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Home Technical  V.92 Trouble:  Interoperability

V.92 Trouble: Interoperability
(Updated 26-Apr-03)

V.92 and V.44 became International standards in November of 2000, and the first "V.92" modems were sold in November of 2000. As of late April 2003, the V.92 feature that provides for higher upstream rates is still basically non-functional: Cisco, Lucent, and Nortel server modems do not support PCM upstream at all. Patton and Commworks do, but the maximum PCM upstream rate you might achieve is 36kbps - 25% lower than the standard's 48k maximum. Some in the industry doubt 48k upstream is achievable. A consumer advocate might find much of the advertising for V.92 to be deceptive: modems or ISPs promising "...up to 48Kbps..." upstream should disclose that this is a future, possibly unachievable capability.

V.92/V.44 drivers for both client and server modems have undergone revisions to resolve connectivity problems. Some interoperability issues are still being addressed. Some ISP V.92 upgrades can cause connectivity problems for users with older V.90 modems, as well as users with new V.92 modems. The most serious problem is inability or difficulty in completing handshake and getting a CONNECT. Updating your modem driver may help in these situations. There are cases where V.44 fails to work between client/server modems which may result in a CONNECT but no data, a failure of the handshake, or a CONNECT without error correction. (Disabling V.44 on the client modem, or updating the modem driver might help with this problem.)

Modem-on-hold (MoH) is the most compelling feature for many users. Many V.92 modems are sold without the necessary MoH software. The drivers that come with the modem may also need updating to properly handle MoH. There is an issue with V.92 servers that have MoH disabled: when a call comes in, the server denies a MoH request and disconnects instead of allowing the client to decide whether to ignore the call or accept it and disconnect. (Level3, the only national V.92 network provider disables MoH by default. Level3 customers include the largest national ISPs - AOL, MSN, Earthlink, etc., and all major Level3 customers except United Online (NetZero/Juno) have requested MoH be disabled.)

Users getting reduced handshake times (Quick Connect) are hard to find. (Again, most modems will need a later driver than is shipped with the modem, and some modems might need extra initialization commands to enable the feature.) There are cases where quick connect fails resulting in a longer handshake, failure to connect, reduced connection speed, or connection without error correction. Quick Connect may need to be disabled. [Feedback: Do you get quick-connect?]

V.44 compression is working for many V.92 client-server connections. The performance difference can be impressive with the right kind of data transfer. Only controllerless modems (DSP and Softmodems) are "ready" to benefit: most Windows PCs cannot support real serial port data rates above 115.2k without a high-speed serial card.

The bottom line: The only difference in V.90 vs a V.92 modem is software. Nearly all client modems being made today are V.92. New systems that bundle a modem are almost always V.92 now. ISPs are faced with a more complicated choice. Upgrading to V.92 will almost certainly cause some problems for some customers; and, the ISPs vendor may require expensive service contracts or hardware upgrades. 

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