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rfc:rfc2734

Network Working Group P. Johansson Request for Comments: 2734 Congruent Software, Inc. Category: Standards Track December 1999

                        IPv4 over IEEE 1394

Status of this Memo

 This document specifies an Internet standards track protocol for the
 Internet community, and requests discussion and suggestions for
 improvements.  Please refer to the current edition of the "Internet
 Official Protocol Standards" (STD 1) for the standardization state
 and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

 Copyright (C) The Internet Society (1999).  All Rights Reserved.

ABSTRACT

 This document specifies how to use IEEE Std 1394-1995, Standard for a
 High Performance Serial Bus (and its supplements), for the transport
 of Internet Protocol Version 4 (IPv4) datagrams; it defines the
 necessary methods, data structures and codes for that purpose. These
 include not only packet formats and encapsulation methods for
 datagrams, but also an address resolution protocol (1394 ARP) and a
 multicast channel allocation protocol (MCAP). Both 1394 ARP and MCAP
 are specific to Serial Bus; the latter permits management of Serial
 Bus resources when used by IP multicast groups.

TABLE OF CONTENTS

 1. INTRODUCTION.....................................................2
 2. DEFINITIONS AND NOTATION.........................................4
    2.1 Conformance..................................................4
    2.2 Glossary.....................................................4
    2.3 Abbreviations................................................6
    2.4 Numeric values...............................................6
 3. IP-CAPABLE NODES.................................................6
 4. LINK ENCAPSULATION AND FRAGMENTATION.............................7
    4.1 Global asynchronous stream packet (GASP) format..............8
    4.2 Encapsulation header.........................................9
    4.3 Link fragment reassembly....................................11
 5. SERIAL BUS ADDRESS RESOLUTION PROTOCOL (1394 ARP)...............11
 6. CONFIGURATION ROM...............................................14
    6.1 Unit_Spec_ID entry..........................................14
    6.2 Unit_SW_Version entry.......................................14

Johansson Standards Track [Page 1] RFC 2734 IPv4 over IEEE 1394 December 1999

    6.3 Textual descriptors.........................................15
 7. IP UNICAST......................................................16
 8. IP BROADCAST....................................................17
 9. IP MULTICAST....................................................17
    9.1 MCAP message format.........................................18
    9.2 MCAP message domain.........................................21
    9.3 Multicast receive...........................................21
    9.4 Multicast transmit..........................................22
    9.5 Advertisement of channel mappings...........................23
    9.6 Overlapped channel mappings.................................23
    9.7 Transfer of channel ownership...............................24
    9.8 Redundant channel mappings..................................25
    9.9 Expired channel mappings....................................25
    9.10 Bus reset..................................................26
 10. IANA CONSIDERATIONS............................................26
 11. SECURITY CONSIDERATIONS........................................27
 12. ACKNOWLEDGEMENTS...............................................27
 13. REFERENCES.....................................................28
 14. EDITOR'S ADDRESS...............................................28
 15. Full Copyright Statement.......................................29

1. INTRODUCTION

 This document specifies how to use IEEE Std 1394-1995, Standard for a
 High Performance Serial Bus (and its supplements), for the transport
 of Internet Protocol Version 4 (IPv4) datagrams. It defines the
 necessary methods, data structures and codes for that purpose and
 additionally defines methods for an address resolution protocol (1394
 ARP) and a multicast channel allocation protocol (MCAP)---both of
 which are specific to Serial Bus.
 The group of IEEE standards and supplements, draft or approved,
 related to IEEE Std 1394-1995 is hereafter referred to either as 1394
 or as Serial Bus.
 1394 is an interconnect (bus) that conforms to the CSR architecture,
 ISO/IEC 13213:1994. Serial Bus permits communications between nodes
 over shared physical media at speeds that range, at present, from 100
 to 400 Mbps. Both consumer electronic applications (such as digital
 VCRs, stereo systems, televisions and camcorders) and traditional
 desktop computer applications (e.g., mass storage, printers and
 tapes), have adopted 1394. Serial Bus is unique in its relevance to
 both consumer electronic and computer domains and is EXPECTED to form
 the basis of a home or small office network that combines both types
 of devices.

Johansson Standards Track [Page 2] 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 [Page 3] RFC 2734 IPv4 over IEEE 1394 December 1999

2. DEFINITIONS AND NOTATION

2.1 Conformance

 When used in this document, the keywords "MAY", "OPTIONAL",
 "RECOMMENDED", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD" and "SHOULD
 NOT" differentiate levels of requirements and optionality and are to
 be interpreted as described in RFC 2119.
 Several additional keywords are employed, as follows:
 EXPECTED: A keyword used to describe the behavior of the hardware or
 software in the design models assumed by this standard. Other
 hardware and software design models may also be implemented.
 IGNORED: A keyword that describes bits, octets, quadlets or fields
 whose values are not checked by the recipient.
 RESERVED: A keyword used to describe either objects---bits, octets,
 quadlets and fields---or the code values assigned to these objects;
 the object or the code value is set aside for future standardization.
 A RESERVED object has no defined meaning and SHALL be zeroed by its
 originator or, upon development of a future standard, set to a value
 specified by such a standard. The recipient of a RESERVED object
 SHALL NOT check its value. The recipient of an object whose code
 values are defined by this standard SHALL check its value and reject
 RESERVED code values.

2.2 Glossary

 The following terms are used in this standard:
 address resolution protocol: A method for a requester to determine
 the hardware (1394) address of an IP node from the IP address of the
 node.
 bus ID: A 10-bit number that uniquely identifies a particular bus
 within a group of multiple interconnected buses. The bus ID is the
 most significant portion of a node's 16-bit node ID. The value 0x3FF
 designates the local bus; a node SHALL respond to requests addressed
 to its 6-bit physical ID if the bus ID in the request is either 0x3FF
 or the bus ID explicitly assigned to the node.
 encapsulation header: A structure that precedes all IP data
 transmitted over 1394. See also link fragment.
 IP datagram: An Internet message that conforms to the format
 specified by STD 5, RFC 791.

