FORM 2

THE PATENTS ACT  1970
(39 of 1970)
&
THE PATENTS RULES  2003

COMPLETE SPECIFICATION
(See section 10  rule 13)

“A system and Method of information propagation between entities in an optical communication network”

Tejas Networks Limited
2nd floor  GNR Tech Park  46/4  Garbebhavi Palya 
Kudlu Gate  Hosur main road 
Bangalore 560 068  Karnataka  India

The following specification particularly describes the invention and the manner in which it is to be performed.

Field of the Invention

The present invention relates in general to systems and methods of information propagation between cards in an optical communication network  and more particularly to system and method of alarm propagation from multiple line cards to a central processing card in an optical communication network  within a stipulated time.

Background of the Invention

Modern communication networks are comprised of data networks and transport networks that transmit data formatted according to different protocols or standards. For example  data networks may transmit data using the Fibre Channel  GbE (Gigabit Ethernet)  Ethernet or ESCON (Enterprise System Connection) standards. Optical transport networks may typically use either the SONET (Synchronous Optical Network) or SDH (Synchronous Digital hierarchy) standards.
SONET is a standard for optical transport formulated by the Exchange Carriers Standards Association (ECSA) for the American National Standards Institute (ANSI)  which sets industry standards in the U.S. for telecommunications and other industries. The standard has also been incorporated into the Synchronous Digital Hierarchy recommendations of the Consultative Committee on International Telegraph and Telephone (CCITT) (now called the International Telecommunications Union [ITU])  which sets standards for international telecommunications. Synchronous Optical Network (SONET) and Synchronous Digital hierarchy (SDH) (hereinafter referred to as “SONET/ SDH) are now mature digital transport technologies  established in virtually every country in the world.
Synchronous optical networking (SONET) and Synchronous Digital Hierarchy (SDH) are two closely related multiplexing protocols for transferring multiple digital bit streams over optical fiber. In general  one of the major advantages of using SONET/SDH standard for optical communication is resilience i.e. ability to switch traffic from work path to protect path in a duration of 50ms. Every node in SDH/SONET network is configured to support this feature. When a node has several line cards  switching traffic from work path to protect path within stipulated time becomes difficult.
Conventionally  several ways of alarm propagation from line cards to the central processing card exists  which are discussed in the following paragraphs.
In one of the known methods where the devices on the line cards are memory mapped i.e. the devices are directly accessible by the processor on the central processing card. In this architecture  in the event of any alarms on the line cards  an interrupt in generated by the line card and sent to the processor on central processing card. This interrupt is generally a point-to-point link between the line card and the central processing card. The processor on getting the interrupts reads the status of the alarm and then takes appropriate action. However  this method has a limitation that all the devices on all the line cards must be directly accessible by the central processor. This places a limit on the maximum number of devices on the line card and also amount of processing that can be done on the line card.
In another known method of the existing arts where the line card has a processor on board  due to the amount of processing required on the line card. In such cases  the devices are accessible only by local processor. The local processor gets the alarm status from the devices directly. The main processor on the central processor card communicates with this local processor through ICC link or some Ethernet link and gets information about the alarms. This communication method is however very slow and it may not be possible to meet the switching time of 50ms in such cases.
Another known method of providing access to local devices from both the local and central processor is cumbersome  as it requires complicated logic to arbitrate between the two processors.
Although above mentioned methods and systems serve the same purpose  but they (i) do not ensure minimum propagation delay for every alarm (ii) do not provide the flexibility to increase or decrease the number of alarms that can be propagated (iii) are not compatible to use the line card for both presence and absence of a local processor (iv) do not provide a simple scheme which is easy to implement.
Thus there exists a need for a method and system for alarm propagation between cards to overcome the above mentioned limitation in an efficient manner.

Summary of the Invention
An aspect of the present invention is to address at least the above-mentioned problems and/or disadvantages and to provide at least the advantages described below.
Accordingly  an aspect of the present invention is to provide a system of information propagation between entities in an optical communication network  wherein the entities include at least one primary card and a plurality of secondary cards  comprising: at least one clock of pre-specified frequency having its source from the primary card  at least one Time Division Multiplexed Bus from at least one secondary card with multiple slots  wherein the multiple slots correspond with the pre-specified frequency of the clock and each slot is adapted to transfer information and at least one framing pulse generated by the primary card and used by the second card  wherein the framing pulse is high for one cycle of the clock and indicates the multiple slots on the Time Division Multiplexed Bus.
Other aspects  advantages  and salient features of the invention will become apparent to those skilled in the art from the following detailed description  which  taken in conjunction with the annexed drawings  discloses exemplary embodiments of the invention.

Brief description of the drawings
The above and other aspects  features  and advantages of certain exemplary embodiments of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings in which:
FIG. 1 shows a connection diagram between a line card and a central processing card according to an embodiment of this invention.
FIG. 2 shows a schematic diagram depicting the processing at the line card according to an embodiment of this invention.
FIG. 3 shows a schematic diagram depicting the processing at the central processing card according to an embodiment of this invention.
Persons skilled in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and may have not been drawn to scale. For example  the dimensions of some of the elements in the figure may be exaggerated relative to other elements to help to improve understanding of various exemplary embodiments of the present disclosure.

