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Can I possibly simulate a 512kbps line between 2 server?

Posted on 2004-11-23
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Last Modified: 2010-04-10
The reason was we need to perform some test to simulate file/data transfer/replication over a 512/256kbps line but we do not have the luxury to actually perform the test on an actual one..

We have 2 servers, 2 switches 1 router.

Anyone know how to do it? with less equipment? any utility tools?
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Question by:stooi
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by:grblades
ID: 12662928
Hi stooi,
You could buy a couple of Cisco 2501 routers cheap off Ebay and then also get a DCE-DTE serial cable. You can then set the speed of the serial port to speeds up to 2Mbps.
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by:stooi
ID: 12663064
Hi grblades,

Thanks.. but can we do it with a crossover cable thru the BRI int instead? I have a couple of those 2503 routers without the DCE-DTE cable.

Please advice
thanks
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Expert Comment

by:muhalok
ID: 12663065
www.shunra.com - is your solution.
They sell the product that emulates WAN conditions (including bandwidth limitation).
Probably you'll need to test it not only on bandwidth limitation, but also on Latency, Packet Loss, Out of Order, Jitter and other network impairments.

They have 2 types of products: Stratus or Cloud for small testing projects and Storm for high rate traffic.

I work with all these tools and they are very good.
Good Luck.
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by:muhalok
ID: 12663068
You can get a free trial for Stratus and download it from the site.
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by:grblades
ID: 12663146
The BRI is an ISDN interface so in order to do what you want you will need an ISDN simulator. A DCE-DTE cable is not expensive and I got mine off Ebay for the equivilent of about $15.
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by:stooi
ID: 12663158
huh? please elaborate...
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by:stooi
ID: 12663177
muhalok,

What h/w does it require?


grblades,

 ok.. will try to get those cables.. hope its cheaper here.. can't wait to order from ebay..

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by:grblades
ID: 12663202
I got mine from the UK ebay site. I think the cables came from hong kong or somewhere like that.
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by:stooi
ID: 12663693
grblades,

can I just get one of those?
or Do I need to get two,
DCE Male---Male
DTE Female--Male ??

or just one of the back-back DCE/DTE DB60 crossover cable?
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Expert Comment

by:grblades
ID: 12664025
You just need a DCE/DTE crossover cable. Just be carefull it has the correct connectors as there are lots of different types available now.
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by:frajico
ID: 12664674
You can use Netlimiter .. a nice program than limits download/upload speed for any program running or network conection ....

Salu2
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by:rafael_acc
ID: 12670165
What is the purpose of simulating a link of 512 kbs without having one?! How could you get accurate results?!
Cheers.
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by:frajico
ID: 12670204
One posible purpose is to analyze if a lease line of 512 Kb would be enought to work properly between two or more locations or it must have a greater speed line.

Salu2
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by:rafael_acc
ID: 12670214
Yes. I know that we do can find some good reasons. But the author is talking about file transfer, isn't it?! So, what's the point?!
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by:rafael_acc
ID: 12670217
"(...) file/data transfer/replication over a 512/256kbps".
Am I missing something here?!

Sorry for the dbl post.
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by:frajico
ID: 12670259
Perhaps they need to work with raster or satellite images between locations, or work with big databases .... and want to evaluate the response time from the user point of view ...

Salu2
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by:rafael_acc
ID: 12670284
Are you really serious or just trying to make some odd point  point. Is this your real conclusion from the initial post??
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by:muhalok
ID: 12670454
rafael_acc, what is so hard to understand?

Salu2 gave you all the right reasons! To emphasize: Yes, that is what Author meant in the initial post.

Emulating network environments helps to predict the behaviour of the application over the real network. And this is a testing action - exactly as it is described in the initial post. "Transfer" is also done via some application and a protocol which needs to be tested for functionality and performance over the WAN network (limited bandwidth here).
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by:rafael_acc
ID: 12670524
Ok. Sorry for not being so clear to me! At least not from the initial post.
What do you care, anyway?! Was frajico asking for help or what?!

Puff ... Whatever ... I still don't agree ... Maybe the author should clarify what kind of transfer are we talking about here! Don't you agree?


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Author Comment

by:stooi
ID: 12671105
Errmm... sorry if I have not made my intentions clear or have mislead anyone here.