Johansson Standards Track [Page 4] RFC 2734 IPv4 over IEEE 1394 December 1999

 link fragment: A portion of an IP datagram transmitted within a
 single 1394 packet. The data payload of the 1394 packet contains both
 an encapsulation header and its associated link fragment. It is
 possible to transmit datagrams without link fragmentation.
 multicast channel allocation protocol: A method for multicast groups
 to coordinate their use of Serial Bus resources (channels) if
 multicast datagrams are transmitted on other than the default
 broadcast channel.
 multicast channel owner: A multicast source that has allocated a
 channel for one or more multicast addresses and transmits MCAP
 advertisements to communicate these channel mapping(s) to other
 participants in the IP multicast group. When more than one source
 transmits MCAP advertisements for the same channel number, the source
 with the largest physical ID is the owner.
 node ID: A 16-bit number that uniquely identifies a Serial Bus node
 within a group of multiple interconnected buses. The most significant
 ten bits are the bus ID and the least significant six bits are the
 physical ID.
 node unique ID: A 64-bit number that uniquely identifies a node among
 all the Serial Bus nodes manufactured worldwide; also known as the
 EUI-64 (Extended Unique Identifier, 64-bits).
 octet: Eight bits of data.
 packet: Any of the 1394 primary packets; these may be read, write or
 lock requests (and their responses) or stream data. The term "packet"
 is used consistently to differentiate Serial Bus primary packets from
 1394 ARP requests/responses, IP datagrams or MCAP
 advertisements/solicitations.
 physical ID: On a particular bus, this 6-bit number is dynamically
 assigned during the self-identification process and uniquely
 identifies a node on that bus.
 quadlet: Four octets, or 32 bits, of data.
 stream packet: A 1394 primary packet with a transaction code of 0x0A
 that contains a block data payload. Stream packets may be either
 asynchronous or isochronous according to the type of 1394 arbitration
 employed.

Johansson Standards Track [Page 5] RFC 2734 IPv4 over IEEE 1394 December 1999

2.3 Abbreviations

 The following are abbreviations that are used in this standard:
    1394 ARP Address resolution protocol (specific to 1394)
    CSR      Control and status register
    CRC      Cyclical redundancy checksum
    EUI-64   Extended Unique Identifier, 64-bits
    GASP     Global asynchronous stream packet
    IP       Internet protocol (within this document, IPv4)
    MCAP     Multicast channel allocation protocol

2.4 Numeric values

 Decimal and hexadecimal numbers are used within this standard. By
 editorial convention, decimal numbers are most frequently used to
 represent quantities or counts. Addresses are uniformly represented
 by hexadecimal numbers, which are also used when the value
 represented has an underlying structure that is more apparent in a
 hexadecimal format than in a decimal format.
 Decimal numbers are represented by Arabic numerals or by their
 English names. Hexadecimal numbers are prefixed by 0x and represented
 by digits from the character set 0 - 9 and A - F. For the sake of
 legibility, hexadecimal numbers are separated into groups of four
 digits separated by spaces.
 For example, both 42 and 0x2A represent the same numeric value.

3. IP-CAPABLE NODES

 Not all Serial Bus devices are capable of the reception and
 transmission of 1394 ARP requests/responses or IP datagrams. An IP-
 capable node SHALL fulfill the following minimum requirements:
  1. it SHALL implement configuration ROM in the general format

specified by ISO/IEC 13213:1994 and SHALL implement the bus

   information block specified by IEEE P1394a and a unit directory
   specified by this standard;
  1. the max_rec field in its bus information block SHALL be at least 8;

this indicates an ability to accept block write requests and

   asynchronous stream packets with data payload of 512 octets. The
   same ability SHALL also apply to read requests; that is, the node
   SHALL be able to transmit a block response packet with a data
   payload of 512 octets;

Johansson Standards Track [Page 6] RFC 2734 IPv4 over IEEE 1394 December 1999

  1. it SHALL be isochronous resource manager capable, as specified by

IEEE P1394a;

  1. it SHALL support both reception and transmission of asynchronous

streams as specified by IEEE P1394a; and

4. LINK ENCAPSULATION AND FRAGMENTATION

 All IP datagrams (broadcast, unicast or multicast), 1394 ARP
 requests/responses and MCAP advertisements/solicitations that are
 transferred via 1394 block write requests or stream packets SHALL be
 encapsulated within the packet's data payload. The maximum size of
 data payload, in octets, is constrained by the speed at which the
 packet is transmitted.
             Table 1 - Maximum data payloads (octets)
                Speed   Asynchronous   Isochronous
              +------------------------------------+
              |  S100 |      512     |     1024    |
              |  S200 |     1024     |     2048    |
              |  S400 |     2048     |     4096    |
              |  S800 |     4096     |     8192    |
              | S1600 |     8192     |    16384    |
              | S3200 |    16384     |    32768    |
              +------------------------------------+
 NOTE: The maximum data payloads at speeds of S800 and faster may be
 reduced (but will not be increased) as a result of standardization by
 IEEE P1394b.
 The maximum data payload for asynchronous requests and responses may
 also be restricted by the capabilities of the sending or receiving
 node(s); this is specified by max_rec in either the bus information
 block or 1394 ARP response.
 For either of these reasons, the maximum data payload transmissible
 between IP-capable nodes may be less than the default 1500 octet
 maximum transmission unit (MTU) specified by this document. This
 requires that the encapsulation format also permit 1394 link-level
 fragmentation and reassembly of IP datagrams.
 NOTE: IP-capable nodes may operate with an MTU size larger than the
 default, but the means by which a larger MTU is configured are beyond
 the scope of this document.

Johansson Standards Track [Page 7] RFC 2734 IPv4 over IEEE 1394 December 1999

4.1 Global asynchronous stream packet (GASP) format

 Some IP datagrams, as well as 1394 ARP requests and responses, may be
 transported via asynchronous stream packets. When asynchronous stream
 packets are used, their format SHALL conform to the global
 asynchronous stream packet (GASP) format specified by IEEE P1394a.
 The GASP format illustrated below is INFORMATIVE and reproduced for
 ease of reference, only.
                     1                   2                   3
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |          data_length          |tag|  channel  |  0x0A |   sy  |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                           header_CRC                          |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |           source_ID           |        specifier_ID_hi        |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |specifier_ID_lo|                    version                    |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                                                               |
 +---                           data                          ---+
 |                                                               |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                            data_CRC                           |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                       Figure 1 - GASP format
 The source_ID field SHALL specify the node ID of the sending node and
 SHALL be equal to the most significant 16 bits of the sender's
 NODE_IDS register.
 The specifier_ID_hi and specifier_ID_lo fields together SHALL contain
 the value 0x00 005E, the 24-bit organizationally unique identifier
 (OUI) assigned by the IEEE Registration Authority (RA) to IANA.
 The version field SHALL be one.
 NOTE: Because the GASP format utilizes the first two quadlets of data
 payload in an asynchronous stream packet format, the maximum payloads
 cited in Table 1 are effectively reduced by eight octets. In the
 clauses that follow, references to the first quadlet of data payload
 mean the first quadlet usable for an IP datagram or 1394 ARP request
 or response.  When the GASP format is used, this is the third quadlet
 of the data payload for the packet.

