Cell Relay Archive

["Saso Stojanovski" <sasos@nortelnetworks.com>]

sumit,


  1) concerning the conceppt of AAL2 overlay networks, here is an excerpt from a IEEE CommMag paper (june 1999, "Applying ATM/ALL2...", Goran Eneroth...):

   "An important consequence of the separation of the AAL2 signalling protocol from ATM signalling is that the AAL2 network can have its own addressing plan and routing, which allows multiple AAL2 overlay networks operating on top of a single ATM network. The addressing can be changed in any of the networks without degrading the efficiency of routing in the others. This mutual independence becomes
crucial when the operator of the ATM and AAL2 network is not the same organisation, since it allows both parties to be in charge of the addressing within their own network. (An example can be a third-generation mobile network operator that leases the underlying ATM connections from an ATM service provider.)"

  2) concerning the signalling transport converters (STC), further below in the same paper:

   "The STC provides a set of generic primitives which are used by the signalling protocol when exchanging signalling messages with the peer signalling entities and receiving info about the conditions of the signalling network. The converter is responsible for translating the generic primitives into primitives offered by a specific signalling transport protocol, and vice versa. It hides all differencies
between the signalling transport services from the signalling protocol."


  3) concerning the AAL-2 end-to-end operation principle being broken: you can think that the end user of an AAL-2 service is the AAL-2 *multiplexer* (or *converter*), not the individual voice or data terminal. in that sense, the AAL-2 switch is also an AAL-2 "end user", since it demuxes and remuxes AAL-2 trunks.

AAL-2 has not much sense (if any) if a single AAL-2 flow is to be packed into a VC. instead, the end user would typically use AAL-1 or AAL-5, and then at some point in the cloud (which is the entry point to the AAL-2 overlay network) the AAL-1/5 streams would be converted + muxed into AAL-2 trunks. these entry points are the AAL-2 "end users".


cheers,
    v
--saso



sumit kasera wrote:

> Hi all,
> I am working on AAL2 Signaling protocol based on ITUT standard Q.2630. I went through it and there were certain things that I found rather strange. The most important being the concept of AAL2 network, an overlay over existing network. My idea was that AALs operated end to end. More specifically, I do not understand what is the function of an AAL type2 switch, and why does it perform routing function.
>
> Also, i did not like the notion of transport converters. I thought signaling could operate over one of the AAL2 channels using CID.
>
> In essence, the standard was rather complicated because of 1) Notion of AAL2 network  and 2) generic transport converters.
>
> Could someone kindly elucidate on these two concepts.
>
> Thanks and regards,
> sumit kasera
>
> Get your FREE Email and Voicemail at Lycos Communications - http://comm.lycos.com