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1.0 Network Infrastructure and Connectivity

TCP & UDP Practice Questions

Transport-layer ports, reliability, sequencing, flow control, and UDP tradeoffs.

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One solved question, so you can see how these are marked

What Layer 4 feature lets one host keep separate web and SSH conversations open at the same time?

Session multiplexing using port numbers

Transport-layer source and destination port numbers identify the application conversations, allowing many sessions to share the same IP address.

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All 9 TCP & UDP questions in this set

Answers and explanations appear when you work through the set above.

  1. A client opens an outbound TCP connection from source port 53124. Which IANA port range does that source port belong to?

    • Well-known
    • Registered
    • Dynamic/private (ephemeral)
    • Reserved network-device interface ports

  2. Which TCP behavior provides reliable delivery when a transmitted segment does not arrive?

    • The sender retransmits unacknowledged data after detecting loss
    • The receiver's advertised window repairs the missing data
    • The sender's checksum recreates the missing segment
    • The connection handshake reserves bandwidth to prevent loss

  3. Packets from a file transfer arrive out of order. Which TCP mechanism lets the receiver reassemble the original byte stream?

    • Sequence numbers
    • Port security
    • Default gateway discovery
    • TTL

  4. Which TCP field participates in flow control by telling a sender how much data a receiver can accept?

    • Window size
    • DSCP
    • Hop limit
    • VLAN ID

  5. Which statement accurately describes UDP at the transport layer?

    • It establishes a connection before data transfer
    • It retransmits every lost datagram
    • It has no sequencing or flow-control mechanism, and it supports checksum-based error detection
    • It always uses well-known ports

  6. Why is UDP often chosen for real-time voice or video?

    • It guarantees every packet arrives in order
    • Its smaller overhead avoids waiting for connection setup and retransmissions
    • It encrypts media by default
    • It prevents packet loss on congested links

  7. A network engineer says a TCP session is identified only by the destination port. What important information is missing?

    • The complete connection uses source and destination IP addresses and ports
    • The switchport's speed and duplex
    • The router's OSPF process ID
    • The frame's preamble

  8. Which range contains IANA well-known port numbers?

    • 0-1023
    • 1024-49151
    • 49152-65535
    • 65536-131071

  9. Which protocol is connection-oriented at the transport layer?

    • TCP
    • UDP
    • IP
    • ARP