Jiri Kuthan wrote:
> The trouble with TCP/keepalive is twofold. One is, as Hadriel mentions, 
> there are OSs that can't deal with it. [...]
> The other problem is very similar: there are NATs that ignore TCP 
> keep-alives to extend bindings.

There is one more problem in TCP keep-alives: they may cause an
otherwise perfect connection between two hosts to be disrupted if
some intermediary router connecting the two hosts hiccups
temporarily.

This is discussed to good length (including the pros and cons
of TCP keepalive) in Chapter 23 of [1].  The reference is old
enough (1994) that it does not contain discussion of NATs, but
the intermediary issue is valid and even mentioned in the more
recent book by Stevens, Fenner, and Rudoff [2]
(see discussion on pg. 201).

[1] W. Richard Stevens, "TCP/IP Illustrated, Volume 1: The Protocols,"
  Addison-Wesley, 1994.

[2] W. Richard Stevens,  Bill Fenner, and Andrew Rudoff,
  "Unix Network Programming: The Sockets Networking API," Addison-
  Wesley, 2004.

Ciao.

- vijay
-- 
Vijay K. Gurbani, Bell Laboratories, Alcatel-Lucent
2701 Lucent Lane, Rm. 9F-546, Lisle, Illinois 60532 (USA)
Email: [EMAIL PROTECTED],bell-labs.com,acm.org}
WWW:   http://www.alcatel-lucent.com/bell-labs
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