High Latency in T1 Line

[alanleyva]

I have a 13 location network, I have T1 (1.5) lines with ATT for every location, since a while I have noticed that sometimes the voice degrades a lot, it happens mainly in the afternoon, when it happens I have tested pinging another addresses inside my VPN, 12, 13 ms is a good reply time in my network, what I discovered is that the replies time goes crazy, I have seen 300, 400, 500 and even 1000 ms for the 32 bytes, this solution has worked for many years but now is not reliable anymore, any thought of what could be happening?

Reply from 192.168.8.1: bytes=32 time=18ms TTL=64
Reply from 192.168.8.1: bytes=32 time=12ms TTL=64
Reply from 192.168.8.1: bytes=32 time=12ms TTL=64
Reply from 192.168.8.1: bytes=32 time=12ms TTL=64
Reply from 192.168.8.1: bytes=32 time=121ms TTL=64
Reply from 192.168.8.1: bytes=32 time=56ms TTL=64
Reply from 192.168.8.1: bytes=32 time=333ms TTL=64
Reply from 192.168.8.1: bytes=32 time=12ms TTL=64
Reply from 192.168.8.1: bytes=32 time=13ms TTL=64
Reply from 192.168.8.1: bytes=32 time=32ms TTL=64
Reply from 192.168.8.1: bytes=32 time=13ms TTL=64
Reply from 192.168.8.1: bytes=32 time=12ms TTL=64
Reply from 192.168.8.1: bytes=32 time=13ms TTL=64
Reply from 192.168.8.1: bytes=32 time=13ms TTL=64
Reply from 192.168.8.1: bytes=32 time=12ms TTL=64
Reply from 192.168.8.1: bytes=32 time=12ms TTL=64
Reply from 192.168.8.1: bytes=32 time=16ms TTL=64
Reply from 192.168.8.1: bytes=32 time=13ms TTL=64
Reply from 192.168.8.1: bytes=32 time=256ms TTL=64
Reply from 192.168.8.1: bytes=32 time=13ms TTL=64
Reply from 192.168.8.1: bytes=32 time=16ms TTL=64
Reply from 192.168.8.1: bytes=32 time=12ms TTL=64
Reply from 192.168.8.1: bytes=32 time=12ms TTL=64
Reply from 192.168.8.1: bytes=32 time=14ms TTL=64
Reply from 192.168.8.1: bytes=32 time=14ms TTL=64
Reply from 192.168.8.1: bytes=32 time=12ms TTL=64
Reply from 192.168.8.1: bytes=32 time=14ms TTL=64
Reply from 192.168.8.1: bytes=32 time=14ms TTL=64