6LoWPAN
6LoWPAN is an IPv6
protocol, and It’s extended from is IPv6 over Low Power Personal Area Network.
As the name itself explains the meaning of this protocol is that this protocol
works on Wireless Personal Area Network i.e., WPAN.
WPAN is a Personal Area
Network (PAN) where the interconnected devices are centered around a person’s
workspace and connected through a wireless medium. You can read more about WPAN
at WPAN. 6LoWPAN allows communication using the IPv6 protocol. IPv6 is Internet
Protocol Version 6 is a network layer protocol that allows communication to
take place over the network. It is faster and more reliable and provides a
large number of addresses.
6LoWPAN initially came
into existence to overcome the conventional methodologies that were adapted to
transmit information. But still, it is not so efficient as it only allows for
the smaller devices with very limited processing ability to establish communication
using one of the Internet Protocols, i.e., IPv6. It has very low cost,
short-range, low memory usage, and low bit rate.
It comprises an Edge
Router and Sensor Nodes. Even the smallest of the IoT devices can now be part
of the network, and the information can be transmitted to the outside world as
well. For example, LED Streetlights.
·
It is a
technology that makes the individual nodes IP enabled.
·
6LoWPAN
can interact with 802.15.4 devices and also other types of devices on an
IP Network. For example, Wi-Fi.
·
It
uses AES 128 link layer security, which
AES is a block cipher having key size of 128/192/256 bits and encrypts data in
blocks of 128 bits each. This is defined in IEEE 802.15.4 and provides link
authentication and encryption.
Basic Requirements of 6LoWPAN:
1.
The device
should be having sleep mode in order to support the battery saving.
2.
Minimal
memory requirement.
3.
Routing
overhead should be lowered.
Features of 6LoWPAN:
1.
It is used
with IEEE 802.15,.4 in the 2.4 GHz band.
2.
Outdoor range:
~200 m (maximum)
3.
Data rate:
200kbps (maximum)
4.
Maximum
number of nodes: ~100
Advantages of 6LoWPAN:
1.
6LoWPAN is
a mesh network that is robust, scalable, and can heal on its own.
2.
It delivers
low-cost and secure communication in IoT devices.
3.
It uses
IPv6 protocol and so it can be directly routed to cloud platforms.
4.
It offers
one-to-many and many-to-one routing.
5.
In the
network, leaf nodes can be in sleep mode for a longer duration of time.
Disadvantages of 6LoWPAN:
1.
It is
comparatively less secure than Zigbee.
2.
It has
lesser immunity to interference than that Wi-Fi and Bluetooth.
3.
Without the
mesh topology, it supports a short range.
Applications of 6LoWPAN:
1.
It is a
wireless sensor network.
2.
It is used
in home-automation,
3.
It is used
in smart agricultural techniques, and industrial monitoring.
4.
It is
utilised to make IPv6 packet transmission on networks with constrained power
and reliability resources possible.
Security and Interoperability with 6LoWPAN:
·
Security: 6LoWPAN security is ensured by
the AES algorithm, which is a link layer security, and the transport layer
security mechanisms are included as well.
·
Interoperability: 6LoWPAN is able to operate with
other wireless devices as well which makes it interoperable in a network.
The 6LoWPAN Architecture
Fig 1 The 6LoWPAN architecture.
·
The 6LoWPAN architecture is made up of low-power
wireless area networks (LoWPANs)2, which are IPv6 stub networks. The overall 6LoWPAN
architecture is presented in Figure 3.1. Three different
kinds of LoWPANs have been defined:
Ø Simple LoWPANs
Ø Extended LoWPANs
Ø Ad hoc LoWPANs.
·
A LoWPAN is the collection of 6LoWPAN Nodes which
share a common IPv6 address prefix (the first
64 bits of an IPv6 address), meaning that regardless of where a node is in a
LoWPAN its IPv6 address remains the same.
·
An Ad hoc LoWPAN is not connected to the Internet,
but instead operates without an infrastructure. A Simple LoWPAN is connected through one LoWPAN Edge Router to
another IP network. A backhaul link (point-to-point, e.g. GPRS) is shown in the figure,
but this could
also be a backbone link
(shared). An Extended LoWPAN encompasses the LoWPANs of multiple edge
routers along with a backbone link (e.g. Ethernet) interconnecting them.
·
LoWPANs are connected to other IP networks through
edge routers. The edge router plays an important role as it routes traffic
in and out of the LoWPAN, while
handling 6LoWPAN compression and Neighbor Discovery
for the LoWPAN. If the LoWPAN is to be connected to an IPv4 network, the edge
router will also handle IPv4 interconnectivity. Edge routers typically have
management features tied into
overall IT management solutions. Multiple edge routers can be supported in the
same LoWPAN if they share a common backbone link.
