[trill] TRILL OAM Requirements: Connectivity

[Thomas Narten <[e-mail]>]

draft-tissa-trill-oam-req-00.txt has the following definition:

>    Connected: The term connected is used to indicate reachability; RB2
>    is connected to RB1 implies that RB2 is reachable from RB1.

This is an unituitive definition to me. In my mind, "connected" means
two device are (essentially) separated by a wire. Or, a node is
"connected" to a network. I.e,. the two nodes are neighbors.

Where does this definition of "connected" come from? Is this taken
from somewhere else? Or is this a new definition for TRILL OAM?

Why not use a term like "reachable"?

Later, one of the requirements is:

>    OAM MUST have the ability to verify an RBridge RB1 is connected to a
>    specific RBridge RB2.

Given the above defintion, the usage of the term "connected" above is
murky to me. The definitions section uses "connected" in a much
broader sense than two neighbors being directly attached.

Is the above requirement that RB1 be able to verify it is a neighbor
of RB2 (and has connectivity?)?

Or, if the requirement is testing connectivity between arbitrary RBs,
how is that different from other requirements that relate to path
verification?

>    OAM MUST provide functions that enable an RBridge to perform a
>    Continuity Check to any other RBridge over a specified path or a set
>    of paths.

This section uses "continuity check", which seems like a more precise
term than "connected". 

Thomas