dual router vs. single "reliable" router

John L Lee johnllee at mindspring.com
Fri Apr 11 16:41:43 UTC 2003

The report seermed to like the boxes from the companies that Alcatel 
bought. On this side of the pond they
did not get alot of traction.

 From my experience with a "large" Cisco network besides the normal too 
many fingers on the CLI to the router there were about one to
 two hardware failures a week on the big "C" devices. Most of these were 
interface cards but some were control cards on switches.

As long as you did not overrun the 12xxx series with too many BGP 
updates per unit of time they as a box were stable.

To calculate "99.99" per cent uptime you -

Define scheduled down time as any maintanance that can be done after 
giving the worldwide network at least five minutes notice of major
network outages ...

Define the device to be up as long as you can secure telnet into the box 
and get a command prompt -

Ignore BGP, routing or forwarding tables or any other routing issues 
because "Up-Time" means the box is up not that it is doing any usefull 
work ...

And finally go back to a "real person" deterministic protocol like "ATM" 
with PNNI and UNI so you
"know" when the network is down and do not have to guess ... My layer 
two network ran for two years with no hardware or routing issues ...

The other minor technical issue is that say you can calculate uptime on 
a "router" how do you calculate up time on the network? ... Since
just because one router is down the "network" is still up so individual 
up-time for a router in an IP network may only affect SLAs for customer
directly attached to it.

John (It Suites Dennis's Needs) Lee

David Barak wrote:

>Okay, I'll bite...
>the mentioned file,
>seems to be fluff to me.
>There are many assumptions and statements about
>reliability, but the methodology of how the numbers
>were reached is not present.  If one assumes that one
>has a router which fails very rarely, this would
>dramatically affect network design.  However, this is
>an assumption, not a conclusion.  The assumption of
>the paper is that the Alcatel box has ultra-low
>failure rates, while the Juniper and Cisco boxen have
>relatively high failure rates.  Personally, before I
>let something like this influence my buying/design 
>decisions, I'd want to see some serious raw data...
>David Barak
>-fully RFC 1925 compliant-
>Do you Yahoo!?
>Yahoo! Tax Center - File online, calculators, forms, and more

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