This image shows the Connection page in the PuTTY Configuration dialog box, labeled Options controlling the connection.
On the left is a navigation tree labeled Category.

Under Sending of null packets to keep session active, the field Seconds between keepalives (0 to turn off) has the value 5 (five). The field is surrounded by a red border.

Under Low-level TCP connection options, there are two options:
Disable Nagle's algorithm (TCP_NODELAY option) (selected)
Enable TCP keepalives (SO_KEEPALIVE option) (selected and surrounded by a red border)

Under Internet protocol version, there are options for Auto (selected), IPv4, and IPv6.

Under Logical name of remote host, there is a blank field labeled "Logical name of remote host (e.g. for SSH key lookup)":

At the bottom there are buttons for About, Help, Open, and Cancel.