a network layer protocol (Layer 3) and does not provide reliable delivery of data. Reliable
delivery is the responsibility of upper layer protocols. The network layer is only responsible for
routing of the data, and is not concerned with actual delivery of that data, which at this level we
call packets. The network layer runs essentially connection-less protocols.
D: HTTP is an application, which would run at the application layer (Layer 7), so it is not a
transport layer protocol. HTTP relies on TCP, so there is reliable delivery of data. Do not get
confused because HTTP is reliable and is a protocol, HTTP runs at layer 7 and the question asks
for a layer 4 protocol.