Telephony Common Questions, Part
By Todd Ogasawara
These questions are some of the most frequently asked questions (FAQ) found on the MSN Computing Central Telephony Forum's Modem Discussion Newsgroup. Please join the discussion about 56K modems, fax modems, and voice modems in that newsgroup.
What is the 56K modem protocol standard?
The 56K modem protocol standard is named V.90. You may see 56K modems that support the older proprietary K56flex (Lucent/Rockwell) or x2 (3Com/USRobotics) protocols. V.90 replaces both K56flex and x2. You should always look for a modem that supports V.90.
A duplex modem operating at data signaling rates of up to 14,400 bit/s for use on the general switched telephone network and on leased point-to-point 2-wire telephone-type circuitsV.34
A modem operating at data signaling rates of up to 33,600 bit/s for use on the general switched telephone network and on leased point-to-point 2-wire telephone-type circuitsV.90
A modem designed for connections which are digital at one end and have only one digital-to-analogue conversion. Download speeds of up to 56,000 bits per second (bit/s) are possible, depending on telephone line conditions, with upload speeds of up to 33,600 bit/s. The International Telecommunication Union Telecommunication Standardization Sector (ITU-T) announced the V.90 56K modem designation in a Feb. 7, 1998, press release, when the technical specification was announced. The V.90 protocol was formally adopted by the ITU-T on September 15, 1998.
There are a number of possible reasons. However, the most likely reason is that your ISP is not able to accept the connection some percentage of the time. According to Inverse Network Technology, even the best ISPs have an evening call failure rate of between 1.5 and 3 percent, based on November 1998 measurements. And seven major ISPs had call failure rates greater than 10 percent.
C|Net and PC World have
published articles that discuss this in detail. You can find
the articles at:
It is important to realize that having a 56K modem does not guarantee a 56Kbps connection. In fact, it is not unusual to consider a connect rate between 36Kbps and 53Kbps as a successful 56K modem connection.
The brief list of possible reasons follow:
It is also important to distinguish between the reported initial connect rate and the actual throughput you see for the life of a session. Throughput is the average bit per second (bps) rate for some given time period (say, the amount of time it takes to download a 4MB compressed shareware file). Throughput can be affected by all kinds of factors, including the load on the FTP or Web server you are trying to access.
You should always check the modem manufacturer's Web site. In fact, it is a good idea to check a manufacturer's Web site before you buy a modem. You can compare how well different manufacturers support their modems by doing so. Click on the Related Links page to find a list of modem manufacturers.