Question

Persistent connection to a mobile device is difficult. Signal conditions can change rapidly, and connectivity types can also change. For instance, I may want to stream audio to my phone as I leave my apartment (WiFi), take a bus (WiMax/LTE), transfer to the subway (intermittent CDMA, sometimes roaming on another carrier), and walk to work (WiMax/LTE and back to WiFi). On this 15-minute trip alone I use at least 4 different IP addresses/networks, and experience all sorts of connectivity issues along the way. However, there is rarely a total loss of connectivity to the Internet, and the times that the signal condition makes connectivity problematic only happen for small periods of time.

I’m looking for a protocol that allows roaming from network to network and is very tolerant of harsh network conditions, while maintaining virtual end-to-end connectivity. This protocol would enable connections between a (usually) mobile device and some sort of proxy server which would relay regular TCP/UDP connections on behalf of the mobile device, over this tolerant protocol.

This protocol would sit around layer 3, and maybe even enable creation of virtual network interfaces that are tunneled through it. Perhaps there is a VPN or SOCKS proxy solution that already meets these needs.

Does such a protocol already exist?

If not, I’m probably going to come up with one, but would rather piggy-back off of existing efforts first.

Answer 1

There are many efforts within the internetworking community to address precisely these "network mobility" concerns.

In particular, Mobile IP (and its IPv6 big sister, Proxy Mobile IPv6) is a broad term for efforts to make IP addresses themselves portable across networks, however I doubt these technologies have reached sufficient maturation/deployment for production use today.

To undertake such mobility without support from the network requires a means of the host announcing to you its new address in an authenticated manner; this is what the Host Identity Protocol is designed for, but it is still at the "experimental" stage of the RFC process. From the abstract of RFC 5201:

HIP allows consenting hosts to securely establish and maintain shared
IP-layer state, allowing separation of the identifier and locator
roles of IP addresses, thereby enabling continuity of communications
across IP address changes.

There are several open-source implementations that are known to interoperate. Without claiming that this is a complete list, nor vouching for any of them (they’re just a few picked off a Google search for "Host Identity Protocol implementations"), there is:

• OpenHIP for multiple operating systems;
• HIPL for Linux;
• cutehip for Java;
• HIP for inter.net for *BSD/Linux.