In einer eMail vom 13.07.2008 18:50:57 Westeuropäische Normalzeit schreibt [EMAIL PROTECTED]:
Unidirectional elements -- in a multiple-source, multiple-destination, network -- also allow for better handling of assymetric load levels among particular station 'pairs' -- i.e., A->B is much higher/lower than B->A, by whatever metric is employed. And, of course, when networks have multiple points of inter-connection, the 'preference' of which inter-connect point ot use may well be different, depending on "where, on which network" one is starting from. Many years ago, in metro Chicago, I had a wonderful real-world example of this. Two systems, less than 3 miles apart, on networks without any direct peering, or regional inter-connect. 'Preferred' path from A to B was via MAE-EAST, but the preferred path from B to A was via MAE-WEST. 'traceroute' clearly identified where the preference changed -- one could clearly see the discontinuity in RTT when packets reached the node where the 'return' preference changed. Thanks for your response. Certainly, the computation of a different path from B to A than from A to B may not only be enforced by some link which is only usable in one direction, but as well by the per link and per direction assigned weight values. In summary, there are many good reasons for replacing a link by either one or two directed arrows. Heiner
