Title: Systems and methods for providing communication between an ATM layer device and multiple multi-channel physical layer devices
Abstract: Systems and methods are provided for providing communication between an ATM layer device and multiple multi-channel PHY layer devices, which increase the number of multi-channel PHY layer ports supported by the ATM layer device. In general, one such system comprises an ATM layer device that supports a plurality of ATM communication channels in which each of the plurality of ATM communications channels correspond to a first class of service or a second class of service, a plurality of physical layer devices each having a first channel port associated with the first class of service and a second channel port associated with the second class of service, and a local interface in communication with the ATM layer device and the plurality of physical layer devices for establishing a plurality of channel connections between each of the plurality of ATM communication channels and the first channel port and the second channel port in each of the plurality of physical layer devices, the local interface having a plurality of addresses. In the system, each of the plurality of channel connections associated with the plurality of second channel ports is via one of the plurality of addresses and at least two of the plurality of channel connections associated with the plurality of first channel ports is via no more than one of the plurality of addresses. In this manner, the system increases the number of physical layer devices communicating with the ATM layer.
Patent Number: 7,023,829 Issued on 04/04/2006 to Holmquist, et al.
| Inventors:
|
Holmquist; Kurt (Largo, FL);
Thoenes; Ed (St. Petersburg, FL)
|
| Assignee:
|
Paradyne Corporation (Largo, FL)
|
| Appl. No.:
|
871351 |
| Filed:
|
May 31, 2001 |
| Current U.S. Class: |
370/341; 370/230.1; 370/232; 370/235; 370/312; 370/395.43 |
| Current Intern'l Class: |
H04Q 7/28 (20060101); H04L 12/28 (20060101); H04H 1/00 (20060101) |
| Field of Search: |
370/475,230.1,229,230,235,389,462,465,468,471
|
References Cited [Referenced By]
U.S. Patent Documents
Primary Examiner: Pham; Chi
Assistant Examiner: Grey; Christopher P.
Attorney, Agent or Firm: Thomas, Kayden, Horstemeyer & Risley, LLP
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATION
This application claims priority to copending U.S. provisional application entitled,
"Technique for Expanding the Effective Number of PHY Ports Connected to an ATM
Switching Device," having Ser. No. 60/208,639, filed Jun. 1, 2000, which is entirely
incorporated herein by reference.
Claims
What is claimed is:
1. A communication system, comprising:
an asynchronous transfer mode (ATM) layer device that supports a plurality of
ATM communication channels, each of the plurality of ATM communications channels
corresponding to a first class of service or a second class of service;
a plurality of physical layer devices, each of the plurality of physical layer
devices having a first channel port associated with the first class of service
and a second channel port associated with the second class of service; and
a local interface in communication with the ATM layer device and the plurality
of physical layer devices and having a plurality of addresses,
for establishing a plurality of channel connections between each of the plurality
of ATM communication channels and the first channel port and the second channel
port in each of the plurality of physical layer devices, the local interface having
a plurality of addresses;
wherein each of the plurality of channel connections associated with the plurality
of second channel ports is via one of the plurality of addresses and at least two
of the plurality of channel connections associated with the plurality of first
channel ports is via no more than one of the plurality of addresses.
2. The system of claim 1, wherein each of the plurality of ATM communication
channels associated with one of the plurality of first channel ports is adapted
to carry priority data traffic and each of the plurality of ATM communication channels
associated with one of the plurality of second channel ports is adapted to carry
non-priority data traffic.
3. The system of claim 2, wherein the priority data traffic is real-time traffic
and the non-priority data traffic is non-real-time traffic.
4. The system of claim 2, wherein the priority data traffic corresponds to any
of the following group of ATM service categories: constant bit rate (CBR), real-time
variable bit rate (rt-VBR), non-real-time variable bit rate (nrt-VBR), available
bit rate (ABR), unspecified bit rate (UBR), and combinations thereof.
5. The system of claim 1, wherein the local interface conforms to Universal Test
and Operations Physical Interface (UTOPIA) level 2 specification.
6. The system of claim 1, wherein each of the plurality of physical layer devices
is adapted to communicate via a first communication channel and a second communication
channel with an external physical layer device.
7. The system of claim 6, further comprising an ATM switch that provides the
plurality of communication channels to the ATM layer device.
8. The system of claim 7, wherein the ATM switch is implemented in a digital
subscriber line access multiplexer (DSLAM).
9. A communication system, comprising:
an ATM layer means for receiving a plurality of ATM communication channels, each
of the plurality of ATM communication channels corresponding to a first class of
service or a second class of service;
a plurality of physical layer means, each for communicating with an external
physical layer device via a first port associated with the first class of service
and a second port associated with the second class of service; and
a communication means for interfacing the ATM layer means and the plurality of
physical layer means and for establishing a plurality of channel connections between
each of the plurality of ATM communication channels and the first and second ports
associated with each of the plurality of physical layer means, the communication
means having a plurality of addresses;
wherein each of the plurality of channel connections associated with each of
the plurality of second ports is via one of the plurality of addresses and at least
two of the plurality of channel connections associated with the plurality of first
ports is via no more than one of the plurality of addresses.
10. The system of claim 9, wherein each of the plurality of physical layer means
is adapted to carry priority data traffic via the first communication channel and
non-priority traffic via the second communication channel.
11. The system of claim 10, wherein the priority data traffic is real-time traffic
and the non-priority data traffic is non-real-time traffic.
12. The system of claim 10, wherein the priority data traffic corresponds to
any of the following group of ATM service categories: constant bit rate (CBR),
real-time variable bit rate (rt-VBR), non-real-time variable bit rate (nrt-VBR),
available bit rate (ABR), unspecified bit rate (UBR), and combinations thereof.
