Rpl pronounced ripple routing protocol for low power and lossy networks interim meeting
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RPL (pronounced ripple) Routing Protocol for Low Power and Lossy Networks Interim Meeting . draft-ietf-roll-rpl-02.txt Tim Winter & Pascal Thubert, editors. RPL Status. WG draft draft - ietf -roll- rpl -02 DT was dissolved. Thanks DT! Added a number of feature Too many? Too complex?

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RPL (pronounced ripple) Routing Protocol for Low Power and Lossy Networks Interim Meeting

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Rpl pronounced ripple routing protocol for low power and lossy networks interim meeting

RPL (pronounced ripple)Routing Protocol for Low Power and Lossy NetworksInterim Meeting

draft-ietf-roll-rpl-02.txt

Tim Winter & Pascal Thubert, editors

IETF 75 – Roll WG – July 2009


Rpl status

RPL Status

  • WG draft draft-ietf-roll-rpl-02

    • DT was dissolved. Thanks DT!

  • Added a number of feature

    • Too many? Too complex?

  • Requires

    • Re-organisation to avoid dups.

    • FSM details, description from a node standpoint

  • Hotest issues

    • Loop avoidance and detection – tradeoff & mechanisms

    • P2P routes, DAO fan out, DIO prefixes

    • MultiDAG, topologies and DV between DAGs

IETF 75 – Roll WG – July 2009


Implementer feedback

Implementer feedback

  • Dev has started

    • 4 candidates,

    • multiple environments

  • Traces available

    • Thanks Thomas and Phil 

  • But complain that

    • Spec too big

    • Protocol too complex

Interim meeting – Roll WG – Sep. 2009


Draft update

Draft update

What did we add recently?

IETF 75 – Roll WG – July 2009


Rpl pronounced ripple routing protocol for low power and lossy networks interim meeting

OCP0

  • OCP 0 is fully spelled out

    • DAG towards the nearest exit

    • Uses abstract rank metric

    • Based on the decimal rank

  • Add OCP1 for floating?

  • Other OCPs => in the metrics draft

Interim meeting – Roll WG – Sep. 2009


Multicast dao

Multicast DAO

  • NA DOA can now be sent to all nodes

  • Allows P2P line of sight

  • Between nodes (not necessarily routers)

  • MUST NOT be used to redistribute info

    • Only about stuff owned by this node

  • Q: redistrib in the unicast NA-DAO?

    • Not done at the moment

    • Doable but probable additional complexity

Interim meeting – Roll WG – Sep. 2009


Discussions on the list

Discussions on the list

What do we want to achieve

IETF 75 – Roll WG – July 2009


Terminology

Terminology

  • Need terms for next hops

    • selectable parents

    • Non selectable parents

    • Siblings

Interim meeting – Roll WG – Sep. 2009


Floating dag

Floating DAG

  • What are they for ?

    • Can be transient for network reconf

    • Can be permanent as an isolated network

  • What about OCP?

    • OCP0 is not ideal for the permanent case

    • Needs OCP1 that builds a wider DAG for any to any

    • Can benefit from minimum preference setting to replace the grounded bit.

Interim meeting – Roll WG – Sep. 2009


Sibling loops

Sibling Loops

  • Sibling is a necessary evil

    • Improves FWD diversity

    • Parents MUST be preferred

  • No absolute detection

    • Difficult when multiple sibling hops

    • But that’s not necessarily so useful

  • Current preventive rules:

    • Aggressive TTL decrement, parent preference

    • No Reverse

Interim meeting – Roll WG – Sep. 2009


Missing dao loops

Missing ~DAO Loops

  • Comes from DAO states not in sync

    • A parent has a DAO route but the child has none

    • Many more or less conplex ways to get there

  • Detected by simple RPF check.

  • Proposed preventive rule:

    A node must drop a packet from a parent if it would route it to a parent (or sibling)

Interim meeting – Roll WG – Sep. 2009


Reconfiguration loops

Reconfiguration loops

  • This is when a parent jumps in its subDAG

  • Risk is reduced by detaching the DAG

    • But imperfectly, based in unreliable mcast

    • Detection is required

  • Can be fully prevented by the seq counter

    • Additional complexity and delay

  • Looking for alternate / simplification

    • DAG merge and split is necessary anyway

    • A great detection could allow more risky

Interim meeting – Roll WG – Sep. 2009


Feature evolution

Feature evolution

Have we gone too far?

