Network Working Group P. Johansson
Internet-Draft Congruent Software, Inc.
<draft-ietf-ip1394-ipv4-13.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
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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 and additionally
defines a method for Address Resolution Protocol (ARP).
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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.................................................5
3. IP-CAPABLE NODES...................................................6
4. BROADCAST CHANNEL MANAGER (BCM)....................................6
5. LINK ENCAPSULATION AND FRAGMENTATION...............................7
5.1 Global asynchronous stream packet (GASP) format................8
5.2 Encapsulation header...........................................8
5.3 Link fragment reassembly......................................10
6. ADDRESS RESOLUTION PROTOCOL (ARP).................................11
7. CONFIGURATION ROM.................................................13
7.1 Unit_Spec_ID entry............................................13
7.2 Unit_SW_Version entry.........................................13
7.3 Unicast_FIFO entry............................................14
7.4 Textual descriptors...........................................14
8. IP UNICAST........................................................15
8.1 Asynchronous IP unicast.......................................16
8.2 Isochronous IP unicast........................................16
9. IP BROADCAST......................................................17
10. IP MULTICAST.....................................................17
10.1 MCAP message format..........................................18
10.2 MCAP message domain..........................................19
10.3 Multicast receive............................................20
10.4 Multicast transmit...........................................20
10.5 Advertisement of channel mappings............................21
10.6 Overlapped channel mappings..................................21
10.7 Transfer of channel ownership................................22
10.8 Expired channel mappings.....................................22
10.9 Bus reset....................................................23
11. SECURITY CONSIDERATIONS..........................................23
12. ACKNOWLEDGEMENTS.................................................23
13. REFERENCES.......................................................24
14. EDITORÆS 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 a method for Address Resolution Protocol (ARP).
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 nodeÆs 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 is 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.
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.
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2. DEFINITIONS AND NOTATION
2.1 Conformance
When used in this document, the keywords "MAY", "OPTIONAL",
"RECOMMENDED", "REQUIRED", "SHALL" and "SHOULD" 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 objects---bits, octets, quadlets
and fields---or the code values assigned to these objects in cases where
either the object or the code value is set aside for future
standardization. Usage and interpretation MAY be specified by future
extensions to this or other standards. A RESERVED object SHALL be zeroed
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 defined by this standard as other than
RESERVED 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 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.
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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
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 10
bits are the bus ID and the least significant 6 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 1394 packets from 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:
ARP Address resolution protocol
BCM Broadcast channel manager
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 the context of 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. Hexadecimal numbers are also used when the value
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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 û 9 and A û 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 1394 devices are capable of the reception and transmission of
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 Std 1394-1995;
- it SHALL support both reception and transmission of asynchronous
streams as specified by IEEE P1394a;
- it SHALL implement the BROADCAST_CHANNEL register as specified by
IEEE P1394a; and
- it SHALL be broadcast channel manager (BCM) capable.
4. BROADCAST CHANNEL MANAGER (BCM)
In order for ARP or broadcast IP to function on 1394, a prerequisite is
the presence of a broadcast channel manager (BCM). The functions of the
BCM specified by IEEE P1394a are as follows:
- the allocation of a channel number for asynchronous stream
broadcast (which includes ARP and broadcast IP); and
- the communication of that channel number to all interested nodes
(which include IP-capable nodes) on the same bus.
All IP-capable nodes SHALL be capable of functioning as the BCM.
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Subsequent to a Serial Bus reset a single BCM SHALL be determined as
specified by IEEE P1394a.
In the case that the BCM is unable to allocate a channel number for
asynchronous stream broadcast (and consequently for ARP and broadcast
IP), a warning SHOULD be communicated to a user that IP initialization
could NOT complete because of a lack of Serial Bus resources. The user
SHOULD be advised to reconfigure or remove other devices if she wishes
to make use of IP.
NOTE: If the BCM is unable to allocate a channel number, IP-capable
nodes are unable to use the ARP and broadcast IP methods specified by
this document. If other methods (e.g., a search of configuration ROM)
permit IP-capable nodes to discover each other, they MAY be able to send
and receive IP datagrams.
5. LINK ENCAPSULATION AND FRAGMENTATION
All IP datagrams (broadcast, unicast or multicast), 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 ARP response.
For either of these reasons, the maximum data payload transmissible
between IP-capable nodes MAY be less than the 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.
