RFC 2734 (rfc2734) - Page 3 of 29

IPv4 over IEEE 1394

RFC 2734                  IPv4 over IEEE 1394              December 1999


   The CSR architecture describes a memory-mapped address space that
   Serial Bus implements as a 64-bit fixed addressing scheme. Within the
   address space, ten bits are allocated for bus ID (up to a maximum of
   1,023 buses), six are allocated for node physical ID (up to 63 per
   bus) while the remaining 48 bits (offset) describe a per node address
   space of 256 terabytes. The CSR architecture, by convention, splits a
   node's address space into two regions with different behavioral
   characteristics. The lower portion, up to but not including 0xFFFF
   F000 0000, is EXPECTED to behave as memory in response to read and
   write transactions. The upper portion is more like a traditional IO
   space: read and write transactions in this area usually have side
   effects. Control and status registers (CSRs) that have FIFO behavior
   customarily are implemented in this region.

   Within the 64-bit address, the 16-bit node ID (bus ID and physical
   ID) is analogous to a network hardware address---but 1394 node IDs
   are variable and subject to reassignment each time one or more nodes
   are added to or removed from the bus.

   NOTE: Although the 16-bit node ID contains a bus ID, at present there
   is no standard method to connect separately enumerated Serial Buses.
   Active development of a standard for Serial Bus to Serial Bus bridges
   is underway in the IEEE P1394.1 working group. Unless extended by
   some future standard, the IPv4 over 1394 protocols specified by this
   document may not operate correctly across bridges.

   The 1394 link layer provides a packet delivery service with both
   confirmed (acknowledged) and unconfirmed packets. Two levels of
   service are available: "asynchronous" packets are sent on a best-
   effort basis while "isochronous" packets are guaranteed to be
   delivered with bounded latency. Confirmed packets are always
   asynchronous but unconfirmed packets may be either asynchronous or
   isochronous. Data payloads vary with implementations and may range
   from one octet up to a maximum determined by the transmission speed
   (at 100 Mbps, named S100, the maximum asynchronous data payload is
   512 octets while at S400 it is 2048 octets).

   NOTE: Extensions underway in IEEE P1394b contemplate additional
   speeds of 800, 1600 and 3200 Mbps.












Johansson                   Standards Track