13. The system of claim 9, further comprising an ATM switch that provides the
plurality of communication channels to the ATM layer device.
14. The system of claim 13, wherein the ATM switch is implemented in a digital
subscriber line access multiplexer (DSLAM).
15. The system of claim 14, wherein each of the plurality of physical layer devices
provides digital subscriber loop services to the corresponding external physical
layer devices.
16. A method for providing communication between an ATM layer device and a plurality
of physical layer devices via a local interface having a plurality of addresses,
each of the plurality of physical layer devices having a first channel port and
a second channel port, comprising:
receiving an ATM cell associated with one of a plurality of ATM communication
channels, each of the plurality of ATM communication channels corresponding to
either a first class of service or a second class of service;
determining a VPI/VCI value associated with the ATM cell;
based on the VPI/VCI value and a predefined set of rules, determine whether the
ATM cell corresponds to the first class of service or the second class of service
and determine which of the plurality of addresses on the local interface to which
the VPI/VCI value is associated; and
where the ATM cell corresponds to the first class of service, providing the ATM
cell to all of the first channel ports via a first unique address on the local
interface and where the ATM cell corresponds to the second class of service, providing
the ATM cell to one of the second channel ports via a second unique address.
17. The method of claim 16, wherein the first class of service corresponds to
priority data traffic and the second class of service corresponds to non-priority traffic.
18. The method of claim 17, wherein the priority data traffic is real-time traffic
and the non-priority data traffic is non-real-time traffic.
19. The method of claim 18, wherein the priority data traffic corresponds to
any of the following group of ATM service categories: constant bit rate (CBR),
real-time variable bit rate (rt-VBR), non-real-time variable bit rate (nrt-VBR),
available bit rate (ABR), unspecified bit rate (UBR), and combination thereof.
20. The method of claim 16, wherein the plurality of ATM communication channels
is received from an ATM switch.
21. The method of claim 20; wherein the ATM switch is implemented in a DSLAM.
22. The method of claim 21, further comprising providing DSL services to an external
physical layer device via one of the plurality of physical layer devices.
23. A method for providing communication between an ATM layer device and a plurality
of physical layer devices, each of the plurality of physical layer devices having
a first channel port and a second channel port, comprising:
receiving an ATM cell associated with one of a plurality of ATM communication
channels, each of the plurality of ATM communication channels corresponding to
either a first class of service or a second class of service;
determining a VPI/VCI value associated with the ATM cell;
based on the VPI/VCI value and a first predefined set of rules, determine whether
the ATM cell corresponds to the first class of service or the second class of service
and determine which of a plurality of addresses on a first local interface to which
the VPI/VCI value is associated; and
where the ATM cell corresponds to the first class of service, providing the ATM
cell to an address expansion device via a first unique address on the local interface
and, based on the VPI/VCI value and a second predefined set of rules, providing
the ATM cell to one of the plurality of first channel ports associated with the
VPI/VCI value via one of a plurality of addresses on a second local interface connected
to the address expansion device and where the ATM cell corresponds to the second
class of service, providing the ATM cell to one of the second channel ports via
a second unique address on the first local interface.
24. The method of claim 23, wherein the first class of service corresponds to
priority data traffic and the second class of service corresponds to non-priority traffic.
25. The method of claim 24, wherein the priority data traffic is real-time traffic
and the non-priority data traffic is non-real-time traffic.
26. The method of claim 25, wherein the priority data traffic corresponds to
any of the following group of ATM service categories: constant bit rate (CBR),
real-time variable bit rate (rt-VBR), non-real-time variable bit rate (nrt-VBR),
available bit rate (ABR), unspecified bit rate (UBR), and combinations thereof.
27. The method of claim 23, wherein the plurality of ATM communication channels
is received from an ATM switch.
28. The method of claim 27, wherein the ATM switch is implemented in a DSLAM.
29. The method of claim 28, further comprising providing DSL services to an external
physical layer device via one of the plurality of physical layer devices.
30. A computer-readable medium for providing communication between an ATM layer
device and a plurality of physical layer devices, each of the plurality of physical
layer devices having a first channel port and a second channel port, comprising:
a first portion of logic for receiving an ATM cell associated with one of a plurality
of ATM communication channels, each of the plurality of ATM communication channels
corresponding to either a first class of service or a second class of service;
a second portion of logic for determining a VPI/VCI value associated with the
ATM cell;
a third portion of logic for determining, based on the VPI/VCI value and a first
predefined set of rules, whether the ATM cell corresponds to the first class of
service or the second class of service and determine which of a plurality of addresses
on a first local interface to which the VPI/VCI value is associated; and
a fourth portion of logic for (i) providing the ATM cell to an address expansion
device via a first unique address on the local interface and for providing, based
on the VPI/VCI value and a second predefined set of rules, the ATM cell to one
of the plurality of first channel ports associated with the VPI/VCI value via one
of a plurality of addresses on a second local interface where the ATM cell corresponds
to the first class of service and (ii) providing the ATM cell to one of the second
channel ports via a second unique address on the first local interface where the
ATM cell corresponds to the second class of service.
31. The computer-read able medium of claim 30, wherein the first class of service
corresponds to priority data traffic and the second class of service corresponds
to non-priority traffic.
32. The computer-readable medium of claim 31, wherein the priority data traffic
is real-time traffic and the non-priority data traffic is non-real-time traffic.
33. The computer-readable medium of claim 32, wherein the priority data traffic
corresponds to any of the following group of ATM service categories: constant bit
rate (CBR), real-time variable bit rate (rt-VBR), non-real-time variable bit rate
(nrt-VBR), available bit rate (ABR), unspecified bit rate (UBR), and combination thereof.
