Mesh Without Wires

December 21, 2010

Layer 2 vs Layer 3 in Wireless Mesh: Do You Have to Choose?

Filed under: Technology,Wireless,Wireless backhaul,Wireless Mesh — kseniacoffman @ 12:37 pm

There are many questions regarding Firetide’s mesh technology, and this posts attempts to address some of them. As you will see from the post, Firetide’s mesh is neither Layer 2 nor Layer 3, but a hybrid, unique to the industry.

Layer 2 / Layer 3 Hybrid Approach

Layer 2 vs Layer 3 benefits and trade-offs have been a topic of discussion for a couple of decades as both approaches have their benefits and drawbacks. Firetide offers a L2/L3 hybrid approach, which leverages the positives from both technologies and does away with the shortcomings, such as Layer 2’s lack of scalability and Layer 3’s latency and chattiness.

Firetide’s technology looks as a Layer 2 switch to outside world. Internally Firetide uses a Layer 3 approach to deliver the packets from an injection point of the mesh to an exit point. In doing so the packets can be load-balanced and re-routed based on advanced metrics maintained within the mesh. The hybrid approach makes the wireless network more scalable as well as enhances its performance.

Distributed Wireless Ethernet Switch

Firetide infrastructure mesh is built out of Firetide mesh nodes, which, combined into a network topology (mesh, point-to-point, point-to-multipoint, or a combination), form a “distributed wireless Ethernet switch.” The mesh nodes (in our terminology) are neither access points nor routers. Hence we call them nodes.

The term “distributed wireless Ethernet switch” means that the features provided are equivalent to a traditional wired Ethernet switch. In a wired Ethernet switch, Ethernet interfaces are provided via line cards on a chassis based model. The central switching is done via a central card that switches Ethernet packets from one line card port to another line card port. Firetide follows a similar approach. The line card equivalent of Firetide’s product offering is the mesh node, while the central switch is the radio medium itself. The nodes may be a mile to several miles apart.

The simplicity of Ethernet switch is illustrated the point that a 100-port Ethernet switch needs one single management IP address. In the same way, a 100-port Firetide mesh (formed with 25 indoor mesh nodes, for example) will have a single management IP address. The distributed Ethernet switch architecture is patented technology of Firetide and provides:

  • Seamless transport of IPV4 and IPV6 packets
  • Load balancing across the entire mesh
  • End-to-end encapsulation (on top of encryption) for added security, reliable handling of multicast traffic, and no introduced jitter
  • Simple installation and expansion of a mesh network. With a ‘routed mesh,’ this would require a complex configuration whereas each node has unique user-described IP address etc.

Firetide is the only provider with a distributed Ethernet switch-based infrastructure mesh. Most other wireless mesh in the market is a simple extension of access point-based technology, although some Layer 3 mesh also exists.

Flow-based Routing

The stitching of Layer 2 and Layer 3 is done on a flow-based model. The flows are Ethernet flows that are maintained within the mesh domain. The flows are then wirelessly switched across the distributed radio infrastructure.

Firetide built a protocol from the ground up with wireless in mind. Our flow-based routing algorithm creates a unique tunnel by encapsulating each packet with a flow instruction header specific to each stream; the header defines the least cost route for that specific packet from its source to its destination. Since flow instruction headers are used to determine the destination, the packets do not undergo deep packet inspection at each hop. In this way, we avoid extra overhead created by the millions of pings involved in resetting routing tables. Reduced overhead means more throughput for the user traffic.

These flows also help maintain unique, synchronous streams end-to-end. By maintaining the packets in these non-interleaved tunnels, the mesh makes sure that the packets arrive at the destination on time, in order, and with no introduced jitter (variation of latency).

Firetide mesh networks use load balancing across multiple paths for maximum network capacity. The mesh nodes manage the traffic across the network and can intelligently decide along which of 3 predefined flows a packet should be sent.

Performance

Firetide offers industry’s only wireless mesh that provides 100-150 Mbps of UDP payload sustained over multiple hops in outdoor deployments (real throughput, not theoretical data rate). When deployed in point-to-point mode, through radio bonding, we can provide real-world throughput of 200-300 Mbps outdoors.

What Firetide Mesh is Not

Even though Firetide mesh looks to the outside world as a Layer 2 switch, it does not perform “Layer 2 switching,” nor is it based on bridging two Wi-Fi radios together in WDS mode. On the switching side, Firetide mesh uses cut-through forwarding, as opposed to store-and-forward methodology. (Here’s a good definition from Cisco: “Whereas a store-and-forward switch makes a forwarding decision on a data packet after it has received the whole frame and checked its integrity, a cut-through switch engages in the forwarding process soon after it has examined the destination MAC (DMAC) address of an incoming frame.” See more on the two approaches: Cut-Through and Store-and-Forward Ethernet Switching for Low-Latency Environments.) In other words, Firetide mesh protocol performs proper routing across multiple hops, with cut-through forwarding approach allowing for industry’s lowest latency in wireless mesh: sub 1 ms per hop.

More questions? Please let me know in comments or via Twitter.

For more discussion on mesh technology, see

By Ksenia Coffman – Connect with me on Twitter or LinkedIn.

