JP2694605B2 - ATM cell transmission method and network system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ATM cell transmission method for transmitting ATM cells in a fiber channel network and a network system for transmitting ATM cells between the fiber channel network and the ATM network using this transmission method. is there.

[0002]

2. Description of the Related Art Fiber Channel
Is a high-speed serial data channel for computers and their peripherals, and is intended for a wide range of applications, such as replacing existing I / O interfaces and connecting LANs.
NSI X3T9.3 task group is in the process of drafting a standard. FIG. 4 is a view showing a frame structure of a fiber channel, 1 is a fiber channel frame, 2 is a frame 1 defined by a special code string of 4 octets (strictly, it is 4 characters using a unit character described later). The start delimiter (SOF: Start of Fra
me), 3 is an end delimiter (EOF: End of Fra) that also indicates the end of frame 1, which is defined by a code string of 4 octets.
me), 11 is a 24-octet frame header (hereinafter,
12 is a variable-length data field of 0 to 2112 octets, and 13 is a 4-octet CRC code (Cyclic Redundancy Check, hereinafter referred to as a trailer) for error checking.

A fiber channel network using such a fiber channel and an ATM (Asynchronous Tra
There are two types of methods for connecting an ATM network using nsfer mode). First, the first method is a method of providing a gateway device that performs protocol conversion processing and routing processing (path selection processing) between these networks. FIG. 5 is a diagram showing protocol processing by the gateway device, 41 is a fiber channel network, 42 is an ATM network, 44 is a gateway device, and FC-PH is a physical medium of the fiber channel protocol system, encoding and decoding, and a frame. Physical interface, which is the regulation regarding the structure, IP is FC-PH
Higher layer Internet protocols (Internet Prot
, PHL is a physical layer that defines the physical medium of the ATM protocol system, ATM is an ATM layer that handles ATM cell multiplexing and switching, and AAL is an ATM adaptation layer that handles functions related to various services.

In this first method, ATM from the ATM network 42 to the fiber channel network 41 is used.
Regarding cell transfer, the gateway device 44 AT
Perform protocol conversion from M to Fiber Channel. That is, the gateway device 44 extracts the payload part (48 octet information field) in the ATM cell, connects some of these to reconstruct the protocol data of the internet protocol IP, and uses this to reconstruct the fiber channel frame 1 The data is divided into the lengths that can be placed in the data field 12 of, and the header 11 and the trailer 13 are attached to the front and the rear by the function of FC-PH, and the data is sent to the fiber channel network 41.

On the contrary, the AT from the networks 41 to 42
Regarding transfer of M cells, the gateway device 44 performs protocol conversion from fiber channel to ATM.
That is, the gateway device 44 removes the header 11 and the trailer 13 by the function of FC-PH, connects some of them to reconfigure the IP protocol data, divides this, and puts it on the payload of the ATM cell, It is sent to the ATM network 42. Then, the routing processing in the gateway device 44 is realized by making a determination based on the IP address or a correspondence relationship between the ATM virtual channel identifier and the fiber channel destination address.

In the first method, the gateway device 44 performs the protocol conversion process and the routing process at the same time, which complicates the process. When transmitting voice data, which has a lower transfer rate than the high-speed data that can be transferred by fiber channel or ATM, but is sensitive to delay,
If you wait until the voice data has accumulated to some extent before transferring, a delay will occur. Therefore, in order to reduce the delay, it is necessary to transmit the data without waiting for the data to be accumulated. As a result, the transfer amount per frame is reduced, and the transfer overhead ratio is relatively increased.

Next, the second method is a method of connecting a terminal device whose ATM cell transmission / reception function is defined by a protocol of a layer higher than the physical interface FC-PH to the fiber channel network. FIG. 6 is a diagram showing the protocol processing by the terminal device and the gateway device, and the same elements as those in FIG. 5 are designated by the same reference numerals. 43 is a terminal device connected to the fiber channel network 41, and 44a is a gateway device.