34. The computer-readable medium of claim 30, wherein the plurality of ATM communication
channels is received from an ATM switch.
35. The computer-readable medium of claim 34, wherein the ATM switch is implemented
in a DSLAM.
36. The computer-readable medium of claim 35, further comprising a fifth portion
of logic for providing DSL services to an external physical layer device via one
of the plurality of physical layer devices.
37. A communication system, comprising:
an asynchronous transfer mode (ATM) layer device that supports a plurality of
ATM communication channels, each of the plurality of ATM communications channels
corresponding to a first class of service or a second class of service;
a plurality of physical layer devices, each of the plurality of physical layer
devices having a first channel port associated with the first class of service
and a second channel port associated with the second class of service; and
a local interface in communication with the ATM layer device and the plurality
of physical layer devices, the local interface establishing a plurality of first
class connections, each first class connection being between one of the ATM communications
channels and one of the first channel ports, all of the first class connections
using a single address on the local interface, the local interface establishing
a plurality of second class connections, each second class connection being between
one of the ATM communications channels and one of the second channel ports, each
of the second class connections having a unique address on the local interface.
38. The system of claim 37, wherein each first channel connection is adapted
to carry priority data traffic and each second channel connection is adapted to
carry non-priority data traffic.
39. The system of claim 38, wherein the priority data traffic is real-time traffic
and the non-priority data traffic is non-real-time traffic.
40. The system of claim 38, wherein the priority data traffic corresponds to
any of the following group of ATM service categories: constant bit rate (CBR),
real-time variable bit rate (rt-VBR), non-real-time variable bit rate (nrt-VBR),
available bit rate (ABR), unspecified bit rate (UBR), and combinations thereof.
41. The system of claim 37, wherein the local interface conforms to Universal
Test and Operations Physical Interface (UTOPIA) level 2 specification.
42. The system of claim 37, wherein each of the plurality of physical layer devices
is adapted to communicate via a first physical layer channel and a second physical
layer channel with an external physical layer device.
43. The system of claim 42, further comprising an ATM switch that provides the
plurality of first channel connections and the plurality of second channel connections
to the ATM layer device.
44. The system of claim 43, wherein the ATM switch is implemented in a digital
subscriber line access multiplexer (DSLAM).
45. A communication system, comprising:
a local interface;
an address expansion device having an address on the local interface;
a plurality of physical layer (PHY) devices, each of the plurality of physical
layer devices having a first channel port associated with a first class of service
and a second channel port associated with a second class of service, each of the
second channel ports having an address on the local interface;
an asynchronous transfer mode (ATM) layer device that supports a first plurality
of ATM communication channels corresponding to the first class of service and a
second plurality of ATM communication channels corresponding to the second class
of service, the ATM layer device being in communication with each of the second
channel ports through each second channel port's respective address on the local
interface, the ATM layer device being in communication with the address expansion
device through the address expansion device's address on the local interface; and
an expansion interface, each of the first channel ports having an address on
the expansion interface, the expansion device being in communication with each
of the first channel ports through each first channel port's respective address
on the expansion interface,
the local interface and expansion interface configured to establish a first plurality
of channel connections, each of the first plurality of channel connections being
established between one of the first plurality of ATM communication channels and
one of the first channel ports, and
the local interface and expansion interface further configured to establish a
second plurality of channel connections, each of the second plurality of channel
connections being established between one of the second plurality of ATM communication
channels and one of the second channel ports.
46. The system of claim 45, wherein each of the first plurality of ATM communication
channels is adapted to carry priority data traffic and each of the second plurality
of ATM communication channels is adapted to carry non-priority data traffic.
47. The system of claim 46, wherein the priority data traffic is real-time traffic
and the non-priority data traffic is non-real-time traffic.
48. The system of claim 47, wherein the priority data traffic corresponds to
any of the following group of ATM service categories: constant bit rate (CBR),
real-time variable bit rate (rt-VBR), non-real-time variable bit rate (nrt-VBR),
available bit rate (ABR), unspecified bit rate (UBR), and combinations thereof.
49. The system of claim 45, wherein the local interface and the expansion interface
conform to Universal Test and Operations Physical Interface (UTOPIA) level 2 specification.
50. The system of claim 45, wherein each of the plurality of physical layer devices
is adapted to communicate via the first and second communication channels with
an external physical layer device.
51. The system of claim 45, further comprising an ATM switch that provides the
plurality of communication channels to the ATM layer device.
52. The system of claim 51, wherein the ATM switch is implemented in a digital
subscriber line access multiplexer (DSLAM).
53. A communication system, comprising:
an ATM layer means for receiving a plurality of ATM communication channels, each
of the plurality of ATM communication channels corresponding to a first class of
service or a second class of service;
a plurality of physical layer means, each for communicating with an external
physical layer device via a first communication channel associated with the first
class of service and a second communication channel associated with the second
class of service; and
a communication means for interfacing the ATM layer means and the plurality of
physical layer means, the communication means establishing a plurality of first
class connections, each first class connection being between one of the ATM communications
channels and one of the first channel ports, all of the first class connections
using a single address on the local interface, the communication means establishing
a plurality of second class connections, each second class connection being between
one of the ATM communications channels and one of the second channel ports, each
of the second class connections having a unique address on the local interface.
54. The system of claim 53, wherein each of the plurality of physical layer means
is adapted to carry priority data traffic via the first communication channel and
non-priority traffic via the second communication channel.
55. The system of claim 54, wherein the priority data traffic is real-time traffic
and the non-priority data traffic is non-real-time traffic.
56. The system of claim 54, wherein the priority data traffic corresponds to
any of the following group of ATM service categories: constant bit rate (CBR),
real-time variable bit rate (rt-VBR), non-real-time variable bit rate (nrt-VBR),
available bit rate (ABR), unspecified bit rate (UBR), and combinations thereof.
