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[tbrimm]

Referring to the attached chart, yellow is downstream data (768K provision), red is upstream data (192K provision), 1% scale = 1 Mbps.  Downstream data is stable and relatively jitter-free with no upstream data.  However, when an upload is started, the 768K downstream data throughput drops to <40K and the jitter goes of the scale.  When the upload is cancelled, the downstream data returns to normal.  There is a Charles industries DSL "Adrenaline" conditioner on this line, with a 36Kft loop length; extreme to the max, but well within the unit's capabilities.   The ADSL modem syncs fine, and never drops.  Downloads are fine, uploads are fine, but never the twain together.  Any thoughts?  The telco guys are all scratching their heads.  The DSLAM card and the modem have both been swapped. 

Since ADSL uses discrete US and DS channels, why would the two clobber each other if there are no sync issues in either direction?

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[roseway]

Hi and welcome

This happens because the upstream and downstream aren't completely independent in practice. When you download, a certain amount of upstream bandwidth is used for acknowledgements. So if you saturate your upstream connection with an upload, then the acknowledgements for the downloads will be badly delayed, and this will choke your download speed.

What you need to do (if it's possible) is cap your upload speed to about 80% of the full capability, so there's still some bandwidth left for acknowledgements of downloads. This is commonly done with P2P for example.

[tbrimm]

Thank you for taking the time to reply.  Since posting this, I have learned a great deal about ADSL traffic, including the phenomenon you described.  Since I had no way of throttling my uploads (they weren't P2P, but HTTP file tranfers) throttling wasn't an option.  Since ACKs were what needed to get through, I starting researching packet and traffic prioritization techniques, which then led me to "traffic shaping" and a German software company who makes a traffic shaping product called cFosSpeed.  http://www.cfos.de

Once I installed their $20 program, everything fixed itself like magic.  I can now achieve full downstream speed while simultaneously uploading.  The program also lets one set custom prioritization levels based on protcols or programs, so, for example, VOIP traffic can be prioritized over HTTP.  I can't believe how simple the "fix" was!  And to think of the countless hours that I, and two different Telco engineers have spent on this.   

For anyone with ADSL, this amazing product is a must.  (Honestly, I do not work for cFos.  This "testimony" is the real deal.)

Regards,

Troy Brimm

[roseway]

Thanks for bringing that product to our attention. It does look interesting, although as I don't use Windows I can't try it myself.

[kitz]

I'm very surprised that your telco company didnt realise that your upstream data would be affecting your downstream attainable speeds due to ACKS

Ive not heard of cfos before so I cant comment..  but an alternative product would be Netlimiter.  Their Netlimiter 2 Lite product for $16.95  allows the shaping and limiting of applications and groups.

I suggest using their free trial to see if it gets the results you want.


One important thing that should be pointed out for both of these applications is that they sit on the local machine...  therefore if you have a network..  then its entirely possible that other machines could also max out bandwidth...  and you'd need to install a copy on each PC on your network.

[orainsear]

Another option to easily shape a whole network's traffic, bandwidth and packet prioritise is to use a router with editable QoS (Quality of Service) functionality.  Unfortunately these don't normally come cheap because they are usually aimed at business use, e.g. some of the higher end Speedtouch models and Cisco etc.  Lower end Speedtouch and Thomson routers do have diffserv QoS functionality which can go some way towards helping shape traffic via packet prioritisation. 

A relatively cheap and powerful option is to use custom firmware such Tomato or DD-WRT flashed onto a router.  These firmwares are only available for select devices, e.g. Linksys WRT54GL etc, and none of them are modem/routers - just routers, so you need to bridge your own modem to it if you are using it with a DSL service (which I actually prefer because I can choose the modem hardware).

[tbrimm]

Kitz, Orainsear,

Thank you for those valuable tips. 

Kitz, true, you'd expect the engineers would know about ADSL characteristics, but ADSL has only become available here (rural Montana) in the last 2 months, and they are self-admitted POTS experts, not TCP/IP-ATM-ADSL engineers.  In their defense , they are more focused at bringing ADSL out 36kft, which involves line conditioners, load points, loop resistance, etc.; a far cry from the field of IP.  I am an engineer as well, and we've all learned something.   I may try the Netlimiter product for fun at a later date; what I like most about cFos, is that it is self-learning, and although it would let me tweak it's parameters as well, I just don't want to bother.  Since I am getting full bandwidth up and down, my problem doesn't exist any longer.

Orainsear, my router is a Siemens Gigaset SE567; a combo modem/router/switch/AP.  According to the datasheet, it has QoS functionality, but obviously ACK's aren't at the top of it's list!  There are no user-settable QoS parms.  I lease it and really don't want to be fiddling with the OS anyway.   I do love it's WLAN AP, though.  Better signal coverage than my Linksys WRT110N "Range Booster".  I do have a couple of WRT54's, and I have, in the past, used the DD-WRT OS.   I suppose I could eventually use the modem portion of the Gigaset (it has a configurable WAN/LAN port, and can operate in bridge mode) with another router.   First, I'll have to learn how to do that!  For now, I have tied up the Linksys WRT110N as an N-only AP on the Gigaset switch.  Were I to use the Gigaset as a modem, then all the WLAN G-clients on it's AP would need somewhere else to go; ostensibly the WRT54G with the DD-WRT OS.   Using the WRT110N in mixed mode for everybody would lose me my 270 Mbps N service.  Moreover, the Gigaset radio is superior to the WRT54G.   If this PC-based software solution keeps working as it has been, and if I can confirm that I am not locked out of a Remote Desktop session while doing FTP uploads, then I good to go.  (Since I will be remotely operating two servers in Montana from the Dominican Republic, my biggest concern was getting locked out of my own servers if either of them were uploading.)  Overall, I agree with you that managing traffic at the router level makes more sense.  Even using the multi-user version of the cFos product installed on all the clients, they don't actually talk to one another, so they can't know what the others are doing.  If I am remoting-in to my terminal server, while the other is uploading, I may not get the results I am looking for.  That particluar test is coming soon, I can assure you!

[BritBrat]

Keep upload speed at or below 80% of maximum.

[tbrimm]

On the subject of bridging, can anyone point me in the right direction of using a different router with my current Siemens Gigaset SE567 modem/router/switch/ap.  I can configure LAN port 4 as a WAN port, and it will operate in bridge mode.  I would like to use the modem part of it, but a different router/switch/ap that has programmable QoS, like my Linksys WRT110N.