0 Replies Latest reply on Feb 21, 2016 12:11 PM by infotelsystems

    Using TCP congestion control for inbound QOS on WAN Internet interfaces

    infotelsystems New Member

      We asked this question in 2011. I believe the topic needs updating as Netflix, Youtube and others now use TCP for video streaming.

       

      To Adtran:

       

      Edgemarc routers claim to be able to control the data download transfer rate of upstream TCP devices by using congestion control mechanisms built into TCP. One process is to withhold acknowledgement of received packets. This results in the upstream devices slowing down their transmit rate (download speed) to the QOS router.  What does Adtran have to say about this? Is this valid? What percentage of upstream ISP routers and /or source devices will respond to this method of QOS?

       

      From: applications.engineer@adtran.com

      Sent: Wednesday, February 16, 2011 10:43 AM

      To: Chuck Brodersen

      Subject: Re: RQST00001190161

       

      2/16/2011 8:49:53 AM

      Summary: General QOS questions Adtran vs Edgemarc

       

      Chuck

       

      It's sort of valid since it's part of the TCP protocol stack but it's nothing special for Edgemarc - everybody does it if they support TCP at all. Some of the algorithms might be different among vendors because there are several flavors out there but everybody does it in one form or another. It is not a method of QoS however, at least not in the generally accepted sense like DiffServ or IP Precedence.

       

      The key things to note about TCP flow control is that it ONLY applies to TCP traffic, not UDP. This is important because most high-bandwidth traffic (most file downloads, streaming from NetFlix, Hulu, YouTube, etc,etc) are delivered as UDP traffic and as such would not be subject to the TCP flow control mechanism.

       

      Also note that routers along the pathway aren't part of the TCP control scheme - the conversation about the window size and flow is between the sender and receiver.  The only way a router influences this is by restricting the egress pathway to the receiver, which forces a slowdown in packet reception and acknowledgments. It makes the senders/receivers think that there is congestion somewhere in the middle and they slow down in response to that.

       

      Whether Edgemarc has some proprietary thing they've implemented to interfere with the normal TCP process is unknown to me but I can assure you that we don't do anything like that.

       

      Regards,

      Ronnie Colvin

      Adtran Applications Engineering

      --------------

       

       

      Details:

      We are an Adtran dealer with about 75 Adtran router installs.

       

      Edgemarc routers claim to be able to control the data download transfer rate of upstream TCP devices by using congestion control mechanisms built into TCP. One process is to withhold acknowledgement of received packets. This results in the upstream devices slowing down their transmit rate (download speed) to the QOS router.

       

      What does Adtran have to say about this? Is this valid? What percentage of upstream ISP routers and /or source devices will respond to this method of QOS?

       

       

      [cid:image002.jpg@01CBCDBD.B165C160]

      Chuck Brodersen

      804-266-6600 and say "Chuck Brodersen"

      804-264-4206 is my www.faxinbox.com<http://www.faxinbox.com>

      Perfect Installs. Uncommon Reliability. We are telecom! We are the telecom authority.