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Claims  |
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What is claimed is:
1. A module and network backplane interface, comprising:
an intelligent hub with a hub backplane, said backplane selected from the
group consisting of a first hub architecture intelligent hub backplane and
a second hub architecture intelligent hub backplane, said first hub
architecture intelligent hub backplane having a backplane architecture
which is either different from a backplane architecture of said second hub
architecture intelligent hub backplane or operates using a different
protocol, said intelligent hub including network management means with a
management processor for generating management signals;
a module selected from the group consisting of a first module type having
first module type operating parameters and a second module type having
second module type operating parameters, said second module type operating
parameters being different from said first module type operating
parameters, said module including a central processing unit for generating
parameter signals;
a backplane interface connector connected to said intelligent hub and
connected to said module;
control means for controlling passage of parameter signals from said module
to said intelligent hub and for controlling passage of management signals
from said intelligent hub to said module: and
mailbox information exchange means for reading information from said
control means and writing information to said module and for reading
information from said module and writing information to said control
means, said module including a module central processing unit and said
mailbox information exchange means including. a management processing
unit, a management processing unit mailbox, a module processing unit
mailbox, flag means associated with said management processing unit
mailbox for indicating said management processing unit mailbox is full and
flag means associated with said module processing unit mailbox for
indicating said module processing unit mailbox is full, said module
processing unit writing to said management processing unit mailbox and
reading from said module processing unit mailbox, said management
processing unit reading from said management processing unit mailbox and
writing to said module processing unit mailbox, said module processing
unit generating data units after connection to said interface means, said
data units being transferred to said management processing unit for
establishing a personality table, said data units establishing management
of said module for connection with said backplane, wherein said management
processing unit and said module processing unit transfer said information
signals based on a mailbox data unit transmission procedure comprising:
(1) checking the mailbox to which the data units are to be transmitted to
see if it is empty;
(2) placing a next data unit octet into the mailbox checked and setting
said flag means; and
repeating steps 1 and 2 until all data unit octets have been transmitted,
data unit reception including the steps of:
checking one of said mailboxes to make sure that it is full;
reading a next data unit octet from the mailbox checked wherein a first
octet of a data unit is used for length indication; and
repeating steps 1 and 2 until all data unit octets have been received.
2. A module and network backplane interface according to claim 1, further
comprising:
backplane to module media interface circuit means for transferring data
packets between said module and said backplane.
3. A module and network backplane interface according to claim 1, wherein
said module includes a module central processing unit and said interface
means includes a management processing unit, a management processing unit
mailbox and a module processing unit mailbox, said module processing unit
writing to said management processing unit mailbox and reading from said
module processing unit mailbox, said management processing unit reading
from said management processing unit mailbox and writing to said module
processing unit mailbox.
4. A module and network backplane interface according to claim 3, further
comprising flag means associated with said management processing unit
mailbox for indicating said management processing unit mailbox is full and
flag means associated with said module processing unit mailbox for
indicating said module processing unit mailbox is full.
5. A module and network back plane interface according to claim 3, wherein
said module processing unit generates data units after connection to said
interface means, said data units being transferred to said management
processing unit for establishing said personality table, said data units
establishing management of said module for connection with said backplane.
6. A local area network backplane interface, comprising:
a concentrator backplane operating one or more local area access methods;
a module for connection to said backplane for providing a local area
network function, said module generating operating parameter signals;
common interface means for establishing a connection between said module
and said backplane, including control means for exchanging information
between said module and said interface means with a first mailbox for
reading information signals including operating parameters from said
module and writing information signals to said interface means and a
second mailbox for reading information from said interface means and
writing information to said mailbox;
parameter table means for listing operating parameters of said module,
received as information signals, said operating parameters for determining
management of said module for connection of said module to said backplane;
backplane to module media interface circuit means for transferring data
packets between said module and said backplane; and
network management means for managing said concentrator backplane including
managing connections to said concentrator backplane, said network
management means for configuring one or more networks on said backplane
and managing said module, based on management attributes established in
said parameter table.
