CIFS Protocol Transport Layer: TCP vs UDP
Short answer
A The statement is FALSE because CIFS operates exclusively over TCP (port 445) to ensure reliability and data integrity, not UDP.
Question
Key Takeaways
The main trap is confusing legacy NetBIOS over UDP with modern CIFS/SMB, which strictly requires TCP port 445 for all operations.
This question tests knowledge of the CIFS protocol's transport layer requirements. The correct answer is FALSE, as CIFS relies solely on TCP for reliable file sharing services.
Common mistake: Candidates may select TRUE by recalling that older Windows systems used NetBIOS over UDP (ports 137-138) for name resolution and datagram services, but this is distinct from the CIFS file sharing protocol itself.
Expert Analysis
CIFS Protocol Transport Requirements
The statement that CIFS can run on UDP is FALSE. Common Internet File System (CIFS), which is Microsoft's implementation of the Server Message Block (SMB) protocol, is fundamentally designed to operate over TCP. Specifically, it relies on TCP port 445 for direct hosting.
Why UDP is Unsuitable CIFS/SMB requires a reliable, connection-oriented transport layer to ensure data integrity and proper session management. Key operations such as file locking, directory traversal, and large block transfers demand guaranteed delivery and ordered packet arrival. UDP is connectionless and does not provide these guarantees; if packets are lost or arrive out of order, the application must handle retransmission and sequencing itself, which SMB does not do at the transport level. Therefore, using UDP would lead to data corruption and session failures.
Historical Context and Trap Avoidance Earlier versions of the SMB protocol (pre-Windows 2000/XP era) could run over NetBIOS over UDP (ports 137-138). However, modern CIFS implementations have deprecated this legacy transport in favor of TCP/IP directly on port 445. Exam questions often test the distinction between legacy capabilities and current standard configurations. The comment provided correctly identifies that CIFS uses only TCP for reliability and data integrity. Confusing the legacy NetBIOS/UDP support with modern CIFS is the primary trap here.
Conclusion Because modern CIFS strictly mandates TCP to function correctly within enterprise storage networks, the assertion that it can run on UDP is incorrect.
Exam Strategy
When evaluating network protocols in storage exams, always distinguish between the core service protocol and its underlying transport. If a protocol involves stateful sessions, file locking, or large data transfers (like SMB/CIFS, NFS, HTTP), assume TCP unless explicitly stated otherwise. Ignore legacy ports (like NetBIOS UDP) unless the question specifically references 'legacy' or 'Windows 9x/NT' eras.
Frequently Asked Questions
Does CIFS use any UDP ports?
Why does CIFS require TCP instead of UDP?
Community Votes
100% of anonymous learners picked answer A. Votes are pick records left by other test-takers — they are not the verified answer.
Discussion 1 contributions
Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors.
From public community threads 1
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10c5cfe 👍 1 Answered Acifs uses only tcp for reliability and data integrity.
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