Re: Proxies and loops
Simon Spero (ses@tipper.oit.unc.edu)
Mon, 27 Nov 1995 12:18:20 -0800 (PST)
There are also reasons why the Forwarded header can lead to incorrect
behaviour in a network of proxies interlinked by long-lived connections.
There are plenty of cases where forwarding a query on through a proxy
though which it has already passed is in fact correct behaviour.
For example, Suppose we have a network of servers in the following topology
1 2 3 4 5
A----B----C----D----E---F
\ /
\-----G-------------/
6 7
Now, lets assume we want to sent a query from A to E. The network
topology tells us that we should use link 6 and send the query via G and F
Suppose however, that in the meantime F crashes, bringing down links 5
and 7. When the query arrives at G, the routing tables will have changed
to make the correct next hop A again (A will have updated its tables to
route queries to E via B).
With a Forwarded header, A would be forced to discard the message, even
though a path exists between A and E.