[j-nsp] auto-negotiation on 1000BASE-X ports

[Olivier Benghozi]

Hi Martin,

> by flow control you mean the 'regular' Ethernet flow control using the
> PAUSE frame mechanism?

Yes: the peers can negotiate its use, and in what direction.
In that case, such explicit flow control replaces the old school "Back pressure" mechanism (a switch can send a fake ethernet collision signal if it wants to slow down what it receives).


> I wasn't aware that remote fault detection is part of the
> autonegotiation. Thanks! I tested this out with two directly connected
> Juniper M series routers and it works exactly as you described.
> However, as I understand, JUNOS allows to enable auto-negotiation
> while at the same keep the local interface online despite the fact
> that link is unidirectional. I mean the [ auto-negotiation
> remote-fault local-interface-online ] and [ auto-negotiation
> remote-fault local-interface-offline ] options. For some reason, this
> did not work: http://s8.postimg.org/nd5zyo0mr/autoneg_and_remote_fault.png
> As you can see, both in case "Remote fault" "Online" or "Offline", the
> local interfaces go down if link becomes unidirectional. Any comments
> on this behavior?

From what I understand from the very-poorly-written-by-alien-monkeys Juniper documentation ( http://www.juniper.net/techpubs/en_US/junos12.2/information-products/topic-collections/config-guide-network-interfaces/book-config-guide-network-interfaces-ethernet.pdf ), pages 330 & more...
Well, I don't understand what they meant in this piece of crap, obviously not expected to be ever read. The most funny is when a little * points to just nothing, in their crappy doc.

However in http://www.juniper.net/techpubs/en_US/junos/topics/reference/configuration-statement/auto-negotiation-edit-interfaces.html , I understand that this might be designed to locally simulate a remote-fault received from the other peer, which would be really useless. Or in fact, maybe to send a remote-fault signal to the other peer, which could be more useful. Or not.
Is this consistent with your tests?

Anyway, it doesn't look like it's expected to allow an unidir link with autoneg activated (which by nature needs both speakers to be able to communicate together, so it makes sense to me).


regards,
Olivier