The reason we would like to simulate a WAN traffic is because, we are proposing a database replication and high availability solution to our client on their exisiting WAN, which is thru a frame relay network. However, we would like to perform a Proof of Concept and testing before the actual implementation. The objective is to ensure that we are prepared for it, know what to expect, and to justify for any bandwidth upgrade if we are able to simulate with multiple bandwidth transfer speed. From a rough calculation, it looks like the replication of their DB will take longer than the allowed duration, and also to simulate the DB accessibility by client when a replication is on-going as well as any other issues that we might encounter.

Frajico and Mulalok are adsolutely right about my objectives and has done great help.

I am still trying to get some trial software and also a DTEDCE crossover cable at the same time.

Will be able to conclude within the next few days.
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by:grblades
ID: 12672838
There are two aspects which can cause a slowdown over a frame relay link.
1) Bandwidth
2) Propegation delay

It may work over a particular bandwidth but if you are doing lots of small SQL queries the propegation delay will really kill your performance. File transfers should be unaffected by propegation delays (apart from windows which is crap in this respect) since they send multiple packets at a time (called windowing) and don't want for the first to be acknowledged before sending the next.
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by:stooi
ID: 12714176
grblades..
should be getting the cable tomorrow...
just wondering if you could help me with the command to limit the bandwidth?

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by:grblades
ID: 12714328
Here is an example configuration to enter on the serial interfaces. Just change the parameter to the 'clockrate' line to set the bandwidth. In this example it is set to 64K.


Router 1 (Using a DCE Cable)
!
 interface Serial0
ip address 172.16.22.1 255.255.255.0
encapsulation frame-relay
bandwidth 64
clockrate 64000
frame-relay local-dlci 20
frame-relay intf-type dce
!

 
Router 2 (Using a DTE Cable)
!
interface Serial0
ip address 172.16.22.2 255.255.255.0
encapsulation frame-relay
bandwidth 64
no fair-queue
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Author Comment

by:stooi
ID: 12723869

did exact same config... even write to mem...
serial interface is up.. but could not even perform a ping on its own ip.. needless to say on the opposite ip
any idea?

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Expert Comment

by:grblades
ID: 12724022
I know there is an issue with pinging the serial interfaces from the routers themselves.

On each router can you post the output of 'show int serial0'.

Have you made sure you have the cable plugged the correct way round?
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Author Comment

by:stooi
ID: 12733407
grblades..

thanks for the infor.. but made some changes at both ends and its up n running for now...thanks.. anyway still gonna paste the router config

DCE
-----
interface Serial0/0
 ip address 12.0.0.1 255.255.0.0
 encapsulation frame-relay
 clockrate 64000
 frame-relay map ip 12.0.0.3 20 broadcast
 frame-relay interface-dlci 20
 frame-relay intf-type dce

DTE
----
interface Serial0/0
 bandwidth 64000
 ip address 12.0.0.3 255.0.0.0
 encapsulation frame-relay
 no fair-queue
 frame-relay map ip 12.0.0.1 20 broadcast
 frame-relay interface-dlci 20

lemme know if there are anything I should amend?
thanks again.


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by:grblades
ID: 12733889
You have different subnet masks on each interface.
I would personally use a private range such as 10.0.0.1,10.0.0.3 instead otherwise you wont be able to access whoever uses these IP addresses on the Internet.
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Author Comment

by:stooi
ID: 12761437
What is the difference between clock rate and bandwidth?

I found that a 128000 bandwith with 500000 clock rate gives better throughput than 256000 bandwith with 250000 clock rate.

Please help to enlighten and differentiate between the two, and also which is the proper config to use for actual bandwidth simulation?

thanks again.
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Expert Comment

by:grblades
ID: 12761781
The 'clock rate' is the actual bandwidth over the serial connections. The 'bandwidth' parameter is only used for routing calculations by some routing protocols.
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Author Comment

by:stooi
ID: 12770250
But I can see there is are limitations on clock rate parameters as only certain fixed numbers could be selected, for example, only 125000 148000 250000 500000 are available. How could we possibly simulate a 384kbps, 256kbps with clock rate?

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Accepted Solution

by:
grblades earned 1260 total points
ID: 12771508
You wont be able to very well. 250000 is very close to 256Kbps. You will just have to test it at the available speeds and then extrapolate to estimate how it will perform at 384kbps. This is fine because in the real world you have contention ratios on DSL lines and propegation delays which you cannot simulate for.
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by:stooi
ID: 12790237
thanks
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