Johansson Standards Track [Page 8] RFC 2734 IPv4 over IEEE 1394 December 1999

4.2 Encapsulation header

 All IP datagrams transported over 1394 are prefixed by an
 encapsulation header with one of the formats illustrated below.
 If an entire IP datagram may be transmitted within a single 1394
 packet, it is unfragmented and the first quadlet of the data payload
 SHALL conform to the format illustrated below.
                      1                   2                   3
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 | lf|          reserved         |           ether_type          |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        Figure 2 - Unfragmented encapsulation header format
 The lf field SHALL be zero.
 The ether_type field SHALL indicate the nature of the datagram that
 follows, as specified by the following table.
                    ether_type   Datagram
                  +-------------------------+
                  |   0x0800   |   IPv4     |
                  |   0x0806   |   1394 ARP |
                  |   0x8861   |   MCAP     |
                  +-------------------------+
 NOTE: Other network protocols, identified by different values of
 ether_type, may use the encapsulation formats defined herein but such
 use is outside of the scope of this document.
 In cases where the length of the datagram exceeds the maximum data
 payload supported by the sender and all recipients, the datagram
 SHALL be broken into link fragments; the first two quadlets of the
 data payload for the first link fragment SHALL conform to the format
 shown below.
                      1                   2                   3
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 | lf|rsv|      datagram_size    |           ether_type          |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |              dgl              |            reserved           |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       Figure 3 - First fragment encapsulation header format

Johansson Standards Track [Page 9] RFC 2734 IPv4 over IEEE 1394 December 1999

 The second and subsequent link fragments (up to and including the
 last) SHALL conform to the format shown below.
                      1                   2                   3
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 | lf|rsv|      datagram_size    |  rsv  |    fragment_offset    |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |              dgl              |            reserved           |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   Figure 4 - Subsequent fragment(s) encapsulation header format
 The definition and usage of the fields is as follows:
    The lf field SHALL specify the relative position of the link
    fragment within the IP datagram, as encoded by the following
    table.
                      lf      Position
                   +------------------------+
                   |   0   |  Unfragmented  |
                   |   1   |  First         |
                   |   2   |  Last          |
                   |   3   |  Interior      |
                   +------------------------+
    datagram_size: The encoded size of the entire IP datagram. The
    value of datagram_size SHALL be the same for all link fragments of
    an IP datagram and SHALL be one less than the value of Total
    Length in the datagram's IP header (see STD 5, RFC 791).
    ether_type: This field is present only in the first link fragment
    and SHALL have a value of 0x0800, which indicates an IPv4
    datagram.
    fragment_offset: This field is present only in the second and
    subsequent link fragments and SHALL specify the offset, in octets,
    of the fragment from the beginning of the IP datagram. The first
    octet of the datagram (the start of the IP header) has an offset
    of zero; the implicit value of fragment_offset in the first link
    fragment is zero.

Johansson Standards Track [Page 10] RFC 2734 IPv4 over IEEE 1394 December 1999

    dgl: The value of dgl (datagram label) SHALL be the same for all
    link fragments of an IP datagram. The sender SHALL increment dgl
    for successive, fragmented datagrams; the incremented value of dgl
    SHALL wrap from 65,535 back to zero.
 All IP datagrams, regardless of the mode of transmission (block write
 requests or stream packets) SHALL be preceded by one of the above
 described encapsulation headers. This permits uniform software
 treatment of datagrams without regard to the mode of their
 transmission.

4.3 Link fragment reassembly

 The recipient of an IP datagram transmitted via more than one 1394
 packet SHALL use both the sender's source_ID (obtained from either
 the asynchronous packet header or the GASP header) and dgl to
 identify all the link fragments from a single datagram.
 Upon receipt of a link fragment, the recipient may place the data
 payload (absent the encapsulation header) within an IP datagram
 reassembly buffer at the location specified by fragment_offset. The
 size of the reassembly buffer may be determined from datagram_size.
 If a link fragment is received that overlaps another fragment
 identified by the same source_ID and dgl, the fragment(s) already
 accumulated in the reassembly buffer SHALL be discarded. A fresh
 reassembly may be commenced with the most recently received link
 fragment. Fragment overlap is determined by the combination of
 fragment_offset from the encapsulation header and data_length from
 the 1394 packet header.
 Upon detection of a Serial Bus reset, recipient(s) SHALL discard all
 link fragments of all partially reassembled IP datagrams and
 sender(s) SHALL discard all not yet transmitted link fragments of all
 partially transmitted IP datagrams.

5. SERIAL BUS ADDRESS RESOLUTION PROTOCOL (1394 ARP)

 Methods to determine the hardware address of a device from its
 corresponding IP address are inextricably tied to the transport
 medium utilized by the device. In the description below and
 throughout this document, the acronym 1394 ARP pertains solely to an
 address resolution protocol whose methods and data structures are
 specific to 1394.
 1394 ARP requests SHALL be transmitted by the same means as broadcast
 IP datagrams; 1394 ARP responses MAY be transmitted in the same way
 or they MAY be transmitted as block write requests addressed to the

