Monday, November 28, 2016

Proper Wi-Fi Design and Deployment: Required Even In the Home

As more and more wireless appliances and streaming media applications permeate the home, the reliability of the Wi-Fi network as the infrastructure for this traffic becomes critical to performance.  This is especially challenging in a multi-vendor environment. While every vendor  technically follows the IEEE 802 networking standards (which are supposed to provide for interoperability), there is the “standard” and then there is the reality.  

Most importantly, the more intense networking demands of a home network REQUIRE a properly designed and integrated system, which is quite antithetical to the conventional consumer “plug and play” approach. 

Architecturally, a home LAN can be broken into the following functions.  Each of these functions are independent of each other, and thus can generally and safely be satisfied by different equipment from different vendors:

  1. Modem:  Converting the Internet connection from the street (coax cable, fiber, DSL, satellite, etc.) into Ethernet
  2. Router:  Defining the local area network (LAN) and providing routing and NAT functionality between the WAN and the LAN
  3. Switch(es):  Providing interconnectivity between wired network devices on the LAN, including infrastructure devices (e.g. routers, APs, other switches) and wired client devices.
  4. Access Points:  Providing multiple wireless client devices access to the wired LAN


Several companies provide physically-integrated equipment that provide multiple functions (e.g. a cable modem Wi-Fi router which provides all four functions in one box), but these should be treated as separate functions.  Within a particular function, it is generally a bad idea to mix and match vendors.  This is especially true in the “access point” function, because there is quite a lot happening “under the hood”, and while all of the vendors are following the IEEE 802.11 specs, they are all doing it somewhat differently which makes co-existence problematic and, at the very least, difficult to do well.   Thus, if you are installing a managed Wi-Fi system, you want to remove or disable any other third party APs installed by the customer or other service providers to the extent possible.   Co-located Wi-Fi systems will interfere with each other and reduce Wi-Fi capacity, even if they are not in “active use”.

For the modem, the general recommendation is to have the ISP provider put their appliance in “bridge mode”, which shuts off all but the modem function.  Some ISPs have a harder time of doing this than others in practice.   At a minimum, the built-in access point in the cable modem should be disabled.  The built in AP is invariably only consumer grade and has very few knobs to turn in terms of performance tuning, making it inappropriate for the performance challenges of larger home Wi-Fi networks, especially those that require multiple APs for both coverage and capacity. 

The built-in router of a cable modem can be used reasonably safely if VLANs are not required.  If VLANs are required, you are definitely best off putting the cable modem into bridge mode and using a wired-only SMB Enterprise router (and thus avoiding a double NAT scenario which lowers performance for some appliances like gaming consoles).  EnGenius currently does not make this type of product, though it is on our long term roadmap.  SonicWALL SOHO is a good example, as if you get the standalone version (i.e. without the content filtering or AV licenses) it is fairly inexpensive and quite capable, though it is certainly difficult to program.  There are several other vendor products on the market in this category.  The key features you want to look for are VLAN support, DHCP, and dynamic DNS.  Firewalls are also useful in many home and SMB applications.

For the switches and APs, I would recommend that you look into EnGenius’s Neutron product line.  The APs are all centrally managed, which makes it easier for you as a service provider to provision and maintain, and can be managed either from the local EWS switch or from a hosted cloud-based server called ezMaster.