7. A local area network backplane interface according to claim 6, wherein
said concentrator is a generic concentrator operating one or more local
area network, each local area network based on a local area network access
method.
8. A local area network backplane interface according to claim 6. wherein
said management includes switching said module between two different local
area networks configured on said backplane.
9. A local area network according to claim 6, wherein said module includes
a module central processing unit and said interface means includes a
management processing unit, a management processing unit mailbox and a
module processing unit mailbox, said module processing unit writing to
said management processing unit mailbox and reading from said module
processing unit mailbox, said management processing unit reading from said
management processing unit mailbox and writing to said module processing
unit mailbox.
10. A local area network backplane interface according to claim 9, wherein
said management processing unit and said module processing unit transfer
said information signals based on a mailbox data unit transmission
procedure comprising:
(1) checking the mailbox to which the data units are to be transmitted to
see if it is empty;
(2) placing a next data unit octet into the mailbox checked and setting
said flag means; and
repeating steps 1 and 2 until all data unit octets have been transmitted,
data unit reception including the steps of:
checking one of said mailboxes to make sure that it is full;
reading a next data unit octet from the mailbox checked wherein a first
octet of a data unit is used for length indication; and
repeating steps 1 and 2 until all data unit octets have been received.
11. A local area network according to claim 9, further comprising flag
means associated with said management processing unit mailbox for
indicating said management processing unit mailbox is full and flag means
associated with said module processing unit mailbox for indicating said
module processing unit mailbox is full.
12. A method for establishing a connection between a local area network
backplane and a module, the module having a module central processing unit
and said backplane having all interface with a management processing unit,
a management processing unit mailbox and a module processing unit mailbox
and having a management processing unit mailbox flag and a module
processing unit mailbox flag, the method comprising the steps of:
(1) initializing communication between said management processing unit and
said module central processing unit, comprising the steps of:
initializing communication between said management processing unit and said
module central processing unit;
transferring module operating parameter information to the management
processing unit;
storing the module operating parameter information transferred to memory;
and
using the information to control a connection of the module to the
backplane and to control the module during a transfer of data packets
between the backplane and the module wherein said step of initializing
communication including transmission which comprising the steps of:
(1) checking an associated mailbox to determine if the mailbox is empty;
(2) placing a next data unit octet into said mailbox and setting the flag;
(3) repeating steps 1 and 2 until all data unit octets have been
transmitted and reception which comprises the steps of:
(1) checking a mailbox associated with the processing unit to which the
transmission is to be sent to determine if it is full or empty;
(2) reading the next data unit octet from the inbox, if the next octet is a
first octet of a data unit, the octet is used as a length indication; and
(3) repeating steps 1 and 2 until all data unit octets have been received.
13. A method according to claim 12, wherein connection of said module to
the backplane is managed by a network management unit associated with the
hub.
14. A method according to claim 12, further comprising transferring data
packets between said module and said backplane via a media interface
circuit.
15. A method according to claim 12, wherein said data units transmitted
from said module processing unit to said management processing unit
include information as to module operation characteristics for managing
connection of said module to said backplane.
16. A method according to claim 15, wherein said interface includes a
parameter table established and accessed by said master processing unit,
said management processing unit writing operational characteristics of
said module to said parameter table for managing connection of said module
to said backplane. |
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Claims |
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Description |
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FIELD OF THE INVENTION
The invention relates generally to local area network (LAN) concentrators
or hubs including concentrators and hubs dedicated to a particular LAN and
especially LAN hubs having a backplane dedicated to more than one network
(such as a concentrator with an ETHERNET network access method, and with
another ETHERNET network access method or a token ring access method).
Even more particularly, the invention relates to a LAN hub having a
backplane which is configurable to one or more access methods, wherein
various different modules can be connected to the backplane, in a
controlled manner for media access, control, bridging and routing etc.
