Asus AM604g - Manual (Page 41)

Tone Settings
The frequency band of ADSL is split up into 256 separate tones,
each spaced 4.3125 kHz apart. With each tone carrying separate
data, the technique operates as if 256 separate modems were
running in parallel. The tone range is from 0 to 31 for upstream
and from 32 to 255 for downstream. Do not change these settings
unless instructed by your ISP.
Port Mapping
Port mapping is a feature that allows you to open ports to allow
certain Internet applications on the WAN side to pass through the
firewall and enter your LAN. To use this feature, mapping groups
need to be created. To do this, follow the below instructions—
1. Click on the Add button as displayed below.
ASUS 4-Port Wireless Ethernet Router
User Manual
40
Version 1.0
Document #: BD-AU0014-10