Overview of Existing Routing Protocols for Low Power and Lossy Networks
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Overview of Existing Routing Protocols for Low Power and Lossy Networks draft-levis-roll-overview-protocols-00. Phil Levis, Stanford Univ. JP. Vasseur, Cisco Systems David Culler, UC Berkeley IETF 70 ROLL WG Meeting. Goal (1).

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Overview of Existing Routing Protocols for Low Power and Lossy Networksdraft-levis-roll-overview-protocols-00

Phil Levis, Stanford Univ.

JP. Vasseur, Cisco Systems

David Culler, UC Berkeley

IETF 70 ROLL WG Meeting


Goal 1
Goal (1) Lossy Networks

  • Provide a discussion platform for building a rough consensus around the suitability, ill-suitability, and technical trade-offs in utilizing existing IETF protocols for Routing Over Low-power and Lossy networks.


In pictures
In pictures Lossy Networks

Future

Existing Protocols

“roll proto”

3. Link State Protocols

3.1. OSPF

3.2. OLSR

3.3. TBRPF

4. Distance Vector protocols

4.1. RIP

4.2. DSDV

4.3. AODV

4.4. DYMO

4.5. DSR

. . . .

Overview ID

Common understanding of basis for analyzing alternatives and rough consensus on assessment


Goal 2
Goal (2) Lossy Networks

  • Provide a discussion platform for building a rough consensus around the suitability, ill-suitability, and technical trade-offs in utilizing existing IETF protocols for Routing Over Low-power and Lossy networks.

  • Not to design a final protocol, but a baseline and framework for the process of defining one.


Outcome

Crit 0 Crit 1 Crit 2 Crit 3 … Lossy Networks

3. Link State

3.1. OSPF

3.2. OLSR

3.3. TBRPF

4. Distance Vector

4.1. RIP

4.2. DSDV

4.3. AODV

4.4. DYMO

4.5. DSR

Outcome

Rough Consensus on the Criteria

Quantitative and qualitative

Rough Consensus on the Analysis


The technical task

Application Domain Lossy Networks

Requirements

Simplifications

The Technical Task

… low rate …

… scalability…

Routing

over

Low-Power & Lossy

Constraints

Challenges

Technological


Preliminary analysis
Preliminary Analysis Lossy Networks

Use Ctrl Routing

ovhd state

3. Link State

3.1. OSPF wired O(NNdc) O(Nd)

3.2. OLSR wireless O(NN) O(Nd)

3.3. TBRPF wireless O(NN) O(Ndd)

4. Distance Vector

4.1. RIP wired O(ND) O(D)

4.2. DSDV wireless O(NCc) O(Cd)

4.3. AODV wireless O(ND) O(D)

4.4. DYMO wireless O(NCch) O(Ch+d)

4.5. DSR wireless O(NNdh) O(Dh)

  • N – nodes

  • C – communicating nodes

  • P – pairs (active routes)

  • D – destinations

  • d – degree (denisty, nbrs)

  • c – link churn

  • h – hops (diameter, route length)

… just to get discussion ROLLing



Routing
Routing Lossy Networks

  • … exchange of information to establish and maintain local tables such that each node can compute

    • next hop, IF := R(destination)

  • in a manner consistent with the underlying connectivity graph

IF := R(d)


Wireless nlp nl routing
Wireless (nLP, nL) Routing Lossy Networks

  • No a priori underlying connectivity graph

    • a link exists if it works when you try it

    • “self-organization”, discovery

  • Next hop is a neighbor node selection

    • nbr set may vary in time due environmental effects, movement, interference, obstacles, other communication, …

  • Topology is determined by physical placement

    • e.g, impact on d? …of d?


Parameters first pass
Parameters (first pass) Lossy Networks

  • N (Nodes): # points of interest

  • d (degree): density of deployment / range

    • max degree may be huge

  • h (hops): physical extent / range

  • c (churn): environmental factors

  • C (Communicators): active portion

  • D (Destinations): concentration of flows


Constraints
Constraints Lossy Networks

  • Low Power

    • lifetime, physical size, rate of activity, cost, applicability, … all dictated by power consumption

    • Short range, high loss rate, small MTU, low rate links

    • Low (ave) data rates typical

      • Routing protocol rate must be << application rate

  • Routing protocol comm. costs matter

    • Discovery, maintenance, repair, …

    • Computed wrt deployment characteristics

      • N, d, h, c, C, D, …


Constraints1
Constraints Lossy Networks

  • Low Power

  • Footprint

    • microcontrollers (outnumber microprocessors 25:1) typically have kilobytes of memory, not megabytes or gigabytes.

    • $s

      • ram $0.40/kb, 100x sram, 10,000x dram

    • Standby power (which dominates in low duty cycle) determined by leakage

      • MB ram => discarded in sleep, restored on wake

  • All routing state matters

    • route tables, neighbor tables, caches, DBs, buffers

      • N, d, h, c, C, D

    • Summarization, partial information, …


Challenges
Challenges Lossy Networks

  • Lossy

    • Low Transmit Power

      • Low SNR, short range [d?, h?]

    • Low sensitivity

    • Physical attenuation, occlusion, interference, motion

      • generally cannot move the node to make the network happy

    • Receiver diversity, in addition to temporal, frequency, spatial

  • loss is typical, not exceptional

    • often transient, not necc. excess data rate [c?]

    • typically, should not trigger costly repair

    • Loss  No Link

    • Reception  Link present

    • Multiple paths permit local rerouting

  • Scale is often very large


Rock and roll
Rock and ROLL Lossy Networks

  • Requires rigorous routing protocol design

    • Can’t just throw resources at it.

    • Can’t just throw bandwidth at it.

    • Must use prolonged observation, not instantaneous.

    • Faces same concerns as embedded applications

  • ROLL operates “between a rock and a hard spot”


Can we tackle such a hard problem
Can we tackle such a hard problem? Lossy Networks

  • Lots of existence proofs in the industry today

  • Application domains introduce important simplifications

    • The “not required” or “infrequent” is as important as the “is required”

    • Routing Requirement drafts are defining these

    • This draft represents them parametrically

  • Example

    • Vast majority of flows are in to and out of a single (or few) points [ D?, C?, P?]

    • Minority of mobile nodes within static extent


Start of a process
Start of a Process Lossy Networks

  • Important to have a analysis template to gain consensus on the relevant parameters, the criteria and the analysis across protocols

  • Each entry in the table will have considerable supporting evidence

  • Goal is common understanding of facts, not “winning the match”.

    • There may be no “winner” but important lessons learned from each entrant.

    • No “sacred cows” assumed.

  • Expect an active, interactive exchange between Phili and Dublin


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