What are the reasons to use IP as key technology for the IoT
standardised
easy accessible for applications
What are the advantages of the Internet Protocol?
standardised, widly used
Why are there needs for optimization of the IP for IoT?
constrained devices, constrained networks
What constraints need to be considered regarding Internet Protocol?
payload, no fragemntation with IPv6
How much payload can be transmitted in an IEEE 802.15.4 base frame
when using IPv6 and TCP?
21 bytes
What is 6LoWPAN?
Low Power Wireless Personal Area Network
Wireless access technology for low-cost and low-data-rate devices powered on
batteries.
Which header types are defined by 6LoWPAN?
Why is there a need for 6LoWPAN?
for low power devices
What is 6LoWPAN used for?
Home and building automation
− Automotive networks
− Industrial wireless sensor networks
− Interactive toys and remote controls
What are the 3 main functions of 6LoWPAN?
1. IPv6 header compression
2. IPv6 packet segmentation and reassembly
3. Layer 2 forwarding (mesh under)
Outline the IP protocol stack with and without 6LoWPAN.
Why is 6LoWPAN header compression used?
bigger payload
How does the 6LoWPAN compression work?
reusing fields from lower levels to get to know needed information into the higher levesl
Explain and outline the 6LoWPAN compression.
Which IP versions are supported by 6LoWPAN header compression?
IPv6 only
Which transport layer protocols can be compressed by 6LoWPAN header compression?
UDP
Why is 6LoWPAN fragmentation used?
Fragmentation of IPv6 packets across multiple layer 2 frames
How does the 6LoWPAN fragmentation work?
The Datagram Size is 11-bit field that encodes the size of the entire IP packet before link-layer fragmentation. The
value of Datagram Size shall be the same for all link-layer fragments of an IP packet. For IPv6, this shall be 40 bytes
(the size of the uncompressed IPv6 header) more than the value of Payload Length in the IPv6 header of the
packet.
This field does not need to be in every packet, as one could send it with the first fragment and elide it
subsequently. However, including it in every link fragment eases the task of reassembly in the event that a second
(or subsequent) link fragment arrives before the first. In this case, the guarantee of learning the Datagram Size as
soon as any of the fragments arrives tells the receiver how much buffer space to set aside as it waits for the rest of
the fragments. The format above trades o simplicity for efficiency.
The value of the Datagram Tag shall be the same for all link fragments of a payload datagram. The sender shall
increment the Datagram Tag for successive, fragmented datagrams. This field is 16 bits long, and its initial value is
not defined.
The Datagram Offset field is present only in the second and subsequent link fragments and shall specify the offset,
in increments of 8 bytes, of the fragment from the beginning of the payload datagram. This field is 8 bits long. The
first octet of the datagram (e.g., the start of the IPv6 header) has an offset of zero; the implicit value of Datagram
Offset in the first link fragment is zero.
Explain and outline the 6LoWPAN fragmentation.
Which IP versions are supported by 6LoWPAN fragmentation?
IPv6
Why is 6LoWPAN mesh addressing used?
forwarding packets over multiple IP hops
How does the 6LoWPAN mesh addressing work?
Link-layer mesh is possible with some wireless technologies that include multihop forwarding features such as the recently completed IEEE 802.15.5 standard [IEEE802.15.5]. The original 6LoWPAN specification [RFC4944] includes an option for carrying mesh source and destination addresses, which can be used by a forwarding algorithm. No standard algorithms for use with this mesh header have been defined, and therefore the realization of LoWPAN mesh has been implementation specific. Currently, the most common technique instead employs IP routing.
Explain and outline the 6LoWPAN mesh addressing.
Is it mesh under or mesh over routing, and why?
What are use-cases for RPL instead of typical routing protocols (RIP, OSPF,…)?
Routers and interconnects are constrained, and many routers
What is a LLN?
routers and interconnects are constrained,
high loss rate, low data rate
few dozen to thousand of routers
What concept is RPL based on?
RPL is based on Directed Acyclic Graph (DAG) concept
Is RPL mesh-over / mesh-under, why?
mesh-over routing because routing is performed at the IP layer
Why is there a need for RPL?
outing protocol for wireless networks with low power consumption and generally susceptible to packet loss,optimized for multi-hop and many-to-one communication, but also supports one-to-one messages
Why are there 2 different modes defined in RPL?
To cope with the constraints of computing and memory that are common characteristics of constrained nodes
What modes are defined for RPL?
Explain both modes.
Storing mode: All nodes contain the full routing table of the RPL domain. Every node knows how to directly reach
every other node.
Non-storing mode: Only the border router(s) of the RPL domain contain(s) the full routing table. All other nodes in
the domain only maintain their list of parents and use this as a list of default routes toward the border router. This
abbreviated routing table saves memory space and CPU. When communicating in non-storing mode, a node always
forwards its packets to the border router, which knows how to ultimately reach the final destination.
Explain the RPL DODAG concept.
What does DODAG stand for?
destination Oriented Directed Acyclic Graph
What is a DODAG root?
DODAG root is a border router of the RPL domain, Connects the LLN to a backbone network
What is a DODAG parent?
Parents provide a path to the root
What RPL messages are defined?
What is a DODAG rank?
Rank of a node is a scalar representation of the node location
within a DODAG
What is DODAG rank used for?
Used to avoid and detect loops
Explain the term Objective Function
Objective Function is the objective of the Linear Programming Problem as the name suggests. In linear programming or linear optimization, we use various techniques and methods to find the optimal solution to the linear problem with some constraints. The technique can also include inequality constraints as well. The objective function in Linear Programming is to optimize to find the optimum solution for a given problem.
What is Objective Function used for?
What is Objective Function based on?
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