Reliability and Resiliency of the Mesh

Reliability is an important part of the Mesh, as with any Internet or communication network. 
As a distributed network of nodes, NYC Mesh has several advantages and disadvantages compared to other internet networks in terms of reliability.

Advantages:

Distributed nodes and independent operation:

NYC Mesh uses a distributed network of nodes, with each node able to communicate with the other nodes around it. This means that the mesh network, or segments of the mesh network can work independently of each other or the greater Internet.

If the mesh were to lose connection with the rest of the Internet however, online services or websites hosted elsewhere on the internet will not be accessible, even if the mesh itself continues to operate.
A list of services that are hosted locally on the mesh is on the Software Services List.

Backup routes and dynamic routing:

The mesh network uses a protocol called OSPF which handles dynamic routing between nodes on the network. This means that each node in the network is aware of the layout of the network and will route traffic via the shortest path to its intended destination. If that path goes down, the next shortest path will be used and traffic will automatically be re-routed.

This networking design makes the mesh largely tolerant of hardware and link failures within the network when designed properly.
Most larger hubs on the network have multiple links to other hubs around them, so if one link goes offline, for example due to an antenna failure, the network will automatically route traffic via an alternate path, and most of the network will remain online.
For this to work, a majority of nodes in the network must have at least two connections to surrounding nodes. For single nodes on rooftops, this is largely handled automatically with WDS, however for large hubs backup connections need to be thought about and planned. Ensuring the backup connection has enough bandwidth to not drastically bottleneck network throughput when it's put into use is important. Often secondary connections are not regularly tested until they are needed, so issues like low bandwidth can remain hidden until the primary connection fails.

Disadvantages:

Large number of power sources required for operation:

Due to having such a large distributed network, there are hundreds of nodes around the city, all of which require power for the mesh network to remain fully online.

In more typical COAX or Fiber distributed network, there is a central office / "head end" which connects via a network of passive splitters to routers/modems in users homes. This central office usually maintains a backup power supply capable of powering the entire network during an outage.

As long as the modems / fiber transceivers in each user’s home remain powered, the network will remain online during an outage, as all the other splitters or signal boosters are powered from the central office / "head end".

In the mesh network, each node in the chain from the supernode / data center to every member's apartment needs to be powered for the network to remain online. (An exception is if there is a secondary backup route across the network also available.)
This often involves a number of nodes powered from normal wall plugs in members’ apartments, which are unlikely to have backup power systems in place during a grid outage. Thus it is likely that a large number of mesh nodes will go offline during a grid outage situation, causing the network to be non-functional for many members.

Power reliability and redundancy:

Most NYC Mesh nodes typically rely on a power supply from either a member’s apartment or from a central location in the building they are located on top of. This power supply is subject to power outages or failures which would cause the node and all nodes reliant on it to go offline.

Many larger NYC Mesh hubs have UPS power supplies installed that can sustain the network equipment during short power outages. These UPS supplies are typically 750VA (Volt Amp) models, which can sustain a typical NYC Mesh node for 45-120 minutes during a power outage.

Most NYC Mesh supernodes and data centers are located in buildings that have their own independent backup power supplies. A listing of these nodes and their backup power capacity is listed below.

Solar, batteries, and small backup generators:

NYC Mesh does not currently have solar or battery backups on our nodes, except for a few small nodes where members have installed their own backup power systems.

Backup Power Installations: