Internet of Things

Lecture 5 - IPv6 and 6LoWPAN

Network Protocols

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Lecture 5 - IPv6 & 6LoWPAN

IPv6

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IPv6 Addressing

• 128 bits
• 8 groups of 16-bit hexadecimal values separated by colons (:)
• Prefix

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• Rule 1 : omit groups of consecutive zeros - Zero Compression
• double colon (::)
• only once in the address
• Rule 2: omit leading zeros from each group

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Lecture 5 - IPv6 & 6LoWPAN

Zero Compression

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Lecture 5 - IPv6 & 6LoWPAN

Zero Compression

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Lecture 5 - IPv6 & 6LoWPAN

Omit Leading Zeros

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Lecture 5 - IPv6 & 6LoWPAN

Combining both rules

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Lecture 5 - IPv6 & 6LoWPAN

IPv6 Address Types

• Unicast
• identifies a single node or interface
• traffic forwarded to a single interface
• Multicast
• identifies a group of nodes or interfaces
• traffic forwarded to all the nodes in the group
• Anycast
• unicast address assigned to multiple devices
• traffic forwarded to the nearest node in the group

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Lecture 5 - IPv6 & 6LoWPAN

IPv6 Unicast Addresses

• Network ID - administratively assigned
• Host ID - manually or auto-configured
• Random
• DHCPv6
• EUI-64 format

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Source: IPv6 Deployment Guide, Cisco Systems

Lecture 5 - IPv6 & 6LoWPAN

Global Unicast Address

• Routable and reachable across the Internet

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• Widespread generic use

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• Structured as a hierarchy to allow address aggregation

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• Identified by their three high-level bits set to 001 (2000::/3).

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Lecture 5 - IPv6 & 6LoWPAN

Global Unicast Address

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Source: IPv6 Deployment Guide, Cisco Systems

Lecture 5 - IPv6 & 6LoWPAN

Global Unicast Address

• Global prefix
• assigned by IANA to a service provider
• SLA / subnet ID
• assigned by service provider to a customer
• LAN ID
• individual networks within the customer site
• Host / interface ID
• 64 bits
• EUI-64 format

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Lecture 5 - IPv6 & 6LoWPAN

Unique Local Unicast Addresses

• Similar to private IPv4 addresses

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• Used for local communications, inter-site VPNs

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• Not routable on the Internet
• routing would require IPv6 NAT

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Lecture 5 - IPv6 & 6LoWPAN

Unique Local Unicast Addresses

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Source: IPv6 Deployment Guide, Cisco Systems

Lecture 5 - IPv6 & 6LoWPAN

Unique Local Unicast Addresses

• Starts with FD00
• Global ID
• do not have to be aggregated
• defined by the administrator of the local domain
• Subnet ID
• defined by the administrator of the local domain
• hierarchical - route summarization
• Interface ID

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Lecture 5 - IPv6 & 6LoWPAN

Link Local Unicast Addresses

• Communication between two IPv6 devices on the same link

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• Automatically assigned by device when IPv6 is enabled

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• Not routable addresses
• Their scope is link-specific only

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• Identified by the first 10 bits (FE80)

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Lecture 5 - IPv6 & 6LoWPAN

Link Local Unicast Addresses

• Remaining 54 bits = zero / any manually configured value

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Source: IPv6 Deployment Guide, Cisco Systems

Lecture 5 - IPv6 & 6LoWPAN

IPv6 Multicast Addresses

• 8-bit prefix, FF00::/8 (1111 1111).
• the second octet = the lifetime and scope of the address

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• Always destination address

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Lecture 5 - IPv6 & 6LoWPAN

IPv6 Multicast Addresses

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Source: IPv6 Deployment Guide, Cisco Systems

Lecture 5 - IPv6 & 6LoWPAN

6LoWPAN

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6LoWPAN Standard

• Internet Engineering Task Force (IETF)
• TCP, UDP, HTTP, CoAP, RPL, etc.
• 6LoWPAN Working Group
• IPv6 communication in LLN
• RFC 4944 - first 6LoWPAN standard
• RFC 6282 - header compression
• RFC 6775 - neighbor discovery

