The MPLS WG Archive

["Adrian Farrel" <adrian@olddog.co.uk>]

Hi Mitchell

> This maybe totally stupid, but what about a walking
> ping when dealing with "a subset". Only the ping reciepents
> respond if the TLL is decremented to 0, or the equiv.
>
> Or only the respondents within the walking radius
> responds..
>
> So, it would be something like:
>
> ping walk 5 : where 5 is the radius of the ping
>
> This way you can build a explicit source route, if
> the ping reciepents are somewhat stable, and/or...
>
> And gives you a different subset of responders.

I'm not completely clear about what you are suggesting.
There are two possiblities in what you are saying.

1. We send echo requests to the tree with TTL 1, then 2, then 3, etc.
When the TTL expires for any single request, every LSR that is processing
the request responds.
This is the technique described in the LSP Ping draft and extended in the
P2MP LSP Ping for traceroute function. As you suggest it can be used to
build an "explicit source route" or ERO.

2. OTOH you might be suggesting that we send echo requests to the tree
with TTL 1, then 2, then 3, etc.
When the TTL expires for any single request, every LSR that is processing
the request responds if and only if it is a leaf of the tree.
Such a technique might help stagger the responses from multiple leaves,
but I suspect that the problem of managing "silent" hops in the tree would
make this unworkable.

Cheers,
Adrian


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