Inter-chip port and method for supporting high rate data...

Details Inter-chip port and method for supporting high rate data... Inter-chip port and method for supporting high rate data...

2000-08-15

2004-07-20

Patel, Ajit (Department: 2664)

Multiplex communications

Communication techniques for information carried in plural...

Combining or distributing information via time channels

C370S541000

Reexamination Certificate

active

06765933

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a method and a device for supporting high rate data streams, with handling overhead layers thereof, and in particular to a chip assembly with an inter-chip communication port capable of processing a layer of transport overhead (TOH) and a layer of path overhead (POH) of high order signals in transport telecommunication networks based on either SDH or SONET standards
BACKGROUND OF THE INVENTION
The Synchronous Digital Hierarchy (SDH) and its North-American equivalent, the Synchronous Optical Network (SONET), are the globally accepted, closely related and compatible standards for data transmission in the public wide area network (WAN) domain. Recently, SDH/SONET has also been adopted by the ATM Forum as a recommended physical-layer transmission technology for ATM (Asynchronous Transfer Mode) network interfaces.
SONET and SDH govern interface parameters; rates, formats and multiplexing methods; operations, administration, maintenance and provisioning for high-speed signal transmission. SONET is primarily a set of North American standards with a fundamental transport rate beginning at approximately 52 Mb/s (i.e., 51.84 Mb/s), while SDH, principally used in Europe and Asia, defines a basic rate near 155 Mb/s (to be precise, 51.84×3=155.52 Mb/s). From a transmission perspective, together they provide an international basis for supporting both existing and new services in the developed and developing countries.
For transmitting data, SDH and SONET use frame formats transmitted every 125 &mgr;s (8000 frames/s). Because of compatibility between SDH and SONET, their basic frames are similarly structured, but differ in dimension which fact reflects the basic transmission rates of 155.52 and 51.84 Mb/s, respectively. To be more specific, a basic frame format of SDH is 9 rows of 270 bytes, or 2430 bits/frame, corresponding to an aggregate frame rate of 155.52 Mb/s. For SDH systems, the mentioned basic frame transmitted at the rate 155.52 Mb/s forms the fundamental building block called Synchronous Transport Module Level-
1
(STM-
1
). For SONET systems, the basic frame has dimensions of 9 rows by 90 byte columns and, being transmitted at the rate 51.84 Mb/s, forms the appropriate fundamental building block called Synchronous Transport Signal Level-
1
(STS-
1
or OC-
3
). The transmission sequence in both SONET and SDH is as follows: the byte in the first row and the first column will be transmitted first; it is followed by the byte to its right, in the same row and so on, from left to right and from top to bottom.
Lower rate payloads (data portions transmitted at rates smaller than the basic ones) are mapped into the fundamental building blocks STM-
1
and STS-
1
respectively, while higher rate signals (payloads) are generated by byte-interleavingly multiplexing N fundamental building blocks to form STM-N signals (in SDH) or STS-N signals (in SONET).
FIG. 1
explains the principle of byte-interleaved multiplexing on a specific example where four STM-
1
s are combined into one STM-
4
. The multiplexing is effected by byte-interleaved multiplexer (BIM) which produces a sequence of bytes where one byte from No. 1 building block is followed by one byte from No. 2 building block and so on. All low-speed signals must be frame-aligned prior to multiplexing.
STM-
4
/STM
4
c
signal having a data rate 622.08 Mb/s (4×155.52 Mb/s) is one of the high order signals (payloads) in the SDH system. In SONET, it corresponds to STS-
12
/STS-
12
c
having the same data rate. The signal STM
4
/STM-
4
c
, being equivalent to STS-
12
/STS-
12
c
, consists of four STM-
1
or four STS-
3
building blocks. The mentioned high order signal STM-
4
/STM
4
c
can be transmitted in two ways.
A first way is to transmit it over at least four individual parallel paths: e.g., four STM-
1
(or STS-
3
) paths. The signal transmitted along parallel paths is called STM-
4
. Each path may itself consist of up to three separate STS-
1
paths, thus the STM-
4
signal may comprise up to 12 individual paths, each transmitting an individual STM-l signal with its individual payload.
Alternatively, the signal can be transmitted as a concatenated stream over a single path; in that case the obtained signal (which is called STM-
4
c
i.e., “concatenated”) is sent as a single combined payload in one synchronous payload envelope (SPE). The fact that the signal follows as a concatenated (multiframe) payload, as well as location of the SPE borders, are indicated using a number of so-called overhead bytes which are present in the frame.
Each basic frame of SONET or SDH comprises an information portion called Information Payload and a service portion called Overhead (OH), the latter being subdivided into a number of areas of overhead bytes (for example a Path Overhead layer POH, a Transport Overhead layer TOH), predestined for various service and control functions. One of such areas is a column of Path Overhead (POH) bytes, which is present both in the SDH and SONET frames and usually resides within the Information Payload area. POH supports performance monitoring, status feedback, signal labeling, user channel and a tracing function in a path, i.e. carries information about the signal from end to end through the entire transmission system. The POH is added and dismantled at or near service origination/termination points defining the path, and is not processed at intermediary nodes.
In SONET, the Transport overhead layer which is responsible for transport through the network, is broken into two parts—Line Overhead (LOH) and Section Overhead (SOH). Section overhead (SOH) is that overhead necessary for reliable communication between network elements such as terminals and regenerators. Line overhead (LOH) was established to allow reliable communication of necessary information between more complicated network elements such as terminals, digital cross-connects, multiplexers and switches.
In SDH, no Transport overhead is directly defined. However, any SDH basic frame comprises a Multiplex Section Overhead (MSOH) being analogous to LOH in SONET, and a Regenerator Section Overhead (RSOH) which play the part of SOH in SONET.
FIG. 2
schematically illustrates an STM-
1
frame with its overhead sections. It is therefore considered, that the layer of Transport overhead in SDH is actually formed by the mentioned MSOH and RSOH. POH column is considered a part of STM-
1
payload. There is also a row of overhead bytes bearing information on so-called AU-pointers (administrative unit pointers) which are considered to belong neither to TOH nor to POH, and are analyzed separately.
It should be noted that, in a not concatenated signal, each of the component building blocks has its individual SPE and bears its own TOH and POH similarly to that shown in FIG.
2
. In a concatenated signal having a single common SPE, the TOH area is assembled from individual TOHs of the component building blocks, while the POH column is one and common for the SPE, since it is intended for identifying and controlling a single path.
During decoding and checking of a SONET or SDH signal transmitted in a path, it is generally “stripped down” in layers by a control system, first decoding and checking the section information, then the line information and thereafter the path information. At each step, error checking is provided and errors (if detected) must be indicated either to the local control system, or to the originating path terminal element to inform about troubles in the path.
TranSwitch corporation entered the market with two products relevant to the subject of the present application. One of them is called SOT-
3
(TXC-
03003
B) being an overhead terminator for STM-
1
/STS-
3
/STS-
3
c
transmission applications. The other is PHAST-
12
(TXC-
06112
) being a highly integrated SONET/SDH terminator device designed for ATM cell, frame, higher order multiplexing, and transmission applications. A single PHAST-
12
device can terminate four individual STS-
3
c
or STM-
1
lines, as well or a single OC
12
/

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