From the terminal device 43 to the ATM network 42
For the transfer of ATM cells to the protocol AAL,
ATM cell is passed from ATML to FC-PH, and FC-P
With the function of H, the header 11 and the trailer 13 of the fiber channel are attached before and after the ATM cell, and the frame is encapsulated by the terminal device 43 and transmitted to the network 41. Then, the gateway device 44a removes the header and the trailer, extracts the ATM cell, and transmits it to the ATM network 42. Further, regarding the transfer of the ATM cell from the ATM network 42 to the terminal device 43, the fiber channel network 41 in the form of a frame in which the header 11 and the trailer 13 of the fiber channel are attached before and after the ATM cell in the gateway device 44a. Send to. Then, at the terminal device 43, the header 11 and the trailer 13 are removed to take out the ATM cell,
Hand over to TML and AAL.

In this second method, 53 octets of A
A 24 octet header 11 and a 4 octet trailer 13 are required for the TM cell, for a total 28 octet transfer overhead. In order to improve this, a method of collecting a plurality of ATM cells and placing them in the data field 12 of one fiber channel frame 1 is also conceivable. However, although the transfer efficiency is improved by this, the delay becomes large in the process of waiting the ATM cells.

[0010]

As described above, the first conventional method has a problem that the processing in the gateway device is complicated and it is difficult to suppress the relay delay due to this processing. Further, when trying to transmit data such as voice data which is sensitive to delay, there is a problem that the ratio of the transfer overhead increases and the transfer efficiency deteriorates. The second conventional method also has a problem that the transfer efficiency is poor because a transfer overhead of 28 octets is required for an ATM cell of 53 octets. Also, in order to improve transfer efficiency, multiple ATs
If M cells are collected and put in one fiber channel frame, there is a problem that the delay in the process of waiting the cells becomes large and the service quality such as voice data cannot be satisfied. The present invention has been made to solve the above problems, and an object of the present invention is to provide an ATM cell transmission method and a network system capable of minimizing a decrease in transfer efficiency due to additional overhead without increasing a delay. And

[0011]

According to an ATM cell transmission method of the present invention, an ATM start delimiter indicating the start of an ATM cell and an ATM end delimiter indicating the end of a cell are codes different from the delimiter group defined by the fiber channel. Defined in columns,
On the transmitting side, an ATM start delimiter, one or more ATM cells and an ATM end delimiter are successively multiplexed between Fiber Channel frames, and a serial signal obtained by coding the multiplexed signal is sent to the Fiber Channel network. The receiving side decodes the received serial signal,
The ATM cell is extracted from the decoded signal based on the ATM start delimiter and the ATM end delimiter. In addition, a 3 octet fill bit is added immediately before or after a 53 octet ATM cell to perform multiplexing.

Further, the network system of the present invention is
The terminal device includes a terminal device connected to the fiber channel network, and a gateway device connecting the fiber channel network and the ATM network. The terminal device transmits an ATM cell by an ATM start delimiter, one or a plurality of ATM cells, The ATM termination delimiter is successively multiplexed between the frames of the fiber channel, the serial signal obtained by encoding the multiplexed signal is sent to the fiber channel network, and the reception of the ATM cell is performed by decoding the received serial signal. An ATM cell is extracted from this decoded signal based on an ATM start delimiter and an ATM end delimiter. The gateway device decodes a received serial signal for cell transfer from the fiber channel network to the ATM network. ,this This was sent to the ATM network by extracting the ATM cell based on the Goka signal to ATM start identifier and ATM termination identifier, the transfer from the ATM network to the Fiber Channel network, ATM start identifier, one or more ATM
A cell and an ATM end delimiter are successively multiplexed between Fiber Channel frames, and a serial signal obtained by coding the multiplexed signal is sent to the Fiber Channel network.

