Operation Manual

SFX SERIES USER’S GUIDE
Rev 2.2 66
In addition to the edit fields there are four table row manipulation keys:
Key Description
Add Add the entered information above the table to the table as the last row.
Remove Delete the selected (highlighted) row.
Up If there is more than one row in the table, move the selected row up one row.
Down If there is more than one row in the table, move the selected row down one row.
TTL Translation
The Time-To-Live (TTL) Translation submenu is responsible for maintenance of the TTL Translation Table. This table
defines up to 25 rules that can be used to modify the value of the TTL parameter in the header of an IP packet being
processed by the receiver, regardless of the network interface the packet originated from.
TTL Translation to incoming IP packets is performed by the receiver according to the following rules:
1. Up to 25 rules can be maintained by the table. Rules are executed from the first rule to the last rule, in
sequence. All rules are executed for every packet.
2. IP packets can originate from any of the available network interfaces and are processed by the receiver in
accordance with the data flow in Figure 2- 12.
3. The TTL value of an incoming packet can never be less than 1.
4. The TTL value of an outgoing packet must be greater than 0.
5. The TTL Translation Table rules are applied before the incoming packet is further processed by the IP Stack
(routing and so on). Multiple rules in the table can applied to the same incoming packet, if they are
applicable, and the effect will be cumulative.
6. The operating system always decrements the TTL value of the incoming packet by 1, after the TTL
Translation Table rules have been applied.
7. If an incoming packet has a TTL of 1 when it arrives, and no TTL Translation rules cause the TTL value to
change, it will be decremented to 0. Therefore, it will not be output on any network device, however, it is still
available if an internal application requires it. If not, the packet is discarded.
8. The legal range of TTL values is 1 to 255. Any TTL SET, INC (increment), or DEC (decrement) operation will
be clamped at 1 or 255, if the operation causes a TTL value to occur outside the legal range.
When the TTL Translation submenu item is selected under Data Delivery, the TTL Translation Table page is displayed
for all applicable TTL Translation rules. A sample TTL Translation Table page is shown in Figure 2- 37.