Check Point UTM-1 Edge User Manual page 154

Using Internet Setup
In this field...
Shape
Downstream: Link
Rate
Advanced
External IP
MTU
140
Do this...
Select this option to enable Traffic Shaper for incoming traffic. Then type
a rate (in kilobits/second) slightly lower than your Internet connection's
maximum measured downstream speed in the field provided.
It is recommended to try different rates in order to determine which one
provides the best results.
Note: Traffic Shaper cannot control the number or type of packets it
receives from the Internet; it can only affect the rate of incoming traffic by
dropping received packets. This makes the shaping of inbound traffic
less accurate than the shaping of outbound traffic. It is therefore
recommended to enable traffic shaping for incoming traffic only if
necessary.
For information on using Traffic Shaper, see Using Traffic Shaper.
If you selected PPTP, type the IP address of the PPTP client as given by
your ISP.
If you selected PPPoE, this field is optional, and you do not have to fill it
in unless your ISP has instructed you to do so.
This field allows you to control the maximum transmission unit size.
As a general recommendation you should leave this field empty. If
however you wish to modify the default MTU, it is recommended that you
consult with your ISP first and use MTU values between 1300 and 1500.
Check Point UTM-1 Edge User Guide