Abstract:
Disclosed is a method for forming a synchronous frame to be transmitted in a Residential Ethernet System, which is capable of discretely transmitting synchronous data and asynchronous data, wherein the synchronous frame includes synchronous packets which are formed according to destinations of synchronous data. The method includes the steps of: receiving the synchronous data having different destinations, and classifying the received synchronous data according to the destinations of the synchronous data; adding a synchronous header to each of the synchronous data classified according to the destinations in order to insert synchronous information into each synchronous data; and adding an Ethernet header for Ethernet processing, thereby forming the synchronous packets.

Description:
CLAIM OF PRIORITY  
       [0001]     This application claims the benefit of an application entitled “Method For Forming Synchronous Data In Residential Ethernet System,” filed in the Korean Intellectual Property Office on Mar. 3, 2005 and assigned Ser. No. 2005-17852, the entire contents of which are incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a Residential Ethernet, and more particularly to a method of transmitting synchronous data through a packet-based routing in the Residential Ethernet.  
         [0004]     2. Description of the Related Art  
         [0005]     Ethernet is the most widely used local area network technology which is defined in a standard from an Institute of Electrical and Electronics Engineers (IEEE) 802.3. In the conventional Ethernet, since an access is achieved by means of a carrier sense multiple access/collision detect (CSMA/CD) protocol stipulated in an IEEE 802.3, a service frame of an upper layer is converted to an Ethernet frame while maintaining an inter frame gap (IFG) during transmission of the Ethernet frames. The upper service frames are transmitted according to a sequence of generation thereof regardless of the frame type. Hence, the Ethernet is generally used when data is transmitted among a plurality of terminals or users.  
         [0006]     Ethernet has been known to be insufficient for transmitting a moving image or voice data susceptible to a transmission delay as the Ethernet employs the CSMA/CD scheme in which every Ethernet frame is given the same priority for transmission. Recently, various methods have been proposed for removing such a problem caused by the transmission delay using the Ethernet scheme.  
         [0007]     IEEE 802.3p is one scheme conventionally-proposed in order to reduce time delay in the Ethernet. According to the IEEE 802.3p, classification of service (COS) is allocated to data such as multimedia data, to which priority must be given. The IEEE 802.3p scheme provides a slightly improved effect with respect to time delay by allocating a priority to multimedia data or the like to be transmitted, as compared with the conventional IEEE 802.3 Ethernet scheme. However, since the IEEE 802.3p scheme does not employ a process of requiring and allocating a bandwidth to each data, a bandwidth manager for managing the allocation of a bandwidth is required, thereby increasing the size of a jitter buffer for such bandwidth management.  
         [0008]     A Residential Ethernet is another conventionally-proposed transmission scheme, in which synchronous data and asynchronous data are discretely transmitted during one transmission cycle. According to the Residential Ethernet, slots of the same size are respectively allocated to synchronous data, so that sub-synchronous frames having the same size are constructed and transmitted.  
         [0009]      FIG. 1  is a view illustrating the structure of a transmission cycle in the conventional Residential Ethernet.  
         [0010]     The conventional Residential Ethernet has a transmission cycle  10  of 125 μsec, which includes an asynchronous frame section  110  for transmission of asynchronous data and a synchronous frame section  100  for transmission of synchronous data.  
         [0011]     In detail, the synchronous frame section  100  for transmission of synchronous data contains data having the highest priority in the transmission cycle. According to a recent proposal, the synchronous frame section  100  includes sub-synchronous frames  101 ,  102 , and  103 , each of which is constructed with 738 bytes. Also, the asynchronous frame section  110  for transmission of asynchronous data includes sub-asynchronous frames  111 ,  112 , and  113 , each of which have a variable size.  
         [0012]      FIG. 2  is a view illustrating the structure of a sub-synchronous frame included in a transmission cycle of the conventional Residential Ethernet.  
         [0013]     In conventional Residential Ethernet, a sub-synchronous frame includes an Ethernet header  21 , a synchronous header  22 , a header check sequence (HCS) field  23 , a synchronous data slot field  24 , and a frame check sequence (FCS) field  25 . The Ethernet header  21  is constructed by 22 octets and contains header information including type information, a destination address, and a source address of a relevant Ethernet frame. The synchronous header  22  is constructed by 32 bytes and contains information about a synchronization frame, such as whether or not the relevant frame is a synchronous frame, frame count information, and cycle count information. The HCS field  23  is used to check header information. The synchronous data slot field  24  is constructed by 768 bytes and contains synchronous Ethernet data to be transmitted, which include 192 4-byte synchronous data slots. The FCS field  25  is used to detect a transmission error.  