57. The system of claim 53, further comprising an ATM switch that provides the
plurality of communication channels to the ATM layer device.
58. The system of claim 57, wherein the ATM switch is implemented in a digital
subscriber line access multiplexer (DSLAM).
59. The system of claim 53, wherein each of the plurality of physical layer devices
provides digital subscriber loop services to a corresponding external physical
layer device.
Description
TECHNICAL FIELD
The present invention is generally related to data communication systems and
methods, and more particularly, is related to systems and methods for providing
data communication between an ATM layer device and multiple physical layer devices.
BACKGROUND OF THE INVENTION
Data communication systems are widely-known in the art. These systems enable
heterogeneous computers to communicate with each other using a defined set of rules
and message exchanges, known as data communication protocols. Data communication
protocols are structured based on the concept of protocol layering. For instance,
the data communication functions are partitioned into a hierarchical set of layers
where each layer performs a related subset of the functions required to communicate
with another system. Each layer relies on the next lower layer to perform more
primitive functions and to conceal the details of those functions. Each layer also
provides services to the next higher layer. Of course, it takes two to communicate,
so the same set of layered functions must exist in two systems. Communication is
achieved by having the corresponding or peer layers in two systems communicate
using predefined protocols. For example, a well-known framework for defining standard
data communication protocols is the Open Systems Interconnection (OSI) reference
model, which was established by the International Organization for Standardization.
In the OSI architecture, each system communicating with another system contains
seven protocol layers: physical layer, data link layer, network layer, transport
layer, session layer, presentation layer, and application layer.
A well-known suite of protocols used in many communications systems is based
on
asynchronous transfer mode (ATM). ATM is a well-known cell-oriented switching and
multiplexing data communication technology that utilizes fixed-length packets or
cells to carry different types of traffic. Each cell is 53 bytes in length and
comprises a 5-byte header and a 48-byte payload. Each cell is switched and multiplexed
throughout the ATM network based on the information contained in the header. The
cell header identifies the destination of the cell, the cell type, and the cell
priority. For example, the header comprises a virtual path identifier (VPI) field
and a virtual channel identifier (VCI) field, which have local significance only
and identify the destination of the cell. The header also comprises a generic flow
control (GFC) field, which allows a multiplexer to control the rate of an ATM terminal.
The header further comprises a payload type (PT) field, which indicates whether
the cell contains user data, signaling data, or maintenance information and a cell
loss priority (CLP) field, which indicates the relative priority of the cell. Using
the CLP field, lower priority cells are discarded before higher priority cells
during congested intervals. The header also comprises a cell header error check
(HEC) field, which detects and corrects errors in the header. The payload field
is passed through the network intact, with no error checking or correction. ATM
relies on higher layer protocols to perform error checking and correction on the payload.
When using ATM, longer packets cannot delay shorter packets as in other packet
switched implementations because long packets are divided into many fixed-length
cells. This enables ATM to carry constant bit rate (CBR) traffic, such as voice
and video, in conjunction with variable bit rate (VBR) data traffic, potentially
having very long packets in the same network.
The two lowest protocol layers in the ATM protocol stack are the physical (PHY)
layer and the ATM layer. The PHY layer provides for transmission of ATM cells over
a physical medium that connects two ATM devices. The bits in the cells are transmitted
over the transmission medium in a continuous stream. All information is switched
and multiplexed in the ATM network in these fixed-length cells.
In ATM communication systems, the ATM layer provides the switching and multiplexing
of virtual path connections (VPC) and virtual channel connections (VCC) between
systems. Systems and methods for providing communication between an ATM layer device
and multiple PHY layer devices are known in the art. For example, the Universal
Test & Operations PHY Interface for ATM (UTOPIA) level 2 specification defines
a standard data path interface between an ATM layer device and multiple PHY layer
devices in an ATM communication system for communicating data in order to effectuate
ATM network switching. The details of UTOPIA may be found in the ATM Forum Technical
Committee document entitled "UTOPIA Level 2, Version 1.0 (af-phy-0039-00), which
is entirely incorporated herein by reference.
The UTOPIA bus was originally conceived for use in ATM switching nodes within
the ATM network where the total number of ports (PHY layer devices) is typically
fairly small. Thus, the UTOPIA bus was designed with a five bit addressing scheme.
Thus, the total number of PHY layer devices that can be connected to the standard
UTOPIA bus is thirty-one, with one invalid address used in the polling discipline
to indicate there is no address or no poll.
It is also known in the art to provide ATM communications via digital subscriber
line (DSL) technologies. DSL technologies have become a widely-used solution for
providing high bit rate transmission over the existing copper wire infrastructure,
known as the "subscriber loop." DSL technologies dramatically improve the bandwidth
of the existing analog telephone system. DSL enhances the data capacity of the
existing copper wire that runs between the local telephone company switching offices
and most homes and offices. The bandwidth of the wire has conventionally been limited
to approximately 3,000 Hz due to its primary use as a voice telephone system. While
the wire itself can handle higher frequencies, the telephone switching equipment
is designed to cut-off signals above 4,000 Hz to filter noise off the voice line.
DSL enables high-speed data traffic from a service provider network, such as an
ATM network, to be provided on the existing wires with voice traffic.
In order to provide DSL service, a digital subscriber line access multiplexer
(DSLAM) is employed at the local telephone company central office or digital loop
carrier (DLC). The DSLAM includes frequency band filters to separate the voice-frequency
traffic provided by the public-switched telephone network (PSTN) from the high-speed
data traffic service provided by the network service provider. A DSLAM multiplexes
the high-speed data traffic and routes it to subscribers on twisted-pair wires,
referred to as a local loop. Many DSLAMs are designed to work with ATM networks.