Detail description of the Invention
The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the invention as defined by the claims and their equivalents. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. Accordingly  those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope and spirit of the invention. In addition  descriptions of well-known functions and constructions are omitted for clarity and conciseness.
The terms and words used in the following description and claims are not limited to the bibliographical meanings  but  are merely used by the inventor to enable a clear and consistent understanding of the invention. Accordingly  it should be apparent to those skilled in the art that the following description of exemplary embodiments of the present invention are provided for illustration purpose only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.
It is to be understood that the singular forms “a ” “an ” and “the” include plural referents unless the context clearly dictates otherwise. Thus  for example  reference to “a component surface” includes reference to one or more of such surfaces.
By the term “substantially” it is meant that the recited characteristic  parameter  or value need not be achieved exactly  but that deviations or variations  including for example  tolerances  measurement error  measurement accuracy limitations and other factors known to those of skill in the art  may occur in amounts that do not preclude the effect the characteristic was intended to provide.
Figs. 1 through 3  discussed below  and the various embodiments used to describe the principles of the present disclosure in this patent document are by way of illustration only and should not be construed in any way that would limit the scope of the disclosure. Those skilled in the art will understand that the principles of the present disclosure may be implemented in any suitably arranged communications system. The terms used to describe various embodiments are exemplary. It should be understood that these are provided to merely aid the understanding of the description  and that their use and definitions in no way limit the scope of the invention. Terms first  second  and the like are used to differentiate between objects having the same terminology and are in no way intended to represent a chronological order  unless where explicitly stated otherwise. A set is defined as a non-empty set including at least one element.
Referring to the drawings  a preferred embodiment of the system for information propagation between cards in an optical communication network is illustrated and indicated as 10.
FIG. 1 shows a connection diagram between a line card 12 and a central processing card 14 according to one embodiment of this invention. The central processing card 14 will be referred as “XC Card” hereafter in the following description. The XC card 14 has a processor and is responsible for taking the switching related decision. The Line card 12  which has several devices like optical ports  which forms a source to generate the alarm. The XC card 14 takes protection switching level decisions based on the alarm generated by the line card devices.
In an embodiment of the present invention the Line card 12 has on-board local processor that configures the local devices. However  it is possible to implement this invention without an on-board local processor on the line card 12.
Referring to FIG. 1  the system 10 according to the present invention comprises a clock 16 having its source from the XC card 14. In an embodiment of the present invention the clock 16 has a frequency of 8.192 MHz. The frequency of the clock 16 depends on the number of alarms to be propagated from Line card 12 to the XC card 14.
The system 10 also comprises a Time Division Multiplexed Bus 18 having multiple slots where each slot represents an alarm. The Time Division Multiplexed Bus 18 is also referred to as alarm_in in the following description and conveys the same meaning. In a preferred embodiment of the present invention a single bit alarm bus (alarm_in) from Line card is used. For a clock frequency of 8.192 MHz  this bus will have 2048 slots repeating every 250 microseconds. So a maximum of 2048 alarms can be propagated to the XC card 14 from Line card 12 in 250 microseconds. If more alarms need to be propagated  then the frequency of the clock 16 may be increased.
Another component of the system 10 according to present invention include a framing pulse (Fsync) 20 which is high for 1 cycle of clock 16 and repeats every 250 microseconds. The framing pulse 20 indicates the (slot 1) of 2048 slots on the alarm (alarm_in) line. This framing pulse is generated by XC card 14 and will be used by line card 12.
It should be noted that that the clock (clk_8m) frequency of 8.192 MHz and a repeating period 250us for framing pulse (Fsync) are mentioned as examples. The values of frequency and repeating period can be changed depending on the number of alarms to be transferred and the minimum time in which the alarms have to be propagated.
FIG. 2 shows a schematic diagram depicting the processing at the line card 12 according to an embodiment of this invention in which the components of this invention are implemented in SDH/SONET with an optical line card. Various devices on the line card 12 may form the sources of alarms which is propagated to the slots of Time Division Multiplexed Bus 18 in a path. There can be different alarm generated for every path. For an STM-16 line card  there can be 3x16 higher order path and 84x16 lower order path alarms. So at maximum there can be a total of 1392 paths. In actual case there can be more than 1 alarm per path on which switching is required.
According to an embodiment of this invention  only one alarm is transferred per path. This alarm is referred to as “signal fail” alarm. All the alarms on which switching is required  can be mapped to this signal fail alarm. This decision is not a time critical decision and can be taken by the local processor by communicating to the central processor on XC card 14 through ICC link or Ethernet link.
Furthermore  for every path  there is a signal fail alarm. So for STM-16  there will be a total of 1392 alarms to be transferred to the XC card 14. These alarms can be mapped on some preplanned slots on the alarm_in bus 18. This mapping of path to the slot number is pre-determined and is known both at the XC card 14 and the Line card 12. A simple look-up table (mapping table) can be maintained for this mapping. At the Line card 12  all the signal fail alarms are mapped on to the alarm_in 18 bus based to the mapping table. At the XC card 14  this alarm_in 18 bus is terminated.
FIG. 3 shows a schematic diagram depicting the processing at the central processing card according to an embodiment of this invention. All the signal fail alarms are regenerated at the XC card 14 based on the look-up table. These alarms are dumped in Memory and an interrupt is generated whenever there is change in the status of any alarm. Based on this interrupt and the status of the alarms  the central processor on the XC card 14 can take decision required for protection switching.
So in 250us it is possible to transfer all the path alarms of STM-16 interface using this protocol. It is also possible to propagate a total of 2048 alarms in 250us using a clock of 8.192 MHz using this protocol.
In a further embodiment where several line cards need to send alarm to the central processor card 14 a single alarm (alarm_in) bus 18 which is shared among all the line cards is used. Each card can map alarms on fixed slots on the alarm (alarm_in) bus 18 based on the slots in which the card is jacked in. For example if each card has to send a maximum of 256 alarms  then the same bus can support up to 8 slots. The time slots on which each card maps the alarms depends on the slot id. In total  there are 2048 time slots.
For example  lets us suppose time_slot [10:0] variable determines the time slot no in alarm_in bus 18. Time_slot [10:8] can be compared with the slot_id of the slot in which the line card is jacked in. Therefore  a line card jacked in slot1 can use time slots from 1-256  line card jacked in slot2 can use time slot 257-512 and so on. Each line card will drive the bus only if the slot_id matched with time_slot [10:8]. Therefore  without an increase in the complexity  the same scheme can be used in a scenario of shared alarm_in bus where many cards map alarms on a single bus.
Various embodiments of this invention provide a method and apparatus for alarm propagation from multiple line cards to a central processing card in an optical communication network. However  the embodiments may be modified in a way that is obvious to a person skilled in the art and all such modifications are deemed to be within the scope of the claims herein under.
FIGS. 1-3 are merely representational and are not drawn to scale. Certain portions thereof may be exaggerated  while others may be minimized. FIGS. 1-3 illustrate various embodiments of the invention that can be understood and appropriately carried out by those of ordinary skill in the art.
In the foregoing detailed description of embodiments of the invention  various features are grouped together in a single embodiment for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed embodiments of the invention require more features than are expressly recited in each claim. Rather  as the following claims reflect  inventive subject matter lies in less than all features of a single disclosed embodiment. Thus  the following claims are hereby incorporated into the detailed description of embodiments of the invention  with each claim standing on its own as a separate embodiment.
It is understood that the above description is intended to be illustrative  and not restrictive. It is intended to cover all alternatives  modifications and equivalents as may be included within the spirit and scope of the invention as defined in the appended claims. Many other embodiments will be apparent to those of skill in the art upon reviewing the above description. The scope of the invention should  therefore  be determined with reference to the appended claims  along with the full scope of equivalents to which such claims are entitled. In the appended claims  the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein ” respectively.