BACKGROUND OF THE INVENTION
Various systems for local area networks (LANs) are known from the prior
art. These include intelligent hubs or concentrators with management for
controlling connections to the concentrator backplane, configuring the
backplane to one or more LAN access method and controlling operations of
connected modules (such as port switching between LANs)
The concept of the "backplane bus" is well established in the computer and
communications field; examples of standardized and proprietary backplane
buses abound. In the most general terms, a backplane bus is a wiring
center common to a single platform and shared by a number of users
(generally implemented as printed circuit boards plugged into the bus via
connectors).
The backplane bus is generally used for communications between the users
according to some common LAN access method. The access method, data format
and data rate, are all often common to all users of the bus. Often, the
actual signaling on the hub's backplane is proprietary to the hub vendor
and therefore interface circuits are required for translation from the
standardized protocols. Also, most concentrator backplanes contain
multiple networks that require switching circuits, controlled via hub
network management means, to select which network the user is connected
to. Concentrators also exist operating one or more of various different
access methods. Specifically in LAN applications of backplane buses, there
are two well established access methods: Carrier Sense, Multiple Access
with Collision Detection (CSMA/CD) (ETHERNET) and Token Passing. Token
Passing further distinguishes to a physical ring and physical bus
manifestation. All of these access methods are used with multiple data
rates and data formats, generating numerous protocols; in addition, there
are other protocols which combine elements of both CSMA/CD and Token
Passing, as well as protocols which use only some elements of the access
methods (e.g. Carrier Sense, Multiple Access without Collision Detection).
The increased flexibility provided by hubs with backplanes which allow for
more than one network to be running simultaneously, has resulted in
various different products becoming available including media modules or
media cards (media processing engine cards) which connect to the backplane
of a hub wherein the media modules may include a specific media type
running a specific media access method. Other products include bridges
routers, remote access devices, modem/terminal servers management modules
and other similar cards or modules (processing engines). The modules are
often switchable back and forth between the one or more networks, running
on the backplane.
It is desirable to provide one processing engine module (media module,
bridge, router, management module, etc.) which is usable on various
different platforms. The designer of the processing engine must become
aware of complex hub backplane interfaces as well as management protocols
and other various protocols, provided for with regard to the specific hub.
This has proven to be a significant problem with regard to new module
development. There is a need to design modules for each specific hub,
thereby limiting the possible uses for the designed modules.
SUMMARY AND OBJECTS OF THE INVENTION
It is an object of the invention to provide a system and method for
connection of LAN modules to a backplane wherein the control of
connections to the backplane is based on information transferred from the
module to an intelligent backplane interface through a separate/simple
management interface.
It is another object of the invention to provide hardware and software to
be used to form an intelligent hub interface to allow designers of a
processing engine module (PEM), such as media modules bridges, and routers
to develop one product that automatically can be used in various different
hubs.
It is a further object of the invention to provide hardware and software
which allows a module designer to develop a single product independently,
without coordination with a network hub developer, which product
automatically works in multiple hub platforms, the hardware presenting a
standardized hardware interface to module designers that defines a simple
signaling method for a transparent interface to the network hub backplane.
The hardware interface is capable of supporting a plurality of connections
into a hub (such as four or more). A group of network connections may be,
for example, for either ETHERNET (IEEE 802.3) or token ring (IEEE 802.5)
media access/media types.
Still another object of the invention is to provide a software interface
for flexible standardized management of any product (including a product
designed by other than the network hub designer), by a hub manager (either
designed by the hub designer or another designer). The software interface
is based on a generic software protocol which is made available to
organizations wherein the software protocol is used to automatically
determine the identity and extent of manageable characteristics of the
PEM. The intelligent network interface uses this information to
automatically link the PEM native management functions to the hubs
management agent. Through this software interface and the method of using
such software and hardware interface, the PEM is automatically manageable
through a common environment provided by the hubs manager via Telnet,
SNMP, and terminal access.
