Multiplex communications – Communication techniques for information carried in plural... – Byte assembly and formatting
Reexamination Certificate
1998-09-02
2004-07-20
Hsu, Alpus H. (Department: 2665)
Multiplex communications
Communication techniques for information carried in plural...
Byte assembly and formatting
C370S375000, C370S379000
Reexamination Certificate
active
06765928
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to communication systems, particularly to the control of communication systems using SONET/SDH standards. More particularly, the invention relates to communication between multiple communication services and a SONET/SDH communication system or network.
BACKGROUND OF THE INVENTION
The Synchronous Optical Network (“SONET”) standard was originally developed as a multiplexing and trunking mechanism to carry a large number of voice channels over a single optical fiber. SONET and SDH are a set of coordinated ITU, ANSI and Bellcore standards that define a hierarchical set of transmission rates and transmission formats. Bellcore originally proposed the standard in the late 1980's. Since then, the SONET standard has gained worldwide acceptance. Europe has adopted the SONET standard with a few minor modifications and is known as Synchronous Digital Hierarchy (“SDH”). Because of the standardization, interoperability between different vendor equipment has been achieved for the first time in WAN applications. In addition, because SONET/SDH transport is efficient, economical, robust and a reliable means to multiplex and transport a large number of voice channels over a single optical fiber, SONET/SDH deployment has progressed quickly and widely.
Although the original motivation for SONET/SDH specification was for transporting voice, the high bandwidth capability of SONET/SDH networks makes it attractive to transport multimedia traffic such as voice, video, and data efficiently on a single network. Recognizing this, SONET/SDH equipment vendors are now offering multimedia capability in their equipment. The solutions available today for incorporating multimedia services are inflexible and expensive because they require several single service devices to support multimedia services. Due to the enormous complexity of implementation, a single multiple service device has been unavailable that could support several protocols and formats of differing service types.
FIG. 1A
illustrates the array of data bytes for a prior art SONET STS-1 frame
100
. The STS-1 frame
100
consist of eight hundred and ten bytes and is always visually illustrated as array of 9 rows of 90 columns so that the Transport Overhead bytes (TOH)
101
line up properly at the beginning of the frame. As indicated in
FIG. 1A
, each byte in the STS-1 frame
100
can be associated with a column and row number of the frame. SONET overhead information is divided into section (SOH), line (LOH) and path (POH) overhead and is provided to manage the network and the transport of payload data
102
. The section and line overhead make up the transport overhead (TOH)
101
of the STS-1 frame
100
and consist of 27 bytes in every STS-1 frame. The SONET payload data
102
is carried in a synchronous payload envelope (SPE), which makes up 9 rows by 87 columns of the STS-1 frame structure
100
or
783
bytes. Path overhead (POH) is contained within the SPE. The SPE can begin in any byte position within the STS-1 frame other than the first three TOH columns. Because there may be jitter and phase differences, the SPE does not need to be perfectly aligned within one SONET frame starting at the first row and fourth column in the STS-1 frame. The SPE may start at a different byte position and carry over into the next sequence of frames. The STS-1 frame is transmitted one row at a time, from top to bottom and from left to right within each row. Therefore, byte (
1
,
1
) in row
1
, column
1
is sent first while byte (
9
,
90
) in row
9
, column
90
of a given frame is sent last. Other higher level SONET frames structures or hierarchies can be derived by knowing the frame structure for the STS-1 frame
100
. For example the higher level SONET frame structure STS-3 has three times as many columns as the STS-1 and expands the SONET overhead information by three times. The overall frame structure of STS-3 is derived by simply interleaving a single byte at a time from each of the three equivalent STS-1s that make up an STS-3. The appearance is that every third column belongs to a given one of the equivalent STS-1 frames. The higher level SONET frame structure STS-48 is made up of 48 equivalent STS-1 frames such that every 48th column belongs to a given one of the STS-1 frames.
