No, DHCP does not use TCP.
DHCP (Dynamic Host Configuration Protocol) relies on UDP (User Datagram Protocol) as its transport protocol. Let's delve into why UDP is preferred for DHCP:
Why DHCP Uses UDP Instead of TCP
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Simplicity and Speed: UDP is connectionless and lightweight, making it faster and more efficient for initial network configuration. DHCP needs to be quick, especially when a device is first booting up and trying to obtain an IP address.
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Broadcast Communication: DHCP clients often don't have an IP address when they initially try to contact a DHCP server. UDP allows clients to broadcast DHCP discovery messages. This is essential for the client to find a DHCP server on the network. TCP requires a pre-established connection, which is impossible without an IP address.
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Well-Known Ports: DHCP utilizes specific UDP ports for communication:
- DHCP Server: Listens on UDP port 67. According to the reference, "DHCP messages that a client sends to a server are sent to well-known port 67 (UDP—Bootstrap Protocol and DHCP)."
- DHCP Client: Listens on UDP port 68.
UDP vs. TCP: Key Differences
| Feature | UDP | TCP |
|---|---|---|
| Connection | Connectionless | Connection-oriented |
| Reliability | Unreliable | Reliable |
| Overhead | Low | High |
| Use Cases | DHCP, DNS, streaming media | Web browsing, email, file transfer |
DHCP Message Exchange
- DHCP Discover: The client broadcasts a DHCPDISCOVER message to find available DHCP servers.
- DHCP Offer: DHCP servers respond with a DHCPOFFER message, containing a proposed IP address, subnet mask, and other network configuration parameters.
- DHCP Request: The client selects one of the offers and sends a DHCPREQUEST message, accepting the proposed configuration.
- DHCP Acknowledgment: The DHCP server confirms the allocation with a DHCPACK message. If there's an issue, it might send a DHCPNAK (Negative Acknowledgment) message.
