Free TCP, UDP, Ports, and Protocols practice questions
10 free 220-1201 questions on TCP, UDP, Ports, and Protocols, each with a full explanation — no account needed. This section sits in the Networking part of the exam. Answer every question to see your score, then read the lessons below for anything you missed.
A network engineer compares packet captures from two applications. One shows transport headers ranging from 20 to 60 bytes with sequence numbers and window sizes. The other shows a fixed 8-byte header with only ports, length, and a checksum. How does this header difference most directly impact application behavior?
The larger header contains fields required for sequencing, acknowledgments, and flow control, which enable reliable and ordered delivery. This added functionality increases overhead compared to the minimal header used by the faster, best-effort protocol.
An online game uses one transport protocol for player position updates and a different one for chat messages and inventory changes. Position updates occasionally drop, but gameplay remains smooth, while chat messages always arrive correctly. What is the most accurate explanation for this hybrid design?
Position updates are sent over UDP because a lost update is replaced by the next one a few milliseconds later, so speed matters more than reliability, while chat and inventory changes ride on TCP because losing one would corrupt game state. Different port numbers is wrong because ports identify applications, not delivery guarantees; the difference here is the transport protocol. Broadcast is wrong because the game sends updates to a specific server, and broadcast is not what makes a protocol fast. Both needing guaranteed delivery is wrong because the scenario states that position updates are allowed to drop, which is the opposite of guaranteed delivery.
A systems administrator is investigating why a file transfer consistently slows down over a high-latency WAN link. Packet analysis shows frequent acknowledgments and pauses in transmission when a single packet is lost, even though later packets have already arrived. Which transport-layer characteristic is directly responsible for this behavior?
The slowdown occurs because the protocol enforces strict ordering. When a packet is lost, subsequent packets must wait even if they arrive successfully. This head-of-line blocking delays delivery until the missing data is retransmitted and received.
You are troubleshooting a real-time video conferencing application in a corporate environment. Users report that when packet loss occurs, the video briefly degrades but the call continues smoothly without freezing. Network captures show no connection establishment packets and no retransmissions. Which transport protocol behavior best explains this application’s performance under packet loss?
The scenario describes a protocol that does not establish connections, does not acknowledge received data, and does not retransmit lost packets. This allows newer packets to be processed immediately, which avoids freezing during real-time communication even when some packets are lost.
During troubleshooting, you observe that a DNS client sends a query and waits briefly before retrying when no response is received. There is no session setup and no notification that the request failed—only silence. Which transport-layer limitation most directly explains why the client must implement its own retry logic?
Because the protocol offers only best-effort delivery and does not acknowledge received packets, the sender has no way to know whether a message arrived. As a result, the application itself must detect timeouts and retry when necessary.
A help desk technician is assisting a user who can receive email on multiple devices but cannot send messages. Incoming messages sync correctly across the phone and laptop. Which port and protocol should the technician check first to resolve the sending issue?
Email delivery uses different protocols for sending and receiving. While IMAP or POP3 handle message retrieval, outgoing mail relies on SMTP. If users cannot send messages but can receive them, the issue is most likely related to the SMTP service or its associated port.
A user reports that visiting internal company websites triggers a browser warning stating the connection is not secure. Network captures confirm traffic is unencrypted. Which port change would most directly resolve this issue?
Unencrypted web traffic uses HTTP on port 80. HTTPS uses SSL/TLS to encrypt communication and operates on port 443. Moving web services to this port ensures data is protected and removes browser security warnings.
A security analyst discovers that credentials are being transmitted in plain text when administrators remotely manage a legacy server. Which protocol and port combination is most likely responsible?
Telnet provides remote terminal access but does not encrypt data. All credentials and commands are sent in plain text, making Telnet a common cause of exposed authentication information.
A ransomware outbreak exploits an unpatched file-sharing service on multiple Windows systems. Which port was most likely targeted?
SMB file sharing operates on port 445. Major attacks such as WannaCry exploited vulnerabilities in SMB services, making this port a common target during ransomware outbreaks.
A company uses a directory service to authenticate users and manage group policies in a Windows domain. Which port is essential for this directory communication?
Directory services such as Active Directory rely on LDAP for querying and authentication. LDAP operates on port 389, making it critical for domain-based user authentication.
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