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 From:  Brian Lloyd <brian dash wb6rqn at lloyd dot com>
 To:  sylikc <sylikc at gmail dot com>
 Cc:  "apiasecki at midatlanticbb dot com" <apiasecki at midatlanticbb dot com>, "Michael Pope" <spotnruby at gmail dot com>, m0n0wall at lists dot m0n0 dot ch
 Subject:  Re: [m0n0wall] Traffic Shaping on Network Perimeter Device
 Date:  Tue, 12 Aug 2008 15:48:37 -0700
> That's why mostly, shaping is done on the perimeter, where the LAN  
> traffic
> exceeds the capabilities of the WAN line.  Any shaping done should  
> feedback
> to the internal nodes to slow down (I don't recall how traffic  
> shaping's
> implemented), and in essence, help control the flow through the pipe.

ICMP source quench was supposed to solve the problem by letting an  
intermediate system send a message to an end system and get it to  
throttle its traffic. Turned out that it ended up making the traffic  
level oscillate. (While not particularly useful, it was fun to watch.)

Today the solution is to just throw packets away and let TCP cope.  
Most TCP implementations assume that lost packets are due to network  
congestion and close the transmit window. It is surprising just how  
well TCP will converge on proper throughput.

(I used to design routers in a previous life.)

Brian Lloyd
Granite Bay Montessori School          9330 Sierra College Bl
brian AT gbmontessori DOT com          Roseville, CA 95661
+1.916.367.2131 (voice)                +1.791.912.8170 (fax)

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