Within the AP for the home, there are three key factors to keep in mind:
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  1. Placement:   APs should be placed as close as possible to the client devices, with as little physical structure (e.g. walls) as possible.  In a multi-AP deployment, APs should be placed as far apart from each other as possible, with as much physical structure in between as possible.  This is true three-dimensionally, so stacking in hallways from floor to floor should absolutely be avoided.
  2. Transmit Power:   Most smartphones and tablets have very weak transmitters, on the order of 100x less powerful than access points.  If the APs are set to their maximum power settings, they can create a false sense of coverage.  The client devices at the far end of the coverage area will hear the APs (since the AP is “shouting”) but the AP can have a lot of difficulty hearing the client devices (since the clients are “whispering”).   Coverage should generally be more balanced, and thus turning down the transmit power of the APs will help to ensure more balanced bi-directional communication.  Additionally, 5 GHz does not travel as far as 2.4 GHz and suffers more attenuation when passing through walls and objects, thus the 2.4 GHz power generally needs to be 6 dB lower than the 5 GHz power to have roughly the same area of coverage.  I usually start at 14 dBm for 2.4 GHz and 20 dBm for 5 GHz, tuning from there based on the environment.  I also generally do not recommend “auto power”, as this changes the coverage area over time and can create either gaps in coverage or co-channel interference with neighboring APs.
  3. Channel:  Neighboring APs will overlap and will interfere with each other, unless the neighboring APs are put on static / non-overlapping channels.  Auto-channeling is a very hard optimization problem, and I have yet to see any vendor do it well, despite marketing claims.  APs should always be put on static / non-overlapping channels with the channel scheme staggered as much as possible.
Ironically, there are several new startups on the market offering home mesh products (e.g. Eero).  These are targeted as a “plug and play” approach for consumers to provide larger areas of coverage by placing more APs and then not requiring Ethernet cabling to interconnect them, instead using the Wi-Fi itself as a backhaul.  These APs also inevitably rely upon auto-channel and auto-power in an attempt to keep things simple for the uneducated user.  These products, however, follow the old mantra of providing “coverage”, when in reality a home network needs to provide adequate “capacity” with room for growth.  The problem with the fundamental approach is that mesh reduces throughput by 50% per hop (spending ½ the time servicing customers, ½ the time for backhaul to a connected AP).  Such APs fundamentally cannot meet the performance (bandwidth and channel utilization) demands of a high-performance network, and generally should be avoided in networks where high performance and large client capacity are driving requirements.

The core problem in home networking lies in the fact that ISP modem / routers are consumer products, and not very capable for more complex or more high-demanding networks.  I’ve run into the issue myself where you cannot practically put the modems into bridge mode because the ISP service people cannot handle it over time – even if you get them to configure it in bridge mode, a firmware upgrade or service issue generally breaks that and the ISP returns their modem to their default configuration. Additionally, if the customer is using their VoIP product, you are stuck with their modem.    

Unfortunately, you are usually stuck with whatever cable modem hardware the ISP provides, and every ISP is going to pick something different.  Most ISPs are fairly large behemoths who don’t care about interoperability with any other vendor’s equipment, and have no real incentive to provide compatibility for services that they undoubtedly view as (current or future) competition.   That is a business reality that is not going to change anytime soon. 

The best you can do, therefore, is to work around it.   I’ve done installations where I’ve literally sealed cable modems in steel boxes to block the Wi-Fi signal from it.  More commonly, I’ve also done installations where you just set the cable modem to some random SSID, fix the channel on 2.4 GHz and 5 GHz, and don’t use it for connecting any client devices.  You set up your real Wi-Fi network with the proper equipment and avoid conflicts on the fixed 2.4 GHz and 5 GHz channel of the cable modem, and basically treat the modem as a 3rd party rogue AP. 

The entire Wi-Fi industry has spent nearly 20 years telling consumers how “easy” it is to install Wi-Fi, yet simultaneously made the protocol more complicated (and thus more sensitive and fragile) in order to cheat the RF physics to squeeze throughput performance.   Performance relies upon establishing and maintaining better control over equipment choice, locations, channel, and transmit power settings.  I concur that the situation in home network environments is fairly untenable, and the introduction of more Wi-Fi appliances and infrastructure products in the consumer space only continues to make the situation worse. 


The reality is that a network needs to be designed, controlled, and properly maintained if you want high performance out of it, and that means a careful mix and match (and control) of vendor products for the modem, router, switch, and APs with proper configuration.  

There is no magic bullet.   

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