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backup solution for WLL (?)

Hello all.

Does anybody has any idea on how to implement a backup solution for a wireless connection between an ethernet and an ATM interface?

The senario is the following:

An LMDS microwave system is used for the access part. The customer connects its router to the LMDS NTU via ethernet interface. The LMDS NTU encapsulates the packets in aal5 format, transmits them to the base station which connects to a cisco IGX switch through ATM interface. Finaly the ATM PVC is switched to a cisco 3640 ATM subinterface with aal5snap encapsulation and atm route-bridged ip configured. This senario works fine but some customers with critical applications, demand a backup solution in order to have maximum redudancy.

The problem on configuring backup solution for this connection is that, at the customer side there isn't a way of detecting carrier transitions (because of the ethernet interface).

My first thought was to use a virtual interface so that i can enable ppp and therefore, protocol transition detection on both sides. The thing is that ethernet doesn't support virtual-template (wich is supported by ATM) and ATM doesn't support multilink (wich is supported by ethernet).

Any suggestion will be highly appreciated!


Thanos Theodoropoulos

Forthnet SA


Community Manager

Re: backup solution for WLL (?)

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If anyone else in the forum has some advice, please reply to this thread.

Thank you for posting.


Re: backup solution for WLL (?)

Hi Thanos,

1.First of all to have any redundant solution one needs to have backup transmission meduim,backup hardware etc. Seems like the wireless microwave multipoint system is your main medium. You probably have 1+1 redunancy at the base station. I presume you might need a similar 1+1 for the NTU.

2.Your second question is directed towards detecting a carrier transition of your ATM PVC. Looks like you are using the 3640 router for routing IP to the respective ATM pvc which is then bridged to the customer ethernet. If that is the case then we can have some routing protocol running between the 3640 and the customer router or generate defaults from the 3640 to the customer router. AT any point of time if the ATM PVC fails the router stops seeing the default and routes it across the backup route.

Hope this helps......


Re: backup solution for WLL (?)

Hello Girish

First i want to thank you for your suggestions.

1)We indeed have a 1+1 redudancy in our Wireless network design but only in the BS side. The aproach to install equipment at the subscriber side in order to have full end-to-end redundancy is a very expencive solution therefore can only be aplied to very hi bitrate subscribers.

2)I already have considered that solution but implementing a dynamic routing protocol between us and the subscriber, is something we would like to avoid (then again, one cannot have everything...).

The aproach I was thinking about, is to have a data link protocol (e.g. ppp) between the two ends by using a virtual interface (such as multilink, dialer, or virtual-template) but i haven't find a sufficient way to do that.




Re: backup solution for WLL (?)

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