Subject: Fwd: SDL-News: PDU parseing in SDL
From: William H. Skelton (W.Skelton#SOLINET.com)
Date: Sun Feb 29 2004 - 11:06:47 GMT
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-----From "William H. Skelton" <W.Skelton#SOLINET.com> to sdlnews -----
One way to do this (and in my opinion the cleanest) is to isolate the PDU
formatting from the protocol state machine, for example by having a codec
process that converts from the PDU format to a signal format depending on
This way you end up with one signal per PDU event and the signal parameters
correspond to the PDU parameters.
In fact a whole stack can be cleanly built using SDL signals for the
primitives between the layers, where each layer has a codec and an
FSM. The signal list for the upper side of an FSM provides the primitives
for layer above it.
Of course this doesn't help with the actual encoding/decoding of the PDU
itself and you may prefer to resort to external procedures written, for
example, in C to handle the low-level formatting.
In the SDL Task Force (www.SDL-Task-Force.org) we are considering some SDL
extensions to make PDU formatting much easier, for example to encode/decode
PDUs according to ASN.1 specifications. Also how to use the same
principles for PDUs that were not defined using ASN.1. There will be an
update to the task force draft document in early March addressing some of
The SAFIRE-SDL tool chain, which is an SDL based environment for the
implementation and validation of signalling systems, already supports some
of these features in pre-release versions. You can contact the SAFIRE-SDL
support team for more details (Support#SAFIRE-SDL.com).
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>Subject: SDL-news: PDU parseing in SDL
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>-----From <livelonger#sohu.com> to sdlnews -----
> I have a problem in establishing a SDL model of a protocol . As we
> all know ,the PDUs in a protocol maybe in all kind of formats
> ,discriminated by a protoocol discriminator . The PDUs are enclosed in a
> primitive ,such as a DATA primitive . If the entity receives the
> primitive, it determines the format of the PDU by the discriminitor .
> Then the problem comes : All the signals in SDL have predefined parameter
> ,namely the PDU format . Then how to express the parsing process ?
> Thanks for answering me .
> Best regard .
> yours steven
>--End text from <livelonger#sohu.com> to sdlnews ---
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William H. Skelton, Engineering Dept.
SOLINET GmbH Solutions for Innovative Networks
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