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Traffic Shaping on DSL?
jackla asks: "I'm now looking for software to do traffic-control on my Windows XP box. I am connected with DSL and my upstream is capped at 96kbit/s (down is 1.5Mbit/s) - this means that high(>70kbit/s) upstream utilisation KILLS my downstream: it just drops down to about 400kbit/s and stays there unless there's more upstream space. That said, I read alot about the Linux shaping solution (wondershaper or something) which sounds exactly right, except I need something that works for Windows. What I want to do is prioritize upstream ACKs (for example) so that my downstream isn't affected by upstream use.
If anyone heard of a peace of software that can do this, I would love to hear about it." It would be nice if something like this existed cheaply for Windows. I am unaware of such, but maybe a few of you have ideas. Could such a traffic shaper be built using low powered computers? If so, how would you build and configure it so it would maintain compatibility for the single Windows machine, behind it? (Think: homebuilt traffic-shapping appliance)
Are you a server, business or home user? I understand that you want as much bandwidth as possible, but if you are just a home user, 400 kbit down stream is not bad at all.
To answer your question directly, my solution would be to buy a cheap box (like say, the Mandrake boxes from Wal-Mart) and use it as your traffic shaper. Linux products for this are much cheaper than any (useable) solution you can find for windows.
There is nothing wrong with being gay. It's getting caught where the trouble lies.
LRP's project might be of some use. Yes, it means getting a cheap box to run Linux, but then you can use all of that real neat networking software that's available for Linux boxes but isn't available for Windoze boxes.
Not everything that can be measured matters; Not everything that matters can be measured.
If you're using Linux on the firewall machine, make sure you enable QoS and ALL the modules in it. Then grab cbq.init and set up the traffic shaping rules. The script file is well documented.
-F-
... has a Tweak Test that tests some connection settings such as your RWIN. I had the exact same problem as you and it turned out that my RWIN was set wrong and once I fixed it, the problem pretty much went away. Try it and I bet it helps.
I'm a minister!
TCP has to send back replies ("ACK"s, or acknowledgements) for each of the packets it receives, so that the sender knows if it needs to retransmit a packet. This is part of how transfer control is achieved by the protocol. So, if there's less space for ACKs going upstream, then the tcp traffic in the other direction can get slowed down.
Napster-to-go says "Fill and refill your compatible MP3 player", which is a lie. It's not MP3. It's WMA with DRM.
All DSL modems have a queue for outgoing packets. The queue will be a fifo queue, so once packets enter the queue there is no way to remove them.
If you are uploading, then the queue on the router will be full of packets...
If you are also downloading, then the ACK packets acknowledging the downloaded bytes will have to wait on the queue on the DSL router.
The fact that these ACK packets are getting delayed will slow down subsequent data packets being sent, and the downstream transfer rate will drop as a result.
By limiting the rate at which packets are sent to the DSL router, we can remove the queue from the router, and move it back onto a linux machine, where we can then prioritise the traffic as we see fit. ACK packets are allowed to skip to the head of the queue, so download speed can be maintained.
Hope that explains things
what is going upstream from your pc. You can download an eval. version of Iris ( a sniffer ) and see the traffic originating from your pc destined to outside your network.
You might find something crazy going on because a non-serving pc should be pretty quite. You will see broadcasts and ACK's but thats normal. If your computer is spewing traffic and you can't find the source your NIC could be off in the weeds or you may have been hacked (not uncommon with windows and DSL/Cable). I have 38 IP's in hosts.deny because of detected port scanning on my DSL.
I came to the datacenter drunk with a fake ID, don't you want to be just like me?
I believe XP comes with the "QoS Packet Scheduler" and has it installed by default. I believe it can do what you ask.
Couldn't he reduce the number of ACK's by increasing his window size?
Could such a traffic shaper be built using low powered computers?
