Properties and Features of Virtual 1394 bus

1. Properties and Features of Virtual 1394 bus Subrata Banerjee PHILIPS Research Briarcliff, New York P1394.1 WG Meeting, Huntington Beach, CaliforniaFebruary 11-12, 1999 PHILIPS Research

2. Motivation • To support multi-portal bridges • P1394.1 deals with only two-portal bridges • Specific scenario: • Multiple bridge portals connected via wireless medium VIRTUAL BUS 2-portal bridge PHILIPS

3. Differences in Operation between a virtual bus (VB) and P1394 bus 1. Concurrent transmission between multiple pairs of nodes allowed in a virtual bus (VB) 2. Non-broadcast asynchronous packets are sent to the destination node only and they may or may not be "seen" by other nodes in the virtual bus. 3. Isochronous packets are sent to only those nodes that have set their link devices to listen to the corresponding channel. PHILIPS

4. Differences in Operation between a virtual bus (VB) and 1394 bus 4. P1394 packets sent from one node in a VB to another may be stored and forwarded via intermediate node(s) in the VB. That is, not all pairs of nodes in a VB can communicate directly. 5. P1394 packets can be segmented and reassembled in a virtual bus, if required 6. VB may employ its own routing scheme 7. In a VB, virtual nodes can be simulated in software if needed. PHILIPS

5. Proposed Properties of a Virtual 1394 Bus 1. Existence of an IRM and Alpha PortalBandwidth Available depends on destination 2. Support for prime portal selection and master clock selection 3. Advertise maximum delay from one BP of a virtual bus to another BP in the same virtual bus 4. Implementation of 1394.1 Config ROM including • Speed map • Topology map PHILIPS

6. Proposed Properties of a Virtual 1394 Bus (contd.) 5. Clock distribution via the virtual bus with some guaranteed accuracy ~1 microsecond for 100ppm clocks 6. Support for fair, immediate and priority arbitration 7. Support of packet sizes allowed in 100Mbps bus or higher i.e., at least 512 bytes for block primary async. packets  isochronous packets size  max. BW reserved 8. Support for all types of serial bus packets including asynchronous stream packets PHILIPS

7. Proposed Properties of a Virtual 1394 Bus (contd.) 9. Support for Virtual Node ID management and related functions. 10. Mechanism for providing virtual bus topology map information. 11. Response packet generated by BP if a node in the virtual bus is unreachable 12. A virtual bus may choose to implement any other feature(s) of IEEE P1394 or IEEE P1394a. PHILIPS