SharePoint: Transport-level error has occurred when receiving results from the server

Problem

SharePoint 2016 (on-prem) farm had weird issues on few application and WFE servers. Namely, the servers couldn't connect to SQL Server, but ULS logs showed error:

Unknown SQL Exception 64 occurred. Additional error information from SQL Server is included below.  A transport-level error has occurred when receiving results from the server. (provider: TCP Provider, error: 0 - The specified network name is no longer available.)

When testing the connection with UDL file, the behavior was also strange, i.e., when testing the connection to server without defining any specific database, the test succeeded:

Also when defining a specific database, the test succeeded:

However, when attempting to list the databases by expanding the "Select the database on the server" dropdown, there was first "Unspesified error" error:

Followed by error "Microsoft Data Link
Login failed. Catalog information cannot be retrieved.":

Solution

Solution was (eventually) to fix the Jumbo Packet setting on the servers having the issue. Other servers had value 1514, while the problematic servers had value 9014 and changing value to 1514 made all the SharePoint servers immediately connect to SQL Server, and also the UDL DB listing started working.