TCP MSS adjustment for NAT services

This feature provides MSS adjustment for TCP packets to be translated by NAT services.

The configuration steps are as follows:

1. Create a NAT-group used for NAT services with MSS adjustment.

   config>isa
      nat-group 1
         active-mda-limit 2
         mda 1/1
         mda 1/2
   

2. Create a NAT-policy that also adjusts MSS.

   config>service>nat
      nat-policy "policy-for-mss-adjust" crate
         tcp-mss-adjust 1452