December 15, 2010

LA County Video Mesh Profiled in Law Officer Magazine

LASD Century Station Dispatch Center

LASD Century Station Dispatch Center

There are some deployments that just “keep on giving” in terms of continued success and resulting press coverage. Los Angeles County Sheriff’s Department (LASD) is among them. I recently came across an article in Law Officer magazine, which details the ASAP (Advanced Surveillance And Protection) program implemented by the LASD’s Century Station in Lynwood, CA (an unincorporated area in Los Angeles.)

The article describes Lynwood and surrounding areas as follows: “Covering a little more than 13 square miles, with a population of about 200,000, LASD’s Century Station deputies patrol some of the most challenging streets in the nation. Prostitution and drug use are common. Gunshots and gang violence are seemingly endemic, and successful solutions to reduce crime are hard to come by.” I was at the station once, and let me tell you, that’s not the neighborhood you want to get lost in (which my companion and I did on the way there).

What’s impressive about the program is the integration of numerous technologies, changing the way law enforcement goes about their daily business: “LASD staff has used a strategy that involves cutting-edge technology to bring about change for these communities. The department has implemented an IP video surveillance system, a gunshot recognition system, license plate recognition (LPR) and in-field fingerprint scanning into a comprehensive approach to policing.” The video wall is right in the dispatch center, so it’s easily accessible to watch deputies. They bring up cameras as they get calls for service, and are able to track suspects or ‘watch over’ a stop performed by deputies on the ground.

The article elaborates on the video mesh system:

“IP Video Surveillance Cameras
In the initial approach to a monumental crime problem, the LASD installed eight surveillance cameras in areas that had a high number of calls for service, particularly for violent crime. These first cameras were funded as a proof of concept through the Safe Cities program. The success led to additional installations that now total 34 cameras, with 10 additional installations planned in the near term.

Because of bandwidth, line-of-sight and other environmental limitations, the construction of a wireless network to support an IP video system posed numerous challenges. Among them, fiber-optic infrastructure is not available in Lynwood, requiring wireless technology that would support real-time, high-quality video (4CIF/30 FPS). The obstacles were addressed in the initial proof of concept, and the successful design was replicated in later installations.

Sgt. Chris Kovac, who oversaw the Lynwood IP video surveillance project, emphasizes that one of the most important factors in the success of a technology project is the selection of a vendor that has the skill and experience to accomplish what they promise.

In the Lynwood case, LASD put the project out for competitive bid. The successful bidder was Leverage Information Systems, a Washington-based company with an office in the area. Sgt. Kovac found that after the first installation, Leverage was able to replicate its initial design, which enabled Lynwood to expand its system easily.

Presently, all cameras are linked via a Firetide wireless mesh network to the Century Station dispatch center, where deputies can both view and control the cameras in real time. Although no one is assigned to continually monitor the cameras, the deputies use them as a response tool. They can later retrieve video to aid in criminal investigations. In fact, the IP video system is now a standard form of doing business in the city of Lynwood.”

Read the full article on Law Officer web site: Caught on Tape: How one agency used technology to slash crime.

For more information on LASD’s use of video mesh technology, see:

By Ksenia Coffman – Connect with me on Twitter or LinkedIn.

December 9, 2010

Is Firetide Mesh Hardware Attractive? SecurityInfoWatch Must Think So

Filed under: Physical Security,Public Safety Wireless,Wireless backhaul,Wireless Mesh — kseniacoffman @ 10:39 am

Ever since we released our HotPort 7000 infrastructure mesh, we’ve been getting comments from resellers and end-customers alike that the hardware is ‘solid,’ ‘great form factor,’ ‘more capacity packed into a smaller package,’ etc. I got further proof of positive vibes that the nodes generate when I was reading an article by Fredrik Nilsson of Axis Communications on SecurityInfoWatch.com entitled “Going the distance with IP video.” The article was interesting, discussing ways to overcome the distance limitations in IP video imposed by the Ethernet cable standards (330 feet). I was encouraged to see that, in addition to wired solution, the article discussed wireless technology, and specifically wireless mesh, as a way to extend the reach of IP networks ‘many miles.’ Nilsson notes:

“Wireless mesh. Self-healing wireless mesh networks are popular when the area that has to be covered is large and requires many cameras. The nodes cover a broad area and provide overlapping and backup coverage through multiple transmission paths. A wireless broadband mesh generally operates at 4.9 GHz [5 GHz is also used for video surveillance, since 4.9 GHz band is reserved for public safety agencies in the US - comment by Ksenia Coffman] and can include hundreds of nodes, which makes it an ideal option for city center surveillance systems covering several square miles. The drawback is that it isn’t very economical for small system implementations.”

But I was completely taken by surprise to see a Firetide 7000 mesh node illustrating the mesh section! SecurityInfoWatch must have supplied the art, as I don’t recall us providing them the image specifically for this article:

Firetide MIMO mesh node on SecurityInfoWatch.com

Firetide MIMO mesh node on SecurityInfoWatch.com

Updated 12/13/2010: I ran into Geoff Kohl at CAA convention in San Francisco, and asked him about the article. Per Geoff, it was Axis who selected the artwork. So thanks SecurityInfoWatch and Axis!

To see Firetide 7000 mesh ‘in the wild,’ check out these posts:

Read the entire article by Fredrik Nilsson: Eye on Video: Going the Distance with IP Video

By Ksenia Coffman – Connect with me on Twitter or LinkedIn.

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