[cisco-nas] v90 vs v92

[Aaron Leonard]

> hi all,

> quick question, if I may.

> we have a bunch of v.90 modems in AS-5200's. Is there any clear advantage to
> buying new boxes ?

If you're only interested in doing dialup modem stuff, then the
main advantage to newer boxes is that the AS5200s are dead-ended
featurewise in 12.1/12.1AA - so with newer boxes you can run current IOS.

> What's up with v.92
> - is PCM upstream implemented yet ?
> - what is the volume of client v.92 modems out there ?

Here's the scoop with the newer modem protocols ...

- compression
  V.44 really is (somewhat) better than V.42bis.  With NextPort
  platforms (AS5350/AS5400/AS5850) you can get as much as 400k
  throughput with highly compressible data over V.44 over a modem
  call.  MICA platforms are limited to around 200k and Microcom
  56k modems are limited to 92k.  (Of course, most big data that
  Internet users download tends to be pre-compressed, in which
  case performance would be basically the same with Microcom vs.
  MICA vs. NextPort.)

- V.92
  - We (still) don't support PCM upstream.  The evidence from the
  few vendors/sites that have implemented PCM upstream is that it
  doesn't actually add any net improved performance.
  - V.92 Quick Connect does however add a real improvement in 
  training time, and is widely implemented
  - V.92 Modem on Hold does work

Aaron