Sonet system having multiple slots providing multiple...

Details Sonet system having multiple slots providing multiple... Sonet system having multiple slots providing multiple...

2000-09-14

2004-10-12

Pham, Chi (Department: 2667)

Multiplex communications

Pathfinding or routing

Switching a message which includes an address header

C370S466000, C370S477000, C370S535000, C370S537000

Reexamination Certificate

active

06804248

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to digital data processing. More particularly, the invention relates to methods and apparatuses for conversion of digital data between a parallel data signal and one or more serial data signals.
BACKGROUND OF THE INVENTION
With the maturation of the computer and surrounding technologies, vast amounts of complex, mixed traffic types are transmitted through synchronous optical networks (SONETs). The SONET standard is described in the American National Standards Institute (ANSI) standards T1.105 and T1.106 and in the Bellcore Technical Recommendations TR-TSY-000253. However, current SONET infrastructure has not kept pace with this rapid information technology shift and, as a result, network throughput is slowing down significantly due to increased traffic load.
Carriers that operate SONET-based metropolitan area networks (MANs) are especially impacted by this growing congestion. These carriers operate SONET rings to provide carrier services. SONET, and its international variant, Synchronous Digital Hierarchy (SDH), are deployed throughout North America, Latin America, Europe, the Pacific Rim and Asia. SONET and SDH are the de facto standard for physical layer optical transport. SONET provides massive transport scalability and the ability to support numerous network elements (NEs).
Traditional SONET signals were designed based on strictly defined and “chunky” telco line rates. Regardless of composition and requirements under such strictly defined line rates, traffic must fit into a specific bandwidth slot whether or not the traffic uses the full bandwidth allocation. Besides these limitations, current SONET equipment does not support non-voice digital data such as Ethernet traffic, local area network (LAN) traffic, asynchronous transfer mode (ATM) traffic, frame relay (FR) traffic, Internet Protocol (IP) traffic. Further, traditional SONET signals are inefficient when carrying non-voice data signals.
The basic building block of SONET networks is the SONET ring connection.
FIG. 1
a
illustrates a basic SONET ring connection. SONET switch
100
and SONET switch
150
receive optical signals from various devices (not shown in FIG.
1
). SONET switch
100
and SONET switch
150
can be coupled to other SONET switches, or other devices that communicate data using optical signals.
SONET switch
100
and SONET switch
150
communicate using two sets of uni-directional signaling pairs. In general, half of the traffic between switches travels over one of the signaling pairs and the other half of the traffic travels over the other signaling pair. SONET switches communicate according to a predetermined protocol, and at a predetermined bit rate.
Telecommunications (Telco) SONET systems have been designed and implemented using digital signaling (DS) technology, which is well known in the art. In the tables that follow, bit rates are set forth as bits per second (bps) and multiples thereof. The following Telco hierarchy provides a foundation for the SONET hierarchy set forth below.
TABLE 1
Telco Hierarchy
Signal
Bit Rate
Channels
DS0
64
kbps
1
DS0
DS1
1.544
Mbps
24
DS0s
DS2
6.312
Mbps
96
DS0s
DS3
44.736
Mbps
28
DS1s
SONET signals are Synchronous Transport Signals (STS) and Optical Carrier (OC) signals. Common SONET protocols include the following:
TABLE 2
SONET Hierarchy
Signal
Bit Rate
Capacity
STS-1, OC-1
 51.840 Mbps
28 DS1s or 1 DS3
STS-3, OC-3
 155.520 Mbps
84 DS1s or 3 DS3s
STS-12, OC-12
 622.080 Mbps
336 DS1s or 12 DS3s
STS-48, OC-48
2488.320 Mbps
1344 DS1s or 48 DS3s
STS-192, OC-192
9953.280 Mbps
5379 DS1s or 192 DS3s
The following table describes SONET inefficiencies when carrying Ethernet signals; however, other protocols can be similarly inefficient.
TABLE 3
Ethernet/SONET inefficiencies
Wasted
Ethernet
Signal
Bit Rate
Bandwidth
10 BaseT (10 Mbps)
STS-1, OC-1
 51.840 Mbps
80.7%
100 BaseT (100 Mbps)
STS-3, OC-3
 155.520 Mbps
35.7%
Gig. E (1000 Mbps)
STS-48, OC-48
2488.320 Mbps
59.8%
In SONET networks, network elements typically convert electrical signals are converted to optical signals for transport over SONET connections. The data, however, is generated and manipulated as electrical signals. For example, telephones convert audio signals to analog electrical signals, which are converted to digital electrical signals and finally to optical signals. Computer systems generate analog and/or digital signals, which are converted to optical signals. The optical signals are transported over SONET connections.
FIG. 1
b
illustrates an example of conversion of electrical signals to optical SONET data. User data
110
can be any type of digital data, for example, a file generated by a computer system, LAN traffic, or a telephone call that has been converted to digital signals. User data
110
coming into the SONET system is typically data based on the Telco hierarchy. Thus, prior to the transport of OC signals, the first stage of the SONET transport mechanism usually creates, multiplexes, and manages SONET signals in their electrical format (e.g., as STS signals).
User data
110
is sent to SONET multiplexing device
140
that adds a path overhead header (POH) to user data
110
to generate a synchronous payload envelope (SPE)
115
, subsequently, SONET multiplexing device
140
adds a transport overhead header (TOH) and STS frame
120
is formed. STS frame
120
is sent to electrical-optical conversion unit
125
, which creates OC-
1
signal
130
.
STS frame
120
can include various frame sizes and may also be transported at various speeds. A standard building block for the STS frame is the STS-
1
protocol, which specifies 810 bytes transmitted every 125 microseconds (&mgr;sec), resulting in a line rate of 51.840 Mbps. Accordingly, in
FIG. 1
b
, an electrical 51.840 Mbps line signal generated by STS-
1
frame
120
would result in an optical OC-
1
signal on the output of electrical-optical conversion unit
125
.
The output of electrical-optical conversion unit
125
can be provided to a second stage of a SONET transport mechanism (not shown in
FIG. 1
b
) that is used to groom multiple signals and add/drop OC-
1
signals to create, for example, OC-
3
or OC-
12
signals. Using this multiple staging format, conventional optical network systems provide a flexible design that creates a robust transport layer for various data formats.
The multiple staging of optical network systems, however, requires a large number of varying components to handle the different levels of communication signals. Accordingly, the cost of development for conventional optical network systems, and the cost of maintaining conventional optical systems is high. Additionally, each time a new communications signal is introduced to an existing SONET transport mechanism, the staging system that receives/transports the new signal must be reconfigured and/or replaced with a new staging system. Accordingly, the integration of multiple staging components would be a desired result. The integration of these multiple staging components into a single optical network design, however, results in several disadvantages.
FIG. 2
illustrates a basic SONET architecture having multiple SONET switches communicating at different bit rates. In general, the SONET architecture of
FIG. 2
illustrates Metro Access loops and a Metro Transport loop. Metro Access loops are relatively low speed (e.g., OC-
3
, OC-
12
) connections between SONET switches, such as SONET switches
210
and
260
, and other devices, such as IP device
200
and FR device
205
coupled to SONET switch
210
and DSL device
270
and Ethernet device
275
coupled to SONET switch
260
.
SONET switch
210
is coupled to SONET switch
220
via two OC-
3
connections. As mentioned above, each SONET connection includes two unidirectional connections having the same bit rate. SONET switch
260
is coupled to SONET switch
250
via two OC-
12
connections. SONET switch
220
is coupled to SONET switch
230
via two OC-
48
connections and to SONET switch
240
via two OC-
48
connections. SONET switch
250
is

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