It is a further object of the invention to provide an open hub environment
based on a unique hardware/software common interface based on IEEE 802.3
and 802.5 for media signals, and the mailbox and SW protocol for PEM to
Hub.backslash.concentrator communications/control; allows independent
parties to design cards based on their products with the "common
interface" which will be capable of working in several hubs via connection
with appropriate carrier modules. Together, the third party product
plugged into a carrier creates a single hub module.
This invention provides a unique means that allows module designers to
develop products quicker (by not having to become aware of backplane
switching and interface circuits) and which are not limited to a single,
particular backplane. This is accomplished by providing a common
interface, one for Token Ring and one for Ethernet, that includes a
common, simple management interface (mailbox protocol). The various hub
vendors can then provide Carrier Modules to PEM vendors that provides all
of the hub specific circuits and software required to connect to that
platform. PEM vendors can then leverage one design across multiple
platforms from a single vendor or multiple vendors.
The invention provides a hub with an intelligent hub interface or carrier
which is associated with a hub of a particular design. A PEM is provided
designed based on a specific protocol. The carrier is provided with a
mailbox and the PEM is also provided with a mailbox. In this way, a simple
protocol is implemented wherein the carrier writes to the PEM mailbox and
reads from the carrier mailbox and the PEM reads from the PEM mailbox and
writes to the carrier mailbox. The PEM central processing unit (CPU)
transfers data to a management processor (MPU) of the carrier. The data is
stored to memory. This builds up a personality table (by storing data to
memory) by the processor (MPU) which is provided on the carrier. The
personality (or parameter) table is built up based on information received
from the PEM wherein a table of attributes or personality information is
established. The personality information includes the product itself and a
list of what is manageable as to the PEM product. This mechanism allows a
single software means for the carrier module that is capable of learning
what PEM is plugged into it, the PEM's media type, number of backplane
ports, number of front panel ports, etc., and what features/functions are
manageable via the hub's network management means.
For example, at power up an echo command is generated ordering the PEM to
write to the carrier mailbox and the carrier echoes back a response.
Subsequently, information is exchanged whereby the carrier builds up a
personality (or parameter) table (P-table), based on information contained
within the personality information of the PEM. For example, this can be
used to note that nothing on the PEM is manageable (by the hub
management). On the other hand, it can be noted that the PEM can be
managed by the hub management as to ports, port speed and other features
which may be managed by the hub management entity.
The carrier module system is based on a specific hub backplane, for example
the concentrator configuration and backplane described in U.S. Pat. No.
5,301,303, which is hereby incorporated by reference.
The hub or concentrator includes a network Management Module (nMM) to
provide an intelligent hub. The network Management Module provides SNMP,
Telnet and direct console management of the hub and each installed module.
The management comprises status and configuration control. In addition,
the network Management Module configures certain physical aspects of the
hub and its modules, including such items as network attachment, LAN
speed, port enable/disable. To implement the management, the management
module implements a concentrator management protocol which is either
specific to a single intelligent hub or is common to several different
intelligent hubs. A Management Processing Unit (MPU) is provided which
implements specific management functions of the intelligent hub.
According to the invention an intelligent network backplane interface is
provided for an intelligent local area network hub. The hub comprises a
concentrator backplane operating one or more network with one or more
local area access method. Modules are provided for connection to said
backplane for providing a local area network function. Interface means, in
the form of a carrier unit having an interface management processor are
provided for establishing a connection between the PEM (or 3rd party,
Independent party) module and the backplane. The processor provides
control means for exchanging information between the modules. A first
mailbox is provided for reading information signals from the independent
party module and writing information signals to the carrier said interface
means and a second mailbox for reading information from said interface
means of the independent module and writing information to said mailbox.
Information acquired by the control means is used to form a parameter
table means for listing features of the module. The features are received
as information signals. The features are used by the intelligent hub for
determining management of said module for connection of said module to
said backplane.