Johansson Standards Track [Page 11] RFC 2734 IPv4 over IEEE 1394 December 1999

 sender_unicast_FIFO address identified by the 1394 ARP request. A
 1394 ARP request/response is 32 octets and SHALL conform to the
 format illustrated by Figure 5.
                     1                   2                   3
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |    hardware_type (0x0018)     |    protocol_type (0x0800)     |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |  hw_addr_len  |  IP_addr_len  |            opcode             |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                                                               |
 +---                     sender_unique_ID                    ---+
 |                                                               |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 | sender_max_rec|      sspd     |     sender_unicast_FIFO_hi    |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                      sender_unicast_FIFO_lo                   |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                        sender_IP_address                      |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                        target_IP_address                      |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
            Figure 5 - 1394 ARP request/response format
 1394 ARP requests and responses transported by asynchronous stream
 packets SHALL be encapsulated within the GASP format specified by
 IEEE P1394a (see also 4.1). The recipient of a 1394 ARP request or
 response SHALL ignore it unless the most significant ten bits of the
 source_ID field (whether obtained from the GASP header of an
 asynchronous stream packet or the packet header of a block write
 request) are equal to either 0x3FF or the most significant ten bits
 of the recipient's NODE_IDS register.
 Field usage in a 1394 ARP request/response is as follows:
    hardware_type: This field indicates 1394 and SHALL have a value of
    0x0018.
    protocol_type: This field SHALL have a value of 0x0800; this
    indicates that the protocol addresses in the 1394 ARP
    request/response conform to the format for IP addresses.
    hw_addr_len: This field indicates the size, in octets, of the
    1394-dependent hardware address associated with an IP address and
    SHALL have a value of 16.

Johansson Standards Track [Page 12] RFC 2734 IPv4 over IEEE 1394 December 1999

    IP_addr_len: This field indicates the size, in octets, of an IP
    version 4 (IPv4) address and SHALL have a value of 4.
    opcode: This field SHALL be one to indicate a 1394 ARP request and
    two to indicate a 1394 ARP response.
    sender_unique_ID: This field SHALL contain the node unique ID of
    the sender and SHALL be equal to that specified in the sender's
    bus information block.
    sender_max_rec: This field SHALL be equal to the value of max_rec
    in the sender's configuration ROM bus information block.
    sspd: This field SHALL be set to the lesser of the sender's link
    speed and PHY speed. The link speed is the maximum speed at which
    the link may send or receive packets; the PHY speed is the maximum
    speed at which the PHY may send, receive or repeat packets. The
    table below specifies the encoding used for sspd; all values not
    specified are RESERVED for future standardization.
                      Table 2 - Speed codes
                          Value   Speed
                        +---------------+
                        |   0   |  S100 |
                        |   1   |  S200 |
                        |   2   |  S400 |
                        |   3   |  S800 |
                        |   4   | S1600 |
                        |   5   | S3200 |
                        +---------------+
    sender_unicast_FIFO_hi and sender_unicast_FIFO_lo: These fields
    together SHALL specify the 48-bit offset of the sender's FIFO
    available for the receipt of IP datagrams in the format specified
    by section 6. The offset of a sender's unicast FIFO SHALL NOT
    change, except as the result of a power reset.
    sender_IP_address: This field SHALL specify the IP address of the
    sender.
    target_IP_address: In a 1394 ARP request, this field SHALL specify
    the IP address from which the sender desires a response. In a 1394
    ARP response, it SHALL be IGNORED.

Johansson Standards Track [Page 13] RFC 2734 IPv4 over IEEE 1394 December 1999

6. CONFIGURATION ROM

 Configuration ROM for IP-capable nodes SHALL contain a unit directory
 in the format specified by this standard. The unit directory SHALL
 contain Unit_Spec_ID and Unit_SW_Version entries, as specified by
 ISO/IEC 13213:1994.
 The unit directory may also contain other entries permitted by
 ISO/IEC 13213:1994 or IEEE P1212r.

6.1 Unit_Spec_ID entry

 The Unit_Spec_ID entry is an immediate entry in the unit directory
 that specifies the organization responsible for the architectural
 definition of the Internet Protocol capabilities of the device.
                      1                   2                   3
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |      0x12     |            unit_spec_ID (0x00 005E)           |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                Figure 6 - Unit_Spec_ID entry format
 The value of unit_spec_ID SHALL be 0x00 005E, the registration ID
 (RID) obtained by IANA from the IEEE RA. The value indicates that the
 IETF and its technical committees are responsible for the maintenance
 of this standard.

6.2 Unit_SW_Version entry

 The Unit_SW_Version entry is an immediate entry in the unit directory
 that, in combination with the unit_spec_ID, specifies the document
 that defines the software interface of the unit.
                      1                   2                   3
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |      0x13     |          unit_sw_version (0x00 0001)          |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
              Figure 7 - Unit_SW_Version entry format
 The value of unit_sw_version SHALL be one, which indicates that the
 device complies with the normative requirements of this standard.

Johansson Standards Track [Page 14] RFC 2734 IPv4 over IEEE 1394 December 1999

6.3 Textual descriptors

 Textual descriptors within configuration ROM are OPTIONAL; when
 present they provide additional descriptive information intended to
 be intelligible to a human user. IP-capable nodes SHOULD associate a
 textual descriptor with a content of "IANA" with the Unit_Spec_ID
 entry and a textual descriptor with a content of "IPv4" for the
 Unit_SW_Version entry.
 The figure below illustrates a unit directory implemented by an IP-
 capable node; it includes OPTIONAL textual descriptors. Although the
 textual descriptor leaves are not part of the unit directory, for the
 sake of simplicity they are shown immediately following the unit
 directory.
                      1                   2                   3
  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |      directory_length (4)     |              CRC              |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |      0x12     |            unit_spec_ID (0x00 005E)           |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |      0x81     |         textual descriptor offset (3)         |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |      0x13     |                unit_sw_version                |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |      0x81     |         textual descriptor offset (5)         |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 | textual_descriptor_length (3) |              CRC              |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                                                               |
 +---                          zeros                          ---+
 |                                                               |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |      "I"      |      "A"      |      "N"      |      "A"      |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 | textual_descriptor_length (3) |              CRC              |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                                                               |
 +---                          zeros                          ---+
 |                                                               |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |      "I"      |      "P"      |      "v"      |      "4"      |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      Figure 9 - Sample unit directory and textual descriptors

