Question-03)

In the stateless packet filter firewall, the Internal network is connected to Internet via router firewall.

Filters packet-by-packet, decision to forward/drop packet can be made based on:

Source IP address, destination IP address

TCP/UDP source, destination port numbers

ICMP message type (In TCP layer)

SYN, ACK bits (In IP header)

Question

Question-03)

In the stateless packet filter firewall, the Internal network is connected to Internet via router firewall.

Filters packet-by-packet, decision to forward/drop packet can be made based on:

Source IP address, destination IP address

TCP/UDP source, destination port numbers

ICMP message type (In TCP layer)

SYN, ACK bits (In IP header)

BlackTom AI · Accepted Answer

Stateless packet filters operate on individual packets and examine header fields (no connection tracking). They can match on IP-layer fields and transport-layer header fields, but the statement contains incorrect protocol-location claims, so it is False.

1. Relevant knowledge points and concepts
- IP header contains source and destination IP addresses. A stateless filter can use these to allow or block traffic.
- TCP and UDP headers (transport layer) contain source and destination port numbers; stateless filters can match these ports.
- ICMP is its own protocol with an ICMP header containing type and code; ICMP information is not part of the TCP layer.
- TCP flags (SYN, ACK, FIN, RST, etc.) are bits inside the TCP header, not inside the IP header.
- Stateless filters make decisions on a per-packet basis (they do not keep connection state), so while they can test TCP flags, they cannot reliably infer full connection state the way a stateful firewall can.

2. Step-by-step reasoning
- The statement correctly lists source/destination IP addresses as match criteria: these are in the IP header — correct for stateless filters.
- The statement correctly lists TCP/UDP source and destination ports: these live in the transport header — correct.
- The statement claims “ICMP message type (In TCP layer)”: ICMP types are part of ICMP messages (a separate protocol over IP), not the TCP layer. That part is incorrect.
- The statement claims “SYN, ACK bits (In IP header)”: SYN and ACK are TCP header flags, not part of the IP header. That is incorrect.
- Because at least one clause in the combined description is wrong (two clauses are mis-located), the entire composite statement is false.

3. Why the correct answer is correct
- Two of the four items are misattributed to the wrong protocol layer. Even though stateless firewalls can filter on ICMP type and on TCP flags, the question’s parenthetical locations are wrong, making the overall assertion incorrect.

4. Why the other parts aren’t fully correct
- ICMP type belongs to ICMP header, not TCP layer.
- SYN/ACK are TCP header flags, not in the IP header.

Conclusion: The correct evaluation is False, matching the provided answer.

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