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#256947 - 25/05/2005 11:56 Congestion Management on Routers
Roger carpal tunnel Registered: 18/01/2000 Posts: 5683 Loc: London, UK	We've got a problem at work: one of our products is saturating a client's routers. Now, our product is supposed to back-off, and only use 40% of the available bandwidth, but instead of doing proper congestion management, the client's router appears to simply drop the packets on the floor. This causes us to issue retries, thus effectively doubling the load. So, my question: does anyone know anything about congestion management? A list of terms I should be googling for would be a help. We think they're using Cisco kit, so anything specific to that would be a great help, too. _________________________ -- roger
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#256948 - 25/05/2005 12:54 Re: Congestion Management on Routers [Re: Roger]
jmwking old hand Registered: 27/02/2003 Posts: 776 Loc: Washington, DC metro	I've heard very good things about Packeteer's packet shaping/throughput management products, though I haven't actually used them. We almost got one, though... -jk
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#256949 - 25/05/2005 13:10 Re: Congestion Management on Routers [Re: Roger]
andy carpal tunnel Registered: 10/06/1999 Posts: 5916 Loc: Wivenhoe, Essex, UK	Is this over TCP, UDP or something else ? _________________________ Remind me to change my signature to something more interesting someday
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#256950 - 25/05/2005 19:11 Re: Congestion Management on Routers [Re: Roger]
wfaulk carpal tunnel Registered: 25/12/2000 Posts: 16706 Loc: Raleigh, NC US	I think you're interested in RSVP. _________________________ Bitt Faulk
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#256951 - 26/05/2005 07:44 Re: Congestion Management on Routers [Re: andy]
Roger carpal tunnel Registered: 18/01/2000 Posts: 5683 Loc: London, UK	Quote: Is this over TCP, UDP or something else ? TCP. Our customer's got a T3 from their data centre, running to a router that is connected to a bunch of 384Kbps lines. The combined bandwidth of the 384Kbps lines exceeds 45Mbps. We've got an application that runs at the other end of each of those 384Kbps lines. It's supposed to conserve bandwidth by monitoring how quickly its (SMB) requests are being serviced -- it uses this to get an idea of the available bandwidth and then backs off to only using a percentage of this. However, their router is dropping packets, and not telling anybody about it, which means that the retry (I think) traffic is saturating the link, and our application isn't getting a realistic measure of the available bandwidth, which means it's not backing off properly. So, I just wanted some terms to search for, so that I could get some general information about how these things should work. _________________________ -- roger
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#256952 - 26/05/2005 11:05 Re: Congestion Management on Routers [Re: Roger]
jmwking old hand Registered: 27/02/2003 Posts: 776 Loc: Washington, DC metro	Quote: TCP. Our customer's got a T3 from their data centre, running to a router that is connected to a bunch of 384Kbps lines. The combined bandwidth of the 384Kbps lines exceeds 45Mbps. This is exactly what the Packeteer product is designed to handle. -jk
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#256953 - 30/05/2005 16:25 Re: Congestion Management on Routers [Re: Roger]
matthew_k pooh-bah Registered: 12/02/2002 Posts: 2298 Loc: Berkeley, California	Quote: However, their router is dropping packets, and not telling anybody about it, which means that the retry (I think) traffic is saturating the link, and our application isn't getting a realistic measure of the available bandwidth, which means it's not backing off properly. Correct me if I'm wrong, but this is exactly what an IP router is supposed to do when it's overloaded. Sending "your packet was dropped" notices would effectively double traffic exactly when the network was trying to reduce traffic. The TCP implementation is supposed to take the dropped packet as the sign to back off. This would appear to be RFC2988. Matthew
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