Johansson Standards Track [Page 15] RFC 2734 IPv4 over IEEE 1394 December 1999

7. IP UNICAST

 A unicast IP datagram may be transmitted to a recipient within a 1394
 primary packet that has one of the following transaction codes:
            tcode   Description     Arbitration
          +--------------------------------------+
          |  0x01 | Block write   | Asynchronous |
          |  0x0A | Stream packet | Isochronous  |
          |  0x0A | Stream packet | Asynchronous |
          +--------------------------------------+
 Block write requests are suitable when 1394 link-level
 acknowledgement is desired but there is no need for bounded latency
 in the delivery of the packet (quality of service).
 Isochronous stream packets provide quality of service guarantees but
 no 1394 link-level acknowledgement.
 The last method, asynchronous stream packets, is mentioned only for
 the sake of completeness. This method SHOULD NOT be used for IP
 unicast, since it provides for neither 1394 link-level acknowledgment
 nor quality of service---and consumes a valuable resource, a channel
 number.
 Regardless of the IP unicast method employed, asynchronous or
 isochronous, it is the responsibility of the sender of a unicast IP
 datagram to determine the maximum data payload that may be used in
 each packet. The necessary information may be obtained from:
  1. the SPEED_MAP maintained by the 1394 bus manager, which provides

the maximum transmission speed between any two nodes on the local

   Serial Bus. The bus manager analyzes bus topology in order to
   construct the speed map; the maximum transmission speed between
   nodes reflects the capabilities of the intervening nodes. The speed
   in turn implies a maximum data payload (see Table 1);
  1. the sender_max_rec field in a 1394 ARP response; or
  1. other methods beyond the scope of this standard.
 The maximum data payload SHALL be the minimum of the largest data
 payload implemented by the sender, the recipient and the PHYs of all
 intervening nodes (the last is implicit in the SPEED_MAP entry
 indexed by sender and recipient).

Johansson Standards Track [Page 16] RFC 2734 IPv4 over IEEE 1394 December 1999

 NOTE: The SPEED_MAP is derived from the self-ID packets transmitted
 by all 1394 nodes subsequent to a bus reset. An IP-capable node may
 observe the self-ID packets directly.
 Unicast IP datagrams whose quality of service is best-effort SHALL be
 contained within the data payload of 1394 block write transactions
 addressed to the source_ID and sender_unicast_FIFO obtained from a
 1394 ARP response.
 If no acknowledgement is received in response to a unicast block
 write request it is uncertain whether or not the data payload was
 received by the target.
 NOTE: An acknowledgment may be absent because the target is no longer
 functional, may not have received the packet because of a header CRC
 error or may have received the packet successfully but the
 acknowledge sent in response was corrupted.
 Unicast IP datagrams that require quality of service other than
 best-effort are beyond the scope of this standard.

8. IP BROADCAST

 Broadcast IP datagrams are encapsulated according to the
 specifications of section 4 and are transported by asynchronous
 stream packets. There is no quality of service provision for IP
 broadcast over 1394. The channel number used for IP broadcast is
 specified by the BROADCAST_CHANNEL register.
 All broadcast IP datagrams SHALL use asynchronous stream packets
 whose channel number is equal to the channel field from the
 BROADCAST_CHANNEL register.
 Although 1394 permits the use of previously allocated channel
 number(s) for up to one second subsequent to a bus reset, IP-capable
 nodes SHALL NOT transmit asynchronous stream packets at any time the
 valid bit in their BROADCAST_CHANNEL register is zero. Since the
 valid bit is automatically cleared to zero by a bus reset, this
 prohibits the use of 1394 ARP or broadcast IP until the IRM allocates
 a channel number.

9. IP MULTICAST

 Multicast IP datagrams are encapsulated according to the
 specifications of section 4 and are transported by stream packets.
 Asynchronous streams are used for best-effort IP multicast; quality
 of service other than best-effort is beyond the scope of this
 standard.

Johansson Standards Track [Page 17] RFC 2734 IPv4 over IEEE 1394 December 1999

 By default, all best-effort IP multicast SHALL use asynchronous
 stream packets whose channel number is equal to the channel field
 from the BROADCAST_CHANNEL register. In particular, datagrams
 addressed to 224.0.0.1 and 224.0.0.2 SHALL use this channel number.
 Best-effort IP multicast for other IP multicast group addresses may
 utilize a different channel number if such a channel number is
 allocated and advertised prior to use, as described below.
 IP-capable nodes may transmit best-effort IP multicast only if one of
 the following two conditions is met:
  1. the channel number in the stream packet is equal to the channel

number field in the BROADCAST_CHANNEL register and the valid bit in

   the same register is one; or
  1. for other channel number(s), some source of IP multicast has

allocated and is advertising the channel number used.

 The remainder of this section describes a multicast channel
 allocation protocol (MCAP) employed by both IP multicast sources and
 recipients whenever a channel number other than the default is used.
 MCAP is a cooperative protocol; the participants exchange messages
 over the broadcast channel used by all IP-capable nodes on a
 particular Serial Bus.
 CAUTION: This document does not define facilities and methods for
 shared use of a single channel number (other than the default channel
 number specified by the BROADCAST_CHANNEL register) by more than one
 IP multicast address.

9.1 MCAP message format

 MCAP messages, whether sent by a multicast channel owner or
 recipient, are transported as the data portion of a GASP packet and
 have the format illustrated below. The first four octets of the
 message are fixed; the remainder consists of variable-length tuples,
 each of which encodes information about a particular IP multicast
 group. Individual MCAP messages SHALL NOT be fragmented and SHALL be
 encapsulated within a stream packet as ether_type 0x8861.

Johansson Standards Track [Page 18] RFC 2734 IPv4 over IEEE 1394 December 1999

                      1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |            length             |    reserved   |     opcode    |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 |                                                               |
 +                          message data                         +
 |                                                               |
 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                  Figure 10 - MCAP message format
 Field usage in an MCAP message is as follows:
    length: This field SHALL contain the size, in octets, of the
    entire MCAP message.
    opcode: This field SHALL have one of the values specified by the
    table below.
     opcode    Name       Comment
    +----------------------------------------------------------------+
    |   0   | Advertise | Sent by a multicast channel owner to       |
    |       |           | broadcast the current mapping(s) from one  |
    |       |           | or more group addresses to their           |
    |       |           | corresponding channel number(s).           |
    |   1   |  Solicit  | Sent to request multicast channel owner(s) |
    |       |           | to advertise the indicated channel         |
    |       |           | mapping(s) as soon as possible.            |
    +----------------------------------------------------------------+
    message data: The remainder of the MCAP message is variable in
    length and SHALL consist of zero or more group address descriptors
    with the format illustrated below.