Typically, a DSLAM includes an uplink interface, a switch concentration
module (SCM), a backplane interface, and multiple line cards. High-speed data traffic
from an ATM network is received by the uplink interface via multiple data communications
channels. The high-speed data traffic is then transmitted to the SCM where it is
transmitted to the backplane interface. The backplane interface provides the high-speed
data traffic to multiple DSL ports in the line cards for subsequent delivery to subscribers.
One known type of DSL-based service is asymmetrical DSL (ADSL). ADSL is the most
common DSL service. It is an asymmetrical technology, meaning that the downstream
data rate is much higher than the upstream rate. The term upstream refers to data
transfer toward the interior of the communication network. The term downstream
refers to data transfer away from the interior of the communication network. In
the context of a DSLAM and referring to the interface between the ATM layer device
and DSL physical layer devices, the downstream direction corresponds to the transfer
of cells from the ATM layer device to the physical layer devices for transmission
over the DSL. The upstream direction corresponds to the transfer of cells received
via the DSL from the physical layer devices to the ATM layer device. This type
of service works well for providing typical Internet services to residential subscribers.
ADSL operates in a frequency range that is above the frequency range of voice services,
so the two systems can operate over the same subscriber cable.
For example, the ADSL standard of the International Telecommunications Union
entitled "Recommendation G.992.1: Asymmetric Digital Subscriber Line (ADSL) Transceivers,"
which is entirely incorporated herein by reference, proscribes two types of channels
to be carried simultaneously over the subscriber loop. One type of channel is characterized
by a reduced error rate. This type of channel, however, does incur considerable
delay because the forward error correction technique incorporates an interleaver.
The other type of channel does not use the interleaver and thus has lower delay
and a potentially higher error rate. The low-delay channel is considered more suitable
for transporting real-time circuits, such as those carrying voice or real-time
video, because real-time circuits are willing to accept some transmission errors
in order to reduce delays. On the other hand, non-real-time circuits, such as those
carrying data, are comparatively intolerant of errors because any single error
requires retransmission of the entire block. Furthermore, circuits carrying data
are not adversely effected by longer delays. Therefore, the low error rate channel
is well-suited for carrying data circuits.
It may also be desirable to provide separate access means for real-time and non-real-time
data paths in a variety of other situations. For example, if the data transmission
technology employed in the physical layer device requires substantial local buffering
of data, such as for half-duplex transmission, separate access for the real-time
data may be necessary to prevent the presence of lower priority data in the internal
buffer from blocking the immediate transmission of high-priority data. In this
case, the separate access means for the real-time (priority) data provides a way
to effectively bypass already buffered lower priority data.
When using both ADSL channels, the entire bandwidth available for payload data
over the DSL must be statically partitioned between the low-delay channel and the
high-reliability channel. From the point of view of the ATM layer device, these
channels are independent circuits and proper management of traffic over the circuits
requires that the ATM layer device provide a scheduling function connected to each
channel. The only way to satisfy this requirement with "off the shelf" ATM layer
devices and UTOPIA interfaces is to provide a separate UTOPIA port for each of
the two channels. Thus, in the context of ADSL, each PHY layer device requires
two separate UTOPIA bus addresses, one for the low-delay channel and one for the
high-reliability channel.
FIG. 1 illustrates a known system for providing communication between an ATM
layer device and multiple dual-channel PHY layer devices via a local interface,
such as a UTOPIA bus. The ATM layer device supports a predefined number (N) of
virtual channels. Each PHY layer device comprises two channel ports corresponding
to two different types of channels. As shown in FIG. 1, each virtual channel communicates
with one of the channel ports in one of the PHY layer devices via a separate address
corresponding to the local interface. Thus, because each PHY layer device supports
two types of channels, the ATM communication system that supports N virtual channels
on the ATM layer device and N addresses on the local interface is restricted to
(N/2) PHY layer devices.
The UTOPIA bus was originally conceived for use in ATM switching nodes within
the network where the total number of ports connected to a switch is typically
fairly small. Thus, as described above, the total number of PHY layer devices that
can be connected to the standard UTOPIA bus is thirty-one (one invalid address).
However, in systems such as those described above where more than one type of channel
is supported by each PHY layer device, the total number of PHY layer devices that
may be used with the UTOPIA address is substantially reduced. For instance, where
two types of channels are employed, the UTOPIA bus can only support half as many,
for instance, fifteen in the example above, dual-channel PHY layer devices.
The reduction in the number of PHY layer devices is very problematic. For example,
in the DSL environment where many subscribers are served by a single ATM switching
node, such as a DSLAM, it is advantageous to be able to connect a very large number
of PHY layer devices to a single ATM layer device.
One known solution to this problem proposes including multiple ATM layer devices
in the communication system. This approach, however, is also problematic. For instance,
including multiple ATM layer devices significantly increases the complexity, cost,
and power consumption of the communication system. Furthermore, where the communication
system also includes a DSLAM, including multiple ATM layer devices also increases
the complexity, cost, and power consumption of the ATM layer device in the DSLAM
and may require modification to the DSLAM backplane. In addition, the inclusion
of additional ATM layer devices may actually require so much space as to preclude
achieving the desired ratio of PHY layer devices. Furthermore, other solutions
all by necessity use a non-standard technique to expand the address space. This
limits the choices for physical and ATM layer devices, and, in so doing, defeats
the purpose of a standard interface, such as the UTOPIA bus, which is to expand
the range of candidate devices for building ATM systems.
Thus, a heretofore unaddressed need exists in the industry to address the aforementioned
deficiencies and inadequacies.