Referring to
FIG. 1B
, the generic higher level SONET frame structure STS-N
105
is made up of N equivalent STS-1 frame structures
100
a
-
100
n
. The STS-N frame structure
105
has N times as many columns as the STS-1
100
and expands the SONET overhead information by N times as well as expanding the payload by N times. Every column represents a column from a given one of the N equivalent STS-1 frames
100
a
-
100
n
that is interleaved into a column of a given one the STS-N frame
105
. For example, the first column of the first equivalent STS-1 frame
100
a
is interleaved into the first column of the STS-N frame
105
. The first column of the second equivalent STS-1 frame
100
b
is interleaved into the second column of the STS-N frame
105
. The first column of the third equivalent STS-1 frame
100
c
is interleaved into the third column of the STS-N frame
105
. The first column of the Nth equivalent STS-1 frame
100
n
is interleaved into the Nth column of the STS-N frame
105
. Similarly, the last column of the Nth equivalent STS-1 frame
100
n
is interleaved into the last column of the STS-N frame
105
. As a result, the transport overhead (TOH)
106
of the STS-N
105
frame structure has N times more bytes than the STS-1 frame
100
and the SONET payload data
107
which carries the SPE
107
has N times more bytes than the SPE
102
of the STS-1 frame
100
. Note that the generic STS-N frame structure
105
reduces to standard frame structures when N is defined. For example, the STS-N frame structure
105
reduces to an STS-1 frame when N is 1. Similarly, the STS-N frame structure
105
reduces to an STS-48 frame structure when N is 48. As indicated in
FIG. 1B
, each byte in the STS-N frame
105
can be associated with a row number, column number, and a subcolumn number. The subcolumn number indicates the association of the equivalent STS-1 frames within the higher level STS-N frame structures. For example byte (
1
,
1
,
1
) of STS-N frame
105
having a row number
1
, a column number
1
, and a subcolumn number
1
is associated with byte (
1
,
1
) of the first equivalent STS-1 frame
100
a
. Byte (
9
,
1
,
3
) of STS-N Frame
105
having a row number
9
, a column number
1
, and a subcolumn number
3
is associated with byte (
9
,
1
) of the third equivalent STS-1 frame
100
c
. Byte (
9
,
3
,N) of STS-N frame
105
having a row number
9
, a column number
3
, and a subcolumn number N is associated with byte (
9
,
3
) of the Nth equivalent STS-1 frame
100
n
. Byte (
9
,
90
,N) of STS-N frame
105
having a row number
9
, a column number
90
, and a subcolumn number N is associated with byte (
9
,
90
) of the Nth equivalent STS-1 frame
100
n.
Unchannelized or nonchannelized carriers are available in the SONET frame structure and are known as concatenated SONET frames. Concatenated SONET frames are referred to as STS-Nc which has N concatenated SONET payload frames. N is presently defined by the SONET specifications for concatenated SONET payloads to be greater than 2.
The SONET payload for an STS-1 can be broken into smaller portions or payloads. The SPE of each STS-1 can be broken into seven virtual tributary groups (VTGs) each consisting of one hundred and eight bytes which occupies 12 columns of an SPE. Within each VTG there may be subrate virtual tributary (VT) types.
Currently defined subrate VT types include VT1.5, VT2, VT3, and VT6. VT1.5 is twenty-seven bytes or three nine byte columns and a single VTG can carry four VT1.5s. VT2 is thirty-six bytes or four nine byte columns and a single VTG can carry three VT2s. VT3 is fifty-four bytes or six nine byte columns and a single VTG can carry two VT3s. VT6 is one hundred eight bytes or twelve nine byte columns and a single VTG can carry o
Joshi Chandra Shekhar
Kane Rajiv
Malladi Srinivasa R.
Nayyarhabibi Amir
Sethuram Jay
Campbell Stephenson Ascolese LLP
Cisco Technology Inc.
Hsu Alpus H.
Nguyen Toan D.
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