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IP1394 Working Group                                        P. Johansson
Internet-Draft                                  Congruent Software, Inc.
<draft-ietf-ip1394-ipv4-19.txt>
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                          IPv4 over IEEE 1394


STATUS OF THIS DOCUMENT

This document is an Internet-Draft and is in full conformance with all
provisions of Section 10 of RFC 2026. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas, and
its working groups. Note that other groups may also distribute working
documents as Internet-Drafts.

Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference material
or to cite them other than as "work in progress."

The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.

The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.


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.















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TABLE OF CONTENTS

1. INTRODUCTION........................................................3
2. DEFINITIONS AND NOTATION............................................4
   2.1 Conformance.....................................................4
   2.2 Glossary........................................................4
   2.3 Abbreviations...................................................5
   2.4 Numeric values..................................................6
3. IP-CAPABLE NODES....................................................6
4. LINK ENCAPSULATION AND FRAGMENTATION................................6
   4.1 Global asynchronous stream packet (GASP) format.................7
   4.2 Encapsulation header............................................8
   4.3 Link fragment reassembly.......................................10
5. SERIAL BUS ADDRESS RESOLUTION PROTOCOL (1394 ARP)..................11
6. CONFIGURATION ROM..................................................13
   6.1 Unit_Spec_ID entry.............................................13
   6.2 Unit_SW_Version entry..........................................13
   6.3 Textual descriptors............................................13
7. IP UNICAST.........................................................14
8. IP BROADCAST.......................................................16
9. IP MULTICAST.......................................................16
   9.1 MCAP message format............................................17
   9.2 MCAP message domain............................................18
   9.3 Multicast receive..............................................19
   9.4 Multicast transmit.............................................19
   9.5 Advertisement of channel mappings..............................20
   9.6 Overlapped channel mappings....................................21
   9.7 Transfer of channel ownership..................................21
   9.8 Redundant channel mappings.....................................22
   9.9 Expired channel mappings.......................................22
   9.10 Bus reset.....................................................23
10. IANA CONSIDERATIONS...............................................23
11. SECURITY CONSIDERATIONS...........................................24
12. ACKNOWLEDGEMENTS..................................................24
13. REFERENCES........................................................24
14. EDITOR'S ADDRESS..................................................24




















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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.

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


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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.

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.


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IP datagram: An Internet message that conforms to the format specified
by RFC 791.

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.

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


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   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:

   - 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;

   - 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;

   - it SHALL be isochronous resource manager capable, as specified by
     IEEE P1394a;

   - 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



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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.

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.














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                       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.

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


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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|      buffer_size      |           ether_type          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |              dgl              |            reserved           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

         Figure 3 - First fragment encapsulation header format

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|      buffer_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.






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                          lf      Position
                       +------------------------+
                       |   0   |  Unfragmented  |
                       |   1   |  First         |
                       |   2   |  Last          |
                       |   3   |  Interior      |
                       +------------------------+

   buffer_size: The size of the buffer, expressed as buffer_size + 1
   octets, necessary for the recipient to reassemble the entire IP
   datagram from all of the link fragments. The value of buffer_size
   SHALL be the same for all link fragments of an IP datagram.

   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.

   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 buffer_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)


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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
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.



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   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.

   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.




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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.

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.


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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

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).


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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:

   - 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);

   - the sender_max_rec field in a 1394 ARP response; or

   - 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).

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.






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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.

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:

   - 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

   - 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



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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.

                        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.









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                        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.

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


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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.

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


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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.

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


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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 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,


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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.

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.




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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.

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.

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


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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 work in progress by 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.

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)

14. EDITOR'S ADDRESS

Peter Johansson
Congruent Software, Inc.
98 Colorado Avenue
Berkeley, CA  94602



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(510) 527-3926
(510) 527-3856 FAX
pjohansson@aol.com





















































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