The invention further provides a method for establishing a connection
between a local area network backplane including vendor proprietary
signaling means (many hub products are close to but do not exactly meet
the IEEE 802.3; 802.5 standard) and a module using standard complaint
media, the module having a module central processing unit and the
backplane having an interface with a management processing unit, a
management processing unit mailbox and a module processing unit mailbox
and having a management processing unit mailbox flag and a module
processing unit mailbox flag, the method comprising initializing
communication between said management processing unit and said module
central processing unit. Information is transferred to the management
processing unit, is stored to memory and is then used by a network
management unit associated with the hub to control connections of the
module to the backplane, to control the module and to report module
identity and status.
The communication between the intelligent interface and the module
includes:
(1) checking an associated mailbox to determine if the mailbox is empty;
(2) placing a next data unit octet into said mailbox and setting the flag;
(3) repeating steps 1 and 2 until all data unit octets have been
transmitted.
Reception comprises the steps of:
(1) checking a mailbox associated with the processing unit to which the
transmission is to be sent to determine if it is full or empty;
(2) reading the next data unit octet from the mailbox (inbox) if the next
octet is a first octet of a data unit, the octet is used as a length
indication; and
(3) repeating steps 1 and 2 until all data unit octets have been received.
The various features of novelty which characterize the invention are
pointed out with particularity in the claims annexed to and forming a part
of this disclosure. For a better understanding of the invention, its
operating advantages and specific objects attained by its uses, reference
is made to the accompanying drawings and descriptive matter in which a
preferred embodiment of the invention is illustrated.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
FIG. 1 is a schematic view showing the connection of the PEM Carrier Module
to the backplane and the connection of a PEM card to the PEM Carrier
Module;
FIG. 2 is a schematic view showing the hardware interface and mailbox
protocol for exchange of information between the MPU of the carrier module
and the CPU of a PEM card;
FIG. 3 is a flow chart showing a mailbox protocol initiation sequence
according to the invention;
FIG. 4A is a diagram showing an example wherein the CPU and MPU send each
other administrative state change notification data units simultaneously;
FIG. 4B is a diagram showing how the MPU enforces coherency;
FIG. 5A is a representation of the structure of a mailbox protocol data
unit (MPDU);
FIG. 5B is a representation of the structure of an echo request MPDU;
FIG. 5C is a representation of the structure of an echo response MPDU;
FIG. 5D is a representation of the structure of a personality notification
MPDU;
FIG. 5E is a representation of the structure of the coding of module
information;
FIG. 5F is a representation of the structure of personality tables showing
a number of complex ports;
FIG. 5G is a representation of the structure of the coding of complex port
information; and
FIG. 6 is a block diagram showing component interconnections according to a
preferred layout of a token ring or ETHERNET intelligent interface
(carrier).
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to the drawings in particular, the invention comprises an
interface between a PEM card 10 and a specific backplane 12. The backplane
may be a backplane designed specifically for a particular LAN network
access method, such as a single ETHERNET network, a single token ring
network, a single FDDI network etc. The backplane 12 may also be a
specific backplane including more than one channel for grouping of
circuits wherein each channel or grouping of circuits is dedicated to a
network access method. With this type of backplane, two different networks
may be operating simultaneously based on a specific, defined network
access method (two ETHERNET networks, an ETHERNET network and a token ring
network etc.). Further, the backplane 12 may be a generic backplane,
configurable to or one or more of numerous LAN network access methods.
The backplane 12 may be part of an intelligent hub or concentrator. A
network management means (NMM) 8 may be connected to the backplane for
configuring the backplane to one or more networks, each running any one of
several known network access methods. The NMM 8 also controls enabling of
ports of connected modules such as PEM card 10 and controls connection of
modules to the backplane such as carrier module 14 and also controls the
modules themselves.
