AS55390: the TUSNET Tokyo University of Science network

AS55390 is an internet Autonomous System operated by TUSNET Tokyo University of Science (Japan). Here is what that means and why this number may show up when you investigate a connection on your network.

What is AS55390?

An Autonomous System (ASN) is a block of networks under a single control with its own routing policy on the internet. The number AS55390 was assigned to TUSNET Tokyo University of Science by an RIR (regional internet registry). All traffic entering or leaving that network is announced under this number.

Reach on the internet

AS55390 currently announces 1 IPv4 block(s), totaling about 65.5 thousand addresses (65,536 in all), registered in Japan. Services from TUSNET Tokyo University of Science are reached through these addresses.

What it means to see AS55390 on your network

When you investigate where a connection from your computer or phone comes from (or goes to), you may find AS55390. That means the other end sits on the TUSNET Tokyo University of Science network (Japan). It can be legitimate — a cloud service, an ISP, a CDN — or an unexpected connection worth checking.

How to see every connection and network your devices reach

Tracing one connection's ASN at a time is tedious. Sentinela, by PC Monitor, maps the devices on your network, shows what is exposed to the internet and helps flag suspicious connections and devices — running on your Windows. Meet Sentinela.