Question

Which one of the following protocols may need to broadcast some of its messages?

• A. SMTP
• B. FTP
• C. DHCP
• D. HTTP

Hint:

A protocol broadcasts only when it does not yet know a specific destination address; DHCP's first message goes out before the client has an IP or knows the server's address.

Answer 1

The Correct Option is C

Step 1: Recall what each protocol does and whether it already knows its destination.
SMTP (Simple Mail Transfer Protocol) sends email between mail servers; the sender always already knows the destination mail server's address, resolved via DNS MX records, before it starts, so it always uses a normal unicast, point to point connection.
FTP (File Transfer Protocol) transfers files between a client and a server; the client must already know the server's IP address to even open the control connection, so FTP is always unicast.
HTTP (HyperText Transfer Protocol) fetches web pages from a specific web server whose address the client already knows, again via DNS, so it too is always a unicast, point to point exchange.

Step 2: Focus on DHCP and why it is different.
DHCP (Dynamic Host Configuration Protocol) is used by a new or newly connected host to automatically get an IP address and other network settings when it does not yet know the address of any DHCP server, and in fact usually does not even have an IP address of its own yet.

Step 3: Trace the DHCP message exchange to see the broadcast step.
The host starts by sending a DHCPDISCOVER message. Since it has no IP address and does not know any server's address, it cannot unicast this message; it sends it as a broadcast (destination address 255.255.255.255) so every DHCP server on the local network can receive and respond to it. The server's DHCPOFFER reply, and the client's later DHCPREQUEST, are also commonly sent as broadcasts for the same reason, until the client has a confirmed IP address.

Step 4: Conclude by elimination.
SMTP, FTP, and HTTP all operate over an already-established point to point, unicast connection to a known server address, so they never need to broadcast. DHCP is the one protocol here whose very first message must be broadcast because the client does not yet have enough information, its own address or the server's address, to unicast it.

Final Answer:
DHCP may need to broadcast some of its messages. \[ \boxed{\text{Option (C)}} \]