The PEM card 10 may be any one of numerous types of modules. For example,
PEM card 10 may be a media module or media distribution card, namely for
connection to the backplane of a specific media type (twisted pair,
coaxial cable, fiber optic cable etc.) running a specific network access
method (ETHERNET, token ring, FDDI, token bus etc.). The PEM card could
also be a local area network management module NMM (for managing the
network, configuring a generic backplane etc.). That is, the NMM may also
be connected to the backplane via an intelligent interface as described
herein. The PEM card could be other entities such as a bridge, router
remote access device and modem terminal server or the like. The main
feature of the invention is that the PEM card could be a yet to be
designed card wherein the designer of the PEM card does not need to know
the specifics as to the backplane connections, management and interface to
the backplane. Furthermore, one PEM card can be used to connect a variety
of backplanes/concentrators via mating with different modules.
The connection of the PEM card to the backplane is made via a PEM Carrier
Module 14. The carrier module 14 provides an intelligent interface between
a specific backplane and the standardized PEM interface to a connected
module. The physical management interaction between the PEM card 10, the
PEM Carrier Module 14 is shown in FIG. 2. FIG. 2 provides schematic view
showing the hardware interface between the MPU 16 and PEM CPU 18 LAN
data/traffic has a separate path that goes directly from the PEM's media
port to the Carrier's backplane interface circuits (for signal
conditioning and switching) via the PEM connector. The PEM Carrier Module
includes a local management processor or MPU 16. The PEM card 10 includes
a processor implementing the native partner functionality (functionality
defined by PEM designer), namely PEM CPU 18.
The hardware interface employs a MPU mailbox (MPUMBX) 22 which is an eight
bit register defined as MPU 16 read only and CPU 18 write only. A CPU
mailbox (CPUMBX) 22 is provided in the form of an eight bit register
defined as CPU 18 read only, MPU 16 write only. The MPUMBX 20 thereby
provides an in-box for the MPU 16 and an out-box for the PEM 18 whereas
the CPUMBX 22 provides an in-box for the MPU and an out-box for CPU 18.
CPUMBX full 24 is a flag indicating that the CPU mailbox 20 is full. MPU
MBX full 26 is a flag indicating that the MPU mailbox 20 is full. The flag
24 can be set only by the MPU 16 by the MPU 16 writing of CPUMBX 22 and
can be reset (cleared) only by the CPU 18 reading CPUMBX 22. Likewise the
flag 26 can be set only by the CPU 18 writing CPUMBX 20 and can be reset
(cleared) by the MPU 16 reading CPUMBX 20. With this action of the CPU 18,
the flag becomes automatically set, and, if desired interrupts the MPU 16.
When the MPUMBX is read by the MPU 16, this flag is automatically cleared.
A specific software interface using the above described mailbox protocol,
is provided according to the invention for communications between the PEM
CPU 18 and the MPU 16 (between the PEM card 10 and the PEM Carrier Module
14).
At the lowest level, the mailbox software interface comprises a processor
(the transmitter) placing an octet in the other processors (the receiver)
in-box (MPU MBX 20 or CPU MBX 22), thereby setting the receivers in-box
full flag (24, 26). The receiver detects the data arrival (either by
polling the receiver full flag or receiving an interrupt indicating the
condition). The receiver, upon reading its in-box, clears the in-box full
flag.
The software interface relies on the mailbox protocol data unit (MPDU)
which is a sequence of octets transferred between a transmitter and a
receiver. MPDUs are exchanged bi-directionally between the PEM CPU 18 and
the MPU 16 (both processors can act as transmitter and receiver).
MPDU transmission includes the following steps: (1) checking the out-box
(MPU MBX 20 or CPU MBX 22) to make sure it is empty; (2) placing the next
MPDU octet into the out-box and setting the flag (full 24, 26); and (3)
repeating steps one and two until the MPDU octets have been transmitted.
The first octet of each MPDU is preferably a length indicator.
MPDU reception includes the following steps: (1) checking the in-box (MPU
MBX 20 or CPU MBX 22) to make sure it is full; (2) reading the next MPDU
octet from the in-box. If this is the first octet of MPDU, using the first
octet as a length indicator; and (3) repeating steps one and two until all
MPDU octets have been received.
