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Q214889: SMS: Remote Chat May Not Work on Slow Link

Article: Q214889
Product(s): Microsoft Systems Management Server
Version(s): winnt:1.2,2.0
Operating System(s): 
Keyword(s): kbnetwork kbClient kbsms200 kbsms120 kbHelpDesk
Last Modified: 21-APR-2000

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The information in this article applies to:

- Microsoft Systems Management Server versions 2.0, 1.2 
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SUMMARY
=======

When you attempt a remote chat session on a slow link (such as a 9,600 bits per
second link) by using only TCP/IP, the Chat window may behave as if the viewer
timed out immediately. Immediately after the viewer closes its window, the
client's Chat window also closes.

MORE INFORMATION
================

The TCP/IP Nagle algorithm that helps reduce small packets on a slow network is
the root cause. Although the Nagle algorithm can be disabled in Microsoft
Windows NT for troubleshooting or remote helpdesk issues, disabling the Nagle
algorithm may be detrimental. If it is not re-enabled, performance could be
degraded.

The Nagle algorithm was developed to help with a couple of problems on the
Internet/ARPANET. Programs such as Telnet sometimes transmit each character at a
time. 1 byte of data and 40 bytes of header information in an environment that
can carry up to 1,500 byte packets is very inefficient. When a packet is sent,
it is sent with a Time to Live value (TTL); if the TTL expires, the sending node
retransmits the packet with a greater TTL, up to a point. In the meantime, as
more and more packets hit a router, the router becomes congested, up to the
point where it starts to drop packets. The Nagle algorithm holds a small packet
200 to 500 milliseconds. If there is more data to be sent to the same
destination, the packet is held. This decreases the overall number of packets,
thereby decrease the router congestion. On a slow link (9600 bits per second),
the wait is long enough that the Chat session does not work. One of the inherent
problems in the Nagle algorithm is finding a delay that works for everything.

For additional information about the Nagle algorithm and how to disable it, click
the article number below to view the article in the Microsoft Knowledge Base:

  Q236316 Performance Improvement for Redirector/Server Connections

Be aware that this change could degrade performance in other areas.

Additional query words: prodsms

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Keywords          : kbnetwork kbClient kbsms200 kbsms120 kbHelpDesk 
Technology        : kbSMSSearch kbSMS120 kbSMS200
Version           : winnt:1.2,2.0
Issue type        : kbinfo

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