[0013]

According to the present invention, on the transmission side, the ATM start delimiter, ATM cell, A
The TM end delimiter is successively multiplexed to create a serial signal, and the receiving side decodes the received serial signal,
A by the ATM start delimiter and ATM end delimiter
The TM cell is identified and cell extraction is performed. Also, by adding a 3 octet fill bit immediately before or after a 53 octet ATM cell and performing multiplexing, it is possible to satisfy the fiber channel frame length requirement of a multiple of 4 octets.

When the ATM cell is transferred from the terminal device to the ATM network, the terminal device multiplexes the ATM start delimiter, the ATM cell, and the ATM end delimiter between the frames of the fiber channel and encodes the multiplexed signal. The serial signal is sent to the fiber channel network. Then, the gateway device decodes the serial signal, identifies the ATM cell by the ATM start delimiter and the ATM end delimiter, performs cell extraction, and sends this to the ATM network. Further, when transferring from the ATM network to the terminal device, the gateway device multiplexes ATM cells between the frames of the fiber channel in the same manner as above, and sends the serial signal obtained by coding the multiplexed signal to the fiber channel network. To do. Then, the terminal device decodes the serial signal and transmits the AT
Extract M cells.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 (a) is an ATM according to an embodiment of the present invention.
FIG. 1B is a diagram showing a serial signal flowing on a fiber channel transmission medium for explaining a cell transmission method.
It is the figure which expanded the location where M cell was multiplexed, and the same code | symbol is attached | subjected to the same element as FIG. 4 is an idle signal defined by a special code string of 4 octets, 5 is A
This is the location where the TM cells are multiplexed.

Further, 6 is an ATM cell having a length of 53 octets defined by CCITT (currently ITU-T), and 7 is an AT of 4 octets indicating the start of the ATM cell 6.
M start delimiter, 8 is a 4-octet ATM end delimiter that indicates the end of cell 6, and 9 is a 3-octet fill bit that is added immediately before or after ATM cell 6 to satisfy the fiber channel frame length specification. .

In the present embodiment, all frame transmission specifications comply with the ANSI standard. That is, the fiber channel frame 1 has a frame structure as shown in FIG. 4, and is transmitted with a start delimiter 2 and an end delimiter 3 defined by a 4-octet special code string before and after each. In addition, from the one frame to the next frame, that is, from the end delimiter 3 to the next start delimiter 2, the idle signal 4 of 4 octets is filled for synchronization. Is 6 according to the ANSI regulations.

All serial signals flowing on a fiber channel transmission medium such as an optical fiber have 8-bit data encoded into 10 bits by an 8B / 10B code defined as a fiber channel transmission code. In FIG. 1, it is correct to call one octet in a unit after encoding (this is called one character), but in the present embodiment, all are expressed in units of octet.

ATM cells 6 are multiplexed at the locations 5 in FIG. 1 with respect to such a fiber channel frame. At this time, the 53-octet ATM cell 6 is multiplexed between the fiber channel frames 1 with the ATM start delimiter 7 and the ATM end delimiter 8 added before and after. Delimiters 7 and 8 are 4-octet special code strings, but AT
In order to identify the transfer of the M cell 6, a code string different from the delimiters defined in advance for the fiber channel such as the delimiters 2 and 3 and the idle signal 4 is used.

By performing the above multiplexing in the same manner, a plurality of ATM cells 6 are connected to the fiber channel frame 1.
It can also be multiplexed in between. When a plurality of ATM cells 6 are continuously transferred, the ATM start delimiter 7
After that, the ATM cells 6 are continuously transmitted, and the ATM end delimiter 8 is added at the end. Then, from the fiber channel end delimiter 3 to the ATM start delimiter 7, from the ATM end delimiter 8 to the next ATM start delimiter 7, and from the ATM end delimiter 8 to the next fiber channel start delimiter 2. , The minimum number of transmissions is filled with 6 idle signals 4.

