Routing & RPL · Study deck

The RPL Standard (RFC 6550)

A building sensor's product sheet lists support for the RPL standard.

Packet Pete is your guide for this deck.

rfc-6550ipv6dodag

Packet Pete, the module guide, in a scene from this chapter.

After studying this chapter

Learning objectives

You will be able to:

check the RPL protocol pieces (messages, modes, headers) in the order RFC 6550 defines them
treat RFC 6550 as the contract that RPL implementations must satisfy
map RPL messages and modes onto their specification sections
Explain: Lower link quality, remove the parent, restart the root, join a second graph, send a downward command, and inject old control state.

Major section

Start With the Contract

Lower link quality, remove the parent, restart the root, join a second graph, send a downward command, and inject old control state.

A formed graph or a product label does not prove the needed packet path.
This opening does not restate the full standard or certify a stack.
Under the Hood examines graph rules, control objects, rank, parent choice, downward modes, headers, and recovery limits.

Major section

Overview: RFC 6550 Defines the RPL Contract

This matters because a routing label or formed topology alone cannot prove that the required traffic path works or recovers at its boundaries.

That evidence resolves the question posed by Overview: RFC 6550 Defines the RPL Contract.

RFC 6550 is the base document, with companion RFCs defining metrics, Objective Functions, Trickle behavior, and packet headers.

Major section

Turn a Support Claim into an Upward-and-Downward Test

These observations show how the claimed standard is being used; a diagram drawn after the test cannot replace the actual control messages.

If all readings arrive but only 3 commands do, the two delivery proportions are 20 divided by 20 = 100% and 3 divided by 5 = 60%.

Major section

Turn a Support Claim into an Upward-and-Downward Test (continued)

A combined 23 out of 25, or 92%, conceals which direction is weak, and none of these small-sample proportions constitutes standard certification.

The standard review should then repeat the command after removing the chosen parent, keeping the fault time and new route state beside the packet capture.
A leaf may regain an upward route before the return path is repaired.
Urgent local action should retain its own safe behaviour when routing repair exceeds the application's deadline, even if the implementation remains a valid RPL participant.

Major section

Summary

RFC 6550 defines the base RPL protocol for constrained IPv6 routing in low-power and lossy networks.

An RPL Instance gives the routing context, while a DODAG organizes routers around a root.
DIO, DIS, DAO, and DAO-ACK are the main RPL control messages to understand before interpreting route state.
Storing and Non-Storing modes differ mainly in where downward route state lives and how downward packets are carried.

Deck summary

Key takeaways

Lower link quality, remove the parent, restart the root, join a second graph, send a downward command, and inject old control state.

This matters because a routing label or formed topology alone cannot prove that the required traffic path works or recovers at its boundaries.
These observations show how the claimed standard is being used; a diagram drawn after the test cannot replace the actual control messages.
A combined 23 out of 25, or 92%, conceals which direction is weak, and none of these small-sample proportions constitutes standard certification.
RFC 6550 defines the base RPL protocol for constrained IPv6 routing in low-power and lossy networks.

Retrieval practice

Recall check 1 of 3

Packet Pete says: answer from memory, then check your reasoning.

Q1Which statement best describes the role of RFC 6550 in an RPL deployment?

AIt defines base RPL objects, messages, modes, and packet-processing rules.

BIt requires every RPL network to use the same Objective Function and metric.

CIt replaces IPv6 routing headers with application-layer destination fields.

DIt guarantees that all downward routes are stored on every constrained router.

Show answer

Answer: A RFC 6550 is the base RPL specification.

Retrieval practice

Recall check 2 of 3

Packet Pete says: answer from memory, then check your reasoning.

Q2A joined RPL node needs to choose a preferred parent for upward traffic. Which check should come before accepting the parent choice?

AVerify the parent fits the instance and preserves movement toward lower Rank.

BPrefer the neighbor with the highest Rank because it is farthest from congestion at the root.

CIgnore the Objective Function once a DIO message has been received.

DSelect only the DODAG root, because intermediate routers cannot be parents.

Show answer

Answer: A Parent selection must be interpreted inside the RPL Instance and must preserve the DODAG direction toward the root.

Retrieval practice

Recall check 3 of 3

Packet Pete says: answer from memory, then check your reasoning.

Q3In a Non-Storing RPL design, where is downward route state primarily held for source-routed delivery?

AAt the DODAG root, using source routing for downward packets inside the RPL domain.

BOn every leaf device, which rewrites the route for packets sent by the root.

COnly in DAO-ACK messages, which replace routing tables during data forwarding.

DIn application payload fields, because RPL does not use IPv6 packet headers.

Show answer

Answer: A Non-Storing mode concentrates downward route state at the root and uses source routing for downward delivery.

Print reference

Answers

Answer key.

A · RFC 6550 is the base RPL specification.
A · Parent selection must be interpreted inside the RPL Instance and must preserve the DODAG direction toward the root.
A · Non-Storing mode concentrates downward route state at the root and uses source routing for downward delivery.