How TCP ensures smooth end-to-end performance

NETWORK WORLD NEWSLETTER: STEVE TAYLOR AND JIM METZLER ON WIDE
AREA NETWORKING
06/30/05
Today's focus: How TCP ensures smooth end-to-end performance

Dear networking.world@gmail.com,

In this issue:

* TCP's effective transmission window
* Links related to Wide Area Networking
* Featured reader resource
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Today's focus: How TCP ensures smooth end-to-end performance

By Steve Taylor and Jim Metzler

Last time, we discussed the fact that TCP has a flow control
mechanism for each connection. The mechanism is based on a field
in the segment header called the "Advertised Window." The
Advertised Window specifies how many additional bytes of data
the receiver can accept.

The goal of congestion control is to ensure that the sending
device does not transmit more data than the network can
accommodate. To achieve this goal, the TCP congestion control
mechanisms are based on a parameter referred to as the
"Congestion Window." Determining the optimum value for the
Congestion Window is somewhat tricky, particularly because
network congestion changes over time.

In order to ensure smooth end-to-end performance, TCP defines a
parameter that is referred to as "Max Window." It is helpful to
think of Max Window as being an upper limit on the number of
bytes that the sender could transmit at any point in time. In
order to ensure that the sending device does not send more data
than the network and the receiving device can accommodate, Max
Window is defined to be the lesser of Advertised Window and
Congestion Window.

However, data is continually being transmitted from the sending
device to the receiving device and acknowledged by the receiving
device. To account for this, TCP defines a parameter called
Effective Window. Effective Window is equal to Max Window minus
the number of bytes that have been sent, but not acknowledged.

The next newsletter will describe some techniques that are used
to compute the Congestion Window.

RELATED EDITORIAL LINKS

The Transmission Control Protocol
http://www.faqs.org/rfcs/rfc2581.html

TCP Performance Issues
http://www.networkworld.com/nlwan2882

Airbus net protects key resources
Network World, 06/27/05
http://www.networkworld.com/nlwan2945
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To contact: Steve Taylor and Jim Metzler

Steve Taylor is president of Distributed Networking Associates
and publisher/editor-in-chief of Webtorials. For more detailed
information on most of the topics discussed in this newsletter,
connect to Webtorials <http://www.webtorials.com/>, the premier
site for Web-based educational presentations, white papers, and
market research. Taylor can be reached at
<mailto:taylor@webtorials.com>

Jim Metzler is the Vice President of Ashton, Metzler &
Associates, a consulting organization that focuses on leveraging
technology for business success. Jim assists vendors to refine
product strategies, service providers to deploy technologies and
services, and enterprises evolve their network infrastructure.
He can be reached at <mailto:jim@ashtonmetzler.com>
_______________________________________________________________
This newsletter is sponsored by Oracle
Boost the quantity and quality of customer interactions!

How can companies get a fuller, sharper picture of their
customers to boost the quantity and quality of customer
interactions? By creating a standardized customer-data model via
an "information grid." IDC analyst Stephen Hendrick explains how
to achieve a "360-degree view" of customers for better selling
and marketing.
http://www.fattail.com/redir/redirect.asp?CID=107450
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ARCHIVE LINKS

Archive of the WAN newsletter:
http://www.networkworld.com/newsletters/frame/index.html
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solutions will soon be available. Click here:
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