[c-nsp] loop guard still useful?

[Lee]

On 1/18/16, Saku Ytti <saku at ytti.fi> wrote:
> On 18 January 2016 at 10:57, Michele Bergonzoni <bergonz at labs.it> wrote:
>
> Hey,
>
>> So the dispute does half of what UDLD does, if I got it right.
>
> Ethernet with autonegotiation on should detect unidirectional links
> automatically and go down on both ends at RTT/2 delay.

I remember 100Mb fiber connections on cat5500s could have
unidirectional links, but a quick search gives me this

  http://www.cisco.com/c/en/us/support/docs/lan-switching/spanning-tree-protocol/10591-77.html
  Most recently, fiber FastEthernet hardware implementations have Far
End Fault Indication (FEFI) functions in order to bring the link down
on both sides in these situations.

so apparently 100Mb fiber doesn't have that problem any more.  I don't
think 1 or 10Gb fiber ever did..

Lee