Messages in this thread | | | Date | Fri, 25 Apr 2008 16:59:45 +0900 | From | "Shigeo N" <> | Subject | Re: XTP for 2.6.25 |
| |
I emulated WAN delay by netem and compared the performance again.
case1) fixed delay
<------------- 100Mbps --------------> Host1 --------- Linux Router ---------- Host2
In this case, just adds a fixed amount of delay to all packets going out on Linux Router by command, "tc qdisc add dev eth0 root netem delay 100ms".
Here is the result.
fixed delay UDP/TCP/XTP throghput --------------------------------------- 10ms 88/85/92 Mbps 30ms 88/70/91 Mbps 50ms 88/63/89 Mbps 70ms 88/52/84 Mbps 100ms 88/36/70 Mbps
case2) random delay
In this case, add a fixed amount of delay + 10% random delay by command, "tc change dev eth0 root netem delay 100ms 10ms 25%".
Here is the result.
fixed delay UDP/TCP/XTP throghput --------------------------------------- 10ms 88/80/92 Mbps 30ms 88/51/91 Mbps 50ms 88/41/89 Mbps 70ms 88/28/80 Mbps 100ms 88/19/66 Mbps
TCP's perfomance looks very poor when delay is long and variable.
Thanks Shigeo
On Thu, Apr 24, 2008 at 10:06 PM, Shigeo N <shigeonx@gmail.com> wrote: > Now I have connected 2 hosts directly, and evaluate the each throughput. > Then all the results of UDP, TCP and XTP are the same and 94Mbps. (My > netwrok is 100Base/TX). > > In this case round-trip time between 2 hosts is less than 0.1ms > because they are directly connected. But my previouse case, round-trip > time between 2 hosts are 4ms. (I use IPSEC between the security > gateways to increase delay). > I think that's the reason TCP throughput is slow. If ACK packets are > delayed, sending window cannot slide and sending packets cannot be > fully bursted. > > If I changes wmem size through /proc/sys/net/ipv4/tcp_wmem, TCP's > throughput may improve, but congestion control becomes more difficult > for TCP. > > That is TCP's disadvantage to XTP. > > Best > Shigeo > > > > On 4/24/08, Andi Kleen <andi@firstfloor.org> wrote: > > "Shigeo N" <shigeonx@gmail.com> writes: > > > > > > I tested in the network where UDP throughput is 29Mbps, then TCP > > > throughput was 13Mbps, but XTP's reached to 25Mbps. > > > > One interesting question is why TCP was so much slower than UDP > > on your test. It shouldn't be on a fair test setup. > > > > Please post details. Was the network losing packets? > > > > New protocols might be interesting, but even more interesting is to > > fix any (real) problems in existing protocols. > > > > -Andi > > >
| |