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5.1 Global asynchronous stream packet (GASP) format
Some IP datagrams, as well as 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 senderÆs NODE_IDS
register.
The specifier_ID_hi and specifier_ID_lo fields together SHALL contain
the value 0x00005E, the 24-bit organizationally unique identifier (OUI)
assigned by the IEEE Registration Authority Committee (RAC) to IANA.
The version field SHALL be zero.
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 ARP request or response. When
the GASP format is used, this is the third quadlet of the data payload
for the packet.
5.2 Encapsulation header
All IP datagrams transported over 1394 are prefixed by an encapsulation
header with one of the formats illustrated below.
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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
+-----------------------+
| 0x800 | IPv4 |
| 0x806 | 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 | signature |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| lf|rsv| buffer_size | rsv | fragment_offset |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| dgl | signature |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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 |
+------------------------+
buffer_size: The size of the buffer, expressed as buffer_size + 1
octets, necessary for the recipient to reassemble the link fragments.
ether_type: This field is present only in the first link fragment and
SHALL have a value of 0x800, 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.
signature: The sender SHALL set this field to the most significant
16-bits of its own NODE_IDS register.
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.
5.3 Link fragment reassembly
The recipient of an IP datagram transmitted via more than one 1394
packet SHALL use both signature and dgl to identify all the link
fragments from a single datagram.
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NOTE: The use of signature for any purposes other than link fragment
reassembly is fraught with error and is strongly discouraged.
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 for the
same signature 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.
6. ADDRESS RESOLUTION PROTOCOL (ARP)
ARP requests SHALL be transmitted by the same means as broadcast IP
datagrams; 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 ARP request. An ARP
request/response is 32 octets and 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 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 - ARP request/response format
Field usage in an ARP request/response is as follows:
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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 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 an ARP request and two to
indicate an 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 senderÆs configuration ROM bus information block.
sspd: This field SHALL be set to the lesser of the senderÆs 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.
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 7. 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.
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target_IP_address: In an ARP request, this field SHALL specify the IP
address from which the sender desires a response. In an ARP response,
it SHALL be IGNORED.
7. 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, and OPTIONALLY a Unicast_FIFO entry, as specified by this
standard.
The unit directory MAY also contain other entries permitted by ISO/IEC
13213:1994 or IEEE P1212r.
7.1 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 (0x00005E) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6 - Unit_Spec_ID entry format
0x12 is the concatenation of key_type and key_value for the Unit_Spec_ID
entry.
0x00005E is the unit_spec_ID obtained by IANA from the IEEE/RAC. The
value indicates that IANA and its technical committees are responsible
for the maintenance of this standard.
7.2 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 7 - Unit_SW_Version entry format
0x13 is the concatenation of key_type and key_value for the
Unit_SW_Version entry.
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A value for unit_sw_version is NOT yet specified. When this standard is
approved it is EXPECTED that unit_sw_version will assume the value of
the RFC number assigned at that time. This provides a means to reference
future standards that MAY define, for example, IPv6 or extensions to the
IPv4 protocol that operate across Serial Bus bridges.
7.3 Unicast_FIFO entry
The Unicast_FIFO entry is an immediate entry in the unit directory that,
when present, SHALL specify the address of the nodeÆs unicast FIFO.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0x54 | unicast_FIFO_offset |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 8 - Unicast_FIFO entry format
0x54 is the concatenation of key_type and key_value for the Unicast_FIFO
entry.
The unicast_FIFO_offset field SHALL contain the offset, in quadlets,
from the base address of initial register space, 0xFFFF F000 0000, to
the address of the unicast FIFO register for the unit. All unit CSRs
SHALL be located at or above address 0xFFFF F001 0000; therefore the
value of unicast_FIFO_offset SHALL NOT be less than 0x4000. The unicast
FIFO address derived from the Unicast_FIFO entry SHALL be equal to the
sender_unicast_FIFO address supplied by the node in ARP requests or
responses.
7.4 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 and the
OPTIONAL Unicast_FIFO entry. 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.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| directory_length (5) | CRC |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0x12 | unit_spec_ID (0x00005E) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0x81 | textual descriptor offset (4) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0x13 | unit_sw_version |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0x81 | textual descriptor offset (6) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0x54 | unicast_FIFO_offset |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| textual_descriptor_length (3) | CRC |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+--- zeros ---+
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| "I" | "A" | "N" | "A" |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| textual_descriptor_length (3) | CRC |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+--- zeros ---+
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| "I" | "P" | "v" | "4" |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 9 û Sample unit directory and textual descriptors
8. 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.
