Note: Descriptions are shown in the official language in which they were submitted.
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SYSTEM AND METHOD FOR IDENTIFYING A PORT
Cross-Reference To Related Annlication
[0001] The present application claims priority to U.S. Provisional Application
Serial No. 60/298,888, filed June 19, 2001, entitled "Addition of Port ID Into
DOCSIS
Standard," the entirety of which is incorporated herein by reference.
Background
[0002] The present invention is generally related to identifying sources and
intended recipients in a communications protocol, and more specifically to
identifying
ports in a cable modem protocol.
[0003] A typical cable modem specification, such as the data over cable
service
interface specification (DOCSIS), restricts communications between a base
station and
remote stations to using Ethernet addressees as the filtering scheme at the
remote stations.
A further limitation is typically presented by the requirement that an
Ethernet address
must be assigned to each POTS (plain old telephone service) interface. An
improved
scheme is desired.
[0004] In one embodiment, a method for identifying an intended recipient of
information conveyed by a signal in a point to multi-point system includes
determining
the intended recipient in accordance with a port identification portion of the
signal. The
signal comprises at least one frame. Each frame comprises a header portion
configured
to identify contents of a respective frame, a protocol data unit (PDU) portion
configured
to contain data, and the port identification portion having a port identifier
configured to
identify an intended recipient of information contained in the respective
frame.
[0005] In another embodiment, a base station in a point to mufti-point system
includes a memory portion for storing at least one port identifier indicative
of an intended
recipient in the point to mufti-point system. The system includes a
transmitter portion
configured to transmit at least one signal comprising at least one frame. Each
frame
includes a header portion configured to identify contents of a respective
frame, a protocol
data unit (PDU) portion configured to contain data, and a port identification
portion
having a respective port identifier in said respective frame. The system also
includes a
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formatter portion configured to format the at least one signal to contain the
port
identification portion within a respective frame.
[0006] In yet another embodiment, a remote station in a point to multi-point
system includes a receiver portion configured to receive at least one signal
comprising at
least one frame. Each frame includes a header portion configured to identify
contents of
a respective frame, a protocol data unit (PDL>7 portion configured to contain
data, and a
port identification portion having a respective port identifier in the
respective frame. The
port identifier being indicative of an intended recipient in the point to
mufti-point system.
The system also includes a decoder portion configured to decode the port
identifier to
determine an intended recipient.
Brief Description of the Drawings
[0007] In the drawings:
[0008] Figure 1 is a diagram illustrating the format of one embodiment of a
signal
having a header portion and a data portion, wherein the data portion includes
a port
identification portion appended to one, in accordance with an embodiment of
the present
invention;
[0009] Figure 2 is a diagram illustrating the format of another embodiment of
a
signal having a header portion and a data portion, wherein the header portion
includes a
port identification portion appended to one end of an extended header portion,
in
accordance with an embodiment of the present invention;
[0010] Figure 3 is a block diagram of a point to mufti-point system utilizing
a port
identifier in accordance with an embodiment of the present invention;
[0011] Figure 4 is a functional block diagram of a base station in accordance
with
an embodiment of the present invention;
[0012] Figure 5 is a is a functional block diagram of remote station in
accordance
with an embodiment of the present invention; and
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[0013] Figure 6 is a flow diagram of an exemplary process for identifying an
intended recipient in a point to multi-point system utilizing a port
identification portion in
accordance with an embodiment of the present invention.
Detailed Description
[0014] A system and method for identifying an intended recipient in a point to
mufti-point system utilizing a port identifier, as described herein include
formatting
signal frames in the communications protocol used to convey information in the
system.
The system and method are particularly applicable to formatting signal frames
of signals
used to convey information between a cable modem (CM) and a cable modem
termination system (CMTS) conforming to the data over cable service interface
specification (DOCSIS). In one embodiment, a port identifier is appended to
the data
portion of the frame, e.g., the protocol data unit (PDU) portion of a frame.