Fire up that 90MHz Pentium, install FreeBSD, and build a kernel with bridging and dummynet enabled. Dummynet is an awesome network simulator. Just set up a couple of ipfw rules for the types of traffic you want to limit, and then set the bandwidth parameters in dummynet. It's very easy to do basic stuff like you're describing, but you can do all kinds of other things with dummynet... latecy, loss, queue limits, simulating multiple hops and multipath links with different latencies. There are no tools of this caliber (let alone free!) for Windows.
Next question?
I'm not a TCP guru, but I think this would potentially cause just as much of a problem. If, for example, he has a larger window, then when he has packet loss there will be a tremendous penalty. Instead of perhaps a number of small lost packets, he loses a number of _large_ packets. I could be wrong.. but I think this is one of those tradeoff situations.. catch-22 and all that.
Unfortunatly this won't help him. The QOS packet service is designed primarily for audio/video applications and would require that every router he connected through strictly obeyed the 802.1p protocol. That is just not going ot happen.It also requires a heck of a lot more then just clicking that little check box on the XP client. You can just consider that an on/off switch, the real work is done at the server and endpoint router levels.
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Have a look at this link for some futher explaination. http://infocenter.cramsession.com/techlibrary/get
If you wanna get rich, you know that payback is a bitch
Don't know if it is his provider or his hardware, but my cablemodem connection does the same thing. And it seems to be dependent on the cablemodem hardware.
When I first got my cablemodem connection, it was with an older hybrid cablemodem. Got about 1.8mbit/sec downstream, and about 500kbit/sec upstream, and I could use all of that upstream and it didn't affect my downstream at all.
About a year after signing up for the cablemodem, my ISP "upgraded" their network, and I got a new cablemodem. DOCSIS 1.0 (1.1?) 3Com USRobotics Cable Modem CMX. It maxed out at about 2.2mbit/sec downstream, but only about 256kbit/sec upstream, and now, when I use all of the upstream, my downstream drops to about 350kbit/sec. (I say "maxed" because I think they dropped the max downstream to about 1.5mbit/sec 6 months ago, a year after I got the new cablemodem.) The computer connected to the cablemodem did not change at all, so this was purely from the cablemodem change.
So I would also be interested in something that can prioritize the packet ACKs, since the cablemodem doesn't seem to do it itself anymore.
I do tend to regard this as a hardware issue with the cablemodem. From reading this, you can probably understand why.
This is my sig. There are many like it but this one is... Oops. Frank, I've got your sig again! Where's mine?
Unless I'm mistaken, that won't hlep.
What the QoS scheduler does in windows is permit applications who specifically request a certain qos to keep it. Í don't think it's a robus, configurable queuing system.
Bandwidth Limiting HOWTO might be of some assitance? Or not... either way. It just caught my eye on linuxdoc.
python -c "x='python -c %sx=%s; print x%%(chr(34),repr(x),chr(34))%s'; print x%(chr(34),repr(x),chr(34))"
So yes, traffic shaping can be your friend. Unfortunately, it may be hard to know what to tune it too, depending on where the bottleneck is.
Bill Stewart
New Fast-Compression-only CPR http://preview.tinyurl.com/dy575ks
I've been running BBIagent
http://www.bbiagent.net
for about the last year or so. I share my DSL with a few neighbors via some cat5 we strung up over the last year, and my counterstrikin was startin to hurt real bad whenever one of the teenager kids was downloading from kazza
Before I was using a linksys router. My current BBIagent setup is a packard bell p60 with 32 megs of ram, and 2 old 16 bit isa 3com nics. The performance increase is stunning.
You can specify what kind of traffic to create priority for, forward, block ports. There are a few options for hack detection blocking. The nicest features of bbiagent is.
1. Single floppy distro which is configured on the fly via the bbiagent website
2. Java app for admining the sucker, very well laid out.
3. Realtime control over your network connection without losing it. On my linkstink whenever I would change a rule or a forward the whole thing would reboot itself, bbiagent doesnt do that.
