john,

While I/we have tested the M5/M10 series from Juniper we did not role them out in the field. The Mid plane design
is / was a standard design to seperate packet, cell, or tdm processing from the electrical or optical interfaces. You would have to
replace the interface card and cables more often than the processing modules and you can have the same processing module
drive one or more interface cards.

Usually the mid plane is passive or only has passive (resistor, capacitor, etc..) components on it for signal enhancement. If the board insertion and extraction hardware works than bent pins are supposed to be eliminated or at least minimized. Some designs allow you to insert the board and then when the pins are lined up apply pressure to positively hold them together. I am not as familiar with the "new" high denisty board interconnect hardware but since tolorances are tighter they have to address alighment, insertion and extraction issues to a greater degree.

In the lab enviroment we swapped cards many more times than you would in an operational system and did not have a
problem. I presume that the cards are hot swappable ( we tested alot of hardware) and if that is the case then there needs to be hardware to ground before circuit contact to not allow floating voltages to destroy the cards cmos and other static sensitive electronics.

>From a Service perspective I would reccomend one or more spare chassis and or fully loaded and configured systems for maintenance. The diagnostics usually allow you to trouble shoot to the board level or power supply level and replace the FRU (field replaceable unit), but to improve mean time to repair I would swap out and I would not do a major repair like a midplane replacement in a POP without space and proper test equipment.

john (I Still Don't kNow) lee

john@chagresventures.com wrote:
 
Been looking at a M5/M10 box and have noticed its
not real easy (unless I'm blind) to replace the 
mid-plane.

Thus I'm wondering what people in the field have 
experienced with respect to mid-plane failures.

1. Bent or broken pins on the PIC side

2. Circuit failures


My eval of this product is for a client and their
infrastructure needs.


Other bits of learned wisdom also excepted and 
encouraged :)

Thanks

john brown