· A LoWPAN consists of nodes, which
may play the role of host or router, along with one or more edge routers.
The protocol stack
· A simple
IPv6 protocol stack with 6LoWPAN
(also called a 6LoWPAN protocol
stack) is almost
identical to a normal IP
stack with the following differences.
· 6LoWPAN only supports IPv6, for which a small adaptation layer (called the LoWPAN adaptation
layer) has been defined to
optimize IPv6 over IEEE 802.15.4
·
6LoWPAN stack implementations in embedded devices
often implement the LoWPAN adaptation layer together
with IPv6, thus they can alternatively be shown together as part of the network layer.
·
The most common transport protocol used with 6LoWPAN
is the user datagram protocol (UDP), which can also
be compressed using the LoWPAN
format.
·
The transmission control protocol (TCP) is not
commonly used with 6LoWPAN for performance, efficiency
and complexity reasons. The Internet control message protocol v6 (ICMPv6) is
used for control messaging, for
example ICMP echo, ICMP destination unreachable and Neighbor Discovery messages.
·
Application protocols are often application specific
and in binary format, although more standard
application protocols are becoming available.
·
Adaptation between full IPv6 and the LoWPAN format
is performed by routers at the edge of 6LoWPAN
islands, referred to as edge routers. This transformation is transparent,
efficient and stateless in both directions. LoWPAN adaptation in an edge router typically
is performed as part of the 6LoWPAN
network interface driver and is usually transparent to the IPv6 protocol stack
itself.
Fig 2 IP and 6loWPAN
protocol stacks
Fig:3 IPv6 edge router with 6LoWPAN support.
Link layers for 6LoWPAN
Ø The most basic requirements for a link layer to support 6LoWPAN are framing, unicast transmission and addressing.
Ø Addressing is required to differentiate between
nodes on a link, and to form IPv6 addresses which are then
elided by 6LoWPAN compression.
Ø It is highly recommended that a link supports unique addresses by default (e.g. a 64-bit extended unique identifier [EUI-64]), to allow for stateless autoconfiguration.
Ø Multi-access links should provide a broadcast service. Multicast service is required by standard IPv6, but not by 6LoWPAN (broadcast is sufficient). IPv6 requires a maximum transmission unit (MTU) of 1280 bytes from a link, which 6LoWPAN fulfills by supporting fragmentation at the LoWPAN adaptation layer.
Ø A link should provide
payload sizes at least
30 bytes in length
to be useful (and preferably larger than 60 bytes). Although
UDP and ICMP include a simple 16-bit
checksum, it is recommended that the link layer also provides strong error checking.
Ø Finally, as IPsec may not
always be practical for 6LoWPAN, it is highly recommended that links include
strong encryption and
authentication.
Addressing
- IPv6 addresses are typically formed automatically from the prefix of the LoWPAN and the link-layer address of the wireless interfaces. The difference in a LoWPAN is with the way low-power wireless technologies support link-layer addressing; a direct mapping between the link-layer address and the IPv6 address is used for achieving compression.
- IPv6 addresses are 128 bits in length, and (in the cases relevant here) consist of a 64-bit prefix part and a 64-bit interface identifier (IID).
- 6LoWPAN networks assume that the IID has a direct mapping to the linklayer address, therefore avoiding the need for address resolution. The IPv6 prefix is acquired through Neighbor Discovery Router Advertisement (RA) messages [ID-6lowpan-nd] as on a normal IPv6 link. The construction of IPv6 addresses in 6LoWPAN from known prefix information and known link-layer addresses, is what allows a high header compression ratio.
Fig:5 6LoWPAN/UDP compressed headers (6 bytes).
Ø The LoWPAN header consists
of a dispatch value identifying the type of header, followed
by an IPv6 header
compression byte indicating which fields are compressed, and then any in-line
IPv6 fields. If, for example,
UDP or IPv6 extension headers
follow IPv6, then these
headers may also be compressed using what is
called next-header compression
[ID-6lowpan-hc].
Ø An example of 6LoWPAN compression is given in Figure 3.4. In the upper packet a one-byte LoWPAN dispatch value is included to indicate full IPv6 over IEEE 802.15.4. Figure 5 gives an example of 6LoWPAN/UDP in its simplest form (equivalent to the lower packet in Figure 3.4), with a dispatch value and IPv6 header compression (LOWPAN_IPHC) as per [ID-6lowpan-hc] (2 bytes), all IPv6 fields compressed, then followed by a UDP next-header compression byte (LOWPAN_NHC)with compressed source and destination port fields and the UDP checksum (4 bytes). Therefore in the likely best case the 6LoWPAN/UDP header is just 6 bytes in length.
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