[rrg] Why a host-based solution does not necessarily add signalling load

[Brian E Carpenter]

Scott,

> As an endpoint, you are interested in reachability of specific
> endpoints.  You don't care if a whole prefix is reachable, if the
> particular endpoint isn't reachable within that prefix.  So if you
> delegate liveness monitoring to an agent, you are asking it to monitor
> specific locators. 

The e2e principle seems to make it clear that, ultimately, liveness is
the endpoint's responsibility, but that is usually interpreted as a
statement about what the transport layer or above should do. And they
already do it, 100% independently of what we do in layer 3 and below.
I think that limiting layer 3 liveness detection to the prefix level
(except presumably in the case of Mobile IP) is a perfectly good
engineering compromise, unless we're planning to repudiate [Saltzer].

    Brian

[Saltzer] End-To-End Arguments in System Design, J.H. Saltzer,
   D.P.Reed, D.D.Clark, ACM TOCS, Vol 2, Number 4, November 1984, pp
   277-288.