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Why MGX?

Hi friends,

I have been working with MGX for the last two to three months. but still i cant be clear about why do we require MGX? Are there any special features in those switches which other equipments do not support? What I mean is, the MGX are very costly, i could not justify the cost-benifit factor. Could anyone help me out.



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Re: Why MGX?

Hello Rajiv,

it all depends from what you want to do.

Are you doing this for job or for learning?

If your company wants to build an ATM network or better has an ATM network of some size it may involve MGX or the bigger BPX or similar devices from other vendors.

ATM is quite complex, for example the use of PNNI routing protocol to route SVCs on demand can be interesting but requires care in implementation.

If you are doing this for your own learning there can be other devices that can be used, that can be cheaper

Other considerations follow.

Twelve years ago ATM had been seen as the technology for core of networks. There was even ATM to the desktop I tested ATM 25 Mbps NICs on PCs for example, now none thinks of using this.

ATM has suffered the following facts:

the fast and cheap advancements in ethernet technologies

the POS tecnnology that allowed to use SDH/SONET without involving ATM

the advent of MPLS that is a virtualized and simplified ATM.

So now ATM is confined on specific niches in service provider networks but it is not in the inner core.

A 2,5 Gbps ATM interface if exists is much more expensive then a 2,5 POS interface.

But from a technical point of view ATM is still better then MPLS Traffic engineering.

Also scalability can be an issue: there are limits in how big can be an ATM network routed by PNNI and this has lead to the need of using multiple domains.

Hope to help


Re: Why MGX?

Hi Rajiv,

I will add my two cents from my experience to Giuseppe's good post. In one of my past jobs we had an ATM core with some low end MGX at network edge (I was working on router side and was not an admin in the ATM core, but I was cooperating with the ATM admin colleague in many cases). The core consisted of IGX's and BPX's. As far as I know, BPX is a high end pure ATM switch (i.e. all cards use ATM as layer 2). IGX's are more versatile (you can have other cards that support frame-relay for example). The MGX's are more versatile than IGX's.

I will now describe to you a characteristic application we had been using MGX's for. It was the transfer of international voice traffic. We had a circuit with Telecom Italia (it's a small world Giuseppe ). On our side the circuit would be connected to a BPX. The MGX would connect to the ATM core and to the voice equipment (I think we were using CESM cards for that last interconnection). We also had a router connected to the BPX for IP traffic. So, by using ATM VC's, we could route IP traffic over the circuit and international voice traffic without the router being involved in the processing of voice. I guess the router couldn't manage the strict voice quality requirements for this setup, while "the main function of the Circuit Emulation Service Module (CESM) is to provide a constant bit rate (CBR) circuit emulation service by converting data streams into CBR AAL1 cells for transport across an ATM network". The setup from the other side was symmetric. I mean, we had something like that for voice:

and simultaneously for IP traffic:

Kind Regards,


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