Why OSPF?

Positives and negatives

OSPF is an interesting choice as an in-neighborhood routing protocol because of its ease of setup (auto convergence, no ASNs), and how ubiquitous it is -- nearly every cheap and expensive commercial and open device supports it. These two positives alone make OSPF worth considering.

On the down-side, it is not specifically designed for an adhoc mesh, it trusts blindly, and has very few tuneables. Additionally, there are a few technical challenges such as the lack of link-local address use, only advertising connected networks (not summaries), and some common defaults on various platforms.  

Many of these challenges can be overcome by taking some care to make good choices for options when setting up a network.

OSPF Selection

NYC Mesh has chosen to use OSPF as the standard mesh routing protocol of choice. This may be a controversial choice, as _most_ mesh networks in Europe are using custom mesh routing protocols, or encrypted routing protocols. We have chosen this path because:

• OSPF is an open-standard with implementations on many platforms, open and closed, including cheap older professional switches
• OSPF hugely reduces the burden for installers and members to maintain the network
• OSPF cooperates well with other protocols such as BGP
• Other Mesh networks (CTWUG in South Africa for example) have scaled OSPF to 1000+ routers.