The software interface preferably provides for a time out (the length of
time may vary between the implementations), utilized between
transmission/reception of successive MPDU octets. During transmission, the
receiver must read its in-box (20, 22) and clear its in-box full flag (24,
26) within a time period from the date of arrival, or the transmitter will
generate a time out. In reception, the transmitter must place a new octet
of data in its out-box within a time period after the receiver clears its
in-box, or the receiver will generate a time out period.
Upon detection of a timeout the error must be propagated up to the higher
layer as a protocol timeout error.
The mailbox hardware provides full duplex data transmission capability,
i.e. both the PEM CPU 18 and the MPU 16 may transmit and receive
simultaneously. Software designers must include sufficient buffer space to
support simultaneous receive and transmit of the largest MPDU.
Parameters passed across the mailbox interface include static and dynamic
information regarding diagnostic testing of the interface, module and port
personality information, module and port status information, and module
and port control parameters. The parameters are not intended to replace
local console, Telnet or SNMP management, but instead are used to augment
concentrator management (NMM) capabilities. The parameters provide
descriptive information about the inserted module and sustain the base
level of control the concentrator management hold for all integrated
products.
MPDUs provide the transport mechanism between the PEM CPU and the carrier
MPU. MPDUs include: Echo Request, Echo Response, Personality Notification,
Operational Status Notification, Administrative State Notification,
Network Configuration Notification, Speed Configuration Notification, IP
Configuration Notification, MAC Configuration Notification, Remote Command
Request, Remote Command Response and Date-Time Notification.
As specified by the mailbox protocol, some of these MPDUs are
bi-directional, able to be transmitted by both the PEM CPU 18 and the MPU
16, while others are uni-directional.
To support a flexible protocol, the notion of capabilities is introduced.
Capabilities indicate the options the PEM CPU 18 will support within the
mailbox protocol. During the initialization of the mailbox protocol, the
PEM CPU transfers a Personality Notification MPDU--which among other items
includes supported capability parameters. Inclusion and exclusion of
capabilities is the method used to vary the level of PEM integration.
Capabilities are provided on a module and per-port basis. If the PEM CPU 18
supports a given defined option, then it must set the appropriate bit
location in the capabilities parameter. If a given option is not
supported, the PEM CPU must clear the bit location to indicate exclusion
of the capability. For example, if the Port Enable/Disable Support bit
location is clear in the module capabilities parameter, MPU 16 will never
send the PEM CPU port enable/disable MPDUs.
Since capabilities indicate supported protocol options, their inclusion and
exclusion have a direct effect upon both the mailbox protocol
initialization sequence and normal mailbox MPDU exchanges.
Ports on modules are placed into one of two categories--simple and complex
ports. A simple port reports only basic information such as port type and
speed, and may be enabled or disabled. Media ports (e.g. terminal server
or WAN ports) are generally considered "simple".
A complex port is one that possesses complex attributes in addition to
those of the simple port. These attributes include MAC Address, IP
Address, and port-to-network switching. Generally parts connected to the
backplane interface circuity (carrier interface circuity via PEM
connector) are complex ports.
This specification for mailbox interactions is intended to cover a wide
range of product offerings, developed with differing levels of required
management integration. In some cases tightly coupled integration may be
in order, where the full capabilities of the protocol will be utilized. In
other cases, management integration will be less of a concern, and only
the minimal set of capabilities will be supported by the partner CPU 18.
The MPU 16 software is able to automatically adjust to the level of
integration desired by the PEM CPU 18.
The mailbox protocol is intended to be a simple protocol that intrudes upon
the PEM CPU as little as possible. To accomplish this goal the protocol
consists of only one mandatory sequence of events--initialization. All
operational exchanges within the mailbox protocol are optional, based upon
the capabilities supported by the PEM CPU.
The mailbox protocol initialization sequence consists of two mandatory
steps, as represented in FIG. 3, in which:
1. the PEM CPU 18 and the MPU 16 determine the health of the mailbox
hardware by exchanging Echo messages;
2. the PEM CPU 18 transmits its Personality information to the MPU 16. This
allows a personality | | |