4. Open source!
5. Linux Based!
I can go on and on about it, but if you're really looking to control what and how packets are handled, I would really recomend giving bbiagent a try.
--toq
The reason your downstream rate gets limited by your upstream rate limit is because of your inability to send acknowledgements upstream for the downstream packets you are receiving because of the congestion on the upstream link.
Once the advertised receive window is filled with packets, the remote side is not going to send any more data until it gets an ack from your computer.
At the point that the rate is being limited, the way to fix this is to give preference to ACK packets -- i.e. packets without payload.
The problem is that this has to be done at the point the rate is being limited, which is at your providers router, not at your router, and not at your Windows machine.
Installing the Microsoft packet scheduler, or some UNIX box with a real netowrking stack that you can exercise fine control over packet priority, as some people have suggested, isn't really going to fix your problem, except by maybe 10% (the exact amount depends on your average outbound payload size relative to an "empty" ACK-only packet).
This is because the problem is the queued data in the transmit buffer in the rate limiting device not containing your ACK's for inbound data.
Really, the TCP/IP protocol wasn't built for asymmetric reates, without equally asymmetric data transfers.
Effectively, you need to be able to control the transmission of data packets from your end based on knowledge of how full the input buffor on the outbound leg for the rate limiting device gets, so that you can throttle your data payload packets accordingly, to keep that buffer as empty as possible.
The only way you can really do this is to put code in your stack to monitor the advertised window from the other side, and the locally classify outbound packets as to whether or not they contain data payload, or are merely acks. You basically have to avoid filling the outbound queue on the rate limiter above 50%.
In an ideal world, the machine doing the rate limiting would do this for you. Some rate limiting machines for asynchronous connection do this, and it's not a problem (you can see the posts from the people who are rate limited, and don't understand your problem). But those machines are more expensive, and it's just as well for the provider if you feel pain as feedback for uploading, since it serves their purpose in providing you asymmetric service in the first place.
The problem's a lot easier when you are trying to avoid filling the inbound receive buffer for a router with a speed differential on one side (e.g. the inbound receive buffer on a router connected to a dialup modem bank, with a customer on a modem wanting to do QoS based on protocol type, so their SSH didn't lock up when an FTP or large HTTP transfer started up). *That's* where things like "AltQ" and the Microsoft packet scheduling engine become useful... not here.
-- Terry
Try changing your local TCP buffering parameters instead to allow a bigger receive window. Set DefaultRcvWindow to something like 32768; the default is 8192, which is low for a DSL line, especially one that asymmetrical. With a bigger setting, you can have more data in flight, which makes the TCP connection more tolerant of delays in ACK return.
Given the numbers you're reporting, your ACK delay isn't that severe. You're only losing 2/3 of your downstream bandwidth. So quadrupling the amount of data allowed in flight should overcome that problem. Prioritizing your uplink traffic should be unnecessary at this time.
A real question to ask is "why are you trying to run a server on a 96Kb/s line". Buy hosting from somebody; it's cheap and they'll have far more bandwidth.
You can play with these settings to get the best performance, but in general these should help out some.
c es\Tcpip\Parameters
e ntVersion\Internet Settings\
Note that, at most, simply disable then re-enable the network adapter in question. No rebooting should be required to make any of this take effect.
Keys: HKEY_LOCAL_MACHINE\System\CurrentControlSet\Servi
GlobalMaxTCPWindowSize:DWORD = 256960
This should be a multiple of MSS, which is generally MTU - 40. Best results - pick a multiple of MSS lower than 16-bit (65535) times a scale factor that's a power of two. In other words, pick any multiple of MSS as long as it's under 65535, them multiply that by any power of two to arrive at the TCP Window size (RWIN).
Tcp1323Opts:DWORD = 1
This enables RFC 1323 options, which allows for a TCP RWIN greater than 64k. If you don't do this, most of the other settings are bunk as they will be limited by the 64k RWIN value.
