Although the Hammer PacketSphere is designed to be a network emulator, Empirix is still working on software to generate packets. So right now this product is more of a LAN packet-degrading device, which can be configured to operate on one full-duplex Gigabit Ethernet connection or eight full-duplex 100Base-T connections.
The PacketSphere sits between two connections of a LAN. Strategic placement of the unit between the Internet connection and servers on one side and workstations on the other lets you have HTTP, FTP, telnet or other TCP- or UDP (User Datagram Protocol)-based sessions over the network, then see how degradation affects data transmission. Because the box sits in the middle of the network, you'll need two Ethernet connections to keep data flowing. The PacketSphere has interface boards for 10/100-based twisted-pair or Gigabit Ethernet connections. I used the Gigabit Ethernet connections in my testing.
Just Plug It In, And It Wreaks
Installation was a breeze. The included software for a Microsoft Windows 95/NT/2000 system resides on the PacketSphere itself -- Empirix does not support any other OS -- so no additional CDs are shipped with the product. Connecting the box to the network is simple: Just plug the device into the Ethernet ports on the two sides being degraded. This requires a brief outage of service between the two sides when connecting and disconnecting the unit, but it shouldn't be more than a few seconds if all the cabling is ready.
I tested the unit on the LAN in my home office, which consists of few desktop computers, servers and a printer. The only trick to getting to the software is turning on not one but two power switches on the box. After configuring my computer to be on the same network as the default PacketSphere address, I could use a Web browser to access the administrative functions. This let me change the password and IP address of the box, which in turn allowed me to download the interface software for my computer.
Starting up the software gave me a laugh as I watched five icons -- all for configuring destructive things to do to your network -- pop up across the top of the screen. At first glance, I thought they were tools for setting the speed of the data flowing through the box. There is a starfish (which I initially thought was a splotch of mud), a snail, a rabbit, a frog and a signpost. Each represents a function for the network: loss, latency, duplication, reorder and reroute, respectively. According to Empirix, these icons will be replaced in the shipping version, but after you figure out what they represent, the images do make sense. I actually became attached to them -- I'd hate to see them go.
Working It
To use the PacketSphere, start by defining a group of IP addresses. You can set a "from ... to" range for both the source and the destination IP addresses. A range of TCP ports from either the source or the destination can also be excluded from the test environment. These ranges determine the packets that the PacketSphere will interrupt: Any IP traffic outside of these ranges will be ignored by the box and will be allowed to pass through undisturbed.
Really cruel things can be done to the poor unassuming packets that belong to your defined group, starting with packet loss. The PacketSphere allows loss of every nth packet or loss based on percentages. An option for losing a percentage only of burst traffic is also available. I tried this with a VoIP (voice over IP) telephone and got some interesting results in voice quality. Even the loss of only 20 percent of the packets made dialing the phone difficult, as some of the dial-tone packets were getting lost and the gateway could not make out the number I was trying to dial.
If you want to slow your packets down a bit, latency changes can be made to them very easily. A constant delay or Gaussian distribution can be added. The option I really like is for uniform distribution. This allowed me to set a minimum and maximum delay with an even distribution pattern. The most impressive aspect of this option is the ability to set a maximum ramp-up or -down timing. With this, you can select the speed at which the millisecond timing is changed per second, which could be used to show a slow degradation of your network. While I was doing an FTP file transfer, I found it interesting to watch as the packets took longer and longer to get from one end to the other.
The PacketSphere can also duplicate or reorder every nth packet or a percentage of packets. By emulating duplicated packets, the PacketSphere can show what would happen if you had a really stupid device on your network. The reroute feature works by delaying packets for a given amount of time over a recurring period. For example, for every 100 ms of packet traffic, 30 ms of delay could be added.
All five operations can be used in any combination to operate on the IP addresses specified. Degradation can occur equally on west/east and east/west connections, or different settings can be created for each direction. The PacketSphere also has graphing capabilities and can actively show what is happening to the traffic on the network by presenting the user with details on lost packets and latency.
The PacketSphere performed very well in all the tests I ran, proving to me the value of having one of these in the lab. Although Empirix is pitching the PacketSphere to vendors and would like the product to be used with its Hammer VoIP Test System, I think that the PacketSphere would be at home in many lab or enterprise situations. You would be well-served to use the box to test LAN and application effectiveness by impairing the network and seeing just what it would take before latency, loss or other variables brought your system to an inoperable state. Anyone wanting to see what would happen with a network in the worst-case scenario could use this box.
Send your comments on this article to Darrin Woods at dwoods@nwc.com.