         [0014]     Also, the synchronous data slot field  24  is constructed by a set of 4-byte data slots  241  and  242 , so that each of synchronous Ethernet data is divided into data slots of 4 bytes and is transmitted.  
         [0015]     In this case, when synchronous Ethernet data are transmitted from a server to each user, the synchronous data slot field  24  contains synchronous Ethernet data for all users in the form of slots. Therefore, synchronous Ethernet data are transmitted to the users in a multicast scheme, rather than a unicast scheme, so that each user terminal must process data for the user terminal according to data slots.  
         [0016]     A destination address included in the Ethernet header  21  is a destination address representing an Ethernet switch for final routing, rather than a destination address of each Ethernet synchronous data. Therefore, the destination address included in the Ethernet header  21  differs from a destination address of Ethemet synchronous data allocated to each user.  
         [0017]      FIG. 3  is a view illustrating the structure of a transmission cycle showing each data slot in the conventional Residential Ethernet.  
         [0018]     The conventional Residential Ethernet has a transmission cycle  300  of 125 μsec, which is divided into a synchronous frame section including sub-synchronous frames  31 ,  32 , and  33 , and an asynchronous frame section including sub-asynchronous frames  34 ,  35 , and  36 , as shown in  FIG. 1 . Particularly, data slots included in the sub-synchronous frames  31 ,  32 , and  33  are inserted into each relevant sub-synchronous frame  31 ,  32 , or  33  while not being classified depending on destinations thereof.  
         [0019]     A first sub-synchronous frame  31  contains data  301  to be transmitted to a first user, data  302  to be transmitted to a second user, and data  303  to be transmitted to a third user. Also, a second sub-synchronous frame  32  contains data  304  to be transmitted to a fourth user, and a third sub-synchronous frame  33  contains data  305  to be transmitted to a fifth user and data  306  to be transmitted to a sixth user.  
         [0020]      FIG. 4  is a view for explaining a transmission procedure for synchronous data in the conventional Residential Ethernet System.  
         [0021]     A Residential Ethernet System includes a server  41 , a first Residential Ethernet switch  42 , a second Residential Ethernet switch  43 , and users  44 - 1 ,  44 - 2 , and  44 - 3 . The server  41  provides synchronous data and asynchronous data to be transmitted to the users  44 - 1 ,  44 - 2 , and  44 - 3 . The first Residential Ethernet switch  42  constructs a Residential Ethernet transmission cycle  400  and transmits the Residential Ethernet transmission cycle  400  downward. The second Residential Ethernet switch  43  receives the Residential Ethernet transmission cycle  400  and transmits the received Residential Ethernet transmission cycle  400  to the users  44 - 1 ,  44 - 2 , and  44 - 3 . Each of the users  44 - 1 ,  44 - 2 , and  44 - 3  receives the Residential Ethernet transmission cycle  400  and processes data destined for himself/herself among the received Residential Ethernet transmission cycle  400 . Herein, the user  44 - 1 ,  44 - 2 , and  44 - 3  represent user terminals for user interface.  
         [0022]     A transmission procedure for synchronous data in the conventional Residential Ethernet System having the above-mentioned construction is as follows: First, the server  41  generates synchronous data  401 ,  402 , and  403  to be transmitted to the users  44 - 1 ,  44 - 2 , and  44 - 3 , respectively, and transmits the synchronous data  401 ,  402 , and  403  to the first Residential Ethernet switch  42 .  
         [0023]     The first Residential Ethernet switch  42  constructs a Residential Ethernet transmission cycle  400  using the synchronous data  401 ,  402 , and  403 , in which the Residential Ethernet transmission cycle  400  includes an asynchronous frame section  400 - 1  and a synchronous frame section  400 - 2 , as shown in  FIG. 1 .  FIG. 4  shows an example of a Residential Ethernet transmission frame, which is divided into the asynchronous frame section  400 - 1  and the synchronous frame section  400 - 2  containing one sub-synchronous frame.  
         [0024]     As shown in  FIG. 4 , all synchronous data  401 ,  402 , and  403  to be transmitted to the users  44 - 1 ,  44 - 2 , and  44 - 3  are gathered in one sub-synchronous frame and then transmitted.  
         [0025]     That is, each of the synchronous data  401 ,  402 , and  403  is inserted in a form of data slots into the synchronous data slot field of the sub-synchronous frame, then transmitted.  
