how to calculate total sum of ip.len field for wireshark trace

You can use TShark.
In this example the interval is 30 seconds.

$ tshark -r test.pcap -q -z io,stat,30,COUNT"(tcp.len)tcp.len",MIN"(tcp.len)tcp.len",MAX"(tcp.len)tcp.len",AVG"(tcp.len)tcp.len" > tcp.len.txt

Output:
IO Statistics
Interval: 30.000 secs
Column #0: COUNT(tcp.len)tcp.len
Column #1: MIN(tcp.len)tcp.len
Column #2: MAX(tcp.len)tcp.len
Column #3: AVG(tcp.len)tcp.len

                |   Column #0    |   Column #1    |   Column #2    |   Column #3  
Time            |          COUNT |            MIN |            MAX |            AVG
000.000-030.000               802                0            29193              354
030.000-060.000              1231                0            36500              397
060.000-090.000              1478                0            37478              342
090.000-120.000               418                0             2372              232