David,
I beg to differ.
You are correct in that the UARTs on most PC's, off-the-shelf, are limited to 115kpbs. However, there are
serial cards on the market which can surpass this data rate by a significant amount. Here's a quad-port PCI
serial adapter which provides almost 1mbps per channel:
*http://www.mycableshop.com/sku/PCI4S9503V.htm
I personally think that the serial card emulation approach is wise. Because:
There will be real-world flow-control issues when throttling between ethernet speeds and T1.
There is flexibility in using man (8) setserial for configuring the emulated WAN
The channels can be individually configured for 7 or 8 bit, thereby supporting test emulation
of 56kbps DS0s on a bit-robbed signaling for T1.
Full T1, fractional T1 and a pair of T1's/PairGain speed can also be emulated.
If the parts are lying around in order to create this hardware test bed, then this is truly a reasonable approach
for developing a flexible test environment.
My 2 bits. Marty
* ==================== David Rasch wrote:
Unfortunately, this isn't going to simulate a T1 very well as a
null-modem cable can only do 115200bps while a T1 can do approximately
1.5Mbps.
Other than the pf firewall mentioned by Aaron, I've done this previously with a VPN connection. For example, openvpn has a "--shaper" parameter which allows you to limit the speed of a connection to an arbitrary number of bytes/sec.
David
On Wed, Aug 11, 2004 at 01:17:21PM -0400, Greg Brown <[EMAIL PROTECTED]> wrote:
I did this once at Oculan.. sort of. I had two ethernet segments with a "wan" in the middle... here's how I did it.
Machine 1: ethernet port 192.168.13.1 network 192.168.13.0/24 serial port 192.168.14.1 Machine 2: serial port 192.168.14.2 ethernet port 192.168.16.1 network 192.168.16.0/24
I connected the serial ports via a null modem cable and, if memory serves, I used ppp to connected them together. Or was it slip? No, it was slip. I think this is the how-to webpage I used:
http://www.dbaoncall.net/references/ht_connect_2pc.html
That's about all I can recall, other than it worked. Hotgrits on the IRC channel might be able to help out with this, as I recall he was a wealth of knowledge regarding serial communication and linux.
Greg
On Wednesday, Aug 11, 2004, at 12:50 US/Eastern, Dan Monjar wrote:
Anyone know of any techniques to throttle bandwidth on a LAN for testing? We want to see how an application would run across a WAN of varying bandwidth. How would I make a Ethernet segment throttle down to something like T1 speeds?--
--
Dan Monjar
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