Thread Links Date Links
Thread Prev Thread Next Thread Index Date Prev Date Next Date Index

Re: Does Ten-Gigabit Ethernet need fault tolerance? (nonredundant NICs)


At 8:28 PM 99/7/27, Roy Bynum wrote:
>You wrote "There is no problem with parts of the segment having non-redundant
>NICs,".  With a full duplex, point to point link, there are only two
>interfaces, one
>at each end.  It was my understanding that 10GbE was to be a full duplex,
>point to
>point implementation only.  Within a data switch, at layer 2 or layer 3,
>links to multiple systems can be implemented, creating virtual segments;
>but each
>10GbE link is itself, full duplex, point to point.  It is the single 10GbE
>link that
>I am writing about when I refer to fault tolerance.  I am not writing
>about fault
>allowance at the virtual segment level, as in the case of allowing for
>nodal data
>switch failures within the virtual segment.  Are we talking about two different

I suspect you are correct.  In my nomenclature, a "link" is bidirectional,
having two independent fibers, and connects NICs to hubs.  It seems to me
that when one speaks of a link in GbE, it's the path from NIC to NIC (via
an unnamed hub); the hub is assumed.  In any case, we will need to arrive
at a common and self-consistent nomenclature.

Is 10GbE expected to have hubs, or will all links be physically point to
point between pairs of NICs?  One would expect that there will be hubs in
10GbE as well, as inability to handle anything but pairs of NICs would be
pretty limiting.

So, my mental picture of 10GbE has been a star topology, with a hub in the
center and the NICs at the points of the star, with duplex fiber-optic
links connecting each NIC to the hub, one link per NIC.

In RTFC, one has the same number of NICs as before, but there are two (or
more) hubs, each hub having its own star of links to those NICs.  Each NIC
now has multiple duplex ports, one per hub.  The whole affair, containing
NICs and hubs, is called a "segment".  Bridges between segments are
two-headed NICs, one head per segment, even if the bridge NIC happens to be
physically colocated with a hub.

If one of the NICs is connected to only one hub, and nothing is broken,
rostering will cause that NIC to be included in the segment, and thus to be
accessible to other NICs.  This behaviour is automatic.  If a NIC having
only one hub connected breaks or loses contact with that hub, rostering
will isolate that unfortunate NIC.  This behaviour is also automatic.


>Joe Gwinn wrote:
>> Roy,
>> At 9:12 PM 99/7/24, Roy Bynum wrote:
>> >
>> >Does RTFC allow a minimally trained individual to simply plug two fiber T/R
>> >pairs into the 10GbE interface to implement fault tolerance and if a
>>second T/R
>> >pair, parallel to the first, is not plugged in the fault tolerance is not
>> >implemented?  This will be the simplest and most common implementation
>> Yes, this will work, by design.  The rostering algorithm will just treat
>> the missing path as broken, and press on.  There is no problem with parts
>> of the segment having non-redundant NICs, although those NICs will be cut
>> out of the segment if those NICs or their links fail.
>> Joe