IETF 6TiSCH, a New Standardization Effort to Combine IPv6 Connectivity by Xavier Vilajosana at...
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Transcript of IETF 6TiSCH, a New Standardization Effort to Combine IPv6 Connectivity by Xavier Vilajosana at...
IETF 6TiSCH, a New Standardization
Effort to Combine IPv6 Connectivity
with Industrial Performancewith Industrial Performance
Xavier Vilajosana
UC Berkeley
Universitat Oberta de Catalunya
CoAP
UDP
6LoWPAN
The Internet of Things Stack
web-like interaction
Internet Integration
6LoWPAN
IEEE802.15.4e
IEEE802.15.4
Low-power reliability
simple hardware
“gap”scheduling
Outline
1. Wireless Challenges
2. IEEE802.15.4e
3. 6TiSCH
Wireless Challenges
First Challenge: External Interference
IEEE802.11
(Wi-Fi)(Wi-Fi)
IEEE802.15.1
(Bluetooth)
IEEE802.15.4
Second Challenge: Multipath Fading
Second Challenge: Multipath Fading
• Separate sender and
receiver by 100cm
• Have sender send bursts of
1000 packets
• Have receiver count the • Have receiver count the
number of received packets
• Move transmitter around in
a 20cmx35cm area and start
over
Second Challenge: Multipath Fading
ch.11
Second Challenge: Multipath Fading
ch.11
ch.13
ch.12
ch.14
ch.19
ch.21
ch.20
ch.22ch.13
ch.15
ch.17
ch.14
ch.16
ch.18
ch.21
ch.23
ch.25
ch.22
ch.24
ch.26
IEEE802.15.4e
CoAP
UDP
6LoWPAN
The Internet of Things Stackweb-like interaction
Internet Integration
6LoWPAN
IEEE802.15.4e
IEEE802.15.4
Low-power reliability
simple hardware
“gap”scheduling
Status
• Published 16 April 2012
• Only amends MAC layer of
IEEE802.15.4-2011:
– Does not modify PHY layer
• “Timeslotted Channel • “Timeslotted Channel
Hopping” (TSCH) mode:
– Ultra low-power operation by
synchronizing nodes
– Ultra high reliability through
channel hopping
A
BC
E
• A super-frame repeats over time
– Number of slots in a superframe is tunable
– Each cell can be assigned to a pair of motes, in a
given direction
Communication Schedule16
cha
nnel
offs
ets
e.g. 31 time slots (310ms)
DE
FG
H
I
J
2.120ms ≤ 4.256ms 0.800ms 0.400ms
9.976ms
A Slot
2.000ms 2.400ms
16 c
hann
el o
ffset
sChannel Hopping
2263 2268 2273 2278 2283 2288 2293
channelOffset=11
slotO
ffset=
14
AS
N*
=2
27
7
16 c
hann
el o
ffset
s
e.g. 31 time slots (310ms)
=1
4
*Absolute Slot Number
frequencyChannel=(channelOffset+ASN)%16+11
Now:
Ch. 11 (2.405GHz)
Next slotframe:
Ch. 26 (2.480GHz)
A
BC
E
• Cells are assigned according to application
requirements
• Tunable trade-off between
– packets/second
– latency
– robustness …and energy consumption
Slotted Structure: Trade-Off16
cha
nnel
offs
ets
e.g. 31 time slots (310ms)
DE
FG
H
I
J
Timeslotted Channel Hopping
D
B
C
A DATA ACK
• Trade-off bandwidth, 10s to 1000s
C->A A->C
D->B
D->C
B->A
C->A
cha
nn
elO
ffse
t
slotOffset
• Trade-off bandwidth,
redundancy, latency for power
consumption.
• 50% PDR: schedule more links
• Average power consumption:
function of number of scheduled
cells.
• How Mechanisms to monitor
and maintain schedule is out of
scope.
Typ
ica
lly
16
10s to 1000s
IEEE802.15.4e: Heritage• 2006: Dust Networks’s Time Sync. Mesh Protocol (TSMP)
– Break-through technology [1]
• 26 days
• 3.6 million packets generated
• only 17 packets lost
• 99.9995% end-to-end reliability
– Applicable to industrial application
• 2008: WirelessHART
Wireless extension of HART, the de-facto standard for – Wireless extension of HART, the de-facto standard for industrial monitoring
• 2012: IEEE 802.15.4e
– Amends MAC protocol of IEEE 802.15.4-2011
• Proven Technology. Commercial solutions are available.
