Hello Frank!
Thursday March 19 1998 05:02, Frank Sexton wrote to Bob Juge:
 -=>> /* Quoting Bob Juge to Frank Sexton */ <=-
 DH>> Have a look at an interesting article on the x2 / K56Flex / v.90
 DH>> state of affairs at Boardwatch magazine's Web page:
 DH>> http://www.boardwatch.com/mag/98/mar/bwm24.html
 FS>> I've seen it. It says that x2 is much better than
 FS>> K56Flex. Doesn't mean much now that v.90 is here.
 BJ>> Read it again.
 FS> What are you getting at?
Reread this part of the article:
=== Cut ===
      V.90 STANDARD IMPLICATIONS
      [...]
      But we're persuaded that most of the differences will remain
      proprietary. Basically, V.90 specifies how the modems will
      talk to each other to make complex decisions about how to
      treat the variety of digital networks across the land. And
      this is almost entirely client modem driven.
         [Image]   Broadly, once the two modems have established that
                   they are V.90 modems and can do this trick, the
      client modem uploads a Digital Impairment Learning Descriptor
      (DILD). This basically tells the server modem what type of
      test tone to transmit over the network. The server modem
      dutifully transmits the tone, and the client modem compares
      the received tone to its internal reference tone. The client
      modem uses this comparison to calculate the best data point
      constellation to use and notifies the server precisely what
      constellation configuration to use in transmitting data
      downstream. The upstream link is still the 33.6 Kbps V.34 at
      best.
         [Image]   V.PCM describes how to upload the DILD, what to
                   respond with, and how to communicate the
      constellation. The magic lies in the client modem calculating
      what constellation to use for any given set of digital network
      conditions. This is NOT specified at all in V.90 and will vary
      entirely between US Robotics, Rockwell Semiconductor Systems,
      or Lucent Technologies.
      The result is that we will have interoperable modems compliant
      with the V.90 specification and able to talk to each other.
      But it appears that large disparities in achievable connection
      speeds will depend on which client modem you are using, and
      which server modem you connect to. Our testing would indicate
      these disparities may be enormous - far beyond anything we've
      seen with previous modem standards. In the previous round of
      V.34, the Rockwell chipset was ubiquitous and modem
      performance was fairly level across the universe of available
      modems. V.34 was basically V.34. In the coming world of V.90,
      we would expect to see an almost implausible range of
      operating performance from modems all purporting to be V.90
      compatible. We'll have a standard, but it won't be very
      standard with regard to performance.
      [...]
-+-------------------------------------------------------------------------
  Editor: Jack Rickard - Volume XI: Issue 3 - ISSN:1054-2760 - March 1998
             Copyright 1998 Jack Rickard - ALL RIGHTS RESERVED
                         [Image]Fable Of Contents
=== Cut ===
This part of the article's findings has NOT been disputed.
Bob
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