Johansson Standards Track [Page 19] RFC 2734 IPv4 over IEEE 1394 December 1999

                         1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |     length    |      type     |            reserved           |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |   expiration  |    channel    |     speed     |    reserved   |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                           bandwidth                           |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    +                         group_address                         +
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
             Figure 11 - MCAP group address descriptor format
    length: This field SHALL contain the size, in octets, of the MCAP
    group address descriptor.
    type: This field SHALL have a value of one, which indicates a
    group address descriptor.
    expiration: The usage of this field varies according to opcode.
    For solicit messages the expiration field SHALL be IGNORED.
    Otherwise, for advertisements, this field SHALL contain a time-
    stamp, in seconds, that specifies a future time after which the
    channel number specified by channel may no longer be used.
    channel: This field is valid only for advertise messages, in which
    case it SHALL specify an allocated channel number, in the range
    zero to 63 inclusive. All other values are RESERVED.
    speed: This field is valid only for advertise messages, in which
    case it SHALL specify the speed at which stream packets for the
    indicated channel are transmitted. Table 2 specifies the encoding
    used for speed.
    bandwidth: This field SHALL be zero; it is allocated in the group
    address descriptor to accommodate future extensions to MCAP that
    specify quality of service and utilize the isochronous
    capabilities of Serial Bus.
    group_address: This variable length field SHALL specify the IP
    address of a particular IP multicast group. The length of
    group_address, in octets, is derived from the length of the group
    address descriptor by subtracting 12 from the length field.

Johansson Standards Track [Page 20] RFC 2734 IPv4 over IEEE 1394 December 1999

9.2 MCAP message domain

 MCAP messages carry information valid only for the local Serial Bus
 on which they are transmitted. Recipients of MCAP messages SHALL
 IGNORE all MCAP messages from other than the local bus, as follows.
 The source_ID of the sender is contained in the GASP header that
 precedes the encapsulated MCAP message. A recipient of an MCAP
 message SHALL examine the most significant ten bits of source_ID from
 the GASP header; if they are not equal to either 0x3FF or the most
 significant ten bits of the recipient's NODE_IDS register, the
 recipient SHALL IGNORE the message.
 Within an MCAP message domain, the owner of a channel mapping is
 identified by the source_ID field in the GASP header of an MCAP
 advertisement. The owner is the node with the largest physical ID,
 the least significant six bits of source_ID.

9.3 Multicast receive

 An IP-capable device that wishes to receive multicast data SHALL
 first ascertain the channel mapping (if any) that exists between a
 group address and a channel number other than the default channel
 specified by the BROADCAST_CHANNEL register. Such a device may
 observe the MCAP advertisements on the broadcast channel for the
 desired channel mapping(s).
 An intended multicast recipient may transmit MCAP solicitation
 requests in order to request multicast channel owner(s) to broadcast
 advertisements sooner than the next ten second interval. Originators
 of MCAP solicitation requests SHALL limit the rate at which they are
 transmitted. Subsequent to sending a solicitation request, the
 originator SHALL NOT send another MCAP solicitation request until ten
 seconds have elapsed.
 In either case, if a mapping exists for the group address for other
 than the default channel, an MCAP advertise message is EXPECTED
 within ten seconds. Upon receipt of an MCAP advertise message that
 describes one or more channel mappings, the intended multicast
 recipient may receive IP datagrams on the indicated channel number(s)
 until the expiration time.
 If multiple MCAP advertise messages are observed that specify the
 same group address, the channel number SHALL be obtained from the
 advertisement message with the largest physical ID, which SHALL be
 obtained from the least significant six bits of source_ID from the
 GASP header.

Johansson Standards Track [Page 21] RFC 2734 IPv4 over IEEE 1394 December 1999

 If no MCAP advertise message is received for a particular group
 address within ten seconds, no multicast source(s) are active for
 channel(s) other than the default. Either there is there is no
 multicast data or it is being transmitted on the default channel.
 Once a multicast recipient has observed an advertisement for the
 desired group address, it MAY receive multicast data on either the
 default broadcast channel or the channel number(s) indicated but it
 SHALL continue to monitor the default broadcast channel for MCAP
 advertisements for the same group address in order to refresh the
 expiration time of channel number(s) in use.

9.4 Multicast transmit

 An IP-capable device that wishes to transmit multicast data on other
 than the default channel SHALL first ascertain whether or not another
 multicast source has already allocated a channel number for the group
 address. The intended multicast source may transmit an MCAP
 solicitation request with one or more group address descriptors.
 Whether or not a solicitation request has been transmitted, the
 intended multicast source SHALL monitor the broadcast channel for
 MCAP advertisements. If a channel mapping already exists for the
 group address, an MCAP advertisement SHOULD be received within ten
 seconds. In this case the intended multicast source may commence
 transmission of IP datagrams on the indicated channel number(s) and
 may continue to do so until their expiration time. The multicast
 source SHALL monitor MCAP advertisements in order to refresh the
 expiration time of channel number(s) in use.
 When no other multicast source has established a channel mapping for
 the group address, the intended multicast source may attempt to
 allocate a channel number from the isochronous resource manager's
 CHANNELS_AVAILABLE register according to the procedures described in
 IEEE P1394a. If the channel number allocation is successful, the
 multicast source SHALL advertise the new channel mapping(s) as soon
 as possible. Once 100 ms elapses subsequent to the initial
 advertisement of a newly allocated channel number , the multicast
 source may transmit IP datagrams using the channel number advertised.
 Multicast IP datagrams may be transmitted on the default channel
 until the sender observes (or transmits) an advertisement that
 specifies non- default channel mapping(s) for the multicast
 addresses. This permits the smooth transition of multicast from the
 default channel to an explicitly allocated channel.

Johansson Standards Track [Page 22] RFC 2734 IPv4 over IEEE 1394 December 1999

 Once a multicast source has advertised a channel mapping, it SHALL
 continue to transmit MCAP advertisements for the channel mapping
 unless it either a) transfers ownership to another multicast source,
 b) permits the channel mapping to expire without transfer or c) in
 the case of overlapped channel mappings, relinquishes control of the
 channel mapping to another multicast source.