A brief history of recent evolution

IETF 75 – Roll WG – July 2009


Dag vs tree

DAG vs. tree

  • Idea:

    • Accept multiple parents and siblings

  • Perceived Benefits

    • Multiple path inwards

  • Reality check

    • More complex implementation (eg sequence)

    • More states. Metrics aggregation.

    • Necessary evil for many link types

Interim meeting – Roll WG – Sep. 2009


Sequence number

Sequence Number

  • Brings true loop avoidance

  • Allows moving down within same DAG

  • Complexity:

    • When to trigger a new sequence

    • What to do of parent with different sequences

    • How often is the sequence flooded

Interim meeting – Roll WG – Sep. 2009


Rank range

Rank range

  • Idea:

    • replace the simple depth incremented by 1

    • with a more complex metric with decimal increment

  • Perceived Benefits

    • Better mapping with real metrics

    • Better resulting DAG

  • Reality check

    • Broken text and greediness rules

    • Unpreferable parents. Harder to get siblings

    • Still discuss on the range. Large enough?

Interim meeting – Roll WG – Sep. 2009


Source route

Source Route

  • Idea:

    • Using source route along the DAG

  • Perceived Benefits

    • Save DAO intermediate states

  • Reality check

    • No path recovery

    • Risk of saturation at the root

    • Need new DIO field / complexity

    • Another necessary evil for certain node types

Interim meeting – Roll WG – Sep. 2009


Dao fan out

DAO fan out

  • Idea:

    • Send DAO to more than one parent

  • Perceived Benefits

    • Multiple path outwards

  • Reality check

    • DAG properties are asymmetrical

    • Fan out not solved yet

    • Broken for source route

Interim meeting – Roll WG – Sep. 2009


Multidag

MultiDAG

  • Idea:

    • Belong to multiple DAGs

  • Perceived Benefits

    • More routes, constrained routes

  • Reality check

    • More complex DIOs and flows

      • Eg: when does parent leave a DAG

      • Distance comparison between DAGS

    • We need to draw a line somewhere

Interim meeting – Roll WG – Sep. 2009


Simplifying rpl

Simplifying RPL

Simpler is better

When it’s REALLY simpler

IETF 75 – Roll WG – July 2009


Sibling loops1

Sibling loops

See Dominique’s presentation

Interim meeting – Roll WG – Sep. 2009


Multiple dags

Multiple DAGs

See Thomas’ Mail Simplifying RPL: (1) multiple DAGs

Suggest support to mDAG

Echoing Richard

Interim meeting – Roll WG – Sep. 2009


Relax loop avoidance

Relax loop avoidance

  • Can we avoid separating the DAG?

  • Proposal on the list:

    • allow DAG inconsistency

    • Use RA-DIO + trickle to fix that quickly

  • But then, back to RIP and count to infinity

  • Also, what about a better detection?

Interim meeting – Roll WG – Sep. 2009


Lowering transient loss

Lowering transient loss

  • A node has to detach when no parent

    • Would allow a child to follow regardless

  • But Children can’t follow rank increase

    • So the node could actually move down

    • To maintain its own connectivity

Interim meeting – Roll WG – Sep. 2009


Oustanding issues

Oustanding issues

Things we might need to consider…

Or not?

IETF 75 – Roll WG – July 2009


Asymmetrical links

Asymmetrical links

  • Problem:

    • Best inwards path might be poor outwards

  • Proposed approach

    • Diff preferred parents inwards and outwards

    • Compute Rank as the worst of the 2

  • Impact

    • Probably limited to OCP

Interim meeting – Roll WG – Sep. 2009


Security

Security

?

Interim meeting – Roll WG – Sep. 2009


More p2p

More P2P

Can forking DAGs suffice?

Interim meeting – Roll WG – Sep. 2009


Mobile nodes

Mobile nodes

  • Problem:

    • Find a DAG that reach Home

    • Default route via the DAG or Home?

  • Proposed approach

    • Tie the movement detection to RPL

    • Hold down routers that do not reach home

  • Impact to RPL

    • Probably limited to OCP

Interim meeting – Roll WG – Sep. 2009


Compression

Compression

In particular for source routing

Labels?

Interim meeting – Roll WG – Sep. 2009


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