The MPLS WG Archive

[Curtis Villamizar <curtis@workhorse.fictitious.org>]

In message <4F9E13BCC53ED411A629009027E8D00C043336E0@msg001.dcat.ops.broadbando
ffice.net>, afarrel@movaz.com writes:
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> 
> > > I find...
> > > > There appears to be a school of thought where it is 
> > > > deemed beneficial to keep forwarding state intact 
> > > > in only very limited cases such as midnight 
> > > > controlled reload of routers for purposes such 
> > > > as software upgrade.
> > > ...odd.  When a line card fails I should like to be 
> > > able to swap to a new card and continue forwarding 
> > > data with only a very short (10s of ms) break.
> > 
> > When a line card fails, that line card will still be in the box for at
> > least a few minutes, more likely the better part of an hour, maybe
> > longer.  I don't know of any technician that can swap a line card in
> > 10 msec.  I also don't know of any line card that can reboot in 10
> > msec.  When a line card fails if there is a TE tunnel and
> > local-protect on the TE tunnel, then the switch over is very fast.  If
> > it is LDP without TE or TE without local protect, the 10s of msec is
> > very likely not acheived.  That has absolutely nothing to do with
> > LDP-FT so I don't see why you brought it up.
> 
> It has everything to do with LDP FT.
> One of the key aims is to be able to switch "seamlessly" to another card
> _that_is_already_in_the_box.
> If the failed card was running LDP you must preserve protocol states etc.
> If the failed card was a line card not running LDP, you must handle the
> failed TCP connection (i.e. LDP session) and re-instate it through the
> replacement card.


I see your point.  This is similar to the redundant control plane
case.  See my prior mail on that and why I suggested per peer
configuration of this option.

Curtis