RE: Routers Part II

["Richard M. Smith" <rms () computerbytesman com>]

Hmm, it sounds like we need 2 PC Magazine articles:  One on real-world WiFi
performance and another on broadband upload/download speeds.

Richard 

-----Original Message-----
From: funsec-bounces () linuxbox org [mailto:funsec-bounces () linuxbox org] On
Behalf Of Dr. Neal Krawetz
Sent: Tuesday, November 29, 2005 8:56 AM
To: funsec () linuxbox org
Subject: [funsec] Routers Part II

Hi folks,

So, I've been benchmarking a bunch of different routers and I've noticed an
oddity with Comcast "high speed internet" cable service.

The service is supposed to provide 4Mbps download (6Mbps in select areas)
and 384K uploads.

All of my benchmarks show uploads around 355K, so 384K is definitely the
correct upper threshold.  (Theoretical 384, actual 355.)

I am in one of the 6Mbps "select areas".
The interesting thing is, I can get over 6Mbps downloads, without uncapping
my cable modem.  Comcast appears to use a threshold trigger at 9Mbps.  If
you download, you can get up to 9Mbps.  But the second you cross that 9Mbps
mark, they cap you and drop back to 6Mbps.
(Benchmarks consistently show 5999Mbps - 6000Mbps after being capped.
That is real 6Mbps, not theoretical.)

Here's the catch: If you don't cross the 9Mbps threshold, then you can
happily live at 7-8Mbps indefinitely.

My configuration:
  Internet -> cable modem -> hub -> firewall -> DMZ -> firewall -> LAN

(When I say "hub", I really mean "hub" and not "switch".) The hub allows my
IDS to sit right outside the firewall.
I have a couple of hubs: 10Mbps and 100Mbps.
(BTW, true 100Mbps hubs are really rare.  I got mine at an auction.  If you
want one, check out your local university auctions.)

If I put in my 100Mbps hub, I can break 9Mbps and get quickly slapped down
to 6Mbps.
BUT: If I put in my 10Mbps hub, then the maximum becomes a fraction over
8Mbps.  (Theoretical 10, actual 8-9.) Benchmarks consistently show 7-8Mbps
sustained.


So my questions are...
(1) If they are supposed to cap at 6Mbps, why do they not enforce the cap
until 9Mbps?  (Not that I'm complaining!  Just curious...)

(2) Does the same cap trigger exist for people in Comcast 4Mbps areas?
Can you get higher than 4Mbps as long as you don't cross some threashold?
If so, what is the threshold?
Some routers permit upstream thresholds for QoS tuning.  The Linksys WRT54G
does this.

(3) Does the cap trigger exist for other cable modem providers?
What provider, and what threshold?

By the way:
- The Linksys RV0041 (router with built-in VPN) is reported to benchmark
  at under 1Mbps -- even over non-VPN connections.  Ouch.
- The Linksys WRT54G has a QoS threshold for WAN bandwidth.
  The factory setting is "auto".  "auto" is 3Mbps.
  If you manually crank it up to anything over 5Mbps (e.g., 10000), then
  you can get 4.5Mbps over 802.11g.  (Wow!  Almost 10%!  Ugh...)
  
                                        -Neal
--
Neal Krawetz, Ph.D.
Hacker Factor Solutions
http://www.hackerfactor.com/

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