Existing traffic stops suddenly, and changing of interface MTU resolved it.

[P.Kumar089697]

Hi Community, 
I have query related to the current issue. I need to dig it more and want to know about the behavior of issue.
Issue: one of the public website is stopped working suddenly, and user unable to access the site.
Behavior is previously it was working and the same MTU value, but its stopped.
I got to know with the counter below client hello not fit in one packet:

ssl_partial_client_hello 103 1 warn ssl pktproc Number of ssl session with client hellos that do not fit in one packet ssl_partial_client_hello_sni 61 0 info ssl pktproc Number of ssl session with sni parsed from partial client hello ssl_partial_client_hello_no_sni 42 0 info ssl pktproc Number of ssl session with no sni parsed from partial client hello 

Want to know the reason why it start suddenly, what can be the reason behind this.
Can any help me to understand why it was working before with the default MTU value ?

[Raido_Rattameister]

You host user or server?

What was interface MTU before and what did you change it to?

Did you change internal or external interface MTU?

[P.Kumar089697]

I host user, and previous MTU was default that is 1500, once I decrease it 1350, its start working.

But what was happened its stop working on 1500 MTU and start working at 1350 MTU

I have changed the MTU at LAN interface side only.