In this way, the ATM cell 6 is transferred to the frame 1
In between, the multiplexed signal is encoded using the 8B / 10B code. As a result, a serial signal as shown in FIG. 1 is generated and sent to the fiber channel transmission medium. The receiving side connected to the fiber channel transmission medium decodes the serial signal and extracts the ATM cell 6 from the decoded signal. That is, the ATM cell 6 is obtained by recognizing and separating the data from the detection of the ATM start delimiter 7 to the detection of the ATM end delimiter 8 as the ATM cell 6. Thus, the ATM cell 6 can be transmitted in the fiber channel network.

As described above, in the present embodiment, all the frame transmission regulations comply with the ANSI standard, and no ATM cell is placed in the fiber channel frame 1 unlike the conventional first method or second method. It eliminates the need for complicated protocol processing. Further, unlike the conventional method, since it is not necessary to attach a 24-octet header and a 4-octet trailer, it is possible to perform transmission with almost no transfer overhead (the overhead in this embodiment is fill bit 9 described later).

Immediately before or immediately after the ATM cell 6, 3
The octet fill bit 9 is added because this is because the transmission channel length is defined as a multiple of 4 octets in the fiber channel regulations, and the ATM cell 6 of 53 octets has a fill bit of 3 octets. By adding 9 to make 56 octets, it is intended to satisfy the above-mentioned regulation. As a result, as will be described later, the processing logic of the fiber channel can be used as it is to increase the speed.

FIG. 2 is a block diagram of a network system showing another embodiment of the present invention, and FIG. 3 is a diagram showing protocol processing in this network system. In FIG. 2, 21 is a fiber channel network, 21
a and 21b are fiber channel transmission media such as optical fibers, 22 is an ATM network, 23a and 23b are terminal devices connected to the fiber channel network 21,
Reference numeral 24 is a fabric device serving as a gateway device that connects the networks 21 and 22, and 25 is a terminal device connected to the ATM network 22.

Further, 31a and 31b are fiber channel interface units for connecting to an external device (not shown) for fiber channel, 32a and 32b are ATM interface units for connecting to an external device (not shown) for ATM, 33a and 33b. Is Fiber Channel Frame 1
A demultiplexer 7, an ATM cell 6, and a delimiter 8 are successively multiplexed in between, and a frame multiplexing unit 34a for transmitting a serial signal obtained by coding the multiplexed signal to the transmission medium 21a,
Decoding units 34b, 36a and 36b decode the received serial signal and extract the ATM cell 6 from the decoded signal, and 35a and 35b are fabric ports.

Further, 37a and 37b are frame multiplexing units for sending out serial signals created by performing the same multiplexing as the frame multiplexing units 33a and 33b to the transmission medium 21b,
Reference numeral 38 is a fiber channel protocol control unit.
Reference numeral 39 denotes an ATM switch section, which is a decoding section 36a, 36
The destination to which the ATM cell 6 obtained from b is determined, the cell 6 is transmitted to the ATM network 22, and which fabric port the ATM cell 6 obtained from the network 22 is to be output based on a routing table described later. To decide. Reference numeral 40 is a routing table that stores the correspondence between information such as virtual channel identifiers included in the cell header of the ATM cell 6 and the fabric port that is the destination of the cell.

In FIG. 3, FC-0, FC-1, FC
-2 is a protocol that constitutes the above-mentioned physical interface FC-PH of the fiber channel. Terminal device 23
a and 23b are fiber channel interface units 31.
a, 31b, ATM interface units 32a, 32b,
Each of the fiber channel ports includes a multiplexing unit 33a, 33b and a decoding unit 34a, 34b.

Then, the terminal devices 23a, 23b and the fabric device 24 have a function of multiplexing the ATM cells 6 between the fiber channel frames 1 as shown in FIG. 1 and extract the ATM cells 6 from the signal obtained by decoding the serial signal. The function to perform is defined in the ATM and AAL in the same layer as the protocol FC-1. The network system according to the present embodiment performs communication between the terminal device 23a or 23b and the terminal device 25 or between the terminal devices 23a and 23b using the ATM cell transmission method of the example of FIG. ,
ATM from the terminal device 23a to the terminal device 25 first
The operation when transmitting the cell 6 will be described.

