super_si

What software do people use to simulate networks?

Id like some pretty decent software to model my final project. Uni is using opnet but its running on Sun systems. I need something ideally windows based!

Si

ozzy

What exactly do you mean by 'simulate networks' ??

Foot_Tapper

Not quite sure what you are after either, but HP Openview may go some of the way.

http://www.managementsoftware.hp.com...tml#evaluation

stevencotton

OpenView is network monitoring software, OPNET is a network modelling environment.

super_si

Basically i design the network using the software then i run the simulation, it shows up potentail bottle necks and flaws in the design

Si

darlodge

I've used routerSim a little bot but this is only really for Cisco kit and its not cheap either.

Darren

ozzy

Ah, right I follow you know.

Only stuff I've ever seen was in huge corporations and the stuff was mega expensive.

Never used anything like that myself, sorry.

darlodge

Stefan is correct, its most likely to be really expensive for what you want.

I've always found it easier designing things on a sheet of A3 paper anyway. It won't show bottle necks, design flaws etc. but it might be easier to see those when clearly list on paper. It is for me anyway.

Regards

super_si

heres another qu.

Is there any software out there that models the whole network "somehow" got a network with some 800 pcs at uni. Now i need diagrams of it and topology but there isnt any..........

ideas!!!!

Si

SiCotty

If you are designing a campus network you first need to understand the apps that are being used by the servers and the PCs. Almost all networks are designed with bandwidth / resource contention. a 48 port 10/100 switch links to the network core using a single gigabit Ethernet connection so you have approximately 5:1 contention if all PCs fill their 100MB pipe at once. If the PC's ran MS Office, did a bit of email, web, and file transfer then this is more than enough. In this environment you will hardly see the uplink utilisation go over 10MB. If you have high power workstations working on uncompressed broadcast quality video or high definition medical images then you would reduce the contention and possibly put in 1000MB to the desktop and a 10G uplink to the core.

Once you know the applications and traffic flows you then design the Layer2/Layer3, such as vlans and ip addressing structure, and pick the equipment. Have a look at security features within the switches and traffic monitoring apps.

If it’s a Uni network then you can bet that they want to stop you plugging in an unauthorised laptop with some PtoP software on it. Or a nice self propagating network worm picked up from the internet. Or you might decide to run a nice little tool such as ettercap (http://ettercap.sourceforge.net/).

A network simulator is only as good as what you give it. Most networks are designed using some basic rules such as oversubscription.

Si

Dazza's-STi

I use network instruments Observer..

Use it to monitor the network generaly for VOIP traffic analysis, but often network trend the network first. With the tool you can then run a what if scenario and the tool predict load and bottlenecks within the network...
Very good bit of software...
Avaialble... with me 4 a day... @ half what the company charges


download the tool and see, but it only works in demo mode... you would need a tool of this sort for sure, and unfortunaly they are quite expensive!

Dazza

super_si

Sicotty that sounds about right regarding the apps. this is what the contact replied to me with

A little lost, because i dont know what MLTS and ISTs are

S

SiCotty

Your contact is probably running a network based upon products from Nortel Networks. Possibly a combination of Baystack switches at the edge for user aggregation and Passports switches at the core.

MLT stands for Multi Link Trunking. The is a method of bonding together multiple 1Gig links to give increased bandwidth and redundancy. The effectiveness of MLT is dependent upon the hashing algorithm used to distribute traffic between the links. You commonly see MLT between core switches but it is also used between access and core/distribution switches. Nortel also have a propriatory varient called Split MLT which allows bonded uplinks to go to separate core switches. Normally when bonding a link using the standard 802.3ad protocol you can only link two switches together.

An IST is just an Inter Switch Trunk, so operates a protocol such as 802.1q which allows Ethernet frames to be tagged with the vlan number they reside in.

If the network is just L2 and you have more than about 150-200 nodes then you should think about using a L3 core.

The networks will probably look something like this:

2 Core switches connected together using MST.
Multiple Access switches either single or in a stack connected back to the core switches.
Each Access switch/stack connects to both core switches for redundancy using GigE.
Spanning tree (802.3d) is used to place one of the links into a blocked state to prevent a loop. One of the core switches will usually be assigned as the spanning tree root, the other as a backup.
If the network is flat L2, only one vlan will be configured (typically)

Si

super_si

Cool, i need to 1st model it. Then run a simluation in Opnet so see if i can indentify bottle necks etc. If what you say is correct L3 core could be a good investment!