SUMMARY OF THE INVENTION
The present invention provides systems and methods for providing communication
between an ATM layer device and multiple multi-channel PHY layer devices, which
increase the number of multi-channel PHY layer ports supported by the ATM layer device.
Briefly described, in architecture, an embodiment of a system according to
the present invention comprises an ATM layer device that supports a plurality of
ATM communication channels in which each of the plurality of ATM communications
channels correspond to a first class of service or a second class of service, a
plurality of physical layer devices each having a first channel port associated
with the first class of service and a second channel port associated with the second
class of service, and a local interface having a plurality of addresses which are
in communication with the ATM layer device and the plurality of physical layer
devices for establishing a plurality of channel connections between each of the
plurality of ATM communication channels and the first channel port and the second
channel port in each of the plurality of physical layer devices. In the system,
each of the plurality of channel connections associated with the plurality of second
channel ports is via one of the plurality of addresses and at least two of the
plurality of channel connections associated with the plurality of first channel
ports is via no more than one of the plurality of addresses. The system may also
be configured so that each of the plurality of ATM communication channels associated
with one of the plurality of first channel ports is adapted to carry priority data
traffic, such as, for example, real-time traffic, and each of the plurality of
ATM communication channels associated with one of the plurality of second channel
ports is adapted to carry non-priority data traffic, such as, for example, non-real-time
traffic. The system may also include an ATM switch, such as a DSLAM, that provides
the plurality of communication channels to the ATM layer device and which is adapted
to provide services, such as, for example, DSL services, to a plurality of external
PHY layer device.
Briefly described, in architecture, another embodiment of a system according
to the present invention comprises an ATM layer device that supports a plurality
of ATM communication channels each corresponding to a first class of service or
a second class of service, a plurality of physical layer devices each having a
first channel port associated with the first class of service and a second channel
port associated with the second class of service, a first local interface in communication
with the ATM layer device and each of the plurality of second channel ports for
establishing a first plurality of channel connections via one of a portion of a
plurality of addresses associated with the first local interface, an address expansion
device in communication with the first local interface via the remaining portion
of the plurality of addresses, and a second local interface in communication with
the address expansion device and each of the plurality of first channel ports.
The present invention can also be viewed as providing methods for providing communication
between an ATM layer device and multiple multi-channel PHY layer devices, which
increase the number of multi-channel PHY layer ports supported by the ATM layer device.
Briefly, one such method involves (1) receiving a plurality of ATM communication
channels, a portion of the plurality of ATM communication channels corresponding
to a first service class and the remaining channels corresponding to a second service
class, (2) providing a first plurality of channel connections between each of the
portion of the plurality of ATM communication channels corresponding to the first
service class and one of the plurality of first channel ports, wherein at least
two of the first plurality of channel connections is via no more than one of the
plurality of addresses, and (3) providing a second plurality of channel connections
between the remaining channels corresponding to the second service class, wherein
each of the second plurality of channel connections is via one of the plurality
of addresses. As with the embodiments of the system according to the present invention,
the plurality of ATM communication channels may be received from an ATM switch,
such as a DSLAM, in which case the method further comprises providing services,
such as DSL services, to an external physical layer device via one of the plurality
of physical layer devices.
Another such method involves (1) receiving an ATM cell associated with one
of a plurality of ATM communication channels, each of the plurality of ATM communication
channels corresponding to either a first class of service or a second class of
service, (2) determining a VPI/VCI value associated with the ATM cell, (3) based
on the VPI/VCI value and a predefined set of rules, determine whether the ATM cell
corresponds to the first class of service or the second class of service and determine
which of the plurality of addresses on the local interface to which the VPI/NCI
value is associated, and (4) where the ATM cell corresponds to the first class
of service, providing the ATM cell to all of the first channel ports via a first
unique address on the local interface and where the ATM cell corresponds to the
second class of service, providing the ATM cell to one of the second channel ports
via a second unique address.
A further method involves (1) receiving an ATM cell associated with one of a
plurality
of ATM communication channels, each of the plurality of ATM communication channels
corresponding to either a first class of service or a second class of service,
(2) determining a VPI/VCI value associated with the ATM cell, (3) based on the
VPI/VCI value and a first predefined set of rules, determine whether the ATM cell
corresponds to the first class of service or the second class of service and determine
which of a plurality of addresses on a first local interface to which the VPI/VCI
value is associated, and (4) where the ATM cell corresponds to the first class
of service, providing the ATM cell to an address expansion device via a first unique
address on the local interface and, based on the VPI/VCI value and a second predefined
set of rules, providing the ATM cell to one of the plurality of first channel ports
associated with the VPI/VCI value via one of a plurality of addresses on a second
local interface and where the ATM cell corresponds to the second class of service,
providing the ATM cell to one of the second channel ports via a second unique address
on the first local interface.
The present invention can also be viewed as a computer-readable medium having
logic for providing communication between an ATM layer device and multiple multi-channel
PHY layer devices, which increases the number of multi-channel PHY layer ports
supported by the ATM layer device. The computer-readable medium may include the
steps of the methods of the present invention as an ordered listing of executable
instructions for implementing logical functions related to providing communication
between an ATM layer device and multiple multi-channel PHY layer devices. The list
of executable instructions, which are embodied in the computer-readable medium,
may be used by or in connection with an instruction execution system, apparatus,
or device, such as a computer-based system, processor-containing system, or other
system that can fetch the instructions from the instruction execution system, apparatus,
or device and execute the instructions.
Other systems, methods, features, and advantages of the present invention will
be or become apparent to one with skill in the art upon examination of the following
drawings and detailed description. It is intended that all such additional systems,
methods, features, and advantages included within this description, be within the
scope of the present invention, and be protected by the accompanying claims.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention can be better understood with reference to the following drawings.
