get traffic Usage of Internet Using SNMP OID

[leo-21]

Hi.
I Used "net.if.in[ifInOctets.2] " with OID of "1.3.6.1.2.1.2.2.1.10.2" to get Traffic Usage of my Internet Interface.
is it the best way to do that?
or should i use sum calculation (maybe ?) to have traffic usage of a month?