In another
embodiment, the port identifier is appended to the header portion of the
frame. The
addition of this port identifier increases the number of potential intended
recipients that
may be addressed. For example, a two-byte, i.e., 16 bit, port identifier
increases
addressability by 216 = 65,536.
[0015] Figure 1 and Figure 2 illustrate two embodiments of a signal frame 12
having a port identification portion 28. Figure 1 is a diagram illustrating
the format of a
signal containing a port identification portion 28 for identifying intended
recipients in a
point to mufti-point system. The frame 12 is a media access control (MAC)
frame. A
MAC frame refers to a portion of a signal formatted to have a header portion
14 and an
optional variable length data protocol data unit (PDU) 30. The MAC frame 12
has a
header portion 14 and a data portion 16, wherein the data portion 16 includes
a port
identification portion 28 appended to one end. The header portion 14 includes
frame
control (FC) field 18, MAC parameter (MAC_PARM) field 20, frame length (LEN)
field
22, optional extended header (EHDR) field 24, and header check sequence (HCS)
field
26. The FC field 18 identifies the contents of the frame 12. In one
embodiment, the FC
field 18 is located at the first byte position of frame 12, as shown in Figure
1. The
MAC PARM field 20 and the LEN field 22 indicate the length of the frame 12.
The
EHDR field 24 is optional. The length of the EHDR field 24 is variable between
0 and
240 bytes, inclusively. The HCS field 26 is used to ensure the integrity of
the header
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portion 14. In one embodiment, the data portion 16 includes a port
identification (ID)
portion 28 and data field 30 formatted in accordance with the packet protocol
data unit
(PDLn format. In another embodiment, as shown in Figure 2, the port ID portion
28 is
positioned within the EHDR field 24. As shown in Figure 1, the port ID portion
28 may
be appended to the data portion 16, or as shown in Figure 2, the port ID
portion 28 may
be appended to the EHDR field 24.
[0016] The port identification portion 28 contains a port identifier having a
value,
which is decodable and is associated with an intended recipient (destination)
of
information contained in the frame 12. The port ID portion 28 may be of any
length. In
one embodiment, the port ID portion 28 is 2 bytes. For example, if the port ID
portion 28
is 2 bytes (16 bits) in length, the value of the port identifier for this port
ID portion 28
may by be selected from 216 = 65,536 unique values. Each of these values may
be
associated with an intended recipient.
[0017] The format for frame 12, with the exception of the port ID portion 28,
is in
compliance with the data over cable service interface specification, referred
to as
DOCSIS. DOCSIS is a specification well known in the art. Further detail
related to
DOCSIS may be obtained from the following documents: Data-Over-Cable-Service
Interface Specifications, Radio Frequency Interface Specification, SP-RFIv2.0-
I01-
011231; Data-Over-Cable-Service Interface Specifications, Cable Modem
Termination
System - Network Side Interface Specification, SP-CMTS-NSI-I01-010829; Data-
Over-
Cable-Service Interface Specifications, Cable Modem to Customer Premise
Equipment
Interface Specification, SP-CMCI-I06-010829; Data-Over-Cable-Service Interface
Specifications, Operations Support System Interface Specification, SP-OSSIv2.0-
I01-
012131; Data-Over-Cable-Service Interface Specifications, Cable Modem
Telephony
Return Interface Specification, SP-CMTRI-I01-970804; Data-Over-Cable-Service
Interface Specifications, Baseline Privacy Plus Interface Specification, SP-
BPI-I07-
010829; Data-Over-Cable-Service Interface Specifications, Radio Frequency
Interface
Specification, SP-RFI-CO1-011119; Data-Over-Cable-Service Interface
Specifications,
Baseline Privacy Interface Specification, SP-BPI-CO1-011119; and Data-Over-
Cable-
Service Interface Specifications, Radio Frequency Interface Specification v
1.1, SP-
RFIvl.l-I07-010829.