We Claim:
1. A system of information propagation between entities in an optical communication network  wherein the entities include at least one primary card and a plurality of secondary cards  comprising:
at least one clock of pre-specified frequency having its source from the primary card;
at least one Time Division Multiplexed Bus from at least one secondary card with multiple slots  wherein the multiple slots correspond with the pre-specified frequency of the clock and each slot is adapted to transfer information; and
at least one framing pulse generated by the primary card and used by the secondary card  wherein the framing pulse is high for one cycle of the clock and indicates the multiple slots on the Time Division Multiplexed Bus.

2. The system of claim 1  wherein the primary card is a central processing card and the secondary card is a line card.

3. The system of claim 1  wherein the number of information depend on the number of slots on the Time Division Multiplexed Bus.

4. The system of claim 1  wherein the pre-specified frequency of the clock depends on the amount of information to be propagated between the cards.

5. The system of claim 1  wherein the number of multiple slots depend on the amount of information to be propagated between the cards.

6. The system of claim 1  wherein the information propagating between cards is mapped in a pre-planned manner on the multiple slots of the Time Division Multiplexed Bus.
Dated this the 29th day of March  2012
S Afsar
Of Krishna & Saurastri Associates
Agent for the Applicant
Registration No. IN/PA-1073

Abstract
A system and Method of information propagation between entities in an optical communication network
The invention relates to a system and method of infomation propagation between entities in an optical communication network. This may be accomplished by at least one clock of pre-specified frequency having its source from the primary card  at least one Time Division Multiplexed Bus from at least one secondary card with multiple slots  wherein the multiple slots correspond with the pre-specified frequency of the clock and each slot is adapted to transfer information and at least one framing pulse generated by the primary card and used by the second card  wherein the framing pulse is high for one cycle of the clock and indicates the multiple slots on the Time Division Multiplexed Bus.

Figure 1

FIGURES – REFERENCE NUMERALS
10 System for information propagation between cards in an optical communication network according to the present invention
12 Line Card
14 Central Processing Card
16 Clock
18 Time Division Multiplexed Bus
20 Framing Pulse