North American Network Operators Group

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Re: IP over SONET considered harmful?

  • From: John G. Scudder
  • Date: Mon Mar 23 16:05:41 1998

At 2:57 PM -0800 3/20/98, Kent W. England wrote:
>As I recall, the world didn't end when the NSFNET NSSs were installed and
>they decremented TTL twice. Weren't they changed to decrement once,
>appearing as one instead of two routers?

You got this part right.  I thought we had heard the last of the TTL
whining then.  Apparently we haven't made much progress in the last eight

>(For those who don't remember the NSFNET "routers" they consisted of an IBM
>RS6000 attached to each of several T1/T3 interfaces, interconnected across a
>FDDI with a route server. Nine RS6000s in all. 200 amp service required. :-)

But this part is wrong.  The description above is kind of a combination of
the T1 NSS (rack of RTs, each RT services at most a single T1 or Ethernet,
they talk to a route processor) and the T3 NSS (RS/6000 with autonomous
port cards, pretty similar to any modern router).

There's a half-decent description of the NSS architecture at

Historically yours,


John Scudder                        email:  [email protected]
Internet Engineering Group, LLC     phone:  (734) 213-4939 x14
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