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Senator Proposes Net Neutrality Bill
Ron Wyden (D-Or) has introduced legislation to prevent
telecoms and cable companies from developing a two-tiered
network where fees would be charged to content providers
to prioritize their Internet traffic...
Open Source Vyatta Takes On Hardware
After years of open source projects like Linux and MySQL
taking share from proprietary software companies, hardware
makers like Cisco and Juniper get to experience the heart-stopping
terror of open source hardware hitting the market...
Secure Routers Go Through Ceiling In 2005
A new study from Infonetics Research reported big numbers
for secure routers in 2005...
Neutrality Divides On Party Lines
The potential to future innovators to build on the success of the Internet may
well hinge on network neutrality, but the two major political parties in Congress
see the issue differently. In a nutshell, or at least in a story
appearing on ZDNet, Democrats noted in the article side with the...
What is Microsoft Terminal Server?
Microsoft Terminal Server is a component of the Windows
operating system that allows users to remotely access
servers and applications over the internet or a local
Keep In Touch (tcp Keepalives Etc.)
You can't please everyone, so you got to please yourself.. (Ricky Nelson)
I don't imagine Ricky Nelson was thinking about tcp timeouts and keepalives in the 70's, and probably isn't still, but the subject comes up fairly often for me and never fails to be annoying.
Annoying? OK, maybe confusing is the better choice. This is one of those areas where the cure can be worse than the disease and where discussions by tcp programmers can get acrid and heated. The biggest problem is that users often really don't know what they want, and if they do know, it probably shouldn't have anything to do with the tcp stack, but next thing you know somebody is changing kernel level values, and probably not getting the results they expected.
Typically it starts on one side or the other of the basic question, which is "when should a connection to another machine be dropped?". The other side has gone away, lost its mind (or at least its network connection) or maybe some router in between the two of you is misbehaving. Whatever. Packets that should be flowing between you and X are not, and you want something done about it now. It is absolutely critical that you be aware of this connection problem immediately so that you can take action to fix it. That's one side. The other side is that you got disconnected from machine X because there was some stupid momentary glitch and that's not what you want to happen: it's critical that your process remain connected so that it doesn't have to restart processing whatever data it was chewing on.
Ricky should sing the chorus now.
So what is poor tcp to do? Break the connection at the first sign of trouble or hang in there waiting for it to come back? Most TCP implementations have "keepalives": (from http://www.ietf.org/rfc/rfc1122.txt)
Implementors MAY include "keep-alives" in their TCP implementations, although this practice is not universally accepted. If keep-alives are included, the application MUST be able to turn them on or off for each TCP connection, and they MUST default to off.
Keep-alive packets MUST only be sent when no data or acknowledgement packets have been received for the connection within an interval. This interval MUST be configurable and MUST default to no less than two hours.
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About the Author:
A.P. Lawrence provides SCO Unix and Linux consulting services. http://www.pcunix.com