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[0018] Figure 3 is a block diagram of a point to multi-point system 300
utilizing a
port identifier as described herein. System 300 includes at least one base
station 34 (also
referred to as a base station), and at least one remote station 36 (also
referred to as a
remote station). Signals conveyed from the base station 34 to remote station
36 are
referred to as downstream signals and signals conveyed from the remote
stations 36 to the
base station are referred to as upstream signals.
[0019] Downstream signals are broadcast to all remote stations 36
concurrently.
Downstream signals are formatted to include a security association identifier
(SAID) for
identifying a remote station as an intended remote station. The SAID is
decoded, also
referred to as filtered, to determine which remote station is the intended
recipient. Thus,
only the ~ remote station with the proper SAID will receive the downstream
signal.
Hardware limitations restrict the maximum number of concurrent SAIDs per
remote
station is limited to 16. Adding a port ID portion 28 to the DOCSIS signal
format
increases the number of potential intended recipients per remote station 36.
[0020] Upstream signals are time domain multiplexed. Thus the base station 34
"knows" which remote station 36 is transmitting by the time period in which
the
communication occurs. The port ID portion 28 of the upstream signal may be
decoded to
further determine the source of the signal associated with a remote station
36. For
example, remote station 36 may have a several devices (lines) attached, such
as Ethernet
addressable lines, El lines, T1 lines, plain old telephone service (POTS)
lines, constant
bit rate clear channels, or a combination thereof. Each of these lines may be
assigned an
associated port identifier. Upon receiving a signal from a remote station,
during its
allotted time slot, the signal frame may be further decoded to determine the
source, e.g.,
line/device, of the signal. Referring again to Figure 3, signal 38 represents
a signal
transmitted by base station 34 to a remote station 36, received by base
station 34 from a
remote station 36, or a combination thereof. The signals 40, 42, and 44 are
signals
transmitted by remote stations 36, received by remote stations 36, or a
combination
thereof. Each of the signals 38, 40, 42, and 44 may comprise an upstream
component and
a downstream component.
[0021] Figure 4 is a functional block diagram of a base station 34. The base
station 34 includes a formatter portion 50, a transmitterlreceiver portion 52,
a memory
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portion 54, and a decoder portion 56. In one embodiment, the transmitter
portion of the
transmitterlreceiver portion 52 of base station 34 is configured to transmit
signal 38,
wherein signal 38 is formatted into at least one frame. Each frame includes a
header
portion 14, a protocol data unit (PDU) portion 30, and a port identification
portion 28
having a port identifier. The port identifier represents the value of the
contents of the
port ID portion 28 indicating an intended recipient, or intended destination,
associated
with a remote station 36. The formatter portion 50 is configured to format the
signal 38
into frames containing the port identification portion 28. As previously
described (See
Figure 1), the port id portion 28 may be appended to the EHDR field 24 or the
header
portion 16 of each frame 12. The memory portion 54 is configured to store the
port
identifiers, which are indicative of respective intended recipients. The
decoder portion 56
is configured to decode, e.g., demultiplex, the time multiplexed signal to
determine the
source remote station 36. The decoder portion 56 is also configured to decode
the port
identifiers of the port ll~ portions 28 of each frame 12 to determine the
respective sources
of the respective frames 12.
[0022] Figure 5 is a functional block diagram of remote station 36. The remote
station 36 includes a transmitter/receiver portion 60 and a decoder portion
62. In one
embodiment, the receiver portion of the transmitter/receiver portion 60 of
remote station
34 is configured to receive at least one of signals 40, 42, and 44, wherein
each of signals
40, 42, and 44 are formatted into at least one frame. Each frame includes a
header
portion 14, a protocol data unit (PDU) portion 30, and a port identification
portion 28
having a port identifier. The port identifier represents the value of the
contents of the
port ~ portion 28 indicating an intended source, associated with a remote
station 36.
The decoder portion 62 is configured to decode the SAID contained in a signal
to
determine the intended remote station 36. The decoder portion 62 is also
configured to
decode the port identifiers of the port ID portions 28 of each frame 12 to
determine the
respective intended recipients of the respective frames 12.
