Your Internet service provider may use either X2 or K56 Flex modems to provide access to the Internet. Your AirPort Base Station connects to either modem type. However, you can only get the maximum connection speed when those modems have been updated to the V.90 protocol.
The modem in the AirPort Base Station, like those of in iMac and PowerBook computers, is K56 Flex V.90 compliant. It connects to an X2 type modem whether or not the X2 modem is V.90 compliant.
If the X2 modem has been updated to the V.90 specification, connection speeds should approach the FCC-authorized maximum of 53 Kbps. But when an X2 modem is not updated to V.90, connection speeds are typically 33.6 kilobits per second (Kbps) or slower.
For additional information on the V.90 specification, please see:
Article 30734: "
V.90 Protocol: Connectivity Discussion"
Additional Information
Immediately after a modem answers a call from another modem, the modems negotiate at what speed they will communicate. Typically each modem will attempt to communicate using a preferred standard at the highest speed possible. For the base station modem that is V.90 at 53 Kbps.
When the other modem does not support a particular protocol standard the modems begin slowing down until a mutually acceptable protocol is found. If V.90 is not available, the base station tries K56 Flex. The next protocol it would try is V.34.
To force the modem in the AirPort base station to begin connection negotiation at V.34 follow these steps:
1. Open the AirPort Admin Utility.
2. Click the Internet tab.
3. Choose Modem (V.34) from the Connect pop-up menu.
4. Click Update.
Note: Wireless Internet access requires an Internet service provider (fees may apply) and AirPort (or AirPort-compatible) wireless Ethernet card and base station. Some ISPs are not compatible with AirPort. For more information, see technical document 106590: "
AirPort: Requirements for Wireless Internet Access"