1. LR-WPAN LoRaWAN 6LoWPAN IPv6 (for IoT) *surprise*
IoT models
LR-WPAN
LoRaWAN
6LoWPAN
IPv6 (for IoT)
*surprise*
Tommaso Pecorella - Davide Magrin
ns-3 training – Jun. 18, 2019

2. Relevant IoT technologies
ns-3 training – Jun. 18, 2019 – IoT
Jun. 18, 2019
Relevant IoT technologies
The most relevant technologies used in IoT are:
NB-IOT
5G (MMTC, URLL)
LoRA
Sigfox
[add here your favourite] …
… along with the “companion” standards used in IoT.

3. What we’ll see today Transmission (NetDevices)
ns-3 training – Jun. 18, 2019 – IoT
Jun. 18, 2019
What we’ll see today
Transmission (NetDevices)
– the “LR-WPAN” module
LoRA - the LoRaWAN module
Adaptation
6LoWPAN
IPv6 quirks related to IoT
A surprise
The summary of what’s not [yet] available (but we’re working on it)

4. IoT communication models
ns-3 training – Jun. 18, 2019 – IoT
Jun. 18, 2019
IoT communication models
Option 1:
Direct communication (i.e., star topology)
Long or short range
Examples: NB-IOT, 5G, LoRaWAN
Option 2:
Multi-hop communication (i.e., mesh and tree topologies)
Short range
Examples: (LR-WPAN)

5. ns-3 training – Jun. 18, 2019 – IoT
Jun. 18, 2019
According to Wikipedia (
IEEE  is a technical standard which defines the operation of low-rate wireless personal area networks (LR-WPANs).
It specifies the physical layer and media access control for LR-WPANs, and is maintained by the IEEE  working group, which defined the standard in 2003.
It is the basis for the Zigbee, ISA100.11a, WirelessHART, MiWi, 6LoWPAN, Thread and SNAP specification, each of which further extends the standard by developing the upper layers which are not defined in IEEE
It maps into a NetDevice.

6. 802.15.4 – problems… The Standard is all but obvious. It defines:
ns-3 training – Jun. 18, 2019 – IoT
Jun. 18, 2019
– problems…
The Standard is all but obvious. It defines:
Multiple operation modes:
Beacon-enabled (star topology)
Non-Beacon-enabled (peer-to-peer topology)
Cluster-tree (peer-to-peer with multihop)
Multiple device roles:
PAN coordinator
Coordinator
Leaf node
Multiple device capabilities
Full Functional Device (FFD)
Reduced Functional Device (RFD)

7. 802.15.4 – … and least but not least…
ns-3 training – Jun. 18, 2019 – IoT
Jun. 18, 2019
– … and least but not least…
It does NOT define exactly the MAC !
Beacon-enabled: the MAC is defined perfectly.
... but nobody uses it.
Non-beacon-enabled: the MAC is defined “more or less”
There are a lot of variants, all “technically” compatible, but different.
The differences are mostly about
How sleep periods are handled
How to wake up and synchronize with neighbors

8. 802.15.4 – MAC variants Beacon-enabled (star topology)
ns-3 training – Jun. 18, 2019 – IoT
Jun. 18, 2019
– MAC variants
Beacon-enabled (star topology)
Potentially interesting, but…
NullMac – the simples possible
The radio is always on
No syncronization problems
Extremely energy hungry
ContikiMac – a complex one
Sleep periods
Syncronization (caveat… nodes don’t drift)
Energy efficient

9. 802.15.4 – Examples Switch to ns-3 cd src/lr-wpan/examples/ …
ns-3 training – Jun. 18, 2019 – IoT
Jun. 18, 2019
– Examples
Switch to ns-3
cd src/lr-wpan/examples/ …
lr-wpan-data.cc
lr-wpan-error-distance-plot.cc
lr-wpan-error-model-plot.cc
lr-wpan-packet-print.cc
lr-wpan-phy-test.cc

10. 802.15.4 – It’s complicated… (on purpose)
ns-3 training – Jun. 18, 2019 – IoT
Jun. 18, 2019
– It’s complicated… (on purpose)
Why didn’t we use the Helper class ?
is not like a “normal” network
Each device should be associated to a PAN
’s packets MTU is small...
It’s so small that IPv6 can’t use it…
…and most IPv4 packets would be too large
Using an Helper class in the NetDevice example would have created too many “silly” mistakes.
It’s wiser to look at the larger picture.

11. 802.15.4 – you don’t use it “bare bones”
ns-3 training – Jun. 18, 2019 – IoT
Jun. 18, 2019
– you don’t use it “bare bones”
The typical node stack is slightly different from the one of “standard” nodes.
Normal IPv6 node
LR-WPAN IPv6 node
Adaptation
layer

12. 6LoWPAN – what’s the purpose
ns-3 training – Jun. 18, 2019 – IoT
Jun. 18, 2019
6LoWPAN – what’s the purpose
Provide an adptation layer between protocol X (in this case ) and IPv6, in order to adapt:
Packet Error Rate (IPv6 assumes that it’s low)
Packet MTU (IPv6 wants 1280 bytes)
Moreover:
Try to not waste bandwidth – compress headers
about 100 bytes datagram and 40 bytes of IPv6 header ? Bad idea
Finally
Adapt some IPv6 mechanisms to the “quirks” of a multihop network

13. 6LoWPAN – How do it works ? Packet Error Rate
ns-3 training – Jun. 18, 2019 – IoT
Jun. 18, 2019
6LoWPAN – How do it works ?
Packet Error Rate
Adds link-level ACKs and retransmissions (optional)
Packet MTU (IPv6 wants 1280 bytes)
Allows link-level fragmentation and reassembly
Header compression
40 bytes are compressed into 6 bytes (best case)
… but the application layer must be “kind”,
Use the right port numbers,
Use a standard Hop Count,
Use UDP and not TCP,
etc.

