RFC 2498 (rfc2498) - Page 2 of 10

IPPM Metrics for Measuring Connectivity

RFC 2498        IPPM Metrics for Measuring Connectivity     January 1999


 +    Using these metrics, an analytic metric, called Type-P1-P2-
      Interval-Temporal-Connectivity, will be introduced to define a
      useful notion of two-way connectivity between two hosts over an
      interval of time.
 +    Methodologies are then presented and discussed for estimating
      Type-P1-P2-Interval-Temporal-Connectivity in a variety of
      settings.

   Careful definition of Type-P1-P2-Interval-Temporal-Connectivity and
   the discussion of the metric and the methodologies for estimating it
   are the two chief contributions of the memo.

2. Instantaneous One-way Connectivity

2.1. Metric Name:

   Type-P-Instantaneous-Unidirectional-Connectivity

2.2. Metric Parameters:

 +    Src, the IP address of a host
 +    Dst, the IP address of a host
 +    T, a time

2.3. Metric Units:

   Boolean.

2.4. Definition:

   Src has *Type-P-Instantaneous-Unidirectional-Connectivity* to Dst at
   time T if a type-P packet transmitted from Src to Dst at time T will
   arrive at Dst.

2.5. Discussion:

   For most applications (e.g., any TCP connection) bidirectional
   connectivity is considerably more germane than unidirectional
   connectivity, although unidirectional connectivity can be of interest
   for some security applications (e.g., testing whether a firewall
   correctly filters out a "ping of death").  Most applications also
   require connectivity over an interval, while this metric is
   instantaneous, though, again, for some security applications
   instantaneous connectivity remains of interest.  Finally, one might
   not have instantaneous connectivity due to a transient event such as
   a full queue at a router, even if at nearby instants in time one does
   have connectivity.  These points are addressed below, with this
   metric serving as a building block.



Mahdavi & Paxson              Experimental