(b) talk to your favorite vendor(s), and ask the vendor(s) to put
a "knob" that would decrement IP TTL by 1 on egress (rather
than copying Tag TTL into IP TTL).
Yakov.
Yakov;
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?
(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. 
This is no reason to raise a harmful alarm.
--Kent
Kent, the "width" of the Internet is a little wider than the
NSFnet days.
- paul
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
years.
(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
http://www.merit.edu/nsfnet/
Historically yours,
--John
You can borrow a frame of our SP/2 to recreate it if you'd like :).
Aside from the TTL issue and worrying about interlopers snooping
a layer 2.5 topology. Was there any thought put into a tool such as
traceroute to follow an Tag/Mpls path.
-pee
Kent W. England wrote:
As I recall, the world didn't end when the NSFNET NSSs were installed and
they decremented TTL twice.
The world didn't end but I have a vague, cobwebby recollection of having
to patch our BSD kernels to use a greater TTL.
One of the nice things going on in the IETF right now is that people are
rethinking many of their assumptions about what goes without saying.
For example, in order for TTL to be effective, not every node needs to
decrement it -- we just need to be sure that no loops can form where it
doesn't get decremented. Similarly, traceroute was a hack from day one
(although a clever one, and over time it even became elegant). If you
want to know underlying hops for a particular subnet, use a tool for
that subnet type -- you don't need to make everything respond to
traceroute.
See you ... Scott