[0023] Figure 6 is a flow diagram of an exemplary process for identifying an
intended recipient and/or source in a point to mufti-point system utilizing a
port ID
portion 28. Potential intended recipients/sources are assigned port
identifiers at step 66.
This may be accomplished by the base station 34, by a remote station 36, by a
separate
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processor, or by a combination thereof. Further, this may be accomplished at
the time the
point to multi-point system is started, or at any appropriate time prior to
communication
between the base station 34 and the remote station 36. The port identifiers
assigned to
each potential intended recipient/source are stored at step 68. The port
identifiers may be
stored in any appropriate memory, such as memory portion 54 of base station
34. The
stored port identifiers are accessible for decoding signals having port ID
portions 28.
Signals are formatted to include the port ID portion 28, having a respective
port identifier
at step 70. This may be accomplished by any appropriate processor, such as
formatter 50
of base station 34. The respective frames of the signals may be formatted to
append the
port ID portion 28 to an end of the data portion 16 or to end of the EHDR
portion 24.
The port ID portion 28 may be encoded. This encoding may be accomplished by
any
appropriate encoding technique, which renders the port ID portion 28 capable
of being
decoded upon receipt of the respective signal. In one embodiment, the port ~
portion is
encoded in accordance with a predetermined extended header type field (EH
TYPE).
The EH TYPE is a field contained in the EHI~R field. A more detailed
description of the
EH TYPE field may be found in the DOCSIS Radio Frequency Interface
Specification,
SP-RFIv2.0-I01-011231, December 31, 2001.
[0024] The signals formatted to contain the port ID portion 28 (such as
signals 38,
40, 42, 44, and/or 44) are conveyed at step 72. Conveying the signal may
involve
conveying signals from the base station 34 to remote stations) 36, e.g.,
downstream, or
from remote stations) 36 to the base station 34, e.g., upstream. These signals
may be
conveyed by any appropriate means, such as transmitter/receiver portion 52
and/or
transmitter/receiver portion 60 for example. If the signal is a downstream
signal (step
74), the SAID of the conveyed downstream signal is decoded to determine the
intended
recipient remote station 36 at step 76. The port ID portion 28 of the signal
frames 12 are
decoded at step 78. This decoding determines the intended recipient of
information
contained in the respective frame of the respective signal. If the conveyed
signal is an
upstream signal (step 74), the time multiplexed signal is decoded, e.g.
demultiplexed, at
step 80 to determine the source remote station 36 of the respective portion of
the signal.
The port ID portion 28 of the signal frames 12 are decoded at step 82, to
determine the
source of the respective portion of the signal.
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[0001] The method and system for identifying a device in a point to mufti-
point
system as described herein may be embodied in the form of computer-implemented
processes and apparatus for practicing those processes. The method and system
for
identifying a device in a point to mufti-point system may also be embodied in
the form of
computer program code embodied in tangible media, such as floppy diskettes,
read only
memories (ROMs), CD-ROMs, hard drives, high density disk, or any other
computer-
readable storage medium, wherein, when the computer program code is loaded
into and
executed by a computer, the computer becomes an apparatus for practicing the
invention.
The method and system for identifying a device in a point to mufti-point
system may also
be embodied in the form of computer program code, for example, whether stored
in a
storage medium, loaded into andlor executed by a computer, or transmitted over
some
transmission medium, such as over the electrical wiring or cabling, through
fiber optics,
or via electromagnetic radiation, wherein, when the computer program code is
loaded
into and executed by a computer, the computer becomes an apparatus for
practicing the
invention. When implemented on a general-purpose processor, the computer
program
code segments configure the processor to create specific logic circuits.
[0002] Although illustrated and described with reference to certain specific
embodiments, the method and system for identifying a device in a point to
mufti-point
system as described herein is nevertheless not intended to be limited to the
details shown.
Rather, various modifications may be made in the details within the scope and
range of
equivalents of the claims and without departing from the spirit of the
invention.
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