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Thursday, February 28, 2013

Delivery notice using XML

<note>
<to>receivers name</to>
<from>senders name</from>
<heading>Reminder</heading>
<body>Please bring that Data Communication book!</body>
</note>

Why does the OSI reference model have seven layers, not six or eight?

Because it was develop in that way. Nowadays, layer 2 is sometimes divided into 2 "sub-layers", and the MPLS protocol is considered to be between the layers 2 and 3, and is therefore sometimes called "layer 2.5", but the traditional 7 layers are usually maintained as the "official" layers. We might say this is for historical reasons.