Which of the following protocols operate at the network layer and provide network address capabilities?

A.
SPX

B.
SMTP

C.
IP

D.
DNS

Explanation:
IP operates at the network layer and provides network addressing capabilities.
Incorrect Answers:
A: The SPX operates at the transport layer.
B: SMTP operates at the application layer and transmit e-mail messages between two e-mail servers. It does not provide network addressing capabilities.
D: DNS operates at the network layer but provides host name to IP address translation. It does not provide network addressing capabilities.
References:
David Groth and Toby Skandier, Network+ Study Guide (4th Edition), Sybex, Alameda CA, 2005, pp. 117, 297.