9.5 Advertisement of channel mappings

 Each multicast source SHALL periodically broadcast an advertisement
 of all IP multicast group addresses for which it has allocated a
 channel number different from the default multicast channel number.
 An advertisement SHALL consist of a single MCAP message with an
 opcode of zero that contains one or more group address descriptors
 (one for each group address assigned a channel number other than that
 specified by the BROADCAST_CHANNEL register).
 Within each group address descriptor, the group_address and channel
 fields associate an IP multicast group address with a Serial Bus
 channel number. The speed field specifies the maximum 1394 speed at
 which any of the senders within the IP multicast group is permitted
 to transmit data.  The expiration field specifies the current time or
 a future time after which the channel mapping(s) are no longer valid.
 Except when a channel owner intends to relinquish ownership (as
 described in 9.7 below), the expiration time SHALL be at least 60
 seconds in the future measured from the time the advertisement is
 transmitted.
 No more than ten seconds SHALL elapse from the transmission of its
 most recent advertisement before the owner of a channel mapping
 initiates transmission of the subsequent advertisement. The owner of
 a channel mapping SHOULD transmit an MCAP advertisement in response
 to a solicitation as soon as possible after the receipt of the
 request.

9.6 Overlapped channel mappings

 When two intended multicast sources wish to transmit to the same IP
 multicast group and no channel mapping exists for the group address,
 there is a chance that both will allocate channel numbers and both
 will advertise the channel mappings. These channel mappings overlap,
 i.e., the same group address is mapped to more than one channel
 number in MCAP advertisements with nonzero expiration times.
 Multicast channel owners SHALL monitor MCAP advertisements in order
 to detect overlapped channel mappings. MCAP advertisements whose
 expiration field has a value less than 60 SHALL be ignored for the
 purpose of overlapped channel detection. When an overlapped channel

Johansson Standards Track [Page 23] RFC 2734 IPv4 over IEEE 1394 December 1999

 mapping is detected, the owner with the largest physical ID (as
 determined by the least significant six bits of source_ID from the
 GASP header) is NOT REQUIRED to take any action. The channel numbers
 advertised by owners with smaller physical IDs are invalid; their
 owners SHALL cease transmission of both IP datagrams and MCAP
 advertisements that use the invalid channel numbers. As soon as these
 channel mappings expire , their owners SHALL deallocate any unused
 channel numbers as described in 9.8 below.
 Recipients of MCAP advertisements that detect overlapped channel
 mappings SHALL ignore the advertisements from multicast channel
 owner(s) with the smaller physical IDs and SHALL NOT transmit IP
 datagrams that use the invalid channel number. It is possible for
 some channel mappings in a single MCAP advertisement to be valid even
 if others SHALL be IGNORED as a result of overlap.

9.7 Transfer of channel ownership

 The owner of a channel mapping may cease multicast transmission on a
 particular channel, in which case it SHOULD invalidate the channel
 mapping and in some cases deallocate the channel number. Because
 other multicast sources may be using the same channel mapping, an
 orderly process is defined to transfer channel ownership.
 The owner of an existing channel mapping that wishes to release the
 mapping SHALL commence a timer to measure the time remaining before
 the anticipated release of the mapping and its associated channel.
 Until the timer counts down to zero, the owner SHOULD continue to
 transmit MCAP advertisements for the affected channel but SHALL
 adjust expiration in each advertisement to reflect the time remaining
 until the channel is to be deallocated. If the owner is unable to
 transmit MCAP advertisements until the timer reaches zero, it SHALL
 initiate a bus reset. Otherwise, the sequence of expiration times
 transmitted by the owner intending to release the mapping SHALL
 decrease with each succeeding advertisement.  If other multicast
 source(s) are using the same channel mapping and observe an
 expiration time less than or equal to 60 seconds, they SHALL commence
 transmitting MCAP advertisements for the channel mapping with
 refreshed expiration times greater than or equal to 60 seconds that
 maintain the channel mapping. Any contention that occurs between
 multiple sources that attempt to claim ownership of the channel
 mapping SHALL be resolved as described in 9.8. If the original owner
 observes an MCAP advertisement for the channel to be relinquished
 before its own timer has expired, it SHALL NOT deallocate the channel
 number.

Johansson Standards Track [Page 24] RFC 2734 IPv4 over IEEE 1394 December 1999

 Otherwise, if the owner's timer expires without the observation of a
 MCAP advertisement by another node, the owner of the channel number
 SHALL subsequently deallocate the channel as described in 9.8. If the
 intended owner of the channel mapping observes an MCAP advertisement
 whose expiration field is zero, orderly transfer of the channel(s)
 from the former owner has failed. The intended owner SHALL either
 stop reception and transmission on the expired channel number(s) or
 allocate different channel number(s) as specified by 9.4.

9.8 Redundant channel mappings

 When ownership of a channel mapping is transferred from one multicast
 source to another, it is possible for more than one device to claim
 ownership. This results in redundant MCAP advertisements, transmitted
 by different sources, each of which specifies the same multicast
 group address and channel. A procedure similar to that of 9.6 SHALL
 resolve the contention for channel ownership.
 Multicast channel owners SHALL monitor MCAP advertisements in order
 to detect redundant channel mappings. MCAP advertisements whose
 expiration field has a value less than 60 SHALL be ignored for the
 purpose of redundant channel detection. When a redundant channel
 mapping is detected, the owner with the largest physical ID (as
 determined by the least significant six bits of source_ID from the
 GASP header) is NOT REQUIRED to take any action. The owner(s) with
 smaller physical IDs SHALL cease transmission of MCAP advertisements
 for the redundant channel number but SHALL NOT deallocate the channel
 number.

9.9 Expired channel mappings

 A channel mapping expires when expiration seconds have elapsed since
 the most recent MCAP advertisement. At this time, multicast
 recipients SHALL stop reception on the expired channel number(s).
 Also at this time, the owner of the channel mapping(s) SHALL transmit
 an MCAP advertisement with expiration cleared to zero and SHALL
 continue to transmit such advertisements until 30 seconds have
 elapsed since the expiration of the channel mapping. Once this
 additional 30-second period has elapsed, the owner of the channel
 mapping(s) SHALL deallocate the channel number(s) and indicate their
 availability in the isochronous resource manager's CHANNELS_AVAILABLE
 register.
 If an IP-capable device observes an MCAP advertisement whose
 expiration field is zero, it SHALL NOT attempt to allocate any of the
 channel number(s) specified until 30 seconds have elapsed since the
 most recent such advertisement.