EnablePMTUDiscovery:DWORD = 1
Enables automatic discovery of the MTU for your line, with the MSS set appropriately. You can set this to "0" to force your own value (see below).
TcpMaxDupAcks:DWORD = 2 (range from 1 to 3)
Number of duplicate ACKs recv'd for the same seq number of sent data before fast retrans is triggered.
NOW on to the MTU: it must be set on a per-interface basis. Find your TCP/IP interface associated with your NIC under Parameters\Interfaces\
MTU:DWORD = 1500 (probably... depends on your provider.)
On an unrelated note, you can force IE to hit up a web server with more connections than normal, which can help web pages load more concurrently.
it's under HKEY_CURRENT_USER\Software\Microsoft\Windows\Curr
MaxConnectionsPerServer:DWORD = 20
MaxConnectionsPer1_0Server:DWORD = 20
First is HTTP1.1+ servers, the other is HTTP1.0 servers. Specifies the max # of connections IE will open to a single web server in the process of downloading a page.
Natural != (nontoxic || beneficial)
ADSL is duplex.
ADSL works by dividing the usable range of frequencies on your phone line into segments.
Lets say that your analogue phone line can support transmission to the local exchange of frequencies from about 0 to 1100 Khz (or there abouts) over copper. The bottom 4Khz is reserved for voice. (I dont know if voice is compressed, I suspect there is some sort of companding in action to give a wider actual response but I dont know.. but the frequency range is adequate.) Then there is a band from about 30Khz to 140 Khz that is used to support the upstream channel, and then frequencies above that out to about 1100Khz are used to support downloads. There is a gaurd band between each band that eliminates crosstalk induced by imperfect transmission conditions.
This arangement gives you 256Kbps Up and 1500kbps down. Filters are used to isolate the appropriate channels at either end for voice, upload, and download. But the point is that its duplex by design, singnals go both ways SIMULTANEOUSLY over the wire. Remember that ADSL transmission is analogue, thats why you have a MODEM (its an acronym, not a noun!)
So as has already been explained by previous posters, the most likely problem is that as you flood the upstream channel, your ACK packets are being queued, the network devices upstream then start to throttle back your downstream feed, as the ACKs are taking too long to come back. This is done to minimise the number of packets that will be dropped and resent to your address. Of course you arent dropping any packets , but the upstream devices dont/cant know that.
Anyway hope that helps. The July 2002 edition of Australian Personal Computer has a lovely graphic that explains how ADSL works and why you can use your phone and have a nice broadband connection at the same time. Unfortunately this article isnt on their site http://www.apcmag.com
Cheers
Micko
His upstream is 96Kbit, and his downstream is 1.5Mbit.
In round numbers, this means his upstream is slightly less than 1/16th his downstream.
Say his MTU is 1500 bytes. Let's say his ACK packets are 64 bytes (we were generous on the 1/16th, so 64 instead of 60 is not that far off).
That basically means that, assuming no packets are lost, and that all ACK packets are precisely equally spaced, then 2/3rds of his upstream bandwidth needs to be dedicated to ACK traffic for the downstream bandwidth.
Why do we have to assume equal spacing? Because he can't control anything other than his send order, because he can't control the rate limiting machine's discard.
Is it possible to do this with a traffic shaper on the client machine? Yes, with a very sophisticated traffic shaper, which maintains stateful information (e.g. like a PIX firewall maintains per connection state information). It's possible because now we know the numbers for his connection -- we don't know the general numbers, though, for *any* assymetric link, so this isn't something you could make into an installable package, without the user having to resort to math/tuning tools.
Even so... this only works if the traffic is connection oriented. So far, people have asked -- and he hasn't responded -- about the kind of traffic he's running.
If the download traffic is RTSP or UDP or any protocol based on packets other than TCP packets, then there's no way to make preference choices on packets sent out. And then he's back in exactly the same boat he was in before.
