DSL Troubles

[David A. Bandel]

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On Mon, 23 Dec 2002 17:46:43 -0500 (EST)
begin  Net Llama! <netllama at linux-sxs.org> spewed forth:

> I'll bet good money that the problem is the MTU.  DSL has a 'black hole'
> where you need to have an MTU of no greater than 1492 or 90+% of the
> traffic gets dropped.  Run ifconfig to see what its set at, and reduce

<rant>

DSL (when run as a pure bridge) has no such problem.  What you're
discussing isn't a DSL problem, it's an encapsulation problem (actually a
misconfiguration problem -- the black hole exists in the knowledge base of
the person who configured the encapsulating system).

I run a Lucent Stinger FS DSLAM.  I run it in bridging mode, not some
lame-ass LANE or PPPoA, etc. mode.  My clients systems talk directly to
the Cisco 4500 via the DSL/DSLAM bridge.  Easiest way to set up a DSLAM. 
All my control is in the Linux PC "helper" behind the Cisco.  No MTU
problem because the ATM framing happens in the DSL modem, deframing in the
Cisco, and no extra headers added anywhere.

I say the above is not limited to DSL because I've seen _exactly_ the same
thing with a wireless provider that uses BreezeCom crap and encapsulates
traffic using a form of PPPoE on a wireless circuit.  I have to
deliberately lower my MTU to 1400 to compensate for his misconfigured
circuit (no ICMP type 3 code 4 -- fragmentation needed and DF set -- being
sent when required).

I swear half the morons running equipment today shouldn't be -- at least
not in a commercial environment -- because they have no clue.

It's called:  learn how shit^H^H^Htuff works before you start
(mis)configuring it.

</rant>

[snip]

Ciao,

David A. Bandel
- -- 
Focus on the dream, not the competition.
		-- Nemesis Racing Team motto
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