More problems with PPPoE

NETWORK WORLD NEWSLETTER: STEVE TAYLOR AND JIM METZLER ON WIDE
AREA NETWORKING
06/09/05
Today's focus: More problems with PPPoE

Dear networking.world@gmail.com,

In this issue:

* Trying to use FTP on a PPPoE ADSL service
* Links related to Wide Area Networking
* Featured reader resource
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Today's focus: More problems with PPPoE

By Steve Taylor and Jim Metzler

Over the past two newsletters, we've been discussing some of the
ins and outs of transitioning to Point-to-Point Protocol over
Ethernet (PPPoE) as the authentication scheme for DSL service.
From an operational perspective, the biggest challenge so far
was that when switching from cable modem to DSL, the router had
to be reconfigured. Of course, the simplest solution would
probably be to purchase yet another router for almost-free, and
switch the cable from the LAN switch to the router rather than
from the router to the cable or DSL modem.

But then Steve hit the wall when an important application - FTP
- started hanging on a somewhat regular basis. The FTP app had
been working for years. (In fact, the application has a
copyright date of 1992-1998. But it works. Or at least it used
to.)

The first time that a large upload began on the newly-configured
PPPoE ADSL service, the application choked on a large file
transfer. Being the empiricist that he is, Steve suspected the
DSL service as the culprit, but he had to get the file uploaded
so he "simply" switched back over to the cable modem,
reconfiguring the router en route. A day or so later, there was
a break in the action so the experiment could continue. Guess
what? It still failed on the DSL link.

So Steve decided to take both a top-down and bottom-up approach.
After e-mailing the DSL provider's director of analyst and
customer relations, whom he happened to know, Steve also started
down the help desk path.

At the help desk, after repeatedly explaining what FTP was -
that it really wasn't e-mail or Web browsing - Steve got to a
level of tech support that at least understood the problem.
Thirty-minutes into the process, Steve was informed that indeed
this was a known problem and that a trouble ticket had been open
on it for about a week. If the problem persisted for a few more
days, then he should call back. (Thank goodness Steve thought to
ask what the trouble ticket number was in order to avoid the
30-minutes of relatively efficiently getting to this point.)

But the top-down approach actually solved the problem.
Relatively soon, Steve got a call from the national tech support
folks, and within about 15 minutes of working with a
knowledgeable tech, it was determined that PPPoE actually adds
about 6 to 8 bytes to the packet size, and with a large
transmission, we were hitting some packets that exceeded the
proper packet size. A quick adjustment was made to the MTU
(Multi-tenant Unit) size on Windows XP to go from the default of
most NICs of about 1,480-bytes down to 1,300-bytes. And,
automatically, the connection started working.

There are a couple of lessons here. Had it not been for the
"inside track," this would have remained an issue for days if
not weeks. Also, "transparent transitions" are not always what
they seem. Glass is "transparent," but don't try running
through it.
_______________________________________________________________
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 Avaya
Evaluating VoIP in the Enterprise

Got VoIP? More and more companies are answering yes...the
reasons vary from cost savings, network flexibility, and ease of
administration. Yet others are drawn to the promise of advanced
VoIP applications such as unified messaging and collaboration.
Register now and get a free copy of Network World's Got VoIP?
Executive Guide, which outlines the keys to successful VoIP
deployments.
http://www.fattail.com/redir/redirect.asp?CID=106328
_______________________________________________________________
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For the latest in VoIP security, check out NW's Research Center
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related to keeping VoIP networks secure. Click here for more:
<http://www.networkworld.com/topics/voip-security.html>
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