Mesh networks winning converts

Ignoring the crimson tracery of the Golden Gate Bridge soaring into a winter sky, Mickey Griffin and George Lowry peered instead at the screen of a notebook with an 802.11b wireless LAN card.

The California Governor's Office of Emergency Services employees, taking part in a trial of new wireless mesh technology, viewed live video of one of the bridge's abutments shot by a wireless IP camera mounted on a police patrol boat.

The image itself, in somewhat grainy quarter-VGA resolution, wasn't remarkable. What was impressive, though, is that the same image was seen at the same time by 30 other people who were stationed at various points on and around the bridge.

Using traditional wireline and wireless technology to achieve this in an emergency is impossible. End users would need to be mobile, yet installing the needed number of access points to blanket an area would be complicated and pricey, and most of all, time-consuming.

"The big strength of wireless mesh is the ability to put it up and tear it down very quickly," says Abner Germanow, program manager for enterprise networking at IDC.

The Golden Gate users had devices with off-the-shelf 802.11b WLAN cards from Proxim or 3e Technologies International and an early version of wireless mesh software from start-up PacketHop.

The PacketHop software creates a peer-to-peer mesh network: Each wireless client becomes a routing node that's aware of all its neighbors and can pass data and images among them. The range depends on what kind of 802.11 radio the client has, radio power levels and antenna design. In the Golden Gate test, the WLAN radios in the NICs ran at the highest power level allowed, 200 milliwatts (by comparison, Buffalo Technologies' 54M bits/sec 11g CardBus adapter runs at 37 milliwatts). PacketHop executives say the 11b client radios meshed with each other at ranges of 1,500-2,500 feet.

PacketHop plans to release a product by year-end and has not set pricing.

Mesh nets use complex algorithms for automatic discovery, routing and fast handoffs. Nodes in a mesh find each other and can route around failures or congestion. Vendors say these multiple pathways boost the reliability and capacity of wireless networks. There is no single point of failure, as there is in traditional hub-and-spoke networks.

Mesh networks minimize the need to install Ethernet cable and electrical wiring, which are the most costly and time-consuming elements of WLAN deployments.

"Wireless mesh offers enterprises a way to get around the big paradox of WLANs, that is, they are wired [to the backbone]," says Sarah Kim, a wireless market analyst with The Yankee Group.

Obstacle course

One obstacle is that the technology, which has been used in military nets, is new to the civilian market. PacketHop doesn't even have a commercial product yet.

There are also no industry standards. The IEEE 802.11 committee has just created a task group for forming a mesh network standard. A final standard probably is two to three years away.

IDC's Germanow cautions that one of the classic problems in a mesh network is the traffic that the networks' auto-discovery mechanism generates. "When you get into a large number of nodes, then the routing traffic volumes can take over with all the nodes saying 'Here I am,'" he says.

David Thompson, PacketHop's vice president of marketing, says that issue is handled by efficient algorithms that minimize chatter. The more nodes added, the more reliable and robust the mesh network becomes, he says.

Vendors also handle security differently. MeshNetworks has a silicon ASIC chip that implements security features; at a higher level, encryption, RADIUS authentication and other network security features run unchanged. PacketHop incorporates digital certificates: Each authorized client joining the mesh presents a pre-provisioned encryption key.

Many start-ups, including BelAirFiretide, MeshNetworks, Strix Systems and Tropos Networks, have wireless mesh products.

BelAir began shipping its first product in March and announced a low-end model, to ship in July. The current BelAir 200 looks like a small, sleek metal barrel that typically mounts on a utility pole. Inside are one or more 2.4-GHz radios for client device connections, just like any other 802.11b access point, and several 5-GHz radios that use 802.11a to create a 54M bit/sec wireless mesh network. Prices range from $3,000 to $9,000, depending on configuration.

But these upstarts will soon be joined by established vendors.

Nortel says it will start volume shipments in midyear of a WLAN mesh access point. It is designed for outdoor use. Clients with 11M bit/sec 802.11b adapters will connect as they do with any access point. But the Nortel devices will connect with each other, in a mesh network, over a separate 54M bit/sec 802.11a network.

Two companies targeting "carpeted" sites are Strix and Firetide. Strix typically uses an 802.11b radio for client connections and a separate 802.11a radio to create the mesh with other Strix boxes. One or two boxes in a mesh then plug into an Ethernet switch. Firetide's boxes have one radio to create their mesh, but several Ethernet ports into which can be plugged a third-party WLAN access point, a printer or other device.

The great outdoors

Most mesh action is taking place outdoors, in municipal and public safety wireless networks.

The cities of Garland, Texas, and Medford, Ore., are replacing 19.2K bit/sec Cellular Digital Packet Data services with public safety networks based on MeshNetworks' technology. Officials expect to see 200K to 2M bit/sec throughput over the mesh network.

City officials were sold on the technology after riding in two vans with laptops, flat-screen TVs and MeshNetworks' client adapters, says Darrell McClanahan, telecom manager for Garland. At 60 mph, they watched streaming video images, pulled down map files from a police server and made push-to-talk voice calls between the vans.

Medford is creating a 24-square-mile mesh, also with MeshNetworks. As in Garland, the mesh is created by mounting radios on utility poles and buildings. About 100 vehicles will have a mounting that includes the MeshNetworks radio and an Ethernet interface for locally attaching other devices, such as an IP camera or an 802.11a access point. The radio lets the vehicles create their own mesh network and connect to the pole-mounted radios for the high-bandwidth backhaul.

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