The following table shows the initial TTL values that are used by a number of operating systems. Why should you care? Well when you are looking at a trace it is sometimes not obvious where the protocol analyzer was in relation to the hosts of interest. By looking at the TTL values recorded by the analyzer and knowing the initial TTL value you can get an idea of the "distance" between the end points and the analyzer. I gleaned the information in this table from looking at traces and when possible system documentation. I have also stolen shamelessly from other sources on the web.