Re: Losing NNTP connections through a cheap NAT router

Re: Losing NNTP connections through a cheap NAT router

[Klaus Uhl]

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Hi Jeff,

when Gnus only has problems if you are behind one of those cheap NAT
routers they might be the problem. A friend of mine also accesses the
internet via a DSL NAT router and he often has problems when he uses
file sharing applications (Kazaa, Edonkey, ...), especially when the
network load is high.

The problem is that a NAT router has to keep track of _all_ open
connections so that it can deliver incoming packets to the correct
destination. To store this information a NAT router needs some
memory. And this is the point: cheap out-of-the-box NAT routers
(eg. DSL routers) usually have only a few MBs of RAM (compare this to
a Linux router which nowadays probably has at least 128MB). If this
memory is used up you the router can either not trace more connections
or has to throw away older ones.

This might be happening when you can't access some of your news
servers. (I must admit that is does _not_ explain why you have no
problems with other news servers. Maybe it's the order in which they
are connected. Maybe your NAT router does not recognize finished TCP
connections and has a long timeout for dropping old
connections. Maybe... There are many things that can influence network
behavior.)

Klaus

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