Subject: Re: draft-ietf-pppext-sonet-ds-00

From: "William Allen Simpson" <[email-masked]>
Date: Wed, 26 Nov 97 23:39:53 GMT

Note that Stuart did not include most of my comments and questions.

> From: Stuart Venters <[email-masked]>
> >I do not understand the latter "level control" with regard to "constant
> >valued bits".  Reference?
>
> For a reference i would suggest looking at Sonet transmitter data sheets.
>
Which ones?  Specifically?  I have a pile from 1991 and 1992....

> "The module input will require a 50% duty cycle or dc balanced signal
> for normal operation.  Failure to provide this may cause the optical
> parameters to move out of specification.  Extinction ratio and duty
> cycle distortion may be affected.  The low frequency cutoff of the
> transmitter control loop is < 20Khz."
>...
> It looks to me like fully compliant transeivers on
> the market (from the best vendors) are not designed to support low frequency
> components in the bit stream.  I suspect this is par for the Sonet
> infrastructure you are targeting to run over.
>
less than 20KHz???

That's many orders of magnitude less than we are talking about here....

> Do you agree that given the right nasty packet, RFC-1619 with prophylactic
> octet stuffing causes on the fiber bit streams with more low frequency
> components than any other current official Sonet/SDH payload?
>
No, I do not agree.  I do not see how any single user could possibly
affect that much data on any multiuser link.  And if it is a single user
so completely dominating his own link, the only data loss would be that
user's data.

Moreover, it is not relevant.  We are talking about complete failure of
the private link, as indicated by LOS.  Not happening.

[email-masked]
    Key fingerprint =  17 40 5E 67 15 6F 31 26  DD 0D B9 9B 6A 15 2C 32

---

From: Stuart Venters <[email-masked]>
Date: Wed, 26 Nov 97 21:17:48 CST

Bill,

> Note that Stuart did not include most of my comments and questions.

   Noted, but the reasons are 1) you are wearing me down, and 2) I
   feel that things will go faster if the scope of the discussion
   narrows until we get to common ground and then look and see
   what issues are left.

> Which ones?  Specifically?  I have a pile from 1991 and 1992....

 Again, the point was that they were _all_ like this.  It appears to be
 the way things are done.  However, the data sheets I looked at today 
 were the current Amp, Lucent, and Hp single mode OC-3 units with Pecl 
 interfaces but no clock recovery.

> That's many orders of magnitude less than we are talking about here....

  Consider an atacker sending a 1500 byte packet thru which results in a 
  fiber bit stream with a one sprinkled every two or three bytes (overhead
  bytes excluded of course).  The nasty pattern detector would be none
  the wiser, but the duty cycle and transition density would be way off
  for 80uS.  This seems sufficient time for something with a
  50uS time constant to be affected.

  What's wrong with this attack senario?

  Sincerely,
  Stuart Venters
  (The views expressed are not necessarily those of my employer.)