Uptime and lifetime of #5ESS [Telecom]

One of the computer groups I moderate is the Yahoo "linux"
group. I recently began a thread about ksplice, a method
of updating the kernel while it's running and not requiring
a reboot.
The following copy'n'pasted lines are from an article appearing
in that thread this morning and I thought it worth sharing since
I learned something new from it; author's name is at the end:
> [...]
> > How do you think telephone switching offices are upgraded?
>
> Interesting... I'd always assumed that (at least in modern
> situations)
> they had redundant backups and were just switched as they would in a
> failover scenario...
During normal operation, when a fault is detected things are a
little more complex than that. Normally the system is running a
hot backup with two systems running side by side, in lockstep,
with a "matcher" between them comparing the results of their
calculations. In the event that a mismatch (indicating a fault)
occurs a "fault isolation" program fires up and determines which
unit has failed. The system is then reconfigured so that the
faulty unit is cut out and the two systems share the good one. A
diagnostic program then is run on the faulty unit, the failing
circuit board identified, and a message is printed on the
maintenance console to replace that board. Once a new board has
been inserted the diagnostic is rerun and, if it passes, the
system is reconfigured to use the repaired unit for one side of
the system (going back to the normal configuration).
How effective is this strategy? The specifications for the #5
ESS (Electronic Switching System) require no more than 2 seconds
of down time over the design lifetime of the system -- 40
years. The last statistics I saw indicated that the systems were
actually accumulating less than 1 second of down time over that
40 year period. As I recall, diagnostic and fault recovery
software comprise about 2/3 of the code in the system.
switch everything from the primary unit to the
> backup, upgrade the primary, switch traffic back and then
> upgrade the backup... or something along those lines...
In essence, that is what the retrofit process does. An important
part of the process, though, is translation of any data in memory
from the format in the old generic to that in the new generic,
and not losing any in-progress information during the switch
over. Upgrading the other processor is then a normal memory
mirroring operation (unless the upgrade included hardware changes
as well).
Pretty neat though. Honestly, the more I hang out with the kernel
> guys and hear them talk about it, the more I'm being converted (or
> at least, more accustomed to the idea)
>
> >> Then again, maybe it's just my curmudgeonness...
> >
> > No, just lack of experience! :-) :-)
>
> Haven't heard someone tell me that in a long time :-) heh... but
> yeah, or at least ignorance... thanks for the bit of info though... > pretty neat!
A good while ago the Bell System Technical Journal had an issue
devoted to the #5 ESS (#5 Electronic Switching System) that you
might find interesting.
Rich Strebendt
Reply to
Thad Floryan
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If anyone has a copy of the DMERT (UNIX-RTR) Operating System installation tapes on media (either disk, images, or DAT tape), I am in need of a replacement for my VCDX (Very Compact Digital eXchange). This is the operating system that runs the 5ESS switch (3B20D/3B21D). I am willing to make a decent offer for the media. Please contact n AT mod.net
Thanks.
-Nivenh
Reply to
nivenh
If anyone has a copy of the DMERT (UNIX-RTR) Operating System installation tapes on media (either disk, images, or DAT tape), I am in need of a replacement for my VCDX (Very Compact Digital eXchange). This is the operating system that runs the 5ESS switch (3B20D/3B21D). I am willing to make a decent offer for the media. Please contact n AT mod.net
Thanks.
-Nivenh
Reply to
nivenh
I could only find one article on No. 5 ESS, published in November, 1982. While it focused on the system's database, it did provide a general picture of the system. It mentions things like "tuple-retrieval primitives".
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The Nov 1982 issue has several articles on database processing.
(The Sept 1964 issue is about No. 1 ESS).
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Reply to
HAncock4

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