         [0026]     Therefore, the second Residential Ethernet switch  43  cannot transmit the synchronous data  401 ,  402 , and  403  in a slot unit according to each user  44 - 1 ,  44 - 2 , and  44 - 3 , but must transmit the entire synchronous frame section  400 - 2  in a multicast scheme. Accordingly, each user  44 - 1 ,  44 - 2 , and  44 - 3  processes slot data included in the transmitted synchronous frame section  400 - 2  in order to receive synchronous data transmitted to himself/herself.  
         [0027]     Such a conventional Residential Ethernet System requires a slot data processing with respect to each synchronous data, so that there is a disadvantage in that a complicated procedure of converting each synchronous data into slot data and gathering the converted slot data in the data area of the sub-synchronous frame must be performed. Also, in order to perform a slot routing task and a slot reservation task with respect to the contained slot data, the data area of the sub-synchronous frame must be managed which is a problem in the prior art. In addition, if synchronous data is converted into slot data while an intermediate area is not used, bandwidth is greatly wasted. Furthermore, since the entire synchronous frame section is transmitted to every user, even unnecessary data for each user are transmitted, thereby largely wasting bandwidth.  
       SUMMARY OF THE INVENTION  
       [0028]     Accordingly, the present invention has been made to solve the above-mentioned problems occurring in the prior art and provides additional advantages, by providing a method for forming synchronous data in a Residential Ethernet System for enabling synchronous data to be independently transmitted to each user without slot processing.  
         [0029]     In accordance with one aspect of the present invention, there is provided a method for forming a synchronous frame to be transmitted in a Residential Ethernet System capable of discretely transmitting synchronous data and asynchronous data, wherein the synchronous frame includes synchronous packets which are formed according to destinations of synchronous data. The method includes the steps of: receiving the synchronous data having different destinations, and classifying the received synchronous data according to the destinations of the synchronous data; adding a synchronous header to each of the synchronous data classified according to the destinations in order to insert synchronous information into each synchronous data; and adding an Ethernet header for Ethernet processing, thereby forming the synchronous packets. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0030]     The above features and advantages of the present invention will be more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:  
         [0031]      FIG. 1  is a view illustrating the structure of a transmission cycle in the conventional Residential Ethernet;  
         [0032]      FIG. 2  is a view illustrating the structure of a sub-synchronous frame included in a transmission cycle of the conventional Residential Ethernet;  
         [0033]      FIG. 3  is a view illustrating the structure of a transmission cycle in order to explain each data slot in the conventional Residential Ethernet;  
         [0034]      FIG. 4  is a view for explaining a transmission procedure for synchronous data in the conventional Residential Ethernet System;  
         [0035]      FIG. 5  is a view illustrating the structure of a transmission cycle for explaining each data slot in a Residential Ethernet according to an embodiment of the present invention; and  
         [0036]      FIG. 6  is a view for explaining a transmission procedure for synchronous data in the Residential Ethernet System according to an embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0037]     Hereinafter, an embodiment according to the present invention will be described with reference to the accompanying drawings. For the purposes of clarity and simplicity, a detailed description of known functions and configurations incorporated herein will be omitted as it may obscure the subject matter of the present invention.  
         [0038]     According to the teachings of the present invention, synchronous data of a synchronous frame section, which are divided into slot data in the existing Residential Ethernet, are packetized depending on the destination of each synchronous data, so that synchronous packets have various sizes and can be routed according to each synchronous packet.  
         [0039]     The present invention will now be described in detail with reference to the accompanying drawings.  
         [0040]      FIG. 5  is a view illustrating the structure of a transmission cycle showing each data slot in a Residential Ethernet according to. an embodiment of the present invention.  
         [0041]     The Residential Ethernet according to an embodiment of the present invention has a transmission cycle  300  of 125 μsec, which includes an asynchronous frame section and a synchronous frame section, as shown in  FIG. 1 .  
         [0042]     Herein, while the asynchronous frame section contains sub-asynchronous frames  34 ,  35 , and  36 , as that in the prior art, the synchronous frame section contains packets grouped according to their destination. That is, packets in the Residential Ethernet according to the present invention have non-uniform sizes.  
         [0043]     More particularly, each of data  301  to be transmitted to a first user, data  302  to be transmitted to a second user, data  303  to be transmitted to a third user, data  304  to be transmitted to a fourth user, data  305  to be transmitted to a fifth user, and data  306  to be transmitted to a sixth user is constructed as one packet.  
