Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
1997-09-29
2001-08-07
Marcelo, Melvin (Department: 2663)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
Reexamination Certificate
active
06272144
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to asynchronous transfer mode (ATM) communication systems and devices and more particularly to techniques for providing in-band line card control capabilities in an ATM switch or other packet-based switch.
BACKGROUND OF THE INVENTION
An ATM communication system provides high-speed, low-delay switching of voice, data, video and other types of user information traffic. In an ATM system, the user information traffic is separated into fixed-length 53-byte cells. Each ATM cell typically includes a 5-byte header and a 48-byte payload. The header incorporates a virtual channel identifier (VCI) and a virtual path identifier (VPI) associated with the corresponding cell. The VCI and VPI together specify a virtual connection (VC) which is established when a user requests a network connection in the ATM system. Additional details regarding these and other aspects of ATM systems can be found in the ATM Forum, “ATM User-Network Interface Specification,” Version 3.1, September, 1994, and in Martin de Prycker, “Asynchronous Transfer Mode: Solution for Broadband ISDN,” Ellis Horwood, N.Y., 1993.
FIG. 1
shows a typical ATM switch
10
. The switch
10
includes a control processor
12
which directs the operation of a switch fabric
14
. The switch fabric in turn drives N line cards
16
-i, i=1, 2, . . . N. Each of the N line cards
16
-i serves to interface the switch
10
to a corresponding physical link or trunk of an established ATM network connection. For example, one of the N line cards may interface with a computer of a network user, while another one of the line cards interfaces with a physical layer of a communication network, so as to allow the user to communicate over the physical layer of the network via the ATM switch
10
. The control processor
12
is responsible for configuring and maintaining the switch
10
.
FIG. 2
illustrates one of the line cards
16
-i in greater detail. The line card
16
-i includes a Utopia port
22
, a transmission convergence (TC) device
24
, a physical media dependent (PMD) device
26
, and a synchronous optical network (SONET) port
28
. The transmission convergence device
24
interfaces an ATM cell-based switch fabric interconnect, such as the Utopia port
22
, to a bit-level physical layer interconnect, such as SONET port
28
. The line card
16
-i further includes a utility bus
30
, a utility bus interface
32
, a local microprocessor
34
, a random access memory (RAM)
36
, and a read-only memory
38
. The elements
30
,
32
,
34
,
36
and
38
are used to provide configuration, status and other control functions for the line card
16
-i. The utility bus
30
is a global utility bus used to provide communication between the N line cards of switch
10
so that the local microprocessors in the line cards can, for example, coordinate configurations or collect statistics.
A significant problem with the conventional ATM switch line card arrangement shown in
FIG. 2
is the added expense and complexity associated with providing a separate utility bus interface and microprocessor-based control circuitry for each of the line cards. Although the utility bus
30
can be of lower bandwidth than the ATM switch
10
, it still needs to be scaled with the size of the switch, and potentially may be required to interconnect hundreds of line cards. The cost of this separate line card control hardware can therefore be excessive. Moreover, the transmission convergence device
24
is required to include additional input/output pins for interfacing with the control hardware, and therefore its die size, package size and power consumption are unduly increased. Other types of conventional line cards do not include a local microprocessor, but instead utilize an on-board microcontroller to interface via a separate line card control bus to a central controller which provides configuration, status and other types of control processing for the line cards. Although the hardware cost of such cards may be less than that of cards including a local microprocessor, the use of the separate control network for providing line card configuration and control still unduly increases the size, cost and complexity of the transmission convergence device, the line card and the ATM switch.
Most conventional ATM switches thus utilize line cards which include some type of separate line card control bus and control hardware. Examples of conventional transmission convergence devices for use in line cards such as that shown in
FIG. 2
include the PM5355 S/UNI-622 and PM5346 S/UNI-155-LITE Saturn User Network Interfaces from PMC-Sierra, Inc. of Burnaby, BC, Canada, the IDT77105 PHY (TC-PMD) from Integrated Device Technology, Inc. of Santa Clara, Calif., and the T7254 Four-Port ISDN User-Network Interface Termination for Switches from the Microelectronics Group of Lucent Technologies, formerly AT&T Microelectronics, of Allentown, Pa. These exemplary transmission convergence devices are designed for integration into a line card, and each is designed to support a separate control bus for the line card. The size, cost and complexity of such devices could be considerably reduced if a mechanism was available for providing line card control without the need for a separate line card control bus or other separate control interface. It is therefore apparent that a need exists for improved line card control techniques for use in ATM switches and other packet-based communication devices.
SUMMARY OF THE INVENTION
The invention in an illustrative embodiment uses an existing ATM connection to provide line card control operations in an ATM switch, thereby completely eliminating the need for a separate line card control bus or other control interface, and considerably reducing the size, cost and complexity of the line card, its transmission convergence device, and the ATM switch. In the illustrative embodiment, control messages from a control processor of the ATM switch are transmitted in one or more ATM cells to a transmission convergence device in the line card. The transmission convergence device filters a stream of cells received in the line card in order to identify cells including control messages directed to the line card. The filtering operation generally involves attempting to match a VPI/VCI portion of a cell header to a specified VPI/VCI address associated with the control messages. After a cell containing a control message cell is identified, the transmission convergence device executes one or more commands associated with the control message. The invention may also be implemented in other types of packet-based communication systems.
In accordance with the invention, each control message may be transmitted in a single cell which includes a header and a payload. A message trailer portion of the payload may include a device-specific data (DSD) field which specifies an interpretation of the payload structure. The message trailer may also include a cyclic redundancy code (CRC) field which is compared with a CRC computed for the cell payload to determine whether the control message sent in the cell should be accepted or rejected. A pass-through data (PTD) field in the message trailer may be returned unmodified from the line card to the switch control processor as part of an acknowledgment of receipt and execution of the corresponding control message.
The present invention considerably simplifies line cards and the corresponding switches by eliminating the need to provide a separate line card control interface. The in-band device configuration of the invention can completely eliminate the need for a utility bus to interconnect multiple line cards, as well as the control hardware associated with the utility bus interface. It can substantially reduce the number of input/output pins required in a transmission convergence device, such that the device can be implemented with a smaller die, a smaller package and lower power dissipation. The in-band device configuration of the invention supports functions such as remote configuration, error
Berenbaum Alan David
Fraser Alexander Gibson
McLellan, Jr. Hubert Rae
Agere Systems Guardian Corp.
Kwoh Jasper
Marcelo Melvin
Ryan & Mason & Lewis, LLP
LandOfFree
In-band device configuration protocol for ATM transmission... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with In-band device configuration protocol for ATM transmission..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and In-band device configuration protocol for ATM transmission... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2539248