[TriLUG] throttling bandwidth in a test environment

[Marty Ferguson]

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 <gregbrown at mindspring.com> 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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>>>      
>>>
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>>    
>>
>
>  
>