Monthly summary of all device bandwidth

We have the individual site bandwidth statistics but want to summarize it into one number for each total bytes transmitted, to bytes received and total bytes transmitted and received for the month 

SELECT [data].[DisplayName] AS [DisplayName]
     , [data].[Node].[DisplayName] AS [DisplayName1]
     , [data].[Traffic].[ObservationTimestamp] AS [ObservationTimestamp]
     , [data].[InstanceSiteId] AS [InstanceSiteId]
FROM orion.npm.interfaces AS data
WHERE (
          (
               (([data].[CustomProperties].[INT_TYPE]) = ('MPLS'))
               OR (([data].[CustomProperties].[INT_TYPE]) = ('Internet'))
               )
          AND (
               NOT (WeekDay(toLocal(([data].[Traffic].[ObservationTimestamp]))) = 6)
               AND NOT (WeekDay(toLocal(([data].[Traffic].[ObservationTimestamp]))) = 0)
               AND NOT (([data].[Traffic].[ObservationTimestamp]) < AddSecond(36000, DateTrunc('day', toLocal(([data].[Traffic].[ObservationTimestamp])))))
               AND NOT (([data].[Traffic].[ObservationTimestamp]) > AddSecond(79200, DateTrunc('day', toLocal(([data].[Traffic].[ObservationTimestamp])))))
               )
          )
WITH NOLOCK

Requires:

• Custom Properties
  • Entity: Interfaces
  • Name: INT_TYPE
  • Datatype: String