However in certain cases where there is no VF ADSL or other land line data service or for example when a business is locked to a corporate network they will occasionally relax the rules.
In certain cases such as in Christchurch there are sub-divisions where the copper or fibre is owned by other ISP's, in such cases VF as an ISP is not a choice available to the customer.
The following is (generally) applicable for Sure Signal to work:
1Mbs downlink and 300K uplink as a minimum. Normally using VF as the ISP!
A fixed Internet IP address when not using VF as ISP.
A locked internal LAN DHCP address for the Sure Signal.
TCP Ports 8, 50 & UDP 123, 500, 4500 forwarded to the Sure Signal (NAT'ed).
Clear view of the sky (for GPS signal)
To prevent the devices being used away from the country of origin Sure Signal uses GPS to provide not only timing but a position fix. Whilst information is sketchy as to how this is implemented by the various vendors the following details the process. Certainly no reference material relating to a GPS signal requirement could be found in any VF documentation however practical tests proved this to be the case.
The information provided by VF NZ is sketchy at best and the tech support virtually non existent. It appears most of the VF tech's have received little or no training as to how these devices actually work. After the SS device I was using failed after a simple router swap I decided to do some digging, using TCPDUMP to capture the network traffic. I was able to dissect the packets and discover a lead as to what was actually going on. I noticed a reference to 'GPS 'in the UTP data coming back from VF which reminded me of an article I read in the past about Femtocells.
To prevent SS being used overseas (thus bypassing exorbitant roaming user charges) the SS device has a GPS chip fitted. http://en.wikipedia.org/wiki/Femtocell (see section under Equipment Location). If for example you connected the SS via a proxy located in the country of origin the device would by rights appear to VF as being located in that country based on IP location tracking or having the proxy sitting on a VF IP or other ISP valid (VF authorised) IP address. To overcome this potential problem the SS uses GPS location fixing.
The process of setting up the device involves linking back to VF using standard (IPSEC) network communication methods.
A timing signal using Network Time Protocol (NTP) is exchanged between the SS and VF which is compared to a GPS time and location signal received by the SS. At this time a failure to obtain a GPS signal will result in a lack of sync for the SS.
Therefore make sure the Sure Signal has a clear view of the sky when initially setting it up. How often the device needs to use GPS positioning is not known however it is safe to say if it looses lock put it next to a window.
One way round the issue of not being able to access VF as an ISP is to set up a link to a proxy which is sitting on Vodafones network. This would involve setting up tunnelling and is potentially messy although in theory should work.