On Wed, Apr 09, 2014 at 03:47:43PM -0400, Sean Breheny wrote:
> Yes - I just don't see why you need to exchange a data block just to
> keep the link open. Why wouldn't the simple message itself be
> sufficient?

Good question.

Because a simple message doesn't prove as much.

By including some random data in the message, the peer can have
reasonable expectation that the return message was generated by a
system that received the data sent.

In the same way, the UNIX ping program embeds data in the ICMP echo
request packet which it checks when the echo reply packet arrives.

Operating system code which responds to ICMP echo requests takes the
packet, changes the header, and sends it right back.  The payload is
sent back unchanged.

--=20
James Cameron
http://quozl.linux.org.au/
--=20
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