The 4020 Gateway - What, Why, How?
by John Watson and Don Bradner
What is it?
Those who read DatastormUsers.com forums will find occasional references to the DW4020, and may find themselves wondering what it is. We were the first two that we know of to have 4020s operational with the Datastorm, but more are being installed every day (two were installed at the Tampa rally).
At the right you will find a picture of the 4020 "modem stack." The term 4020 is used to refer to all of the stack, and also to just the 4020 gateway box, which is on the bottom of the stack. The other two boxes are standard DW4000 Receive (top) and Transmit (bottom) modems.
The 4020 gateway is a complete server computer. It is running a unix variant, and is fully loaded with Direcway software. Hughes updates the software automatically from the satellite as they choose (you can't stop it from updating). It has a USB port that connects to the receive modem, where the receive modem would otherwise be connected to a PC. It has a power splitter cable so that it can share the power supply with the modems, and a slightly larger power supply is included with it to handle the increased needs. Don has tested the 4020 as only requiring 4 watts at 120 volts, and we both have found that it boots up in about 30 seconds.|
And why would you want it?
Also on the back are 4 standard RJ-45 ethernet ports that can connect to computers, hubs, wireless access points, etc. If it were not for the need to have a PC to run the Datastorm software there would not be a need for a PC at all.
That's the primary reason for wanting a 4020, for most people - easy networking. We both had another reason, which was a new, higher speed, service offering from Hughes. That service, currently still in beta for Datastorm users, connects to a higher-speed gateway at Hughes and provides typical upload speeds around 100k with consistent ping times under 800 ms. It is a higher cost service (double or more) than regular BE, but we both are "will pay for speed" sort of users. The importance here is that the new service requires a 4020 to work.
A final relatively minor item is that 4020 service, both regular and the higher speed service, is unlimited. Most Datastorm users don't appear to have much trouble with the standard 500 megabyte FAP (Fair Access Policy) throughput of the BE service, unlike the lower 169 meg FAP that home users have, but if you have heavy binary file movement needs you may find that your get FAPped and your system slows to a crawl. The 4020 won't have that issue.
How do I get one?
You must be with a VAR that handles 4020 service to mobile customers. We are with Ground Control, which does. If you involve an installer they may be willing to send the installer the 4020 and have them attach it to your existing 4000 modems. Otherwise they will probably require that you send your modems in to be "married" to a 4020. It is a fairly costly piece of equipment, around $750.
How do I set it up?
In a perfect world, you would just plug it in. In practice there will be TCP/IP settings on the client computers, and there will have to be software on at least one PC to control the Datastorm and communicate with the 4020. At this time, a copy of the Direcway installer software is run on that machine, and it is important that the Datastorm software be installed after the Direcway software - uninstall the Datastorm software if it already exists. It needs to "find" the 4020 during installation.
There are two ways to configure the 4020: Static IP and Dynamic IP. This must be selected when you purchase your service, and the Static will (generally) cost more per month. Don has Dynamic, John has Static. If you choose Dynamic, then Network Address Translation (NAT) and DHCP are turned on in the 4020. Simply set the PCs to acquire an IP address automatically and they will be assigned 192.168.0.xx with 192.168.0.1 as gateway and net mask of 255.255.255.0. The 4020 will be accessed by the DW pointing utility at address 192.168.0.1. The end user can also access the status screen at that address. That is the normal configuration for most users. It is least susceptible to virus invasions. It is not suitable for some Virtual Private Network configurations or Voice over I/P applications (see John's VPN and VoIP articles).
If you choose Static IP, then NAT and DHCP are not enabled. This means that the PCs will need to have their network addresses set. When you sign up for a single IP address, the 4020 is programmed to use a 4 IP subnet. The first and last address are not useable, for reasons that date back to be beginnings of the Internet. The 2nd address is used by the 4020, and that becomes your gateway address. The 3rd address is your ‘single’ IP address. The 4th address is called the broadcast address, and also not useable here. The other valid choice is 5 IP's, which corresponds to an 8 IP subnet. Here is a sample of data from the serial port of a 4020:
LAN1 IP Address: 126.96.36.199
LAN1 Subnet Mask: 255.255.255.252
IP Gateway IP Address: 188.8.131.52
From the second line, Subnet Mask, we can see that this configuration is for a 4 IP subnet, 1 useable. Simplified math is, if the first 3 numbers are all 255, then subtract the 3rd number from 256 and the result is the number of IP addresses assigned to this sub-network.
The first line, 'LAN1 IP Address', is the address of the 4020, to be used as the gateway by the PCs. In this example, 184.108.40.206 is used for the address of the first PC.
The last line, 'IP Gateway' is not needed to configure the network. It is the address used by the 4020 to contact the HNS network.
The same system with 5 IPs would look like this:
LAN1 IP Address: 220.127.116.11
LAN1 Subnet Mask: 255.255.255.248
IP Gateway IP Address: 18.104.22.168
The usable addresses for computers, printers, or other network items would be:
It is also a good idea to have a "null-modem" serial cable available to connect a PC to the 4020 for configuration issues (or use an N-Port net-to-serial device, see Don's All wireless article). The primary issue is the internally set location within the 4020, which is latitude and longitude expressed in degrees and minutes. The Datastorm software is supposed to override this location with your actual location, but doesn't always succeed. Of course if you close DSServer, it wouldn't have mattered because the override goes away. In any scenario where the override doesn't happen, and you are a few hundred miles from the internal setting, the 4020 will fail to range (TX 13 error most often). Using Hyperterminal to access the 4020 allows you to change the latitude and longitude to match your actual location. Both of us do this routinely at every setup, and will probably continue to do so even if improvements make the Datastorm override foolproof. John has ordered a 2-port N-Port to simplify his as well.
An obscure note for 4020 users with static IPs:
While it is possible to use the gateway address, to view the status of the 4020 using a web browser, that is NOT how the DW software, including the pointing software used by DataStorm, does it. The DW software continues to use 192.168.0.1, just as though Dynamic IP and NAT were in use. This is possible because that address is routed via the gateway to the router, and internally the 4020 "knows" that it refers to itself. The problems happen when the 192.168.0.X subnet is used within the end users network, perhaps to access a serial port (N-Port) controller as mentioned above. If you change your IP settings to allow a 192.168.0.x network on your computer, you won't be able to see the 4020. Not good. The answer, if you need local addresses, is to use a different subnet such as 192.168.1.x. That would be done by using the advanced settings page of the network configuration on the PC. Fortunately, XP and Win2K do not have any problem running multiple IPs on the same network interface.