So it's not possible to say "install this", and it's not possible to say "install this, and set these tuning values based on your relative upstream and downstream speeds", unless you really limit the problem you are trying to solve.
Doing that will probably not be satisfying, since the primary reason for a (mostly) unidirectional pipe is to push content to users, and most content streaming protocols are not based on TCP or other things which can be stateful.
-- Terry
For those interested in knowing how to tweak your ADSL, cable modem settings in Windows, the following link contains excellent and comprehensive information on how to achieve peak download speed: Navas Cable Modem/DSL Tuning GuideTM
¦ ©® ±
You might want to have a look at the following projects:
Traffic Control - Next Generation
Differential Services
GTC - A Graphical frontend the Linux kernel Traffic Control
WRR and WIP
And, yes, those are all Linux solutions, but that's simply because that' all I found available without paying 20.000 dollars.
echo '[q]sa[ln0=aln80~Psnlbx]16isb572CCB9AE9DB03273snlbxq' |dc
Increasing the window size will not change the packet size. The packets requireing retransmission will retransmitted irrespective of the window size.
There are two things he could do that might improve things, increase window size which means that the sender will not require an ACK so often or increase packet size so not as many ACKs are needed in the first place. Both may help but don't confuse them.
Zero Sum (don't amount to much). [root@localhost]
The latency is -- most likely -- caused by the huge buffers in the modem. It *is* possible to improve the situation locally. It's got nothing to do with asymetric lines or somesuch.
It's simple: what happens is that the upstream buffer in the DSL modem does'nt prioritize traffic at all, most likely it's just FIFO and big. So if the buffer is 128kB and you're serving a big file, your next Telnet packet is going to have to wait for these 128kB to go up before going itself.
The solution: have a router that artificially limit the outgoing bandwidth to slightly less that the DSL line permits to make sur the modem's buffer never fills up. Then it's the router's buffers that are filling up; but your router is smarter and you can have it order packet. IE if you have 128kB worth of warez0r waiting to go up, it can decide to let that lone Telnet packet go first.
Me I installed Wonder Shaper, works very well esp. when you've identified what causes the contention (just add the relevant ports to the junk traffic list), even if I completely saturate the link. There's one thing that doesn't work tho: I discovered that at times I had huge ping, again, even with wshaper. What happens (*I think*) is that my ISP is getting overloaded at times, and my actual bandwidth goes below what I set it to in Wshaper. I have to find a way to improve this.
"By increasing the recieve window you are essentially reducing the amount of ACK's that must be sent per data recieved."
The problem with this theory is that you need to keep sending ACKs all the time to keep the window sliding. Yes, if you were to only send ACKs starting at 50% of the window size received, and you had a large enough receive window that the propagation delay for an ACK through a totally saturated link was less than 50% of the time necessary to receive the data being ACK'ed, and the rate limiter queued all packets, instead of just droping them, then you'd be right.
But that's not what you do.
The point of a windowed protocol is that you eat a single round trip latency over a very large data stream consisting of a large number of packets, and what you are saying is that it will act as if TCP/IP is a lock-step fixed window protocol. This just isn't true.
So you compete for transmit space with the same number of ACK packets.
The problem is still that you need 2/3 of the send bandwith just for ACKs on a saturated receive bandwidth.
I would be really surprised if the send bandwidth limit wasn't set with *exactly this* in mind: large enough to handle full speed receives with an MTU of 1500 and an ACK packet size of 60 bytes, plus 50% (1.5Mb/96Kbit = 16, 1500/60 = 25, 25/16 = 150%).
-- Terry
Like others said, get a cheapo box throw two ethernet cards in it, load Linux, and use it as a router. I have this setup myself, along with 4 Windows machines behind it.
Believe me, I sleep better at night, knowing that I have Linux between the Internet and my Windows boxes. There are a number of good firewall/proxy/router tools for Linux. You can then use the traffic shaping software, and more importantly, you don't have to worry about the constant security weaknesses found in Windows that make your machine an easy target for hackers.
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