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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 target_max_rec field in an ARP response. This document requires
a minimum value of 8 (equivalent to a data payload of 512 octets).
Nodes that operate at S200 and faster are encouraged but NOT
REQUIRED to implement correspondingly larger values for
target_max_rec; 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.
8.1 Asynchronous IP unicast
Unicast IP datagrams that do NOT require any quality of service SHALL be
contained within the data payload of 1394 block write transactions
addressed to the target_node_ID and target_unicast_FIFO obtained from an
ARP response.
If no acknowledgement is received in response to a unicast block write
request the state of the target is ambiguous.
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.
8.2 Isochronous IP unicast
Unicast IP datagrams that require quality of service SHALL be contained
within the data payload of 1394 isochronous stream packets.
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The details of coordination between nodes with respect to allocation of
channel number(s) and bandwidth are beyond the scope of this standard.
9. IP BROADCAST
Broadcast IP datagrams are encapsulated according to the specifications
of section 5 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
ARP or broadcast IP until the BCM allocates a channel number.
10. IP MULTICAST
Multicast IP datagrams are encapsulated according to the specifications
of section 5 and are transported by stream packets. Asynchronous streams
are used for best-effort IP multicast while isochronous streams are used
for IP multicast that requires quality of service.
CAUTION: The working group has yet to define facilities and methods for
the provision of quality of service for IP multicast.
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 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
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broadcast channel used by all IP-capable nodes on a particular Serial
Bus.
CAUTION: The working group has yet to 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.
10.1 MCAP message format
MCAP messages, whether sent by a multicast channel owner or recipient,
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 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 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.
10.2 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 source_ID from the GASP header; if it is NOT equal to the most
significant 16 bits of the recipient's NODE_IDS register, the recipient
SHALL IGNORE the message.
10.3 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 10
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 phy_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 10 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 SHALL continue to monitor the broadcast channel for
MCAP advertisements for the same group address in order to refresh the
expiration time of channel number(s) in use.
10.4 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
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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 Std 1394-1995. If the channel number allocation is successful, the
multicast source SHALL advertise the new channel mapping(s) as soon as
possible; once such advertisement has been made, the multicast source
MAY transmit IP datagrams using the channel number obtained.
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.
10.5 Advertisement of channel mappings
Each multicast source SHALL periodically broadcast an advertisement of
all 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 a multicast group address with a Serial Bus channel
number. More than one multicast group address MAY be mapped to a single
Serial Bus channel number by means of separate group address
descriptors. The speed field specifies the maximum 1394 speed at which
any of the senders within the multicast group is permitted to transmit
data. The expiration field specifies 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 10.7 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.
10.6 Overlapped channel mappings
When two intended multicast sources wish to transmit to the same
multicast group and no channel mapping exists for the group address,
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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.
Multicast channel owners SHALL monitor MCAP advertisements in order to
detect overlapped channel mappings. When an overlapped channel mapping
is detected, the owner with the largest phy_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 overlapped
channel number. As soon as these channel mapping(s) are no longer valid,
their owners SHALL deallocate any unused channel numbers as described in
10.8 below.
Recipients of MCAP advertisements that detect overlapped channel
mappings SHALL ignore the advertisements from multicast channel owner(s)
with the smaller physical IDs. 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.
10.7 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 SHALL 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. 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 30 seconds, they SHALL commence transmitting MCAP advertisements for
the channel mapping with refreshed expiration times greater than or
equal to 30 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 10.6. 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 deallocate the channel as described below.
10.8 Expired channel mappings
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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). The owner of the
channel mapping(s) SHALL deallocate the channel number and indicate its
availability in the isochronous resource manager's CHANNELS_AVAILABLE
register.
10.9 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 multicast group address.
Intended or prior transmitters of multicast on other than the default
channel that did not own a channel mapping for the 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 10.4 to
allocate a channel number and advertise the channel mapping.
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
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active participants, either on the reflector or at face-to-face
meetings, which have advanced the technical content.
13. REFERENCES
[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. EDITORÆS ADDRESS
Peter Johansson
Congruent Software, Inc.
98 Colorado Avenue
Berkeley, CA 94602
(510) 527-3926
(510) 527-3856 FAX
pjohansson@aol.com
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