In one of the last interviews given by Stanislaw Lem before his death he made it quite clear that he's not fond at all of the "Solaris" version made by Steven Soderbergh.
I do not have the text ready to quote it here, but he said that his book was about the relation of the humans to that oceanic intelligence and not a silly love story. He also added "well, at least they've paid me a nice compensation".:-)
Very well, so these guys claim to have a working traffic shaping router that will keep your latency down over ADSL under any condition.
Now let me tell you in brief what they, too, will have missed in their solution:
Since ADSL modems usually use ATM as their low-level protocol over the actual modem line, you get additional overhead when transmitting small packages. The problem is that this overhead is not accounted for by the kernel in question, since the kernel cannot know about the actual encoding used behind the network interface of the router in question (usually an ethernet device).
The size of an ATM frame is 40 bytes. This is less than the size of the smallest TCP package you can generate (due to the size of the TCP header). In turn, this leads to, say, all ACK packets being split up into two ATM frames with about 25% of additional overhead that is not accounted for by the kernel if you are using the built-in traffic control facilities.
Now have a download running and you will already be generating loads of ACK packets. You would have to severely cut down the permitted upload rate to keep the modem queue empty under this circumstance. Furthermore, the maximum to be allowed upload rate will differ depending on what you are doing with your line at a given moment.
Dan Singletary has written a user space traffic control daemon for Linux that is taking this very fact into account. You can download this here.
Even with such a solution in place, you still won't be able to get your guaranteed latency below a certain theoretical minimum while your line is fully saturated. This minimum depends on your base latency and upstream capacity.
Latency sensitive games will suffer, regardless what you do, and in many cases the typical hard-core gamer will not be satisfied.
Of course traffic shaping still really helps with interactive applications (SSH and the like) and even web browsing.
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In one of the last interviews given by Stanislaw Lem before his death he made it quite clear that he's not fond at all of the "Solaris" version made by Steven Soderbergh.
:-)
I do not have the text ready to quote it here, but he said that his book was about the relation of the humans to that oceanic intelligence and not a silly love story. He also added "well, at least they've paid me a nice compensation".
--Sigi
Very well, so these guys claim to have a working traffic shaping router that will keep your latency down over ADSL under any condition.
Now let me tell you in brief what they, too, will have missed in their solution:
Since ADSL modems usually use ATM as their low-level protocol over the actual modem line, you get additional overhead when transmitting small packages. The problem is that this overhead is not accounted for by the kernel in question, since the kernel cannot know about the actual encoding used behind the network interface of the router in question (usually an ethernet device).
The size of an ATM frame is 40 bytes. This is less than the size of the smallest TCP package you can generate (due to the size of the TCP header). In turn, this leads to, say, all ACK packets being split up into two ATM frames with about 25% of additional overhead that is not accounted for by the kernel if you are using the built-in traffic control facilities.
Now have a download running and you will already be generating loads of ACK packets. You would have to severely cut down the permitted upload rate to keep the modem queue empty under this circumstance. Furthermore, the maximum to be allowed upload rate will differ depending on what you are doing with your line at a given moment.
Dan Singletary has written a user space traffic control daemon for Linux that is taking this very fact into account. You can download this here.
Even with such a solution in place, you still won't be able to get your guaranteed latency below a certain theoretical minimum while your line is fully saturated. This minimum depends on your base latency and upstream capacity.
Latency sensitive games will suffer, regardless what you do, and in many cases the typical hard-core gamer will not be satisfied.
Of course traffic shaping still really helps with interactive applications (SSH and the like) and even web browsing.