endpoint liveness (RE: Do ATM-based Exchange Points make sense an ymore?)

Sat Aug 10 12:52:09 UTC 2002

On Fri, 9 Aug 2002, Lane Patterson wrote:

> BGP keepalive/hold timers are configurable even down to granularity 
> of link or PVC level keepalives, but for session stability reasons, 
> it appears that most ISPs at GigE exchanges choose not to
> tweak them down from the defaults.  

Endpoint liveness may also start to become more of an issue as more
networks choose to private peer, or reach ethernet exchanges, over L2
pseudowires.

When the router at the far end goes away for whatever reason - the router
has really gone away, the MPLS provider in the middle is banjaxed, etc -
this isn't immediately visible to the other end, which will still see
"link up" from the PE.

I think someone (can't remember who, maybe Riverstone) is implementing a
method of dropping link on the ethernet ports at both ends of a pseudowire
if something goes bang in the middle, and end-to-end connectivity fails.

But, how does that work when you may be delivering multiple q-tags on a
single GigE port (for example)? If only one tag is affected, you don't
want to drop link, right?

So, we're back to detection at layer 3, can I ping it, do I have
adjacency, etc.

Some sort of lower-level heartbeat (maybe like OAM), not dependent on IP
reachability, would be a bonus - and it's probably low in the tax stakes,
if it can be made simple enough.

Mike