The components in the drawings are not necessarily to scale, emphasis instead being
placed upon clearly illustrating the principles of the present invention. In the
drawings, like reference numerals designate corresponding parts throughout the
several views.
FIG. 1 is a block diagram illustrating a prior art system for providing communication
between ATM layer device and multiple multi-channel PHY layer devices.
FIG. 2 is a block diagram illustrating an embodiment of a system for implementing
the present invention.
FIG. 3 is a flow chart illustrating the architecture, functionality, and operation
of an embodiment of the ATM layer device in the system of FIG. 2 according to the
present invention.
FIG. 4 is a flow chart illustrating the architecture, functionality, and operation
of an embodiment of the address expansion device in the system of FIG. 2 according
to the present invention.
FIG. 5 is a block diagram illustrating another embodiment of the address expansion
device in the system of FIG. 2 according to the present invention.
FIG. 6 is a block diagram illustrating another embodiment of a system for implementing
the present invention.
FIG. 7 is a flow chart illustrating the architecture, functionality, and operation
of an embodiment of the ATM layer device in the system of FIG. 6.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Having summarized the invention above, the invention will now be described
in detail with reference to the drawings. While the invention will be described
in connection with these drawings, there is no intent to limit it to the embodiment
or embodiments disclosed. On the contrary, the intent is to cover all alternatives,
modifications and equivalents included within the spirit and scope of the invention
as defined by the appended claims.
FIG. 2 shows a block diagram of a communication system
10 according to
one of a number of embodiments of the systems and methods of the present invention.
System
10 includes an ATM layer device
12, a local interface
14,
an address expansion interface
16, an address expansion device
18,
and physical layer (PHY layer) devices
20. ATM layer device
12 and
PHY layer devices
16 communicate via local interface
14 and address
expansion interface
16. System
10 may be bi-directional in that ATM
data cells may be transferred from ATM layer device
12 to PHY layer devices
20 (downstream) and from PHY layer devices
20 to ATM layer device
12 (upstream) simultaneously.
ATM layer device
12 may be any ATM switching device which is adapted to
communicate with another ATM layer device via a plurality of ATM communication
channels and route the communication channels to appropriate physical layer devices.
ATM layer device
12 may be implemented in hardware, software, firmware,
or a combination thereof. For example, ATM layer device
12 may be implemented
in software or firmware that is stored in a memory and that is executed by a suitable
instruction execution system. ATM layer device
12 may also be implemented
in hardware with any or a combination of the following technologies, which are
all well known in the art: a discrete logic circuit(s) having logic gates for implementing
logic functions upon data signals, an application specific integrated circuit (ASIC)
having appropriate combinational logic gates, a programmable gate array(s) (PGA),
a field programmable gate array (FPGA), etc.
PHY layer device
20 may be a modem, such as, for example, a DSL modem,
or any other PHY layer device. Each PHY layer device
20 comprises a first
channel port
22 and a second channel port
24. However, one of ordinary
skill in the art should understand that, PHY layer devices
20 may be configured
with additional channel ports. Channel ports
22 and
24 may be adapted
to communicate with, and provide data services to, any external PHY layer device.
Specifically, first channel port
22 is adapted to communicate with an external
PHY layer device via a first communication channel and second channel port
24
is adapted to communicate with an external PHY layer device via a second communication
channel. As described in more detail below, first communication channels
22
are restrained to a first class of service and second communication channels
24
are restrained to a second class of service. First and second communication channels
22 and
24 are not necessarily separate transmission paths, but may
be distinguished only as to the treatment, for example, the priority in internal
buffering, that is afforded to cells arriving via a particular interface to PHY
layer devices
20.
Local interface
14 communicates with ATM layer device
12, address
expansion device
18, and each second channel port
24 in each PHY
layer device
20 via a plurality of data addresses. The plurality of addresses
on local interface
14 is allocated as follows. Each of the second channel
ports
22 on each of the PHY layer devices
20 has an address on local
interface
18, and ATM layer device
12 is in communication with each
of these second channel ports
22 through its respective address. Address
expansion device
18 has an address on local interface
18, and ATM
layer device
12 is in communication with address expansion device
18
through this address. Thus, address expansion device
18 appears as another
PHY layer device to ATM layer device
12.
Address expansion interface
16 communicates with address expansion
device
18 and each first channel port
24 in each PHY layer device
20 via a plurality of data addresses. The plurality of addresses on address
expansion interface
16 is allocated as follows. Each of the first channel
ports
22 on each of the PHY layer devices
20 has an address on address
expansion interface
18 and address expansion interface
16 is in communication
with each of these first channel ports
24 through its respective address.
Local interface
14 and address expansion interface
16 may be
any data path interface capable of providing communication between an ATM layer
device and a plurality of PHY layer devices. In the preferred embodiment of system
10 local interface
14 and address expansion interface
16 conform
to the UTOPIA level
2 specification described above.
Address expansion device
18 communicates with local interface
14
and address expansion interface
16. As will be described in more detail
below, address expansion device
18 is adapted to provide the ATM cells associated
with the ATM communication channels received from ATM layer device
12 to
the appropriate first channel port
22 based on predefined logic by which
address expansion device
18 is programmed. Address expansion device
18
may also be implemented in hardware, software, firmware, or a combination thereof.
For example, address expansion device
18 may be implemented in software
or firmware that is stored in a memory and that is executed by a suitable instruction
execution system. Address expansion device
18 may also be implemented in
hardware with any or a combination of the following technologies, which are all
well known in the art: a discrete logic circuit(s) having logic gates for implementing
logic functions upon data signals, an application specific integrated circuit (ASIC)
having appropriate combinational logic gates, a programmable gate array(s) (PGA),
a field programmable gate array (FPGA), etc.