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Lecture 5 - IPv6 & 6LoWPAN

6LoWPAN Standard

• Over IEEE 802.15.4
• Adapted to work with other low-power technologies
• Bluetooth Smart
• Wi-Fi low-power

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Lecture 5 - IPv6 & 6LoWPAN

Network Architecture

• 6LoWPAN mesh network
• Edge router (6LBR)
• Generates & manages 6LoWPAN network
• Transfers between 6LoWPAN nodes and the Internet
• Transfers between 6LowPAN nodes
• Network level

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Source: Olsson, Jonas. "6LoWPAN demystified." Texas Instruments 13 (2014).

Lecture 5 - IPv6 & 6LoWPAN

Network Architecture

• Routers (6LR)
• Routes traffic from one node to another
• Hosts (6LN)
• Do not route traffic
• Low power nodes
• Duty-cycle

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Source: Olsson, Jonas. "6LoWPAN demystified." Texas Instruments 13 (2014).

Lecture 5 - IPv6 & 6LoWPAN

Networking Stack

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Source: Olsson, Jonas. "6LoWPAN demystified." Texas Instruments 13 (2014).

Lecture 5 - IPv6 & 6LoWPAN

IPv6 over IEEE 802.15.4

• Main challenges for using IPv6 over 802.15.4
• IPv6 MTU is 1280 bytes
• 802.15.4 frame size is 127 bytes
• IPv6 has MTU 10 times larger
• IPv6 - 40 bytes headers, TCP - 20 bytes, UDP - 8 bytes
• Solution: Fragmentation & header compression

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Lecture 5 - IPv6 & 6LoWPAN

IETF - RFC 6282

• Encapsulation of IPv6 packet into 802.15.4 frame => RFC 6282
• 1. Header compression
• Stateless or context-based compression
• The elimination of header fields that can be derived from other headers (data link)
• Determine IPv6 addresses and field sizes
• Example: same network prefix

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Lecture 5 - IPv6 & 6LoWPAN

IETF - RFC 6282

• 2. Fragmentation
• Fragment data to fit in 802.15.4 frames
• 3. Stateless auto-configuration
• 6LoWPAN nodes generate their own addresses
• Uses NDP
• Duplicate address detection (DAD)

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Lecture 5 - IPv6 & 6LoWPAN

Header Compression

• Stateless & shared-context compression
• IPv6 address
• 128 bits
• network prefix on 64 bits + interface ID on 64 bits
• Interface ID - derived from MAC address
• 802.15.4 MAC address

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Lecture 5 - IPv6 & 6LoWPAN

Header Compression

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1. Between nodes from the local network
• exclude both link-local addresses
• useful for routing protocols
2. Destination is external but prefix is known
• exclude src addr & dest prefix
• include only destination interface ID
3. Destination is external and prefix is not known
• exclude source interface ID

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Image source: Olsson, Jonas. "6LoWPAN demystified." Texas Instruments 13 (2014).

Lecture 5 - IPv6 & 6LoWPAN

Fragmentation

• Packets are divided into smaller segments
• Additional information in the headers for the reassembly

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• Depends on the type of routing
• mesh-under routing:
• packets are reassembled at the destination
• quick routing of fragments, reduced delay
• if a single fragment is lost the whole packet must be retransmitted

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Lecture 5 - IPv6 & 6LoWPAN

Fragmentation

• route-over routing:
• packet is reconstructed at each hop
• hops are devices with more resources - store all fragments

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• Avoid fragmentation - consumes resources
• small payload
• header compression

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Lecture 5 - IPv6 & 6LoWPAN

Stacked headers

3 types of sub-headers:

• mesh addressing
• multi-hop topology
• forward packets
• fragmentation
• identify fragments
• header compression

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Image source: Olsson, Jonas. "6LoWPAN demystified." Texas Instruments 13 (2014).

