[Ns-bugs] [Bug 74] Redundant routing table lookup for setting src addr of outoging IP packets

[bugzilla-daemon@nsnam-www.ece.gatech.edu]

http://www.nsnam.org/bugzilla/show_bug.cgi?id=74





------- Comment #1 from tomh at tomh.org  2007-09-14 01:03 -------
Gustavo, I agree with your point that a route cached from first packet can
become stale.  What about, though, just doing a per-packet lookup but doing it
in UDP when the transport header needs to be created?

I think source address selection needs to be done in the transport layer,
particularly when things like IPsec can be inserted before the packet hits IP. 
Source address selection typically requires the destination to be determined.  

As a first step, one could have the transport layer do the pre-route step per
packet and store the route in a packet tag.  This would ensure per-packet
lookups like you want.

For optimizations, one could consider registering a callback with the routing
layer that flushed cached routes at the transport layer when any routing
protocol routes changed.


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