Copyright 1999, S.D. Personick. All Rights Reserved. Telecommunications Networking II Lecture 28 IEEE 1394: FireWire ref: IEEE Spectrum April 1997

Copyright 1999, S.D. Personick. All Rights Reserved. IEEE 1394: FireWire Invented by Apple Computer Inc. Standardized by IEEE (1394) Targeted toward networks that combine computers and audio-video equipment (e.g., consumer home networks) Up to 400 Mbps data rate Asynchronous and Isochronous traffic

Copyright 1999, S.D. Personick. All Rights Reserved. IEEE 1394 FireWire (cont’d) Asynchronous data: You deliver a packet of N bytes ( 8 x N bits) to the node, with a nominal bit repetition rate (e.g., 10 Mbps +/- 10 ppm). Each separate packet has an associated destination address. It is inserted by its node into the bus using a contiguous sequence of available bytes.

Copyright 1999, S.D. Personick. All Rights Reserved. IEEE 1394 FireWire (cont’d) Isochronous data: There is a master clock that generates a continuous stream of clock pulses, and a periodic sequence of “cycles” (frames) that repeat every 125 microseconds. Bytes delivered to a node are inserted into these “cycles” using time slots that are reserved by the node.

Copyright 1999, S.D. Personick. All Rights Reserved. IEEE 1394 FireWire (cont’d) Isochronous data (cont’d): Bytes inserted into a cycle are identified by a “channel number” (not by a packet address). Streams of isochronous bytes are buffered in their associated node. By asking for more or fewer bytes per cycle, the buffers can be managed so that they don’t overflow or “underflow”.

Copyright 1999, S.D. Personick. All Rights Reserved. IEEE 1394: FireWire (cont’d) “Cycle start” 125 microseconds Isochronous data Asynchronous data

Copyright 1999, S.D. Personick. All Rights Reserved. IEEE 1394: FireWire (cont’d) Standard IEEE 1394 cable contains: two (2) twisted pairs and two power wires - supports up to 4.5 meters between nodes -daisy chain + branch configuration (no loops) -power wires keep all parts of the bus alive, even if a node is “not energized” Standard rates are 100, 200, and 400 Mbps Faster rates planned

Copyright 1999, S.D. Personick. All Rights Reserved. IEEE 1394: FireWire (cont’d) Self-configuring; “plug-and-play” -One node becomes the “root node” upon the initialization of the “bus” -New nodes can be added when the network is “hot” (Topology automatically configured) -Up to 63 nodes per bus (6-bit ID) -Up to 1023 buses per “system”

Copyright 1999, S.D. Personick. All Rights Reserved. IEEE 1394: FireWire (cont’d) The “root node” generates the master clock (“cycle master” function) and “cycle start” indicators; and manages access to the bus. The “isochronous resource manager” allocates reservations of time slots to nodes requesting to send isochronous data The “bus manager” performs functions such as power management and performance optimization

Copyright 1999, S.D. Personick. All Rights Reserved. IEEE 1394: FireWire (cont’d) Asynchronous packets are reserved a minimum of 20% of the bytes per cycle Layer 2 format is: “quadlets” (4 bytes), with a minimum of 4 quadlets for the header of an asynchronous packet Isochronous “packets” must be a minimum of 2 quadlets long (for channel number, …)

Copyright 1999, S.D. Personick. All Rights Reserved. IEEE 1394: FireWire (cont’d) Asynchronous and Isochronous packets contain two CRC’s: one for the header, and one for the payload