Graphic: Comparing Wireless Technology Range and Data Rates

This graphic helps visualize the different use-cases for various wireless technologies by comparing range and data rates.

A few notes:

• LTE could be included in the same area as WiMax, and could probably be re-named "4G".
• Wi-Fi will soon approach Gigabit speeds with 802.11ac and 802.11ad and would shift upward in the graphic.

Cheers,
Andrew

Mesh Network Performance Impact

I've been "noodling" (yes, I scientific term, I assure you) on Wi-Fi mesh networking of late. There exists this "rule-of-thumb" that is often quoted in Wi-Fi circles that goes something like this:

For every mesh hop (after the first hop), throughput degrades by 50% [or more] per hop.

Not being the type to take statements like that at face value, I dug in and did a bit of research. The statement, on its face value, is very plausible. Given a single-radio mesh backhaul where all ingress and egress traffic must share the same frequency, throughput will degrade because each frame transmission must be repeated to the next hop on the same channel.

Note - I will not discuss multi-radio mesh backhaul solutions that use separate radios and frequencies for simultaneous ingress and egress transmission within the mesh network. These solutions are more mature and do not result in such dramatic throughput degradation.

This is very logical, but in my estimation, also a bit misleading.

My line of thought went something like this:

Yes, the 2nd mesh hop results in a 50% throughput degradation because each frame must be transmitted a second time across the backhaul from the 1st hop to the 2nd hop. Hence 50% loss.

But then we get to larger mesh networks, which have 3 or more hops. If a frame must be transmitted across 3 hops with all backhaul radios on the same frequency, then the total throughput should be 1/n, where 'n' represents the number of mesh hops the frame must traverse. The corresponding throughput degradation is 1 - 1/n. This results in 1/3 or 33% of original throughput, resulting in 66% degradation.

However, the rule-of-thumb dicatates that throughput degradation in a 3 hop mesh network would be 50% to 2nd hop and another 50% to the 3rd hop, net 1/4 or 25% of original throughput, resulting in 75% degradation.

This is the gap in analysis that prompted my research. What should engineers be using as planning values for single-radio backhaul mesh networks? 50% loss per hop, or 1 - 1/n loss based on the total number of hops a frame must traverse?

Both Calculations are Valid [based on your assumptions]
After researching it, both throughput models are technically accurate based on assumptions made during the analysis and design.

Single-Radio Mesh Backhaul Bandwidth Degradation
(courtesy of Strix Systems)

The best-case scenario is 1 - 1/n degradation. This assumes the mesh hops are deployed linearly and can only hear their two neighboring mesh nodes, one upstream and one downstream.

The worst-case scenario is 1 - 1/( 2^(n-1) ) degradation, which is 50% loss per hop (our rule-of-thumb). This assumes that the mesh network is designed as more of a web of mesh nodes that can hear three, four, or more neighboring nodes for failover and self-healing capabilities.

Using either method, it's clear that single-radio backhaul mesh networks result in substantial throughput degradation and should only be used when alternatives such as wired networking or traditional wireless access point deployments cannot be used.

Best-Case Mesh Throughput Degradation
(courtesy of Strix Systems)

Conclusion
Although the single-radio mesh backhaul rule-of-thumb gives the desired impression of performance degradation when mesh solutions are discussed, it should be used cautiously for explaining mesh performance issues from a conceptual point of view.

However, for real-world network planning, use either method as a starting point, and then verify through testing in your environment.

Know you know :)

Cheers,
Andrew

HP Wi-Fi Direct Printing in the Enterprise

Have you been thinking that Wi-Fi Direct will mainly be limited to consumer applications? Think again. HP just announced support for Wireless Direct Printing, which allows any Wi-Fi capable device to print directly to the printer when in proximity without connecting through the corporate network.

This solution works by leveraging the Wi-Fi Direct standard that was developed last year by the Wi-Fi Alliance and the Apple AirPrint technology that eliminates software or driver installation on Apple mobile devices. The user simply needs to connect to the Wi-Fi network that the printer advertises, then print.

Pros: Easy printing from mobile devices in the enterprise

This should help simplify support for BYOD (bring your own device) initiatives. Since BYOD typically is also designed with security restrictions around corporate network access, and printers are usually distributed throughout the network, providing access to those printers would be a management headache to say the least.

Also, mobile device printing via Apple AirPrint on a corporate network is not usable at this point due to protocol limitations that prevent printer discovery and access across layer 3 network boundaries. The ability to connect directly to the printer and print documents will allow immediate adoption of AirPrint in the enterprise.

HP Wireless Direct Printing is Easy using AirPrint
(but appears to lack any security)

Cons: Unproven security


The security issues involved with a Wi-Fi network being advertised by a printer that is directly cabled into your network are significant. Printers have historically been easy targets for attackers to gain access to corporate networks due to their lack of focus on security. Just look here! By allowing direct wireless access to the printer, enterprises risk exploitation of numerous printer vulnerabilities which could result in broad internal network access for an attacker.

HP's implementation also appears to use an open Wi-Fi network, which makes the risk even greater! The Wi-Fi Direct faq states the use of a separate "security domain" from the corporate wireless network. What this means is that security of the Wi-Fi Direct connection can be different (and simpler) than security required to access the corporate network. But that doesn't require an open connection. Wi-Fi Direct supports strong WPA2 pre-shared key security and ease-of-setup using WPS. However, HP's documentation implies a wide-open wireless network.

HP Wireless Direct Printing Appears to Lack Any Security

Recommendation: Wait and see

I can't provide a solid recommendation on this technology or use in the enterprise until I learn more about HP's implementation. I have more questions than answers at this point. The prudent path for enterprises will be to wait and see what is discovered about this solution by the community over the coming weeks / months and engage your HP account team to learn more about the solution and security features.

Additionally, verify if the printers that your organization are purchasing support this technology, what the default settings are, and what controls can be put in place to prevent use of this feature until its use is appropriately secured and approved.

Cheers,
Andrew