The interface unit 31a outputs the Fiber Channel frame 1 sent from the external device for Fiber Channel to the multiplexing unit 33a, and the interface unit 32.
The a outputs the ATM cell 6 sent from the external device for ATM to the multiplexing unit 33a. Then, the multiplexing unit 33a
Is a delimiter 7, AT between the fiber channel frames 1.
The M cell 6 and the delimiter 8 are multiplexed as shown in FIG. 1, and the serial signal obtained by encoding the multiplexed signal using the 8B / 10B code is sent to the transmission medium 21a.

Next, the decoding unit 36a, which has received the serial signal via the transmission medium 21a, decodes this into the original 8-bit code. Then, the data from the detection of the ATM start delimiter 7 to the detection of the ATM end delimiter 8 is recognized as the ATM cell 6 and extracted, and the extracted ATM
The cell 6 is output to the ATM switch unit 39. Also, AT
The received data other than the M cell 6 is output to the protocol control unit 38.

The protocol control unit 38 includes a decoding unit 36a.
The fiber channel frame 1 for the terminal device 23b output from the multiplexer 37 of the fabric port 35b.
Output to b. The multiplexing unit 37b multiplexes the frame 1 as shown in FIG. 1 (however, since there is no ATM cell 6 here, only the delimiters 2, 3, the frame 1 and the idle signal 4 are present), and the 8B / 10B code is transmitted. It is used, encoded, and transmitted to the transmission medium 21b.

The decoding unit 34b of the terminal device 23b decodes the received serial signal and outputs the fiber channel frame 1 to the interface unit 31b. Thus,
Communication is performed from the terminal devices 23a to 23b.

On the other hand, the ATM cell 6 from the decoding unit 36a
The ATM switch unit 39 that has received the information determines the distribution destination of the ATM cell 6 based on the information such as the virtual channel identifier, which is the destination information included in the cell header of the ATM cell 6, and performs the virtual channel identifier replacement, etc. To the ATM network 22. Thus, the ATM cell 6 for the terminal device 25 is sent to the terminal device 25.

Next, the operation when the ATM cell 6 is transmitted from the terminal device 25 to the terminal device 23a will be described.
First, the ATM switch unit 39 which receives the ATM cell 6 from the terminal device 25 via the ATM network 22
The routing table 40 is referred to on the basis of the information such as the virtual channel identifier included in the cell header of the ATM cell 6 to determine to which fabric port it should be sent.

When the ATM cell 6 is output to the multiplexing unit 37a of the fabric port 35a according to this determination, the multiplexing unit 37a multiplexes the delimiter 7, the ATM cell 6, and the delimiter 8 between the fiber channel frames 1, and this multiplexing is performed. A serial signal obtained by encoding the signal using the 8B / 10B code is sent to the transmission medium 21a. Then, the decoding unit 34a of the terminal device 23a decodes the received serial signal, and decodes the ATM signal from the decoded signal in the same manner as the decoding unit 36a.
The cell 6 is extracted and output to the ATM interface unit 32a. In this way, the communication from the terminal device 25 to the terminal device 23a is performed.

Further, the ATM cell 6 can be similarly transmitted from the terminal device 25 to the terminal device 23b. By doing so, the ATM cell 6 can be transferred regardless of the communication state of the fiber channel.

Although the fill bit 9 of FIG. 1 is not multiplexed in this embodiment, addition of the fill bit 9 can speed up the process. That is,
The processing logic of the Fiber Channel is 4 octets (3
(2 bits) It is supposed to process in parallel,
This is because such processing logic can be applied to the terminal devices 23a and 23b and the fabric device 24 by adding the fill bit 9 as described above. If the fill bit 9 is not added, the processing may be performed in units of 1 octet.

