Re: [ledbat] list of reasons for needing multiple TCP connections

Most home "routers" have all been modified by now not to crash when
> BitTorrent has opened thousands of TCP connections. These connections
> consume mapping table resources and were a problem until it they were
> garbage-collected.
>
>
I claim to have no handle on what "most" home routers do, but I doubt this
assertion.

NAT table size continues to be a problem with NAT limit, and not because
BitTorrent typically opens thousands of TCP connections (it doesn't, nor do
trackers generally provide the thousands of peer addresses necessary to go
with those connections), but because the combination of the UDP-based DHT in
addition to 100 TCP connections and a decent amount of WAN-LAN traffic is
enough to overcome NAT tables in popular routers being sold today.

http://www.smallnetbuilder.com/component/option,com_chart/Itemid,189/chart,124/
(note 200 is the upper limit of their test method, but of use to this
message is the number and market position of routers that support less than
200)

Belkin's F5D8232-4 is 41st in Amazon's sales rank for "routers" and maxed
out at 180 connections.
Netgear FVS124G is 14th in "gigabit routers" and maxes out at 196.
Apple's BL053LL/A is 1st in "gigabit routers" and maxes out at 128.

Do they crash?  Beats me.  But NAT table size limit is definitely a
consideration.  The behaviors when those limits are reached are varied and,
even on some recently sold equipment, sometimes less than graceful. One of
the most common failure modes I've run across is that DNS Relay stops
working or the configuration pages stop responding while pre-existing
connections continue uninterrupted!  (I'm guessing that the daemons
supporting these functions either get killed or lack enough memory to do
anything, they themselves are shut out of the NAT table, or maybe they won't
launch when CPU load is greater than some amount.)

I think it continues to deserve inclusion.  If someone has data to the
contrary, please bring it.

-- 
Robb Topolski (robb@funchords.com)
Hillsboro, Oregon USA
http://www.funchords.com/