Cable Modem + Router = half speed... help!

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bitstream
DD-WRT Novice


Joined: 07 Jul 2006
Posts: 4

PostPosted: Fri Jul 07, 2006 2:02    Post subject: Cable Modem + Router = half speed... help! Reply with quote
I have been using DSL for a couple years now and it has worked well, though peak download speeds are limited to 1.5mbit/sec. I activated 6mbit cable modem service today and was surprised that speed tests were around 1mbit!

I decided to take the router out of the picture and was SHOCKED to see speeds ranging from 4-6mbit/sec!

I turned off QoS and my speeds went up to 3mbit or so, though this is only half the speed I should be getting.

I am running DD-WRT v23 SP1 Final (05/16/06) mini with default settings for everything except wireless, though that shouldn't matter since all tests were run using a wired connection.

What on earth would cause this sort of performance hit?

I have tried tweaking MTU, using values from 1200-1500, as well as auto. Anything below 1500 just slowed things down. Is there anything else I can try? Question
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gjcomputer
DD-WRT Novice


Joined: 08 Jun 2006
Posts: 12

PostPosted: Fri Jul 07, 2006 5:16    Post subject: Re: Cable Modem + Router = half speed... help! Reply with quote
bitstream wrote:
I have been using DSL for a couple years now and it has worked well, though peak download speeds are limited to 1.5mbit/sec. I activated 6mbit cable modem service today and was surprised that speed tests were around 1mbit!

I decided to take the router out of the picture and was SHOCKED to see speeds ranging from 4-6mbit/sec!

I turned off QoS and my speeds went up to 3mbit or so, though this is only half the speed I should be getting.

I am running DD-WRT v23 SP1 Final (05/16/06) mini with default settings for everything except wireless, though that shouldn't matter since all tests were run using a wired connection.

What on earth would cause this sort of performance hit?

I have tried tweaking MTU, using values from 1200-1500, as well as auto. Anything below 1500 just slowed things down. Is there anything else I can try? Question


not running any p2p programs?
is this a fresh dd-wrt install?
are you wireless or wired?
bitstream
DD-WRT Novice


Joined: 07 Jul 2006
Posts: 4

PostPosted: Fri Jul 07, 2006 12:05    Post subject: Re: Cable Modem + Router = half speed... help! Reply with quote
gjcomputer wrote:
not running any p2p programs?
is this a fresh dd-wrt install?
are you wireless or wired?


Nope... no P2P. Yes, it was a fresh install. All connections are wired right now.
Matthiaz
DD-WRT Guru


Joined: 12 Jun 2006
Posts: 635

PostPosted: Fri Jul 07, 2006 12:13    Post subject: Reply with quote
Did you ever test the cable modem directly connected to your PC?
pugsly0014
DD-WRT Novice


Joined: 09 Jun 2006
Posts: 15

PostPosted: Fri Jul 07, 2006 12:40    Post subject: Reply with quote
It's problay your RWIN configuration on your workstation. I had this problem when I went from DSL over to FioS.

There is an awsom tool here which can tweek your RWIN values.

http://www.speedguide.net/downloads.php

This jumped my speeds from 3Mb/s up to 5Mb/s.
bitstream
DD-WRT Novice


Joined: 07 Jul 2006
Posts: 4

PostPosted: Fri Jul 07, 2006 12:59    Post subject: Reply with quote
pugsly0014 wrote:
It's problay your RWIN configuration on your workstation. I had this problem when I went from DSL over to FioS.

There is an awsom tool here which can tweek your RWIN values.

http://www.speedguide.net/downloads.php

This jumped my speeds from 3Mb/s up to 5Mb/s.

The problem isn't the desktop... it's the router. When I take the router out of the loop, speeds skyrocket. Is this a setting I can tweak in the router itself?

Or will the RWIN make a difference when connected to the router?
pugsly0014
DD-WRT Novice


Joined: 09 Jun 2006
Posts: 15

PostPosted: Fri Jul 07, 2006 13:36    Post subject: Reply with quote
It made a difference for me when connected to the router, at least when using wireless.

I can't connect my FioS dirrectly to my computer since it's PPoE. I will test again once Verizon goes to DHCP later on this month.
ReyRey
DD-WRT Novice


Joined: 10 Jul 2006
Posts: 2

PostPosted: Mon Jul 10, 2006 19:42    Post subject: Reply with quote
Are your router and modem close together? On another site I read that electrical interference was the problem, his case was just like that. If they are, move them further apart.
bitstream
DD-WRT Novice


Joined: 07 Jul 2006
Posts: 4

PostPosted: Mon Jul 10, 2006 19:49    Post subject: Reply with quote
They sit a few inches from each other.

I don't think electrical interference would cause this sort of problem with a wired connection. I have also noticed occasional stalls since upgrading to the cable modem, which leads me to believe that there's an issue with the software on the router.

I may try downgrading to the vanilla Linksys firmware and see what happens.
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