[0038]

According to the present invention, on the transmitting side, the ATM start delimiter, ATM cell, and ATM end delimiter are successively multiplexed between the frames of the fiber channel to create a serial signal, and on the receiving side, the ATM start delimiter and ATM are generated.
Since the ATM cell is identified and the cell is extracted by the end delimiter, the ATM cell can be transmitted with almost no transfer overhead, and high transfer efficiency can be realized. Moreover, since it is not necessary to perform complicated protocol processing, the transmission delay can be reduced.

Further, by adding a fill bit of 3 octets immediately before or after the ATM cell of 53 octets and performing multiplexing, it is possible to satisfy the fiber channel frame length requirement of a multiple of 4 octets. Higher speed can be achieved by using the processing logic of the channel.

Further, by configuring the network system from the terminal device and the gateway device, it is possible to realize the network system which can minimize the decrease in the transfer efficiency due to the additional overhead without increasing the delay.

[Brief description of the drawings]

FIG. 1 is a diagram showing a serial signal flowing on a fiber channel transmission medium for explaining an ATM cell transmission method according to an embodiment of the present invention.

FIG. 2 is a block diagram of a network system showing another embodiment of the present invention.

FIG. 3 is a diagram showing protocol processing in the network system of FIG.

FIG. 4 is a diagram showing a frame structure of a fiber channel.

FIG. 5 is a diagram showing protocol processing by a conventional method for connecting a fiber channel network and an ATM network.

FIG. 6 is a diagram showing protocol processing by another conventional method for connecting a fiber channel network and an ATM network.

[Explanation of symbols]

1 ... Fiber channel frame, 2 ... Start delimiter, 3
... End delimiter, 4 ... Idle signal, 6 ... ATM cell,
7 ... ATM start delimiter, 8 ... ATM end delimiter, 9
... fill bit, 21 ... fiber channel network, 22 ... ATM network, 23a, 23b ... terminal device, 24 ... fabric device.

Claims (3)

(57) [Claims] 1. ATM in a fiber channel network
An ATM cell transmission method for transmitting a cell, wherein an ATM start delimiter indicating the start of an ATM cell and an ATM end delimiter indicating the end of a cell are defined by a code string different from the delimiter group defined by the fiber channel. On the transmission side connected to the channel network, an ATM start delimiter, one or more ATM cells, and an ATM end delimiter are successively multiplexed between the Fiber Channel frames, and the serial signal obtained by encoding the multiplexed signal is transmitted to the fiber. The receiving side connected to the fiber channel network transmits to the channel network, decodes the received serial signal, and extracts ATM cells from the decoded signal based on the ATM start delimiter and ATM end delimiter. AT to
M cell transmission method. 2. The ATM cell transmission method according to claim 1, wherein a fiber channel frame length is satisfied.
An ATM cell transmission method characterized in that the multiplexing is performed by adding a fill bit of 3 octets immediately before or after a 53 octet ATM cell. 3. A terminal device connected to a fiber channel network, a fiber channel network, and an AT.
A network system for transmitting ATM cells between a fiber channel network and an ATM network, comprising a gateway device for connecting between M networks, wherein the terminal device is an ATM device for transmitting ATM cells.
An ATM start delimiter indicating the start of a cell, one or more ATM cells, and an ATM end delimiter indicating the end of this cell are successively multiplexed between the Fiber Channel frames,
A serial signal obtained by encoding the multiplexed signal is transmitted to the fiber channel network, and for reception of ATM cells, the serial signal received through the fiber channel network is decoded, and the A signal is decoded from the decoded signal.
A based on TM start delimiter and ATM end delimiter
The gateway device extracts a TM cell, and when the cell is transferred from the fiber channel network to the ATM network,
The serial signal received via the fiber channel network is decoded, ATM cells are extracted from the decoded signal based on the ATM start delimiter and ATM end delimiter, and this is sent to the ATM network.
For transfer from the M network to the fiber channel network, the ATM start delimiter, one or more ATM cells received from the ATM network, and the ATM end delimiter are successively multiplexed between the fiber channel frames, and the multiplexed signal is transmitted. A network system for transmitting an encoded serial signal to a fiber channel network.