         [0044]     Referring back to  FIG. 2 , in the present invention, each packet includes an Ethernet header  21  constructed by 22 octets so as to include Ethernet information, a synchronous header  22  including synchronous information of a synchronous frame, a header check sequence (HCS) field  23 , and a frame check sequence (FCS) field  25  for detecting a transmission error. In this case, the Ethernet header  21  or synchronous header  22  includes information about the destination of each relevant packet.  
         [0045]     Since synchronous data are packetized according to their destination, each synchronous data can be transmitted in a unicast scheme, rather than a multicast scheme, which was used in the conventional Residential Ethernet.  
         [0046]      FIG. 6  is a view for explaining a transmission procedure for synchronous data in the Residential Ethernet System according to an embodiment of the present invention.  
         [0047]     A Residential Ethernet System includes a server  61 , a first Residential Ethernet switch  62 , a second Residential Ethernet switch  63 , and users  64 - 1 ,  64 - 2 , and  64 - 3 . The server  61  provides synchronous data and asynchronous data to be transmitted to the users  64 - 1 ,  64 - 2 , and  64 - 3 . The first Residential Ethernet switch  62  constructs a Residential Ethernet transmission cycle  600  according to an embodiment of the present invention, and transmits the Residential Ethernet transmission cycle  600  downward. The second Residential Ethernet switch  63  receives the Residential Ethernet transmission cycle  600 , and transmits each synchronous packet included in the received Residential Ethernet transmission cycle  600  to the users  64 - 1 ,  64 - 2 , or  64 - 3  corresponding to the destination of each synchronous packet. Each of the users  64 - 1 ,  64 - 2 , and  64 - 3  receives and processes a synchronous packet. Herein, the user  64 - 1 ,  64 - 2 , and  64 - 3  represent user terminals for user interface.  
         [0048]     A transmission procedure for synchronous data in the Residential Ethernet System according to an embodiment of the present invention is as follows: First, the server  61  generates synchronous data  401 ,  402 , and  403  to be transmitted to the users  64 - 1 ,  64 - 2 , and  64 - 3 , respectively, and transmits the synchronous data  401 ,  402 , and  403  to the first Residential Ethernet switch  62 .  
         [0049]     The first Residential Ethernet switch  62  constructs a Residential Ethernet transmission cycle  600  using the synchronous data  401 ,  402 , and  403 , in which the Residential Ethernet transmission cycle  600  includes an asynchronous frame section  600 - 2  and synchronous packets  601 ,  602 , and  603  grouped according to each user.  
         [0050]     Herein, the synchronous packets  601 ,  602 , and  603  grouped according to each user are constructed in such a manner that the first Residential Ethernet switch  62  receives synchronous data having a different destination according to each user, classifies the received synchronous data according to each destination, attaches a synchronous header to each synchronous data classified according to its destination in order to insert synchronous information into each synchronous data, and adds Ethernet information for Ethernet processing to each synchronous data to which a synchronous header is attached. In this case, an HCS field for preventing an error in header construction and/or an FCS for detecting a transmission error may be added.  
         [0051]     Since information about each destination is included in an Ethernet header or synchronous header, packets can be routed even with only header information without checking a payload section, differently from conventional Residential Ethernet.  
         [0052]     Thereafter, the second Residential Ethernet switch  63  transmits each of the synchronous packet  601 ,  602 , and  603  to corresponding user  64 - 1 ,  64 - 2 , and  64 - 3 , respectively, in a unicast scheme.  
         [0053]     Note that the method according to the present invention can be realized by a program and can be stored in a recording medium (such as a CD ROM, a RAM, a floppy disk, a hard disk, a magneto-optical disk, etc.) in a format that can be read by a computer.  
         [0054]     According to the present invention as described above, since the Residential Ethernet System constructs the synchronous frame in a packet unit, a complicated procedure of converting synchronous data into slot data is not required. Further, it is unnecessary to manage the data area of a sub-synchronous frame which has been required for a slot routing task and a slot reservation task with respect to the slot data in the prior art.  
         [0055]     Moreover, differently from the conventional Residential Ethernet System in which frames are constructed in the same size, the Residential Ethernet System according to the present invention allows packets to be constructed in different sizes, thereby reducing waste of bandwidth.  
         [0056]     Furthermore, according to the Residential Ethernet System of the present invention, since synchronous data can be transmitted to each user according to their destination in a unicast scheme, the transmission of unnecessary data is prevented, thereby preventing waste of bandwidth with respect to each user.  
         [0057]     While the present invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of. the invention as defined by the appended claims. Accordingly, the scope of the invention is not to be limited by the above embodiments but by the claims and the equivalents thereof.