and NEMO Basic Support
The IPv6 Protocol
In today's Internet, most communications between end-to-end nodes are using the IP protocol. This protocol assigns a unique address to all nodes connected to the Internet, and provides the mechanisms to transport data between two nodes.
IP version 4 (known as IPv4) is the current version of this protocol and was the first widely deployed IP protocol. It was standardized 25 years ago. It now suffers from several design problems and will certainly restrain the creation of new usages of the Internet. The most debated problem with IPv4 is the lack of addresses, but it is not the only important one.
The need of addresses will increase in the near future. With the voice-over-IP becoming more and more popular, we can guess than billions of people will use an IP phone. Each vehicle will embed tens of IP sensors as well as some multimedia devices. Obviously, all of these equipments need an IP address. The lack of addresses that can be assigned with IPv4 was solved with the Network Address Translation (NAT) system. However, many peer-to-peer applications (such as video-conference or voice-over-IP softwares) suffer from this mechanism: with NAT, the real address of the host is not directly reachable from its correspondent. The communication cannot be directly established and sometimes need a third-part.
We expect more and more equipments will be connected to the Internet, but the IPv4 protocol is not appropriate anymore to distribute and manage the IP addresses. The IPv4 scheme to allocate addresses is not based on any hierarchical scheme and the high fragmentation of the address space will lead to a heavy load on backbone equipments (the routers). This is one of the most critical problems with the current IP protocol as it might cause the core routers of the Internet to stop working without prior notice.
Eventually, the IPv4 protocol has a monolithic design that makes it difficult to extend, and contains mechanisms that prevent new protocols like mobile IP to work flawlessly.
As IPv4 cannot meet the demand anymore, the IPv6 protocol (RFC 2460) has been standardized in 1998. It can allocate much more addresses and allows to interconnect undecillions (10e36) of nodes at the same time. Nodes that connect to the Internet can automatically acquire an address thanks to an auto-configuration mechanism (RFC4862 "IPv6 Stateless Address Autoconfiguration"). IPv6 also simplifies the use of multicast, that allows many to many (including one to many) communications without wasting bandwidth.
Besides these core features, IPv6 also allows the integration of new features such as improved security, quality of service where IPv4 only provides best effort, and mobility mechanisms with Mobile IPv6 and NEMO Basic Support.
The scalability offered by IPv6 will thus allow to interconnect any equipments and to design new services (such as connecting each car to the Internet) and new usages of the Internet (for instance use the vehicle connectivity for monitoring purposes) that we could not imagine with IPv4.
The Mobile IPv6 Protocol
When a wirless node connected to the Internet physically moves, it can be at some point of time out of the coverage area of its access network and needs to move to another one. In addition, because distinct operators may operate or the public target is different (pedestrians, cars etc.), no single access technology usually covers one big area (such as a city). The moving node thus has to select the best access technology available.
When a node moves from one access network to another or switches between its access technologies, it acquires a new IPv6 address and is not reachable to its previous one anymore. It implies that all current communications (for example streaming video from the Internet) are stopped and must be restarted by the user or the application.
The Mobile IPv6 protocol (RFC 6275) has been defined to address these issues and allow the node to be always reachable at the same IPv6 address whatever the access network it uses. It allows the host to move transparently for the applications and the users, without the need to reset all the current connections each time the host moves to another access network.
With Mobile IPv6, a host has two addresses while moving in the Internet topology: one permanent address that identifies the host, and the other representing the location in the Internet topology. The Mobile IPv6 protocol takes care of the binding between these two addresses (thanks to a Home Agent), and ensures that the host is always reachable at its permanent address even if it moves in the Internet topology.
The NEMO Basic Support Protocol
On one side Mobile IPv6 manages mobility for only one host, on the other side NEMO Basic Support (RFC 3963) manages mobility for one whole network. Such a network can be for instance a PAN (Personal Area Network, a small network made of IPv6 sensors and PDAs), or an access network deployed in cars, buses or trains. Thanks to NEMO Basic Support, the only device that needs to have mobility functionalities when the whole network moves is the one that connects the network to the Internet (this device is called a Mobile Router), whereas with the Mobile IPv6 approach each host in the network would have to handle mobility.
Running Mobile IPv6 on each node can be expensive, especially for little devices such as sensors. NEMO Basic Support only requires changes on the router, all others hosts in the moving network do not need any new feature. Thus all movements in the Internet topology will be handled by the router, transparently to the hosts.
With NEMO, we can imagine lots of senarios where mobility can play an important role. Using Network Mobility in a train would allow the customers to stay connected to the Internet without disruption during all their trip. Network Mobility in cars can allow to set up a PAN (Personal Area Network) made of tiny IPv6 sensors that can be queried from outside, and PDAs that can have permanent access to the Internet.
Real-life demonstrations using IPv6 and mobility support mechanisms
Kuntz, Romain and Lorchat, Jean and Ernst, Thierry (Keio University)
JSF, Tokyo, Japan, November 2005
A Live Light-Weight IPv6 Demonstration Platform for ITS Usages
Ernst, Thierry and Kuntz, Romain and Leiber, Francois (Keio University)
5th International Conference on ITS Telecommunications (ITST), Brest, France, 27-29 June 2005
IPv6 Network Mobility, Usage and Demonstration
Kuntz, Romain (Keio University)
JSF, Tokyo, Japan, November 2004