14. 6LoWPAN – Examples Switch to ns-3 cd src/sixlowpan/examples/ …
ns-3 training – Jun. 18, 2019 – IoT
Jun. 18, 2019
6LoWPAN – Examples
Switch to ns-3
cd src/sixlowpan/examples/ …
 example-ping-lr-wpan.cc
 example-sixlowpan.cc

15. 6LoWPAN – interesting facts
ns-3 training – Jun. 18, 2019 – IoT
Jun. 18, 2019
6LoWPAN – interesting facts
6LoWPAN pretends to be a NetDevice (it is not)
This is because IPv6 wants to talk to a NetDevice
6LoWPAN implementation supports both HC0 and IPHC compressions
6LoWPAN is not enough (ouch…)

16. LR-WPAN / 6LoWPAN – missing features
ns-3 training – Jun. 18, 2019 – IoT
Jun. 18, 2019
LR-WPAN / 6LoWPAN – missing features
This line says it all:
lrWpanHelper.AssociateToPan (lrwpanDevices, 0);
It is the sign of a missing feature:
The node bootstrap
During the bootstrap the node should
Find a PAN coordinator
Register itself, and receive a short address
Generate its IPv6 link-local and global addresses (!?!?!?!)
The last point is done by 6LoWPAN-ND

17. 6LoWPAN-ND – why I miss it so much
ns-3 training – Jun. 18, 2019 – IoT
Jun. 18, 2019
6LoWPAN-ND – why I miss it so much
The purpose of 6LoWPAN-ND is not “just” to distribute addresses:
Ensures the uniqueness of addresses
Provides a substitution for DAD and NDP
Allows more advanced and efficient 6LoWPAN compression types
Without 6LoWPAN-ND, we have to use an “all-knowing” NDP
… which is as bad as using a normal NDP – it’s not realistic
… but it’s more realistic than using a plain NDP.

18. ns-3 training – Jun. 18, 2019 – IoT
Jun. 18, 2019
So, what now ?
Now you should be able to build an IPv6-based, network, with the following limitations:
No realistic NDP
missing 6LoWPAN-ND
No realistic node association to a PAN
no mobility, not a big issue
No more than 1-hop…
because you miss the routing !

19. ns-3 training – Jun. 18, 2019 – IoT
Jun. 18, 2019
[add your title here]
Now you should be able to build an IPv6-based, network, with the following limitations:
No realistic NDP
missing 6LoWPAN-ND
No realistic node association to a PAN
no mobility, not a big issue
No more than 1-hop…
because you miss the routing !

20. What’s wrong with multihop ?
ns-3 training – Jun. 18, 2019 – IoT
Jun. 18, 2019
What’s wrong with multihop ?
All the nodes in a PAN belong to the same IPv6 prefix
Are they on the same link ? => NO
Is there a single router ? => NO
What is the “optimal” router => difficult to say
In general, multihop routing protocols are complex
Esisting multihop protocols (AODV, DSDV, DSR, etc.) are made for ad-hoc networks, not for IoT
Plus… they’re built for IPv4.
IPv6 extensions are possible, but…
… they’re not efficient for IPv6.

21. Routing – mesh-under (transparent)
ns-3 training – Jun. 18, 2019 – IoT
Jun. 18, 2019
Routing – mesh-under (transparent)

22. Routing – mesh-under (6LoWPAN)
ns-3 training – Jun. 18, 2019 – IoT
Jun. 18, 2019
Routing – mesh-under (6LoWPAN)

23. ns-3 training – Jun. 18, 2019 – IoT
Jun. 18, 2019
Routing – route-over

24. Vaporware… Vaporware [noun] Examples of Vaporware:
ns-3 training – Jun. 18, 2019 – IoT
Jun. 18, 2019
Vaporware…
Vaporware [noun]
In the computer industry, vaporware (or vapourware) is a product, typically computer hardware or software, that is announced to the general public but is never actually manufactured nor officially cancelled.
Examples of Vaporware:
Half-Life 2: Episode Three
AirPower (Apple’s wireless charging pad)
ns-3’s RPL module …

25. RPL for ns-3 is Vaporware (sorry about that)
ns-3 training – Jun. 18, 2019 – IoT
Jun. 18, 2019
RPL for ns-3 is Vaporware (sorry about that)
Built in ns-3.15
Four complete refactorings
… and I’m still unhappy.
The bad news: it doesn’t work (anymore)
Half-finished refactoring, and
Changes in ns-3
The good news:
We have people willing to complete it, and

26. RPL Development status
ns-3 training – Jun. 18, 2019 – IoT
Jun. 18, 2019
RPL Development status
What you’ll find:
Mode of Operation:
Storing mode
Objective Functions:
OF0 and MRHOF
Metrics:
HC, ETX, and LQL
What you’ll not find:
Documentation
Clear examples
Working out of the box
Summarizing: feel free to ask to join the project on github