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Reducing the RADIUS of the Internet

Posted: Wed Jan 10, 2018 11:17 am
by bscloutier
Beginning with JANOS v1.6.4 you will be able to adjust the Time-To-Live (TTL) parameter used by the network stack.

The IpConfig/TTL Registry key defines the lifespan of a network packet. The time-to-live value is a kind of upper bound on the time that an IP datagram can exist in the Internet system. The value is reduced with the passage through a router. If it reaches 0 the packet is discarded. The default value has been increased to 128 from the value of 64 used prior to JANOS v1.6.4.

The TTL setting can be considered to limit the maximum radius (in terms of hops) of the network within reach of the JNIOR. The default setting should allow packets to reach the far end of the globe. A low setting would limit access to the unit as only those in the local vicinity could communicate. In this respect the TTL setting can be used to improve device security.

A very low setting of 1 or 2 would constrain the JNIOR to the local network. One must consider the need to reach Doman Name Servers (DNS) and Network Time Servers (NTP). There may also be the requirement for email transfers wherein the JNIOR needs to reach out to a SMTP Server. To help determine the minimum setting you may be able to use your PC's TRACERT command to detect the hop count involved in reaching those destinations. The JNIOR does not support a route tracing function.