Johansson Standards Track [Page 25] RFC 2734 IPv4 over IEEE 1394 December 1999

9.10 Bus reset

 A bus reset SHALL invalidate all multicast channel mappings and SHALL
 cause all multicast recipients and senders to zero all MCAP
 advertisement interval timers.
 Prior owners of multicast channel mappings may reallocate a channel
 number from the isochronous resource manager's CHANNELS_AVAILABLE
 register and resume broadcast of MCAP advertisements as soon as a
 channel is allocated. If channel reallocation is attempted, the prior
 owner SHOULD use the same channel number allocated prior to the bus
 reset and may commence reallocation immediately upon completion of
 the bus reset so long as the same channel number is reused. If the
 prior owner elects to allocate a different channel number, it SHALL
 wait until at least one second has elapsed since the completion of
 the bus reset before attempting to allocate a new channel number.
 Intended or prior recipients or transmitters of multicast on other
 than the default channel SHALL NOT transmit MCAP solicitation
 requests until at least ten seconds have elapsed since the completion
 of the bus reset.  Multicast data on other than the default channel
 SHALL NOT be received or transmitted until an MCAP advertisement is
 observed or transmitted for the IP multicast group address.
 Intended or prior transmitters of multicast on other than the default
 channel that did not own a channel mapping for the IP multicast group
 address prior to the bus reset SHALL NOT attempt to allocate a
 channel number from the isochronous resource manager's
 CHANNELS_AVAILABLE register until at least ten seconds have elapsed
 since the completion of the bus reset. Subsequent to this ten second
 delay, intended or prior transmitters of multicast may follow the
 procedures specified by 9.4 to allocate a channel number and
 advertise the channel mapping.

10. IANA CONSIDERATIONS

 This document necessitates the creation and management of a new name
 space (registry) by IANA. The need for such a registry arises out of
 the method by which protocol interfaces are uniquely identified by
 bus standards compliant with ISO/IEC 13213:1994, CSR Architecture.
 This is explained in more detail in section 6; the essence is that a
 globally unique 48-bit number SHALL identify the document that
 specifies the protocol interface. The 48-bit number is the
 concatenation of 0x00 005E (a registration ID, or RID, granted to
 IANA by the IEEE Registration Authority) and a second 24-bit number
 administered by IANA.

Johansson Standards Track [Page 26] RFC 2734 IPv4 over IEEE 1394 December 1999

 The IEEE RA RECOMMENDS that the policy for management of the second
 24-bit number be chosen to maximize the quantity of usable numbers
 with the range of possible values. In particular, the IEEE RA
 RECOMMENDS that the assignment scheme not apply a structure to the
 number (e.g., the allocation of a version field within the number)
 since this would tend to waste large portions of the range.
 The new name space is "CSR Protocol Identifiers". The values zero and
 0xFF FFFF are reserved and SHALL NOT be allocated by IANA. The value
 one is allocated to this document. The remaining numbers SHALL be
 managed by IANA and allocated as necessary to identify Internet-
 Drafts that become IESG standards track documents.
 Regardless of the assignment method elected by IANA, a registry of
 all assigned version numbers SHOULD be maintained at one or more
 Internet sites and should clearly identify the relevant standard
 identified by the combination of the RID and version number.

11. SECURITY CONSIDERATIONS

 This document specifies the use of an unsecured link layer, Serial
 Bus, for the transport of IPv4 datagrams. Serial Bus is vulnerable to
 denial of service attacks; it is also possible for devices to
 eavesdrop on data or present forged identities. Implementers who
 utilize Serial Bus for IPv4 SHOULD consider appropriate counter-
 measures within application or other layers.

12. ACKNOWLEDGEMENTS

 This document represents the efforts of the IP/1394 Working Group.
 The editor wishes to acknowledge the contributions made by all the
 active participants, either on the reflector or at face-to-face
 meetings, which have advanced the technical content.

Johansson Standards Track [Page 27] RFC 2734 IPv4 over IEEE 1394 December 1999

13. REFERENCES

 Normative reference to standards under development at the time of
 this document's publication shall utilize the most current draft
 until such time as it is replaced by an approved standard.
 [1] IEEE Std 1394-1995, Standard for a High Performance Serial Bus
 [2] ISO/IEC 13213:1994, Control and Status Register (CSR)
     Architecture for Microcomputer Buses
 [3] IEEE Project P1394a, Draft Standard for a High Performance Serial
     Bus (Supplement)
 [4] IEEE Project P1394b, Draft Standard for a High Performance Serial
     Bus (Supplement)
 [5] Postel, J., "Internet Protocol Darpa Internet Program Protocol
     Specification", RFC 791, September 1981.
 [6] Bradner, S., "Key words for use in RFCs to Indicate Requirement
     Levels", RFC 2119, March 1997.

14. EDITOR'S ADDRESS

 Peter Johansson
 Congruent Software, Inc.
 98 Colorado Avenue
 Berkeley, CA  94602
 Phone: (510) 527-3926
 Fax:   (510) 527-3856
 EMail: pjohansson@aol.com

Johansson Standards Track [Page 28] RFC 2734 IPv4 over IEEE 1394 December 1999

15. Full Copyright Statement

 Copyright (C) The Internet Society (1999).  All Rights Reserved.
 This document and translations of it may be copied and furnished to
 others, and derivative works that comment on or otherwise explain it
 or assist in its implementation may be prepared, copied, published
 and distributed, in whole or in part, without restriction of any
 kind, provided that the above copyright notice and this paragraph are
 included on all such copies and derivative works.  However, this
 document itself may not be modified in any way, such as by removing
 the copyright notice or references to the Internet Society or other
 Internet organizations, except as needed for the purpose of
 developing Internet standards in which case the procedures for
 copyrights defined in the Internet Standards process must be
 followed, or as required to translate it into languages other than
 English.
 The limited permissions granted above are perpetual and will not be
 revoked by the Internet Society or its successors or assigns.
 This document and the information contained herein is provided on an
 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Acknowledgement

 Funding for the RFC Editor function is currently provided by the
 Internet Society.

Johansson Standards Track [Page 29]

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