[1] Channel-Specific Wireless Sensor Network Path Data,
Doherty, Linday, Simon, ICCCN 2007
6TiSCH
CoAP
UDP
6LoWPAN
The Internet of Things Stackweb-like interaction
Internet Integration
6LoWPAN
IEEE802.15.4e
IEEE802.15.4
Low-power reliability
simple hardware
“gap”scheduling
6TiSCH: Status
• Discussions started in December 2012
• Very traditional IETF procedure
– IETF mailing list created 01/24/2013
– 160+ members (mix between academic and non-
academics)academics)
– First face-to-face meetings at IETF 86 in Orlando
(March 2013)
– BOF at IETF 87 in Berlin
– IETF 88 draft adoption in Vancouver
6TiSCH: In Practice
• Mailing list
– https://www.ietf.org/mailman/listinfo/6tisch
• Weekly Webex calls
• Homepage
– https://bitbucket.org/6tisch/
• Internet drafts:• Internet drafts:– An Architecture for IPv6 over Time Synchronized Channel Hopping
– Terminology in IPv6 over Time Slotted Channel Hopping
– Using IEEE802.15.4e TSCH in an LLN context: Overview, Problem Statement and Goals
– 6TiSCH Operation Sublayer (6top)
– Minimal 6TiSCH Configuration
– 6TiSCH Data Model for CoAP
– Security Framework and Key Management Protocol Requirements for 6TiSCH
– A standard compliant security framework for Low-power and Lossy Networks
Charter
• Define an architecture to describe the design of 6TiSCH networks.
• Define an Information Model containing the management requirements of a 6TiSCH node.
Define a Minimal mode of operation outlining • Define a Minimal mode of operation outlining how to build a 6TiSCH network using the Routing Protocol for LLNs (RPL) and a static TSCH
schedule.
SCOPE: Charter limit the scope to distributed routing over a static schedule
Architecture
6top Operational Layer
• Logical positioning of layers
Higher Layers
802.15.4e TSCH
6top
Information and Data Model for
interacting with 6top
Commands
LLN
Using 6top with a PCE• PCE has full knowledge of
topology and traffic
requirements
• PCE computes schedule
• Communicates with nodes
to configure their schedule
PCE
BBR
backbone
LLNto configure their schedule
• PCE-node protocol
– e.g. CoAPCoAP
• PCE typically schedules hard
cells
• Charter Scope: define
operational API an 6top
mechanismsnode
TSCH
6top
CoAP
6top with distributed scheduling• Distributed scheduling can
use RPL routes
• Neighbor schedule
bandwidth with each other,
rather than explicit cells
– Soft cellsB
A
– Soft cells
• 6top monitoring process
monitors performance of
cells and reschedules the
ones that perform bad.
• Charter Scope: define
operational API an 6top
mechanisms
D
C
B
E
6TiSCH Resources
• Management Resources using CoAP
Name Accessibility 6top Commands URI path
6top management resources and the related URI paths
Neighbor Table CREATE/READ/DELETE/UPDATE 6t/Neighbor
Slotframe Table CREATE/READ/DELETE/UPDATE 6t/slotframe
Cell Table CREATE/READ/DELETE/UPDATE 6t/Cell
Time Source CREATE/READ/DELETE/UPDATE 6t/TimeSource
Bundle Table CREATE/READ/DELETE/UPDATE 6t/Bundle
Track Table CREATE/READ/DELETE/UPDATE 6t/Track
EB Table CREATE/READ/DELETE/UPDATE 6t/EB
Minimal Static Schedule
RPL on Minimal
• RFC6552 “Objective Function Zero for the
Routing Protocol for Low-Power and Lossy
Networks (RPL)”
• Definitions• Definitions
– Rf: rank_factor
– Sp: step_of_rank
– Sr: stretch_of_rank
P
N
R(P)
R(N)=R(N)+rank_increase
rank_increase = (Rf*Sp + Sr) * MinHopRankIncrease
Example
• Given:– Rf = 1
– Sp = 2* ETX
– Sr = 0
– minHopRankIncrease = 256 (default in RPL)
– ETX=(xmit/ack)
– r(n) = r(p) + rank_increase
0
1
2
R(0)=0
DAGRank(R(0)) = 0
R(1)=R(0)+683=683
DAGRank(R(1)) = 2
R(2)=R(1)+683=1366
DAGRank(R(1)) = 5
– r(n) = r(p) + rank_increase
– rank_increase= (Rf*Sp + Sr) * minHopRankIncrease
– rank_increase=(512*xmit/ack)
• Example:– 5-hop network
– r(0)=0
– xmit=100 ack=75 for all links
3
4
5
R(3)=R(2)+683=2049
DAGRank(R(1)) = 8
R(4)=R(3)+683=2732
DAGRank(R(1)) = 10
R(5)=R(4)+683=3415
DAGRank(R(1)) = 13