Referring again to FIG. 2, the operation of system
10 in the downstream
direction will now be described. ATM layer device
12 receives a predefined
number of ATM communication channels from an external ATM layer device, which may
be an ATM switch, a DSLAM, or any other type of ATM layer device. System
10
is configured so that each of the ATM communication channels corresponds to either
a first class of service or a second class of service. As will be described in
more detail below, ATM communication channels corresponding to the first class
of service is routed to one of the plurality of first channel ports
22 on
each PHY layer device
20. Each of the ATM communication channels corresponding
to the second class of service is routed to one of the plurality of second channel
ports
24 on each PHY layer device
20. In accordance with the systems
and methods of the present invention, where local interface
14 supports
N addresses, system
10 enables an increased number of multi-channel PHY
layer devices
20 to communicate with ATM layer device
12. For example,
where multi-channel PHY layer devices
20 support two channels, system
10
enables (N-1) PHY layer devices
20 to communicate with ATM layer device
12 via local interface
14 via N addresses.
The two different classes of service define the service attributes and/or traffic
attributes associated with the particular type of ATM communication channel. The
two different classes of service may be chosen based on a variety of factors related
to service categories and/or traffic attributes associated with communication system
10. For instance, the selection of classes of service may be based on any
of the following standard ATM classes of service: constant bit rate (CBR), variable
bite rate-non-real-time (VBR-NRT), variable bit rate-real-time (VBR-RT), available
bit rate (ABR), and unspecified bit rate (UBR). The selection of classes of service
may also be based on, for example, any of the following standard traffic parameters,
quality of service parameters, and feedback characteristics: peak cell rate (PCR),
sustained cell rate (SCR), maximum burst size (MBS), minimum cell rate (MCR), cell
delay variation (CDV), maximum cell transmission delay (maxCTD), and cell loss ratio.
In certain embodiments of system
10, the first class of service corresponds
to priority traffic, such as real-time traffic (conventionally CBR and VBR-RT)
and the second class of service corresponds to non-priority traffic, such as non-real-time
traffic. Thus, each ATM communication channel corresponding to the first class
of service may be referred to as a priority channel and each ATM communication
channel corresponding to the second class of service may be referred to as a non-priority channel.
Typically, a PHY layer device
20 controls the transfer of cells
from an ATM layer device
12 to the PHY layer device
20 so that the
number of cells transferred matches the transmission capacity of the PHY layer
device
20. The availability of the PHY layer device
20 for the transfer
of a cell from the ATM layer device
12 may be indicated by a binary-state
signal, such as, for example, the "transmit cell available" or "TxClav" signal
prescribed for the UTOPIA bus. This regulation of the flow of cells from the ATM
layer device
12 to the PHY layer device
20 is sometimes termed "push-back,"
referring to the ability of the PHY layer device
20 to push back against
the flow of cells from the ATM layer device
12 in order to throttle this
flow to the required rate.
When the transmit data for multiple PHY layer devices
20 is transferred
via a single UTOPIA interface, this "push-back" signal becomes meaningless because
there is not a logical combination of the "transmit cell available" signals of
the multiple PHY layer devices
20 that is valid. For example, if the "transmit
cell available" signal presented to the ATM layer device
12 is formed as
the logical "OR" of the same signals presented by the individual PHY layer devices
20, a cell could be transferred any time at least one of the PHY layer devices
20 was able to accept another cell. However, the ATM layer device
12
has no way of knowing specifically which PHY layer devices
20 are in this
state. Therefore, there is no way to guarantee that the next cell transferred will
go to a PHY layer device
20 that is actually in this state, as opposed to
one that cannot currently accept a transmit cell. This results in buffer overflow
in the PHY layer device
20 causing loss of a transmit cell. If, on the other
hand, the "transmit cell available" signal presented to the ATM layer device
12
is formed as the logical "AND" of the same signals presented by the individual
PHY layer devices
20, a cell cannot be transferred from the ATM layer device
12 unless all PHY layer devices
20 are able to accept another cell.
As a result, if at least one PHY layer device
20 is operating at a transmit
speed that is less than that of the other devices that receive cells via the same
port, this device may prevent transfer of cells to the higher speed PHY layer devices
20, thereby preventing these devices from transmitting data at their currently
supported rates.
As a result of the above limitation, it is impractical to use the "transmit cell
available" signal for control of the flow of cells from the ATM layer device
12
to the multiple PHY layer devices
20 via a single port. It must be possible
to transfer priority cells, such as real-time cells, from the ATM layer device
12 to any of the PHY layer devices
20 whenever such a cell is available.
This seemingly impractical requirement can be made practical by taking advantage
of the fact that the maximum rate of an ATM channel can be both specified via the
"traffic contract" for the service provided by the virtual circuit and enforced
via the "usage parameter control," better known as "policing" functions that are
also specified for ATM data transmission. This maximum data transmission rate is
referred to as the "peak cell rate" or PCR. If the sum of the PCRs for the virtual
circuits carried on a given PHY layer device
20 is no greater than the total
transmit data rate provided by the PHY layer device
20, there will never
be a need for the PHY layer device
20 to "push-back" against the flow of
cells for these circuits. In other words, there is no need for the "transmit cell
available" signal in this case. It is acceptable for the single interface to the
ATM layer device
12 to always present its "transmit cell available" in the
asserted condition.
Therefore, traffic carried over priority channels must be limited to a
certain bandwidth. For example, because CBR, VBR-RT and VBR-NRT service categories
always specify PCR, channels corresponding to these service categories may be carried
on the priority channel. Channels corresponding to ABR and UBR service categories
may also be carried on priority channels provided