Lecture 5 - IPv6 & 6LoWPAN

Fragment header

• IPv6 packet is bigger than 802.15.4 frame => fragmentation
• 3 fields:
• datagram size
• whole payload size
• datagram tag
• identify a set of fragments of the same payload
• datagram offset
• location of fragment in payload

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Lecture 5 - IPv6 & 6LoWPAN

Mesh addressing header

• Used in multi-hop topologies for routing
• 3 fields:
• hop limit
• decremented at each hop
• drop packet when hop limit reaches 0
• source address
• destination address
• 802.15.4 MAC addresses - 16 or 64 bits

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Lecture 5 - IPv6 & 6LoWPAN

Routing

• Mesh-under
• Uses 802.15.4 MAC addresses to forward packets
• Forwarding is done at link layer
• IP subnet
• The edge router is the only IP router
• A single broadcast domain
• All messages are sent to all nodes
• Fit for small networks

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Lecture 5 - IPv6 & 6LoWPAN

Routing

• Route-over
• Works at network layer
• Each node is an IP router
• Each node implements all functionality (including DAD)
• Recommended for large networks
• RPL is a route-over protocol

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Lecture 5 - IPv6 & 6LoWPAN

Routing

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Lecture 5 - IPv6 & 6LoWPAN

Link-local Address

• Auto-generate IPv6 link-local address
• Link-local address derived from 802.15.4 address (64 or 16 bits)
• Link-local prefix is FE80::/64

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Lecture 5 - IPv6 & 6LoWPAN

Link-local Address

• Mesh-under routing
• local-link address is sufficient to communicate within the local 6LoWPAN network
• cannot be used for communicating outside the local network
• Router-over routing
• local-link address for communicating only with direct neighbors
• for multi-hop communication it needs routable address

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Lecture 5 - IPv6 & 6LoWPAN

Auto-configuration

• Auto-configuration
• IPv6 = network prefix + 802.15.4 MAC address
• Advantage of deriving the IPv6 address from 802.15.4 MAC address
• eliminate some fields to compress headers
• Same prefix in the network
• also good for header compression
• prefix is discovered through RS/RA messages (NDP)

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Lecture 5 - IPv6 & 6LoWPAN

Neighbor Discovery Protocol (NDP)

• RFC 6775 - Neighbor Discovery for 6LoWPAN
• Used for discovering neighbor devices
• Maintain information about available devices
• Configure default routes
• Propagate configuration parameters
• Critical for auto-configuration
• discover network prefix
• discover duplicates

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Lecture 5 - IPv6 & 6LoWPAN

Neighbor Discovery Protocol

• 4 types of messages:
• Router solicitation (RS)
• Router advertisement (RA)
• Neighbor solicitation (NS)
• Neighbor advertisement (NA)

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• RS/RA
• discover routers
• find network prefix

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Lecture 5 - IPv6 & 6LoWPAN

Neighbor Discovery

• NS/NA
• find duplicate addresses (DAD)
• node generates address and sends NS for verification
• if it receives NA with duplicate flag, the address is not unique
• finding neighbours
• detect when neighbours are not available

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• Using these 4 messages a node can auto-generate a unique address

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Lecture 5 - IPv6 & 6LoWPAN

Bibliography

• IPv6 Deployment Guide: https://www.cisco.com/c/en/us/td/docs/voice_ip_comm/uc_system/IPv6/vtgs_b_ipv6-deployment-guide-for-cisco.html
• https://www.networkacademy.io/ccna/ipv6/ipv6-address-representation
• RFC 4944: https://datatracker.ietf.org/doc/html/rfc4944
• RFC 6282: https://datatracker.ietf.org/doc/html/rfc6282
• RFC 6775: https://datatracker.ietf.org/doc/html/rfc6775
• Olsson, Jonas. "6LoWPAN demystified." Texas Instruments 13 (2014).

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Lecture 5 - IPv6 & 6LoWPAN

Keywords

• IPv6
• Unicast address
• Multicast address
• Anycast address
• 6LoWPAN
• Header compression
• Fragmentation
• Routing
• Auto-configuration

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Lecture 5 - IPv6 & 6LoWPAN