Can someone explain this???

I posted a few days ago a message about a strange issue. To summarize we
have two offices connected with LANlink. This link is provided by network
provider. Office A (cisco 4503) is connected with 1GBits and office B (cisco
3750) is connected with 100Mbits.
When I do one large file ftp from A to B, the maximum speed I got is 2
Mbytes/s. The strange thing is: if I try to send 5 large files in the same
time then I got 2 mbytes/s for eeach file. Thus in total 10 Mbytes/s (the
maximum bandwidth).
These test have been done between two servers. The NICs have set to 100 full
duplex as well a the switch ports. I also checked that the FTP
server/client are not limiting the speed.
Thanks for thoughts
Reply to
Slimo
Loading thread data ...
There could be a per-connection rate-limit put on the link. It would be interesting to try ttcp with udp and tcp and see what results you get.
Can you hang another host off of the 4503 or 3750 and test the rate through that equipment without going through the WAN link, in order to double-check that it isn't something internal?
Reply to
Walter Roberson
~ I posted a few days ago a message about a strange issue. To summarize we ~ have two offices connected with LANlink. This link is provided by network ~ provider. Office A (cisco 4503) is connected with 1GBits and office B (cisco ~ 3750) is connected with 100Mbits. ~ ~ When I do one large file ftp from A to B, the maximum speed I got is 2 ~ Mbytes/s. The strange thing is: if I try to send 5 large files in the same ~ time then I got 2 mbytes/s for eeach file. Thus in total 10 Mbytes/s (the ~ maximum bandwidth). ~ ~ These test have been done between two servers. The NICs have set to 100 full ~ duplex as well a the switch ports. I also checked that the FTP ~ server/client are not limiting the speed. ~ ~ Thanks for thoughts ~
Sounds normal enough to me. You might, for example, be using TCP window sizes that are preventing each individual connection from fully using the available bandwidth.
Aaron
Reply to
Aaron Leonard
I did the test internally I can use the full bandwidth (10 Mbytes/s) per connection. The internal test was done using different vlan. So I can eliminate that my devices are not faulty.
Aaron Leonard a =E9crit :
Reply to
Slimo
Aaron isn't meaning that your devices are faulty but that they may need to be configured correctly to get full benefit of the LANlink connection. If you can tell us the delay on that link or the rough distance between Office A and Office B that would help. You might also want to have a look at Brian Tierney's TCP Tuning pages at .
Sam
Reply to
Sam Wilson
Thanks for the reply.
Delay between office A and office B is 4ms. We do not use any traffic shaping or policies. This is just a basic config with some static routes. The office are distant about 200km. Office A is connected with fiber optic single mode.
Please let me know if you need more info
Sam Wilson a =E9crit :
te:
Reply to
Slimo
If that 4ms is one-way delay then that suggests you will need about 100KB buffer size to utilise the 100Mbps that you have. says
buffer size = 2 * bandwidth * delay = 2 * 100e6 * 4e-3 bits = 800e3 bits = 100e3 bytes = 100KB approx
Have look at the OS tuning pages at that URL. If you're using Windows servers the documentation suggests that the default window and buffer size is 8KB or 16KB. Doing the inverse calculation
bandwidth = buffer size / 2 / delay = 16 * 1024 * 8 / 2 / 4e-3 =~ 16 Mbps =~ 2MB/sec
suggests that if you're seeing 2MB/sec that may be your problem.
Sam
Reply to
Sam Wilson

Cabling-Design.com Forums website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.