Re: Port numbers and IPv6

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Thus spake "Noel Chiappa" <jnc@xxxxxxxxxxxxxxxxxxx>
   > From: Ned Freed <ned.freed@xxxxxxxxxxx>

Let me make sure I understand you here:

   > IMAP4 has the characteristic that you often have a huge number
   > of incoming connections, only a few of which are active at any
   > given time.  Designing servers to accomodate huge numbers of
   > connections is a bit tricky, but workable: ...
   > The 65536 limit, OTOH, has to be dealt with by using multiple
   > server IP addresses, which in turn usually require multiple
   > interfaces ...
   > ... that doesn't mean nobody is hitting the 65536 limit imposed by
   > source port numbers. They are, it causes problems

You're saying that there are servers which have close to (or more)
than 65K connections to a *single client IP address* (i.e. it may be a
NAT, with a number of hosts behind it)? (If a server is talking to a
number of different client IP addresses, it can have up to 65K
connections to *each*.)

That assumes the client is directly talking to the IMAP server. Some servers are behind an "SSL accelerator" such that all connections come from a single IP address, so only 64k clients are possible. Other servers may be behind a webmail application, with the same effect.

The number of folks experiencing this has to be pretty low, but it'd be a severe problem for them.

S

Stephen Sprunk      "Those people who think they know everything
CCIE #3723         are a great annoyance to those of us who do."
K5SSS --Isaac Asimov

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