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Seeing Into the Stack The proposed IMA (Inverse Multiplexing for ATM) specification defines features and functions that apply at a number of different ATM layers and sublayers. For instance, it affects the PMD (physical medium-dependent) sublayer, which handles bit timing, line encoding, and the physical medium interface, and is the layer at which IM A timing comes into play. IMA also affects the transmission convergence sublayer, which handles the placement of cells onto the physical wire. This is where the ATM cell stream is split and reconstructed in a round-robin fashion. It's also where compensation for differential delay between the composing links is performed, in addition to cell delineation (which makes recognition of the end of the cell possible) and HEC (header error check) generation and verification (which makes error control possible). Finally, IMA affects the management layer, where alarm detection and processing take place. The spec makes use of particular alarms to delete links from the group automatically. --P.Z. [ Home ] [ Registration | Subscriptions ] [ Contact Us | E-Mail ] Home Contact Editors Lab Tests Registration Tech Tutorials Buyer's Guide Global Networks Opinion / Columns FAQs Subscriptions