science

Martian packet

Martian packet is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Martian packet rather than just read about it. In short: A Martian packet is an IP packet seen on the public Internet that contains a source or destination address that is reserved for special use by the Internet Assigned Numbers Authority (IANA) as defined in RFC 1812, Appendix B Glossary (Martian Address Filtering). On the public Internet, such a packet either has a spoofed source address, and it cannot actually originate as claimed, or the packet cannot be delivered.

Key takeaways

Martian packet belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Martian packet to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Martian packet from memory before moving on to harder problems.

Reference excerpt

A Martian packet is an IP packet seen on the public Internet that contains a source or destination address that is reserved for special use by the Internet Assigned Numbers Authority (IANA) as defined in RFC 1812, Appendix B Glossary (Martian Address Filtering). On the public Internet, such a packet either has a spoofed source address, and it cannot actually originate as claimed, or the packet cannot be delivered. The requirement to filter these packets (i.e., not forward them) is found in RFC 1812, Section 5.3.7 (Martian Address Filtering). Martian packets commonly arise from IP address spoofing in denial-of-service attacks, but can also arise from network equipment malfunction or misconfiguration of a host. In Linux terminology, a Martian packet is an IP packet received by the kernel on a specific interface, while routing tables indicate that the source IP is expected on another interface. The name is derived from packet from Mars, meaning that packet seems to be not of this Earth.

IPv4 and IPv6 In both IPv4 and IPv6, a Martian packet has a source address, a destination address, or both within one of the special-use ranges.

Transition mechanisms

6to4 6to4 is an IPv6 transition technology where the IPv6 address encodes the originating IPv4 address such that every IPv4 /32 has a corresponding, unique IPv6 /48 prefix. Because 6to4 relays use the encoded value for determining the end site of the 6to4 tunnel, 6to4 addresses corresponding to IPv4 Martians are not routable and should never appear on the public Internet.

Teredo tunneling Teredo is another IPv6 transition technology that encodes the originating IPv4 address in the IPv6 address. However, the encoding format encodes the Teredo server address and tunnel information before the IPv4 client address. Thus there is no definable set of prefixes more specific than 2001:0::/32 for Teredo packets with Martian end-site addresses. It is, however, possible to spoof Teredo packets with the Teredo server IPv4 address set to a Martian.

Implementation Some of the large routers have functionality to filter out specifically for Martian Filtering packet and address.

Juniper Junos OS has martians. Cisco IOS does not have Martian Filtering, and uses ip access-list Cisco Small Business has Martian Addresses

See also Bogon filtering Christmas tree packet Broadcast storm

References

Worked examples

Example 1 — a first encounter with Martian packet

Start with the simplest possible case. Write down what Martian packet claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Martian packet before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Martian packet ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Martian packet

In research: Martian packet appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Martian packet in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Martian packet is common in secondary-school and first-year university syllabi. It links to neighbouring topics Denial-of-service attacks, IP addresses, Mars in culture, so understanding it makes those chapters shorter.
In everyday life: Look for Martian packet outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Martian packet in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Martian packet means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Martian packet out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Martian packet in simple terms?

Why does Martian packet matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Martian packet?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Martian packet.